Please criticize my piping diagram

[emesine]

This is what I am thinking for my boiler piping- please take a look.

During heat storage, P1 and P2 are activated. V3 and V4 are open. V5and V6 are closed. P3 is activated for thermostat calls. The E180 acts as the heat source for both the house and for thermal storage.

Once the heat storage is full (probably according to a timer set by the user at the time of firing), All pumps are shut down, and the valve settings are reversed. V3 and 4 are closed, and V5 and V6 are open. Thermostat calls activate P1 and P3. The E180 acts as the heat source for the house only.

Once the E180 cools down (when it runs out of wood) V1 closed and P1 turns off. Thermostat calls activate P2 and P3. The thermal storage is the heat source for the house.

V2 is a boiler protection shunt that injects warm water into the boiler return to avoid thermal shock (set to 180F.)

The 4 valves around P2 act to reverse water flow in the thermal storage in order to change from storing heat to delivering heat to the house.

There is room for expansion on the far right- in case I need to heat a pole barn, hot tub, etc.

Thanks- I appreciate your input!

Andrew

 

[emesine]

Here is a larger image.

 

[DaveBP]

The line from the V2 shunt to the pipe between P1 and the boiler- is that a wire to a temp sensor in the return water? If it is, then I think I understand how it would work but without knowing how that valve is controlled I'd be worried that if it runs full open/full closed it would introduce slugs of cold water into the boiler before it could react and open back up to warm the return water. I think pro boiler slang for this is "Bang Bang" control. A floating action mixing valve would prevent that but your sketch makes it look more like a zone valve than the other mix valve supplying your radiant circuits.

 

[emesine]

Dave BP-

V2 is an injection type mixing valve, not a zone valve. That isn't really clear from my diagram. It is connected to a temerature sensor on the boiler return and will stay open enough to keep the boiler return water warm enough (I am thinking 180F). Once the E180 runs out of fuel it will open completely and form a boiler loop. Once the boiler water temp reaches about 120F, V1 will close and P1 will be inactivated, which will shut off this entire end of the circuit.

Thanks!

Andrew

 

[Nofossil]

It's not clear to me that V2 is correctly configured. I don't have experience with that type of valve, but I'd assume that the pressure at the V2 port that goes to the outlet of P1 is higher than the pressure at either of the other V2 ports. Given that, I don't think you'll get flow from V2 to the boiler inlet. Generally, P1 would draw from the mixed outlet of a valve that would attempt to maintain a safe outlet temp (140 or more) by mixing cold water and recirculated water.

 

[emesine]

Again, I appologize for my drawing. The line from the right side of the V2 directly to the boiler return is the sensor, not a pipe (it is more clear in my original color diagram). The valve dumps hot water from the boiler supply directly into the boiler return. The valve opens based on the temperature of the boiler return to keep the boiler return at 180F. I'll make sure that is more clear on future drawings!

Andrew

 

[emesine]

Error above- I am referring to the line on the LEFT side of the V2, not the right side. My understanding of this valve is that it is not an on/off valve, but opens just enough to allow enough water to flow through to defend a certain temperature. TACO makes them. I am interested in the 2 way valve.

(broken link removed to http://www.taco-hvac.com/uploads/FileLibrary/102-145.pdf)

Andrew

 

[Gooserider]

I may be missing something in my understanding of how the pumps and mix valves work, but I don't quite see how you will operate off the storage tank...

P2 will definitely run hot water through the storage tank side of the heat exchanger.

P3 will move water from the mix valve through the radiant loop - I'm not sure I quite see what will happen on the return end.

What I don't see is anything to move the water from the system side of the heat exchanger to the mix valve, or the DHW heat exchange loop other than P1 which is shut down...

The other thing that I didn't see mentioned was anything about P4 on the water heater loop - I am not sure why you need a pump there, as it would look like P1 would push water through the WH loop if the boiler is operating, and the same concern about what moves water from the heat exchanger when running off the tank would apply - it would look to me more like a place for a zone valve...


Gooserider

 

[pybyr]

On the tank side of the plate HX, you may want to look into the double/ back-to-back (reverse facing) pair of circulators (only one runs at a time, to control direction) as pioneered by WoodNotOil. Simpler than a number of valves; uses no more electricity than a single circulator, as only one ever runs at a time. He's apparently been happy with the way that they work/ perform. There are some old threads along those lines here in the boiler room.

 

[Dune]

Once the heat storage is full (probably according to a timer set by the user at the time of firing)

Not sure how a timer would work. I would think some type of aquastat would be better.

 

[emesine]

Thanks everyone for your input. I attached three diagrams indicating water flow during the three states, boiler storing, boiler heating house with hot storage, and heating with storage.

Interesting idea on the two opposing pumps.... I'll have to contact woodnotoil. I considered that, but I was concerned there might be a problem with pumping water through an off pump- would there be a lot of resistance or pump damage? Ideally, a reversable pump would be great.

On the timer- a fully automated system would be great- it's just beyond my abilities at this point. Using a simple aquastat is a problem as the system would attempt to store heat in the thermal storage as long as the thermal storage is cool... This would work well if the boiler is running, but when the house is heated from thermal storage it would kick back on and run the wrong direction. I figure the easiest way to do it is to turn on a timer when you load the wood that will store heat in thermal storage for a few hours.

Thanks!

Andrew

 

[pybyr]

Thanks everyone for your input. I attached three diagrams indicating water flow during the three states, boiler storing, boiler heating house with hot storage, and heating with storage.

Interesting idea on the two opposing pumps.... I'll have to contact woodnotoil. I considered that, but I was concerned there might be a problem with pumping water through an off pump- would there be a lot of resistance or pump damage? Ideally, a reversable pump would be great.

On the timer- a fully automated system would be great- it's just beyond my abilities at this point. Using a simple aquastat is a problem as the system would attempt to store heat in the thermal storage as long as the thermal storage is cool... This would work well if the boiler is running, but when the house is heated from thermal storage it would kick back on and run the wrong direction. I figure the easiest way to do it is to turn on a timer when you load the wood that will store heat in thermal storage for a few hours.

Thanks!

Andrew

here's the thread in which WoodNotOil (with input from others such as NoFossil) hit upon the reverse-facing pumps, and got technical confirmation from a pump Mfgr. that it will be OK in terms of both flow and pump durability.
https://www.hearth.com/talk/threads/19476/

I was in touch with W.N.O. by e-mail during the heating season, and he confirmed that it's been working well in practice, too. His descriptions of his install, and some other interesting info, are at:
(broken link removed to http://woodnotoil.googlepages.com)

 

[emesine]

pybyr-

Thanks, I'll look into that. It would be cheaper and more simple to have two opposing pumps. My only concern is that I am asking for high flow rates (15 gal/minute) if I want to store heat as fast as the wood gun can burn.... which would be convenient as I want to start the fire when I get home from work, then add some wood a few hours later before I go to bed. At 15 gpm I can store 150K btu per hour. I am concerned that two opposing pumps might slow that down. I'll look into that thread.

Gooserider-

This design should work with the boiler off and only pumps P2 and P3 running. If I understand it right, if you pull water through the mix of the mixing valve, it will pull water from the hot side as well as the cold side appropriate to keep the temperature right. Water pulled from the hot side will be pulled through the heat exchanger (there is no other path), through the pump, to the radiant floor heating, then back to the heat exchanger. Water pulled from the cold side will be pulled directly from the radiant floor heating. Therefore, with only P3 running on the main loop and P2 supplying hot water to the exchanger, I should be able to get heat to the flooring. This design is, BTW, a slightly modified knock-off of the sticky above on pressurized storage.

Andrew

 

[Gooserider]

This design should work with the boiler off and only pumps P2 and P3 running. If I understand it right, if you pull water through the mix of the mixing valve, it will pull water from the hot side as well as the cold side appropriate to keep the temperature right. Water pulled from the hot side will be pulled through the heat exchanger (there is no other path), through the pump, to the radiant floor heating, then back to the heat exchanger. Water pulled from the cold side will be pulled directly from the radiant floor heating. Therefore, with only P3 running on the main loop and P2 supplying hot water to the exchanger, I should be able to get heat to the flooring. This design is, BTW, a slightly modified knock-off of the sticky above on pressurized storage.

Andrew

It might... The other issue w/ the hot water loop and P4 still looks a bit questionable to me... I don't see anything that would circulate water through the DHW tank loop, and indeed if P3 is pushing through the floor loop it looks to me like you might actually get flow going the other direction through the tank loop back to the hot side of the mixing valve, bypassing the tank heat exchanger - it would depend (I think) on which path offered the least flow resistance. Maybe a flow check valve in the heater loop to prevent reverse flow, and P4 comes on only when the DHW tank calls for heat?

Gooserider

 

[jebatty]

My personal experience with a plate HX is to expect a material "efficiency" drop (water out temp < water in temp), unless you go with quite a large and expensive HX, and that pump head increases substantially as gpm's increase. Be sure to check the stats on pushing 15 gpm's through the plate HX with a goal of 150K btuh on the output side of the HX to make sure you end up with what you want.

 

[emesine]

It might... The other issue w/ the hot water loop and P4 still looks a bit questionable to me... I don't see anything that would circulate water through the DHW tank loop, and indeed if P3 is pushing through the floor loop it looks to me like you might actually get flow going the other direction through the tank loop back to the hot side of the mixing valve, bypassing the tank heat exchanger - it would depend (I think) on which path offered the least flow resistance. Maybe a flow check valve in the heater loop to prevent reverse flow, and P4 comes on only when the DHW tank calls for heat?

Gooserider[/quote]

Goose-

I see your point on the water heater pump. I had better make sure that P4 is wired to the water heater aquastat in order to force water throught that circulation (and not the other way around). It looks like I will also need a zone valve there- When P1 is running there might be enough pressure on the boiler supply side to push water through P4 and the hot water heater. It might be a bit of a surprise when our hot water comes out at 180F......

I like your answer, Goose- here I am building the sole heating system for my house, spending lots of $$$$.... "It might work."

Thanks a lot for your input- I am trying to get as many opinins as I can to make sure this is going to work right.

Andrew

 

[emesine]

My personal experience with a plate HX is to expect a material "efficiency" drop (water out temp < water in temp), unless you go with quite a large and expensive HX, and that pump head increases substantially as gpm's increase. Be sure to check the stats on pushing 15 gpm's through the plate HX with a goal of 150K btuh on the output side of the HX to make sure you end up with what you want.

It is a problem. GEA has a calculator that, given the temperature difference you are looking for, etc. will tell you how big of an exchanger you need. According to this, If I want to transfer 150 K BTU with a 20* temp difference I am looking at a 5X12 inch 60 plate heat exchanger. This is a significant expense, but I still think I am better off going unpressurized as I can have a much larger thermal storage for less $$ overall.

http://flatplateselect.com/site/pub/login.aspx?ReturnUrl=/site/Default.aspx

Andrew

 

[jebatty]

If I want to transfer 150 K BTU with a 20* temp difference I am looking at a 5X12 inch 60 plate heat exchanger.

I don't know if this is the calc you ran, but the example I tested was 190F on the input side of the hx, 15 gpm, and 160F in on the output side of the hx, 182F out, and 14 gpm = 5 x 12 x 60 plate with 1-1/4" ports (154,000 btu). Pressure drop on both sides is about 10 psi = 24' pump head. Do you know what your total system head on both sides of the hx will be? You need to add this to the hx pump head.

A Taco 0013 will move just about 14 gpm's at 24' head, but your total head on both sides of the hx will be higher, won't it? Have you determined what circulators you will need based on pump head and required gpm's. Also, with the Taco 0013 the output is on the top side of the curve, and the usual goal is to hit about the middle of the curve.

A Taco 0013 is drawing 230 watts, and you likely will be running at minimum 2 of these (or even larger capacity), one on each side of the hx: 230 watts x 2 = 460 watts = almost 1 kwh for every two hours of operation. Electrical costs will add up over time. You may want to do some calculations and decide whether an even larger hx with lower gpm's and pressure drop will pay off over time in reduced electrical usage with smaller circs.

Also, at these high gpm's you're likely going to need to use 1-1/2 pipe or pump head with flows above 14 gpm's is going to rise fairly quickly.

I started with a plate hx and open system storage but never was very satisfied on the performance. I could get high storage temps but the cost was quite a bit of boiler idling because btu throughput just wasn't there. Then I switched to pressurized 1000 gal storage, with the boiler feeding storage directly, eliminating the hx. Improvement in performance was substantial and now I am extremely satisfied - idling is just about eliminated and starts to occur only at the high end of storage temp as bottom of the tank starts to get above 165F. At this point top of tank is 190-193F, and everything above the bottom of the tank is higher than 165F. I can easily drive the entire 1000 gal tank to 190F if I'm willing to tolerate a little idling, but I usually don't do this as I just don't need 1000 gal of 190F water.

You're doing the right thing by thinking through your system very carefully. Keep at it.

 

[emesine]

What would you recommend for a storage tank? If I could find a good tank I would do it in a heartbeat- much faster heat transfer, etc. What sort of tank do you have?

On the other hand, I have an empty space under my porch made out of concrete walls. It would be extremely easy for me to put in an open storage tank of several thousand gallons. I just wrote AES- the wood gun is a stainless unit- I asked them if it would be possible to run the WG directly into an open storage tank. I am sure they will fret over the oxygen levels, etc., but it would be an interesting solution- run the wood gun at full tilt into an open storage tank then take the heat out via heat exchanger..... Of course it would only save me the energy of one pump (the energy is going to end up in my house anyhow), and it would put my $$$$$ boier at risk....

Andrew

 

[Gooserider]

The "standard" pressurised storage tank that most people seem to be using is a re-purposed propane bulk storage tank. There was a recent thread where someone had found a bunch of used Amonia "nurse tanks" in W. VA. Essentially what you need is any kind of pressure vessel in the 1,000 gallon range, that is made from materials that are compatible with boiler chemistry / water, and can handle at least 100psi pressure (for safety reasons, your system pressure shouldn't go over 20-30psi)

The biggest single problem that I see w/ pressurised storage is getting it into place - a non-pressure tank is relatively easy to "site build" out of materials that can be carried into the desired location in relatively small sized peices - so doorways, stairs, tight corners and so forth are not a big challenge to deal with. OTOH, large pressure tanks are big, non-flexible, and heavy... You are NOT going to get one through a typical 34" wide door, or around any sort of tight corner, and while stairs might be possible, they will be a definite challenge.

This is largely why I'm planning on non-pressured storage for my setup, as there is no way I'd ever get a pressure tank into the basement...

Gooserider

 

[emesine]

I can put in an 8X8X6 foot storage, over 2000 gal, for the cost of asking my concrete guy to put in one extra wall. The fun part is my front porch will never have ice or snow because of heat loss through the slab.

Assuming with a pressurized storage I can get it to withing 5 degrees of the boiler, lets say 190F. 1000 gal at 120-190. 1000X8X70 = 560k btu.

For non-pressurized, with no idling, I would estimate you can get within 25 degrees of the boiler fairly easily- 170F. For a 2000 gallon system that comes out to 800k BTU.

The other cost is electricity to run the storage pump, pump costs, and hx costs.

That's a hard one. I certainly see the benefits of pressurized storage.

Andrew

 

[DaveBP]

Yet another hit you take when using pressurized storage is the very large expansion tanks required to accomodate the thermal expansion of such a large volume of water. If you were to purchase a commercial bladder type tank figure on $500 or more per 1000 gallons. If your state requires an ASME rated tank as does Mass. then it's a whole lot more.

The added efficiency of pressurized storage comes at a cost. Really efficient flat plate heat exchangers that are not undersized are also very expensive as Jim says. Lots to consider and yes it can be confusing.

 

[emesine]

On pressurized vs. non-pressurized....

There will be an empty space under our porch slab 9X 10 feet. Assuming 8 inches for cement wall and 2 inches for insulation... I am looking at a 3000 gallon storage tank if I can fill it to 6.5 feet deep.

Assuming the highest I can get my storage is 175F... that still yields 1.4 million BTU of storage between 120 and 175. I think I can live with that!

Andrew