delta p circulator or delta t?

[velvetfoot]

The tank zone valve is for charging the tank - when open, it allows top-to-bottom flow through the HX coil, using the wood boiler circulator. In that mode, storage is just another zone that I can put heat into.

I like that a lot for my pellet boiler. "If boiler temp = (say) 178, valve opens to charge tank, boiler temp = 175, valve closes". No excess hot water going to storage, boiler modulates, temperature flow to load high. Heat only going to storage when there actually is excess while modulating at 30%. A mixing valve, mixing water going to the tank with the bottom of the tank, set to 178 or whatever, might make things smoother, bring less cooler water from the bottom of the tank back to the boiler, and keep the boiler from changing it modulation drastically. 1.25" mixing valves are expensive though, I imagine, as I imagine 1.25" zone valves.

I like the concept a lot though. Why send heat to a buffer tank if it's not necessary?

Edit: Thanks for the rules. It helps this non Vesta person as well.

Edit: DHW comes from a pipe inside the buffer tank, so it can't get too cool.

 

[Nofossil]

1.25" mixing valves are expensive though, I imagine, as I imagine 1.25" zone valves.

I just used a 3/4" zone valve. They make models with a fairly high CV, and you don't need much flow if you can achieve high delta T from good tank stratification.

 

[velvetfoot]

I just used a 3/4" zone valve. They make models with a fairly high CV, and you don't need much flow if you can achieve high delta T from good tank stratification.

Alas, I must make do with what I have, which is a 1.25" pipe that goes in the top that has bi-directional flow.