Boiler System Redo

[Mid Michigan]

Hello Everyone,

I have been enjoying all the post and info from here. I have a HWB, Corn Boiler, and Electric Boiler all that I have built over the last 5 years. I am planning on building a shop next spring and will need to relocate and rework my entire system next summer. I am in the planning stages now. My house is 2500 sq' single story and the shop will be 1800 sq'.

I have a HW Coil in my propane furnace and a Heat Exchanger for DHW in my house. I will be adding a AHU, IFH, and DHW Heat Exchanger for shop. Also I want to put a Unit Heater in my crawl space as a place to dump heat in an emergency and to play with just to see how much heat it will take to warm up my floors. The UH will be in series with my storage tank.

I also plan on retiring the home built wood boiler and get a high efficiency one. (Still not sure what to buy). I start the old girl in the middle of Nov. and run it into April or until the wood runs out. I burn 10 pulp cords a year right now. The corn burner works well. It cannot keep up with the load of my house in the coldest part of winter. I have not used it in two years due to corn prices (Damn ethanol plants). First year corn was $70.00 a ton. I shut it off when it hit $150.00 a ton.

I want to run my secondary loop circulating pump off of a aquastat in the storage tank.
I am having a hard time wrapping my arms around the idea of starting a fire everyday with high efficiency boiler.
A picture is worth a thousand words so I will try to attach plan. All equipment possible will be in shop.

Drawing from TACO Software.

I am looking for comments

Thanks,

 

[heaterman]

What do you want to accomplish in your new setup? Will you be using the storage tank as the primary "heat source" with all other inputs and outputs tied into it. Or......do you want to isolate your other heat sources from the tank and let the wood alone drive it?

One thing I can see right at the git go here is that you have the 1000gl storage right in the main loop. Sometimes that's OK but usually a person wants to isolate it from the rest of the loads to avoid very long warm up times when temps are down.

I really want to try a system with as many different loads as you have there on zone valves with a Wilo or Grundfos variable speed circ driving the whole works.

 

[Gooserider]

First off welcome to the forums, looks like you already have some good ideas, which is a good thing... It helps when people have already got at least the basics down as it makes it easier to handle their questions.

A few comments...

1. I am not sure the unit heater would be the best form of heat dump, as it needs power both to operate, and to get the excess heat TO the heater... What we usually tell people is that emergency heat dumps should be setup to work without pumps or power, as the most likely emergency scenarios involve power and or pump failure.

2. I notice on the hydro separator in your drawing, you have it plumbed so the supply water goes in and out the bottom, and the return goes through the top. From what I've seen it should be the other way.

3. Part of the reason I think you are having trouble with the idea of firing the wood boiler intermittently is that your storage is somewhat in the wrong place... Instead of having it sitting up on the return line, you should have it in the same row with your boilers, or even put it where the hydro separator is, (and replace it with the storage tank) Essentially storage is a very unusual part of the system as it is BOTH a load and a source - everything else in the system is one or the other... When the boiler is running, it is a load that gets charged by the excess boiler heat. When the storage is charged, you let the boiler go out, and the storage becomes the heat source for the system instead of the boiler. When the storage is discharged, you fire the boiler and repeat the cycle... Given your drawing, what I'd be inclined to do is plumb the storage into the supply and return lines with a large tee top and bottom, with supply on top, with possibly a pair of zone valves to bypass the tank and use a regular hydro separator if running off the electric or corn boilers (where you don't really want to be using the energy to charge the storage tank)

4. I wouldn't necessarily want the crawl space unit heater in the main loop - unless you have some really good insulation on the floor and sides of the crawl space, I suspect you won't find it very practical as a floor warmer, especially if you have insulation under the house floors.

Gooserider

 

[Mid Michigan]

Thanks for the input. I am new to this and have been just doing my own this for the last 5 years. I see where this Forum is a wealth of info.

I am also new to the idea of storage. I have 250 Gal. in my system now and have had as much as 400 Gal. in it. I have mostly used the storage as a cushion on the heat gain to help the set point on the boilers not hunt so much.
I have never used it as a source and a load both. It was just always there to absorb some heat. I can see with the gassification wood boilers how you need the storage. From what I have picked up you generally do not have a fire in your boiler 24/7. Is this the case?

I like the idea of zone valves and VFD. I am guessing with that set up all the loads would be piped in parallel across the supply and return so one pump can do it all. Would you use circuit setters to balance out your loads then?

As far as my heat dump unit heater, I would like to give it a try to see if I can make Mama happy with warmer floors. When I built I used Blue Max forms so my walls are concrete from footings to trusses. I have same R-value below floor as I do above it. Seems like if it was 90 deg. down there the floors would have to be a little warmer than when its 50 deg.

I see the Hydraulic Separator is piped wrong. I definitely drew it wrong. I like the idea of having one of them to help balance primary and secondary loops together. Are they popular in the wood boiler set ups? I do not have one in my system now.

I hope to get a intelligent design for next season and put my new system in right the first time.
Thanks for anymore insight you may have,

 

[Gooserider]

Thanks for the input. I am new to this and have been just doing my own this for the last 5 years. I see where this Forum is a wealth of info.

I am also new to the idea of storage. I have 250 Gal. in my system now and have had as much as 400 Gal. in it. I have mostly used the storage as a cushion on the heat gain to help the set point on the boilers not hunt so much.
I have never used it as a source and a load both. It was just always there to absorb some heat. I can see with the gassification wood boilers how you need the storage. From what I have picked up you generally do not have a fire in your boiler 24/7. Is this the case?

Exactly - it depends somewhat on the season, as you only build a fire when the storage temps get down close to your minimum level. The "gating factor" is a combo of what sort of loads you use, and the minimum acceptable temperature they will run at... For those that use fairly good radiation, and do DHW, the DHW tank is usually the "trigger" for building a fire, but if you set up the DHW properly, you can get a LOT of hot water out of the DHW system, far more than the actual tank capacity... From typical reports, a gasser will burn 4-6 hours of high output heat, and probably keep enough coals to refuel for 8-12 hours, after that it's build a new fire from scratch time... During peak demand times, most users seem to burn 1-2 fires a day, with possibly a reload on each one. "Shoulder season" when the demands are less, maybe one fire every 3-4 days, and if using the boiler for DHW in the summer when that's the only load, maybe one fire a week...

I like the idea of zone valves and VFD. I am guessing with that set up all the loads would be piped in parallel across the supply and return so one pump can do it all. Would you use circuit setters to balance out your loads then?

Again, it depends on your exact setup... (like everything else) How many different loops or other things are you putting on a zone? My understanding is that the less flow resistance anywhere in the system, the better, and that circuit setters are essentially just for fine tuning by dialing in small restrictions if you have different loops or some such... A better approach may be to use thermostatic valves that open and close according to the demand. The VFD pump is always "on" but senses the increased flow resistance when all the loads are satisfied and the thermovalves close, and idles down to almost no power draw. When the loads start to call for more heat again, the pump ramps back up and increases it's pumping power.

As far as my heat dump unit heater, I would like to give it a try to see if I can make Mama happy with warmer floors. When I built I used Blue Max forms so my walls are concrete from footings to trusses. I have same R-value below floor as I do above it. Seems like if it was 90 deg. down there the floors would have to be a little warmer than when its 50 deg.

It might, but I suspect that you will find that unless you have really insulated the walls and floor of the crawl space so that they have at least as much R-value as the floor you want to warm up, you will find that most of your heat will be going into the ground, not the floor... If you really want to do it right, you would be better to retrofit infloor radiant somehow...

I see the Hydraulic Separator is piped wrong. I definitely drew it wrong. I like the idea of having one of them to help balance primary and secondary loops together. Are they popular in the wood boiler set ups? I do not have one in my system now.

Some use them, some don't - I haven't seen all that many in the drawings that people have posted, but as I mentioned, in many cases the storage tank can act like a giant separator... This works nicely as it gives automatic balancing between heat going to the loads and charging the storage tank...

I hope to get a intelligent design for next season and put my new system in right the first time.
Thanks for anymore insight you may have,

No problem - I hope that some of the other guys that do this stuff for a living will chime in as well, since they will probably have more insight into what you should be doing...

Gooserider

 

[Mid Michigan]

Here is my next draft with some adjustments.

I like the idea of VFD on Secondary Pump and zone valves on all the loads. I will control it by differential pressure transmitter on secondary loop supply line. There will always be some flow through Shop IFH 3-way valve. Thinking about removing Shop DHW HX valve too so I will have more secondary flow. Not sure about that. Have to see how low of a GPM Secondary Pump can go.

Also 3-way modulating valve controlled by secondary return temp of say 160 deg. as the input will heat the storage as the building is satisfied. It will be on a PID loop so there is still heat going to the loads if necessary. So at 160 I start dumping a small % into tank and at 180 100% into tank.

Any possible problems or comments?

Thanks,

 

[Gooserider]

Looks pretty good, I'm not seeing any major problems.

Gooserider