Backup Boiler Piping Question

[blackdoglabrador]

Hi,

I have a tarm innova with 750 gallons of storage.

I been running it since 2012 without a backup boiler. Finally started in on a backup boiler project. I bought a bosch greenstar boiler and want hook it into my piping. See the attached diagram. Will this work? My specific question is do I have the primary secondary backwards? Every primary secondary diagram I see is the opposite of what I have here (boiler feeding into a loop with closely space tees, rather then the boiler be the loop and have closely spaced tee to pull heat out of that "boiler loop" and feed to my existing wood boiler piping network. I would rather keep it the way I have it drawn, unless I won't get the flows I want.

I am also contemplating adding a zone valve to the backup boilor loop to prevent unwanting flows during wood boiler operation. Is that needed?

 

[maple1]

Does the wood boiler/storage have another circ that is not shown or out of the pic? (Aside from the boiler/load circ itself).

In your diagram, I'm think you might need another circ between the backup boiler loop, and the house loop, to inject from one to the other. I don't have any experience with close T setups though so not sure. You might have some ghost flow thru the backup when heating with wood, but I found that hard to predict when I was doing my system. And I'm not sure about having a zone valve in a main boiler loop - but if you put it in the 'close T connecting loop', that might be good.

 

[blackdoglabrador]

Does the wood boiler/storage have another circ that is not shown or out of the pic? (Aside from the boiler/load circ itself).

In your diagram, I'm think you might need another circ between the backup boiler loop, and the house loop, to inject from one to the other. I don't have any experience with close T setups though so not sure. You might have some ghost flow thru the backup when heating with wood, but I found that hard to predict when I was doing my system. And I'm not sure about having a zone valve in a main boiler loop - but if you put it in the 'close T connecting loop', that might be good.

Yes there is another circulator that loads the storage and circulates water through boiler.

 

[salecker]

Hi Blackdog
I have an oil boiler as a backup.In my system it is plumbed into the supply line with closely spaced t's. Both would be in your top line labeled radiant supply.
I questioned how it would work,at the time i was a newbie to hydronic heating.The guy who told me how to arrange and build my system told me it would work. And he was right.
I just fired my wood boiler yesterday.It was a busy fall and i had lots of free old summer diesel to burn.I was monitoring the lines with an IR gun and it was neat to see how the temps changed as the wood boiler took up the load from the oil boiler.
The only difference in my system is the wood boiler is all water with water in the storage tanks.The oil boiler is on the glycol side of my system.I have a big plate heat exchanger between the two.

 

[blackdoglabrador]

In I put the tees their the return water would not be able to circulate because the wood zone valve would be closed.

 

[maple1]

Is that zone valve shown in the diagram already in place? Or is it a contemplated one?

Here are my simple thoughts, and what I would try [NOTE: the try might not end up successful]:

-I would just plumb one loop from the backup boiler. I.e. direct, without the primary/secondary close T setup. But the rest the way you have it.
-I would put a check valve in the load/zone return line, on the wood boiler side of the diagram T.
-I don't think the zone valve in the diagram would be needed.

Unless I missed something (likely a real possibility), that should do it. When the backup boiler calls, its circ should circulate through the backup boiler, and pull through the loads/zones, without pulling water through the wood boiler/storage side, because of the check valve. And, if you also didn't want water going through your backup boiler when the wood/storage was supplying, you could put another check valve in the backup boiler return line, and move the load/zone circ to the load/zone return line, on the wood boiler side of the diagram T in the same general location as the first mentioned check valve. Or, if that circ & the backup boiler circ both have built in check valves, you might not need to add any other check valves. You would need to control that load/zone circ so that when the wood side has cooled off to where it is not useful, and the backup is about to be called, the load/zone circ gets shut down - my controls were already doing that, not sure your existing control setup.

That is a similar arrangement to what I have. I have separate check valves & circs - I ended up drilling a small hole in one check valve flapper to allow just a little bit of flow through storage when the backup was running to reduce short cycling and maintain a little bit of storage heat.

I think....