Tenative storage plan for next year, please critique ...

[patch53]

Hi gents, well, since I'm allready convinced that I want storage for next season, could you please comment on this layout with any changes and/or recommendations?

Basically just sending hot water into the storage tank via HX coils and back into my existing propane boiler via another HX and then out to the zones as needed. My current set-up has the hot water from the Seton going directly to my back-up boiler . I did forget to put a circulating pump in the diagram from the back-up boiler to the storage.

I would obviously need expansion tanks and auto fill valves along with the usual pop offs and aquastats.

TIA, Pat

 

[Gooserider]

It would work, (I think) though it probably isn't the way I'd do it..

1. Tank size - 500g seems a bit small - especially for a 3K²' house... Might be OK depending on your heat loss calcs (which I didn't see...) but might not give you that much time running on storage.

2. Why two separate heating systems? If both systems are pressured, why not tie them together, so that you would only need ONE HX coil in the tank, and allow you to directly send heat from the wood boiler to the house loads w/o having to cycle through the storage tank (which would involve 2HX penalties, and thus be less efficient)

3. As drawn, putting the charge coil in the bottom and the draw coil on top will do strange things to your stratification.... If you do want to do separate coils, I'd put them next to each other, each going top to bottom in the tank, with the charge coil flowing top to bottom, and the discharge coil flowing bottom to top - this will give the best stratification.

4. How long is the boiler - house loop? How much heat will you be trying to cycle through it? - is 1.25" PEX going to be enough to carry the required number of BTUs/hr with reasonable pump sizing? (Have you done the pump sizing calculations from the Taco paper I link to in the "tidbits" sticky?)

As a rough idea, what I would probably do with the diagram you gave, is tie the two systems together, with one coil in a larger tank, and stick a 3-way valve on the pipes going into the tank set up so as to allow the flow from the wood boiler to feed the house and / or the storage depending on the exact amount of call coming from the house loads. I'd put a flow check in the barn / storage loop, and an extra pump (smaller since it will have a shorter distance to pump) in the storage / house loop to reverse the flow direction to discharge the storage into the house when the boiler is out. I would connect the backup boiler to the house loops in parallel so that the storage would not feed through it...

Gooserider

 

[patch53]

It would work, (I think) though it probably isn't the way I'd do it..

1. Tank size - 500g seems a bit small - especially for a 3K²' house... Might be OK depending on your heat loss calcs (which I didn't see...) but might not give you that much time running on storage.

500 gallon tank is about all I have room for. I would be happy if I could run off the storage for 4-5 hours. I am looking for a situation where my Seton will run for perhaps 2 hours and then idle for 3-4 hours. I would add wood 2X/day like I do now. I want to have some extended burn times to eliminate/minimize creosote builup.

2. Why two separate heating systems? If both systems are pressured, why not tie them together, so that you would only need ONE HX coil in the tank, and allow you to directly send heat from the wood boiler to the house loads w/o having to cycle through the storage tank (which would involve 2HX penalties, and thus be less efficient)

OK yes, sounds good, how do I do that?

3. As drawn, putting the charge coil in the bottom and the draw coil on top will do strange things to your stratification.... If you do want to do separate coils, I'd put them next to each other, each going top to bottom in the tank, with the charge coil flowing top to bottom, and the discharge coil flowing bottom to top - this will give the best stratification.

I was wondering about that when I drew it. My thought was that the hotter water would be near the top of the tank, but I see your idea would be better, but I still like the other idea of having only 1 HX coil.

4. How long is the boiler - house loop? How much heat will you be trying to cycle through it? - is 1.25" PEX going to be enough to carry the required number of BTUs/hr with reasonable pump sizing? (Have you done the pump sizing calculations from the Taco paper I link to in the "tidbits" sticky?)

My boiler is about 50 feet from the inside propane boiler. I have no idea on the required BTU's. I have a Taco 0011 on the Seton now, seems to be moving the water pretty good. Haven't checked out the Taco paper.

As a rough idea, what I would probably do with the diagram you gave, is tie the two systems together, with one coil in a larger tank, and stick a 3-way valve on the pipes going into the tank set up so as to allow the flow from the wood boiler to feed the house and / or the storage depending on the exact amount of call coming from the house loads. I'd put a flow check in the barn / storage loop, and an extra pump (smaller since it will have a shorter distance to pump) in the storage / house loop to reverse the flow direction to discharge the storage into the house when the boiler is out. I would connect the backup boiler to the house loops in parallel so that the storage would not feed through it...

You really lost me here, I have no idea what this would look like or how it would work. I know basic plumbing and can do all my own work, but don't understand what you mean here.?



Gooserider

thanks for the help, Pat

 

[patch53]

Goose, could you elaborate on this? I don't understand this at all.

"As a rough idea, what I would probably do with the diagram you gave, is tie the two systems together, with one coil in a larger tank, and stick a 3-way valve on the pipes going into the tank set up so as to allow the flow from the wood boiler to feed the house and / or the storage depending on the exact amount of call coming from the house loads. I’d put a flow check in the barn / storage loop, and an extra pump (smaller since it will have a shorter distance to pump) in the storage / house loop to reverse the flow direction to discharge the storage into the house when the boiler is out. I would connect the backup boiler to the house loops in parallel so that the storage would not feed through it…"


thx, Pat

 

[Gooserider]

OK - here's a modified version of your sketch, I simplified a bit on the house loads, and didn't put in details like boiler trim and such... Actually once I started drawing, I think I figured a simpler way, so here goes...

If the WB is burning, P1 runs. M1 cycles some water back to the return as protection, but mostly sends towards the house. If the WB goes out, P1 turns off, and M1 will close to send most of it's water to the return when the WB is refired. Between these flow resistances and the head of the barn loop, there should be little or no flow in this loop w/ P1 off. This action is pretty much independent of what the house side is doing.

If the house is NOT calling for heat, ZV1 and ZV2 closes, and Pn (note n = any one or more of the house load pumps) is off - all output from P1 is forced through the storage tank, charging it.

If the house IS calling for heat, AND the storage tank is above minimum temp OR heat is coming down the line from P1, then ZV2 closes, and ZV1 opens - Pn turns on, diverting some of the P1 output, and / or pulling from storage (If P1 is on, it should be supplying more than Pn is requiring) to feed the house loads, with any surplus flow from P1 continuing to charge the storage.

If the house IS calling for heat, AND the storage tank is below minimum temp ZV1 closes, preventing flow through the storage loop, ZV2 opens, and the fossil boiler fires. Pn turns on and pulls water from the fossil boiler loop...

I think it works...

Gooserider

 

[patch53]

Thanks a lot Goose, I like it. I'll probably come up with a few questions later.

thanks again, Pat