Proposed hydronic scheme…..questions, comments, criticisms welcome

[fixmyboat]

Hello all,
After much study on this site and with the consultation of John at Precision Hydronic Products I believe I have finalized the concept for my wood/solar/propane heating system. Based on a hydraulic separator produced by PHP.

Components
WB Thermo-Control 500W 125k BTU (Theoretical output)
GB Weil-McLain Gold 105k BTU
Solar 4 X 8 flat plates (still sourcing)
DHW Amtrol Boilermate classic 41 gal
Storage 300-500 gal propane tank (sourcing)
Zone 1 1000 square feet staple up radiant (first floor)
Zone 2 21ft of baseboards (second floor)
Zone 3 200-300 square feet radiant slab (attached sunroom/greenhouse and mudroom)
BTU loss as calculated by SlantFin Heat Loss Calc is 60kBTU/HR @ -10F
This is my first house a 1500sqft Cape in central VT built in 1992 2 X 6 construction, nice and tight with good insulation. Now that I got it to look like I want I figured I’d turn it over to you lot before I commit myself any further. Please view attachments. Thank You

 

[WoodNotOil]

My only thoughts are that you have no way of heating zones directly from the wood boiler. You will have a much faster response to heating zones when the tank needs charging if your wood boiler can supply heat while the tank is charging. Also, I would suggest sizing your baseboard loop (or adding to it if it already exists) to give ample heat with 140* water. That way you have a much lower usable temp from your tank and won't need to charge as soon. Lastly, you may want to talk to someone with solar collectors about where they have that heat enter the tank. I seem to remember a thread saying the solar water doesn't get as hot as boiler water and should enter in the middle of tank and not the top. (Not sure about that one though) Good luck.

 

[fixmyboat]

Hi WoodNotOil,

I considered plumbing the WB as you suggested and it could still be done with the current arrangments with a few more bits and pieces. I'm hopping to be able to fire the stove twice a day during the heating season with the storage helping stretch out the time in-between. If the GB fires some for the high temp loads (a short run existing baseboards in 2nd floor bedroom areas, DHW) while the storage comes back up to temp I think its a fair tradeoff for increased simplicity/cost. Reality may be a different matter and if it presents a problem I'll change it. Adding to the baseboards to lower the temp is a good idea. Do you know where to find a converion chart for baseboard out put at lower temps? Mabye a radiant wall panel for the bathroom? I'll think about it. I have been thinking about the solar arrangment some and am currently leaning towards some type of HX in the tank. Which will be tipped up under a set of stairs to maximize stratification. I will be installing the system in waves but have included solar at this point for planning only. Thanks for the tips, I have read many of your and Nofossils post and am also leaning towards the NoFossil homebrew controller.

 

[Jersey Bill]

I checked out the hydraulic separator. it seems to be like a manifold for flow decoupling.
I don't like the setup. I think that there are advantages to combining like temperature range equipment and disadvantages combining unlike ranges.
For instance, the wood boiler and the solar are connected to the same storage tank. The optimum range for solar is 90-120, where the wood boiler works in the 160-200 area.
I think that the solar should be on a low temp loop with the radiant slab and possibly the radiant staple-up. the 2 boilers, DHW, and the baseboard should be on a high temp loop with its own high temp storage.
The model to use here is the Primary-secondary setup.

 

[fixmyboat]

I've been planing to drain the solar dry from September to may so there will not be much overlap between the solar and WB. I feel that the benefits of solar hot water aren't worth the efforts in VT in the winter. Here's an article on the benefits of hydraulic separator.

http://www.pmengineer.com/Articles/Cover_Story/BNP_GUID_9-5-2006_A_10000000000000166945

Temp control for the radiant zones is regulated by 3-way mixing valves. Actually supply temp to the Separator shouldn't matter as long it is above the the temp called for in the zone. Also WoodNotOil had the good idea to expand the baseboard zone upstairs to function properly at lower temps which would require another mixing vavle if overheat was common. Some kind of radiant pannell in the bathroom would work nicely. Thanks for the comments

 

[kabbott]

This is my setup except my wood boiler is piped to the primary side of the separator so I can heat the baseboard directly when storage is cold.
My storage is ~1800 gallons so waiting for it to get to temp to heat the house is not an option(it took me about two days to get it to temp from room temp)

Downside to this is more pumps and a bit of a control headache. Storage is PEX coil in tank with two pumps, one flows one way for charge and the other flows opposite for heating.
Boilers and storage are on primary side of separator and loads on secondary. I made my separator and manifolds out of copper, all welded in one piece, pumps mounted directly on manifolds to PEX out of pumps.

I can shut down any part of the system and the rest is un affected.
Can't beat it for flexibility and flow, plus all loads get the same temp water.
I will post some pics of the manifold / separator in the next few days.

 

[fixmyboat]

Hey Kabbott,
Do you have any lower temp loads like radiant? I'm curious about motorized 3 way mixing valves reliability, brands and cost. Initially I'll be using my existing 40 gal water heater for a buffer tank untill I get the storage up and running. The permant tank will be 300-500 gal so heating it up wont take all that long. I'll have to crunch some numbers but estimating actually hot water output for an older coil type boiler like mine is some what of a issue. I'd love to see your homebrew separator. What are you using for a controller? Thanks

 

[kabbott]

I do not have any radiant now but my entire second floor is going to be in floor radiant.
I just posted some pics of my setup here https://www.hearth.com/talk/threads/29488/

Kris