newbie to storage concept, need help understanding plumbing

[biodieseler]

Hi everyone. I've been reading up on this site for a while and looks like a great resource of information here. Being this is my first post, I hope to gain some of your knowledge on how to make an efficient system that I am trying to build.

So I am not a stranger to OWBs but am relatively new to the gasifying technology. I recently bought a house that is 1380 sq.ft. on the ground with a full basement. I was given a used Empyre elite 100 (version 1) for free and was able to make it work for this past winter but it has developed several leaks and I intend to build my own gasifying boiler for next season as I think I have a grasp on how the boiler itself works and my brother is a machinist/welder and we are pretty capable fabricators.
I intend to keep the boiler in an un-heated garage as I don't need to heat the garage and don't want to bring the boiler or wood inside the house. It just works better for me to plan this as an OUTdoor wood boiler.

Now on to what I'm really posting for... I understand that gasifying boilers are susceptible to corrosion due to idling (creosote) and high moisture, etc. So I am prepared to put in a large storage tank somewhere in the system to make more of a batch burn. I get the theory of why storage is better for the boiler longevity and efficiency but have a couple questions.

With this being an boiler install in an un-heated garage, and storage tank being in the garage also, I am wondering how much of a concern is the water temp in the boiler getting fairly low (below say 140 where we try to keep condensation from causing corrosion) when doing a batch burn and knowing the fire goes out and water in the storage tank starts to stratify and we either shut the circ. pump off or are pulling in colder water to the boiler?. Do people who plumb their boiler to storage with return from storage to boiler coming off the bottom of the storage tank not have an issue with the boiler being under the safe range when lighting the next fire? or is it just not a big enough concern to worry about?
I understand many systems out there turn the circulation pump from boiler to storage off when the boiler is done burning its load, so in an outdoor application how do you keep the lines from risking freezing if the pump is off and its an outdoor application, short of good insulation? I suppose it's probably not that long between firings that they would ever freeze?

When you guys talk about pressurized storage vs non-pressurized storage, how much "pressure" are we talking? obviously there needs to be expansion room for say a 1000 gal storage tank but I would like to avoid relying on the boiler to hold much of any pressure but also don't want it to be able to breathe to atmosphere where the system picks up oxygen from the air and causes the water to be more corrosive on boiler / other system components... I'm wondering if it's wise to put in a bladder rather than a pressure/expansion tank so it can remain under virtually no pressure but still allow room to expand and contract without pulling in oxygen from the air every time the system breathes.
Am I on the right track with this thinking?

I feel like it would be super simple to just put a storage tank in-line between the boiler and the house and let it circulate enough to allow the tank to absorb and discharge heat while one pump runs continuously but I understand that means no stratification and I like the idea of all the benefits a stratified storage has... just not quite wrapping my head around how it works.

Does the water from boiler go through the tank directly with the help of one pump, and another pump take that same water from storage to the heat load in the house? Based on the plumbing diagrams I've seen that looks to be the case, but I also see videos of people who have say 100 feet of copper tubing inside their storage tank both for heating up the storage and for taking heat out of storage... so I'm confused how the water flows through the storage tank.

I hope these questions make sense. I will leave it at that for now. Thanks in advance for any input!

Allan

 

[biodieseler]

Ok so I have a bit more of some specifics that maybe will be helpful in people answering these questions.
I make biodiesel to fuel our cars, and so I have a lot of tanks around... While looking to see what I have I came across a few possible options for storage tanks.
I have 3 separate tanks. 2 are approx. 500 gallon tanks and 1 is a 1000 gallon tank. I hope to leave the 1000 gal one in place as it's full of old vegetable oil and would be hard to fit where I want it anyways though I could make it work if that's really the best tank to use.. but I have the 2 other tanks. One is 48" in diameter and 72" long. The other is 45" in diameter and 82" long. Both are pretty heavy tanks. Not ones that would expect to hold any substantial pressure but they're not made of light tin either. Obviously they are metal tanks and so I can weld fittings of whatever size, wherever I need. I would like to plumb the tanks in parallel and stand them on end beside each other, and obviously insulate around them once set in place behind my boiler.
Not sure if this is relevant or not but my house works with one loop that goes through the DHW side arm heat exchanger and then tee's to go through a couple radiators that fans force air through and is then ducted to each zone from the utility room. It's kinda crude, but it worked very well this past year at keeping the house warm. Anyways, its one loop and I know I can keep the house warm with 140 degree water, though 170 or so just means the fans run less often.. I can't say I know for sure what the flow was or delta T was. I doubt I need much flow to keep heat in the house. So do I need to calculate heat load and size the circulating pump from storage to house accordingly based on size of heat exchangers, etc. to help keep the storage tanks stratified?

And how do I keep the boiler from getting too cold between firings while still allowing the storage tanks to stratify properly - in a cold garage environment? I do have it going in a room of its own in the garage that I could potentially insulate but hoping not to have to do that just right away if I don't have to. The bigger the storage tank(s) the longer I expect to be able to go between firing the boiler and therefore the colder I'm afraid the boiler would get. Any suggestions on how to plumb it to be effective, or what components I'm missing to make this work properly?

Thanks,
Allan

 

[jebatty]

Many of us respond promptly to questions, but your inquiry has not resulted in this. Your lengthy posts were a bit intimidating to me. While it might not be easy or well organized, this forum is full of answers to most of your questions if you take the time to read the various posts/threads. Another approach is to study the literature. And you might try to ask a more focused question or two, or to consult with a hydronic expert who could engage in a more lengthy discussion.

 

[maple1]

Some fundamental tidbits.

How does the heat get to your system now from your Empyre? There must be a heat exchanger in between? Otherwise your whole system is open, which is not good for it.

You do not want any pressure at all on those tanks you have. That means they must be open, and use heat exchangers (the copper coils you mentioned above are heat exchangers - or flat plate exchangers). Which has corrosion potential for the tanks (unless they are stainless). Most open tanks use liners, inside a box of some sort. Some have used stainless milk tanks. So not sure that using those tanks are the best approach. You also will not likely want to pressurize this boiler you are thinking of making - which means it will also need to be open. More corrosion potential - a good strict water treatment regime will be important there. But a well designed/engineered boiler will be very important, for very good heat exchange/transfer. (Along with combustion efficiency). Otherwise you won't get enough heat into storage tanks to make storage worthwhile. So there are a lot of things to get right, in your proposal - and lots of potential for disappointment. You also would want to insulate the space the boiler will be in, I think. Insulating walls that are already there should be an easy one. Storage usually involves batch burning - the fire is let to go out when storage is up to temp, and re-lit when storage is depleted. So the fire burns wide open at max burn efficiency, and doesn't get dampered or smolder. So would be a bit of a balance with a boiler that is exposed to outside temps all winter - hence the insulation. You would also want proper (more expensive) underground piping - Thermopex or Logstor type - big enough for needed flows. Not wrapped pipe.

Return temperature protection is a must - might be part of why the Empyre failed? That can be done with separate pump & thermostatic valve (eg. 'Danfoss'), or all-in-one loading unit (eg. 'LK810'). It maintains 140 return to the boiler by incorporating flow from a boiler bypass loop. Some boilers accomplish return protection by using two pumps, one that kicks in on the bypass loop varying with return temperature ('bang bang' approach, I believe).

You mentioned 'garage' - better run this by your insurance person. Usually boiler + 'garage' is not a good combo.

 

[woodsmaster]

It doesn't matter how cold the boiler gets between burns as long as it doesn't freeze and you have return temp protection. I personally would do pressurized storage and boiler. we are talking a max pressure of 30psi and could keep max as low as 18psi if you have enough expansion. Find an old propane tank or two to convert to storage tanks. Can even make your own expansion tank from a 125 propane tank or similar. Insulate the building the boiler is in and you shouldn't have any worries about it freezing. you will have a heated building no matter how well you insulate the boiler and storage. Do lots of reading older post and such on here and you will get it figured out. Post more specific questions and ask only one or two at a time and you will get more responses. Boiler room is a little slow as summer approaches and will get busy in the fall.

 

[warno]

I'm in the same boat as you right now. I'm installing storage tanks heated with an open boiler and plumbing to my garage and house. I'm putting 3) 250 gallon tanks in my garage heated through a plate heat exchanger off my boiler. My storage will be pressurized and like stated my boiler is open.

Like others said there's a ton of info on this site. If you look through my most recent threads you will find where people help me with my storage questions. This place really is about a ghost town until around late summer early fall, so don't be offended if your questions don't get answered right away.

 

[jebatty]

My first storage foray included three 275 gal retired fuel oil tanks for un-pressurized open storage. Not understood as to effect or known by me was my slightly acidic well water/boiler fill water. Those tanks were thin steel, and acidic corrosion was fast and furious. Venting of each tank also became an issue. Short outcome was a quick switch to a retired 1000 gal LP tank and a pressurized system -- also self-implemented water treatment to raise pH and scavenge oxygen. Later I implemented a full commercial water treatment regimen. System now has been in operation since the first heating season of 2007-08.

 

[dogwood]

Biodieseler, I'll do my best to try and answer some of your questions based on my limited experience of having installed a wood gasification heating system to heat our 3000 square foot home. The real experts on this site, which I don't pretend to be, would be better resources,

I have three separate tanks. two are approx. 500 gallon tanks and one is a 1000 gallon tank.

Would your tanks be suitable for a pressurized system? If you have a properly designed pressurized system with suitable air eliminators to bleed air from the pipes, plus appropriately treated water, you shouldn't experience corrosion issues. A thousand gallons of storage allows us to burn full out, usually twice a day only in single digit weather. Once I started weighing wood loads I rarely had idling, and have had little creosote this first season

I intend to keep the boiler in an unheated garage as I don't need to heat the garage and don't want to bring the boiler or wood inside the house.

This location is potentially dangerous. It is a building code violation in my county due to the danger of mixing gasoline, or other flammable fumes, and fire. A garage location would cause State Farm to cancel our homeowners insurance policy. To avoid this, I partitioned off part the garage for the insulated boiler room, having the boiler room entrance from the outside yard only. Partitioned off, the boiler room is technically and literally separate from the garage and it's potential flammables. Sounds like you may be thinking of doing something similar.

I'm wondering if it's wise to put in a bladder rather than a pressure/expansion tank?

I've 1000 gallons of storage with two floor-standing Amtrol Extrol 86 gallon SX-160 bladder type expansion tanks. One was insufficient to keep pressure below the mid-twenty psi range when running the boiler. As you're aware, a bladder tank won't introduce corrosion causing air into the system.

I feel like it would be super simple to just put a storage tank in-line between the boiler and the house and let it circulate enough to allow the tank to absorb and discharge heat while one pump runs continuously but I understand that means no stratification and I like the idea of all the benefits a stratified storage has... just not quite wrapping my head around how it works.

That's how my storage is plumbed, but without running the circulator continuously. I have our 1000 gallon insulated storage tank walled off in our unheated garage adjacent to the boiler room. Whenever the top layer of stratified water in the tank gets below 140 degrees Farenheit, I reload the boiler with wood, fire it up, and bring the tank back up to 180 degrees F. (140 degrees is the low design temp for our water to air heat exchanger which located in the plenum over our forced air furnace) The system is plumbed so the boiler automatically bypasses storage and heats the house directly first if need be. Soon as the house is up to 70 degrees F, the boiler then heats storage back to 180 degrees. There is no reason to circulate continuously.

How do you keep the lines from risking freezing if the pump is off and its an outdoor application, short of good insulation? I suppose it's probably not that long between firings that they would ever freeze?

My piping is roughly 120 feet of 1.5 inch black iron covered with 1.5 inch of Dow Corning pipe insulation. It runs and returns forty feet in an unheated attic. To avoid that run of pipe freezing in the coldest weather, I built in a pipe chase and have a small fan on a thermostat to pull warm house air through the chase if the temp in the pipe chase gets down near freezing. The black iron seems to conduct enough heat from storage by itself, so that fan didn't have to kick on even once last winter. Then again, I live in Virginia, not Ontario. I have a backup electric wall heater in the unheated boiler room in case the temp in that room ever got near freezing, It never even got close either.

If your piping is underground I don't know anything about how that's done to prevent freezing.

Does the water from boiler go through the tank directly with the help of one pump, and another pump take that same water from storage to the heat load in the house?

Yes, and a pressurized system should not need a heat exchange coil within your storage tank. In my case a Termovar loading unit services the boiler to storage loop. It, as well, provides appropriate temperature return water to the boiler. A three speed Grundfos circ pumps heated water to the water to air heat exchanger above our forced hot air furnace. Another three speed Grundfos circ pumps heated water to a a flat plate heat exchanger servicing our standard 40 gallon DHW tank.

Check out the many piping diagrams on the Tarm Biomass site to find out which suits you best. I'm guessing those diagrams are still posted. Studying those diagrams will clue you in on what parts you will need to complete your system too.

So do I need to calculate heat load and size the circulating pump from storage to house accordingly based on size of heat exchangers, etc. to help keep the storage tanks stratified?

That's what I did to help size the boiler, heat exchangers, circulators, and pipe diameters also considering head and friction loss etc. Site members provided excellent advice to guide me through this process. I used multiple online heat loss calculators. No two yielded the same results.

Your storage tank will stratify of its own accord.

Good luck with your project. By the way how do you make biodiesel? Never heard of anyone doing that at home. That's impressive.

Mike

 

[biodieseler]

Thank you all for the information! I've been busy the last week and have just now sat down to look through your replies in detail.

I realize my posts were long and could leave lots of questions about what I'm asking. I'll try to be more specific.

Though I called this a "garage" location, it will be a room of it's own with no access to the actual garage directly other than they share 1 wall. It will have its own entrance door from outside only and I am now planning to insulate that room so it can hold as much heat as possible that radiates off the boiler and storage tanks (which will also be insulated to hold the heat in as well as possible)

I already have proper underground insulated pipes that I'm sure is fine running from the (now I'll call it as it should be) "boiler room" to the house.
I want to do a batch burn operation, thus the need for storage. I'll get used to how much wood to put in etc.

Some fundamental tidbits.

How does the heat get to your system now from your Empyre? There must be a heat exchanger in between? Otherwise your whole system is open, which is not good for it.
.

You can scold me for this, but no, there was no heat exchanger... The manual I got with the empyre doesn't say anything about adding a heat exchanger that I remember. The water just circulated from the boiler, through the pump to the house where it went through the DHW side arm heat exchanger and the radiators, then back to the boiler. I was aware that it would have been better to have a mixing valve to keep the return water up but I was diligent at checking it multiple times/day and not letting it get cold. In the boiler I want to build I fully intend to put in a proper mixing valve or whatever is required to get the boiler up to temp first and then send heat to the house and/or storage.

It doesn't matter how cold the boiler gets between burns as long as it doesn't freeze and you have return temp protection. I personally would do pressurized storage and boiler. we are talking a max pressure of 30psi and could keep max as low as 18psi if you have enough expansion. Find an old propane tank or two to convert to storage tanks. Can even make your own expansion tank from a 125 propane tank or similar. Insulate the building the boiler is in and you shouldn't have any worries about it freezing. you will have a heated building no matter how well you insulate the boiler and storage. Do lots of reading older post and such on here and you will get it figured out. Post more specific questions and ask only one or two at a time and you will get more responses. Boiler room is a little slow as summer approaches and will get busy in the fall.

Is it possible to run less pressure and still keep a closed system somehow? (without massive expansion tanks too) I know with the heatmor OWBs I've seen there is a tire inner tube at the top of the boiler that allows for a bit of expansion and acts as a reservoir to keep the water jacket of the boiler full. They build a couple psi, but are they don't really breathe to the atmosphere much at all do they? I can't help but wonder if I could use some large inner tubes as bladders to allow room for expansion without having to build much of any pressure at all or allowing the system to breathe to air. Why the need to run 18+ PSI? Is that only due to the fact that expansion tanks do not breathe to the atmosphere at all and therefore end up pressurizing an "air cushion" sealed in the top of the expansion tank? I would think something like a big tractor tire inner tube plumbed into the top of the storage tanks (which in my case would be at the highest point in the system) would act as a place for water to go as it heats up, but cause virtually no pressure... it may be hard to say what size it should be, but if sized properly and in the right location would it possibly work? I won't use the following idea but it comes to mind it could be like a big old water bed, where the water sloshes around under no pressure but can give or take a lot of water as the rest of the system expands - but doesn't breathe to the air.

I have a couple friends who work at local propane companies and are going to see if they can find me any big retired tanks. If not I may be limited to using big old fuel oil tanks like what I have now. If I can keep the pressure down but keep the system closed off from the air that would be ideal I think. I can install anode rods anywhere in the system, intend to use water treatment, and will do regular tests on water quality and I like to think I could get many years out of it that way... but if you guys tell me if I'm planning something bad by doing that, I'm happy to listen.

For what it's worth, our water here has been tested before going into my brothers Heatmor and comes back almost as good as de-mineralized water straight out of the well. And my dad's boiler is pushing 27 years old and still going strong with that water... Our Heatmor dealer says it's the best water he's ever seen go into a system. So I have that in my favour...

Again, thanks for the replies so far! I will continue to research where I can and will post my ideas/plans here before I start building it and with your help here I hope to nail down a good design the first time.

Allan

 

[maple1]

Usually minimum system pressure relates to being able to get water to the highest parts of the system (e.g. upstairs rads) while maintaining necessary water pressure to the inlet of circ pumps so they won't cavitate. Most circs spec 4psi inlet pressure (I think). So for example if your circ is at the bottom of a basement system that has 2 floors above it, you would need say (20 ft. of elevation rise) x 0.4 = 8psi, plus the 4 at the pump = 12 psi minimum at the bottom. Throw in a couple extra for good measure. Otherwise system will be prone to airlocks.

Can't say about the bladder - interesting concept but not one I've read of being used for storage tanks. You would want it to be high enough that it would drain back into the tanks & boiler when cold - that height may or may not introduce too much static pressure at the bottom of the tanks. Example 10' high = 4psi at the bottom. 4psi could well be too much for a tank that is not designed for any pressure. Plus, when the bladder expands it will introduce some pressure (think blowing up a balloon - might be easy going first couple of puffs, but the puffing gets harder with each one). Not sure how much - but you would need a seriously big balloon to avoid much, with that much water.

Your boiler design will also have final say in whether storage is even worth it. My old one would not make any extra heat above what it took to keep the house warm, so storage would have been absolutely useless with it. Building a boiler from scratch for the first time, and getting the results you want with it, is likely the biggest question mark in the whole scenario.

 

[biodieseler]

Thanks maple1
I have very little elevation difference between the highest and the lowest point in the system, and the highest point would be the top of the storage tanks. But before going too far with plans of using these tanks I will see if I can find some good propane tanks.

I appreciate the concern about the home made boiler to be not being able to hear enough to make storage worthwhile. But somehow I'm not too worried about that. I know my old empyre elite 100 was rated for something like 45000 btu /hour on a 12 hour burn and I could get 12 hour burn on most of the coldest days of the year. So I'm pretty confident I can build the new boiler to put up quite a bit more than that. I plan to make a boiler slightly bigger than the empyre 100 and believe I can make it pretty efficient. No guarantees but I'm optimistic and not too intimidated by the boiler build.

I hope to find more information on what parts I need and where in the plumbing system to make it as effective as possible though.

Can someone point me to the key components I'm likely to need in this system? I'm still a bit fuzzy on the difference between a loading valve and mixing valve, and what other parts am I looking for to keep the storage tanks stratified while maintaining flow to the house as needed?

Allan

 

[maple1]

A loading unit, uses a thermostatic mixing valve. Along with its own circ, all in one unit. You could also use a separate mixing valve (examples Danfoss, or the Termovar type) and circ. I think the latter might be cheaper. I have a loading unit (LK810), it works very well. But they are pricey.

Stratification comes down to managing flows, and orientation of the tanks. The more verticality the better, but I have two stacked tanks with total height of about 6' and they do well. Low flows on the load side is likely the key aspect, along with balanced flow through tanks if using more than one. I have an Alpha pump for my loads, its variable speed aspect allows some tuning of flows by throttling of ball valves on the loads - it will ramp up & down to maintain a constant pressure differential between inlet & outlet. Should be mandatory equipment on a system with multiple loads using a single pump, IMO. If your loads need constant and/or high flow to keep things warm, there isn't much you can do to stop that from messing up stratification - so things like more radiation or lower temp emitters (e.g. cast iron rads, in-floor heat) help there.

 

[ewdudley]

You could also use a separate mixing valve (examples Danfoss, or the Termovar type) and circ. I think the latter might be cheaper.

I went the "cheaper" route and ended up with a nice assembly, which includes a low-resistance swing check made by replacing the brass arm and plate from a conventional swing check with an equivalent part cut out of high density poly. I'm quite happy with it, but it sure took a lot of time and figuring, and the assembly takes up a lot of space in an area where space is tight.

I would recommend that if the power-off-fail-safe low-resistance check valve is a requirement, then a loading unit would be a better choice.

 

[biodieseler]

Thanks guys. I think I'm getting more confidence that I can put this together and it will work. I have yet to get my hands on better tanks than what I have, but I also have the summer ahead to piece this together... just wanting to get planning now so I don't freak out in the fall when I need heat!

So it sounds like a loading unit would be ideal to put on the back of the boiler. Especially if it also builds in a "power-off-fail-safe" as I would want there to be something to allow it stay safe in a power outage.

Low flows on the load side is likely the key aspect, along with balanced flow through tanks if using more than one. I have an Alpha pump for my loads, its variable speed aspect allows some tuning of flows by throttling of ball valves on the loads - it will ramp up & down to maintain a constant pressure differential between inlet & outlet. Should be mandatory equipment on a system with multiple loads using a single pump, IMO. If your loads need constant and/or high flow to keep things warm, there isn't much you can do to stop that from messing up stratification - so things like more radiation or lower temp emitters (e.g. cast iron rads, in-floor heat) help there.

My heat load is all one loop, going first through the DHW side-arm heat exchanger, then goes through a few T's and through 3 radiators that have thermostatically controlled fans to blow air through them (cheap easy to do make-shift kind of air handler that worked well for some zone control too) Then the water goes back to the boiler (or soon to be storage, hopefully)

So I have little heat radiating off without some flow. I don't think I need huge flow but definitely some.

How do the Alpha pumps (or equivalent) know when to ramp up or down the speed of circulation? Would it be that when there is power to any of the zones calling for heat (radiator fan kicks in) the pump speeds up flow until no heat is called for and then it slows down/stops?

 

[maple1]

So it sounds like a loading unit would be ideal to put on the back of the boiler. Especially if it also builds in a "power-off-fail-safe" as I would want there to be something to allow it stay safe in a power outage.

That safeness would come down to how well the boiler & storage are laid out to allow good convection flow. Typically that would be the storage right next to the boiler, with as much direct upward run as possible from boiler to storage, and piping that is big enough. (Usually all pressurized). Given that you are going to be working with an unpressurized boiler & heat exchangers somewhere - that may or may not be possible. So I would likely also plan on a heat dump zone. And maybe a UPS to run the pump while you are getting a generator going, depending how the heat dump zone handles the heat.

How do the Alpha pumps (or equivalent) know when to ramp up or down the speed of circulation? Would it be that when there is power to any of the zones calling for heat (radiator fan kicks in) the pump speeds up flow until no heat is called for and then it slows down/stops?

With multiple zones/loads, and one pump, the Alpha senses when a zone valve opens by sensing the reduced pressure it is seeing on the outlet side. (Or maybe more aptly, the difference in pressure between inlet & outlet). It speeds itself up to maintain that pressure differential. Then slows itself down to maintain that same differential as zone valves close.

Have you ever determined how hot your supply water needs to be to maintain house temperature? I.e., how low can it go before the house starts feeling cool? That might be quite hot, coming from an OWB - and if so, that would be another factor that would reduce the effectiveness of storage. I can run mine down to 130 on top or so before I need to make another fire, which is a lot less than what an OWB would normally supply. W-A HXs (rads & fans) like you have typically require some fairly high supply temps, but that would come down to their sizing. Quite a few factors in play here, from boiler to rads.

 

[biodieseler]

That safeness would come down to how well the boiler & storage are laid out to allow good convection flow. Typically that would be the storage right next to the boiler, with as much direct upward run as possible from boiler to storage, and piping that is big enough. (Usually all pressurized). Given that you are going to be working with an unpressurized boiler & heat exchangers somewhere - that may or may not be possible. So I would likely also plan on a heat dump zone. And maybe a UPS to run the pump while you are getting a generator going, depending how the heat dump zone handles the heat.

I'm waiting to hear back from the contacts I have in the propane business to see if I can get a good sized propane tank or two for storage. If I can I may be able to do a pressurized system, but will want to keep pressures to a minimum. As far as location of storage tanks I intend to put the tanks directly behind the boiler, with only whatever clearance I need to be able to work around things. So that might be quite possible to use big lines and get a convective loop in the event of a power outage.
So why does a pressurized system allow better convective flow in the event of a power outage? Just not sure I'm connecting the dots about why it is usually all pressurized.

With multiple zones/loads, and one pump, the Alpha senses when a zone valve opens by sensing the reduced pressure it is seeing on the outlet side. (Or maybe more aptly, the difference in pressure between inlet & outlet). It speeds itself up to maintain that pressure differential. Then slows itself down to maintain that same differential as zone valves close.

Are these zone valves basically just switched valves that allow flow only when a loop is calling for heat? If so it would be easy for me to tap into the power wires that run the fans so when each zone calls for heat it opens the valve, then shuts off when there is no call for heat.

Have you ever determined how hot your supply water needs to be to maintain house temperature? I.e., how low can it go before the house starts feeling cool? That might be quite hot, coming from an OWB - and if so, that would be another factor that would reduce the effectiveness of storage. I can run mine down to 130 on top or so before I need to make another fire, which is a lot less than what an OWB would normally supply. W-A HXs (rads & fans) like you have typically require some fairly high supply temps, but that would come down to their sizing. Quite a few factors in play here, from boiler to rads.

I don't have an exact number on this, no... However I do know from the experience I had this past winter that I can keep the house warm even when the water temp. drops off quite a bit (from the few times the boiler temp dropped) And as the fans/radiators don't run all that often. So if I run cooler water through them obviously the fans will run more, but that's okay sometimes. I believe I would be able to keep the house and hot water warm enough down to 140 for sure... maybe lower depending on outside temps and how much I'm willing to let the fans run, etc.
I would estimate about 70% of the houses heat comes from a really big radiator I have downstairs. When it kicks in I get a lot of heat and it only runs maybe 50% of the time on the very coldest days of the year (-40 is quite unusual and about the coldest we ever see) usually it only runs maybe 20% of the time. The other radiators are actually old heater cores out of our 1986/1992 Volkswagen Jettas. They are small radiators and fans but believe it or not they pump out a lot of heat. When they are running while the water temp. is at 180 I can't hold my hand on the duct work or register upstairs. They function only to take the chill off upstairs as we don't have good air flow from the basement up the stairwell. They run more often than the downstairs heater if we want to warm the upstairs up much extra (Despite being intense enough heat, the fans behind them don't put up a lot of volume)

Anyways, all that to say I believe I can benefit from storage as I think I can get enough heat into the house with temps down in the 130-140 degree range. I am going to research more about how to keep it stratified by reducing flows.

Is there an easy way to calculate how many GPM is required to get "X" number of BTU's out of the water and hit a target Delta T ? obviously the faster the flow, the lower the Delta T, but how can I figure out what the flow rate actually needs to be?
I just know that I had my Grundfos circ. pump (don't know the exact size/model of the pump off hand) set on the mid-speed. It worked fine on low speed too but I bumped it up to the middle setting thinking maybe I'd get faster recovery temps in the house... I never noticed any difference with the amount I played with its speed... probably because it was always pumping more than enough flow. I could never "feel" the difference in return water temp vs. supply water temp, so wasn't getting much Delta T obviously, meaning I can probably slow the flow down.

Thanks again!

Allan

 

[biodieseler]

Update: Over this past weekend I picked up a 1000 gallon insulated milk tank. Found it from someone who had this tank in their system being used for the same purpose but they are scaling up as their heating demand is increasing (new shop to heat, need bigger system)

So I may be forced to do an open tank design with the milk tank but I think I can actually seal the tank tight and allow room for no pressure and room for expansion with a huge tire inner tube (would be only as much pressure as the extra foot or two of water above the tank would create) Anyways, I'll figure that part out, or go with a traditional open tank design.

Still curious on how to figure out GPM required to get the BTU I need into the heaters in the house... Though I am likely going to get a PLC to measure the temperature of the water coming out of the heat load, and speed up/slow down the circulating pump to keep it at a set point. But there may be an easier way? I know PLC's are great for regulating things like this though and are completely programmable, so I may put a couple in this system to monitor and control temps and flows.

 

[maple1]

Update: Over this past weekend I picked up a 1000 gallon insulated milk tank. Found it from someone who had this tank in their system being used for the same purpose but they are scaling up as their heating demand is increasing (new shop to heat, need bigger system)

So I may be forced to do an open tank design with the milk tank but I think I can actually seal the tank tight and allow room for no pressure and room for expansion with a huge tire inner tube (would be only as much pressure as the extra foot or two of water above the tank would create) Anyways, I'll figure that part out, or go with a traditional open tank design.

Still curious on how to figure out GPM required to get the BTU I need into the heaters in the house... Though I am likely going to get a PLC to measure the temperature of the water coming out of the heat load, and speed up/slow down the circulating pump to keep it at a set point. But there may be an easier way? I know PLC's are great for regulating things like this though and are completely programmable, so I may put a couple in this system to monitor and control temps and flows.

Do you know the BTUs you need?

1°f temperature change of one pound of water = 1 BTU. 8 pounds per gallon - then go from there.

(Example, 5gpm with 20°dT is 48,000 BTU/hr).

There are also dT pumps (the Alpha is a dP) that use temperature sensors. Taco Bumblebee would be one. I have no experience with them.

 

[biodieseler]

I know I could always get a 12 hour burn out of my empyre elite 100 which is rated at about 45000 btu/hr on a 12 hour burn. Beyond that I'm not sure.. just making the assumption that on the coldest times of the year that's about what I'd need. obviously can get away with a lot less on the warmer days.

Good to know there are delta T pumps... might be simpler than a PLC to control the pump speed.
Thanks.
Allan