Connection to existing boiler

[OldStoneHouse]

I've had my Innova connected and running happily for a few weeks now. I am having some problems with making the existing gas boiler coexist with the wood system. I've attached a schematic of what I did and what the existing setup was. I have to close the supply valve from the primary loop to prevent ghost flow from the wood system. That works fine except if I want the gas to come on. I could put a zone valve there but there isn't space to do it without making huge changes which I don't want to do at this time of the year.

My zones are piped as a secondary loop off the primary but the silly thing is that the gas boiler is in the primary loop. I had considered just using one of the tees and connecting to that gas primary loop. The pump there is a Taco 0011 which is a bit power hungry (~200 watts) which is what is discouraging me from doing that. I could do that as a short term solution until the heat is off at the end of the season.

Does anyone have suggestions about other ways to integrate the two systems? I can take some photos if that would be helpful too.

 

[OldStoneHouse]

I should add that the gas boiler is a Weil-Mclain Ultra - it's direct vent and holds 1.17 gallons of water. I was wrong about the pump too - it's a 0014.

 

[heaterman]

Are zones all radiant floor? If so, what water temp are you running in them and how is that controlled?

Without knowing all the details.......I'd say the best way to pipe that would be two closely spaced tees just ahead of your zone pump would be the best way to go. As it's drawn, your wood boiler circ will be causing flow in any zone that's open at a given time from the way it looks to me.

On those closely spaced tees, the first one would be the return to your wood boiler placed just ahead of your present wood boiler supply, and the second one (closest to the pump) would be the supply from the wood boiler coming back to your system. This assumes of course that you have a pump on the wood boiler moving water from it to your system.

 

[OldStoneHouse]

Thanks Heaterman - that's what I was thinking of doing but I'm very glad you agreed.
The zones are actually cast iron rads. They can handle any temp but I sized them to only need 140 degrees when we put it in. In reality the system works well with water below 135 which was great for the mod/con boiler on ODR.

I was actually thinking that if I used the closely spaced tees as you suggested that I could do injection mixing from the wood system to get outdoor reset to control the water temp. My hope was that would help my storage last just a bit longer. Today for example, I only need about 90 degree water. I have a controller that take care of the injection.

 

[OldStoneHouse]

Heaterman: just to be clear, are you suggesting adding closely spaced tees in the zone loop not in the existing gas boiler's primary loop? Thanks!

 

[heaterman]

Heaterman: just to be clear, are you suggesting adding closely spaced tees in the zone loop not in the existing gas boiler's primary loop? Thanks!

Yep. Unless I'm missing something in the way your system is set up, that's where I would pull water off to be reheated by your wood boiler, and then dumped back in to be sent out to the system.