Radiant: zero delta ?

TAG

While I have done many houses with radiant -- have never done a whole house with only radiant. Have also never used a condensing wall boiler. Viessmann 200 in this case.

So my question: It seems that after playing with the system now for some weeks. The goal should be to pump so as to get as close to zero delta as possible.

Am I missing something?

When the temps were down around 15 -- I had the whole place almost a perfect 65 (it's under construction) with just some slight tweaking of the flow. Surprised it was working so well.

Looks like all my expensive controls may be a waste -- key was keeping the supply alpha pump on high (pressure - not speed) Running about 43 watts. Have the boiler loop on speed 2. This gave me more flow to all the loops and a very small delta.

Zman

I think you are thinking about this backwards. BTU/Hrs = Delta T x GPM x 500.
On the emitter side a delta of ~10 degrees once it has reached steady state is a good goal for a comfortable even heat.
On the boiler side, you will run more efficiently with higher delta and lower flows.

EBEBRATT-Ed

The heat transfer from the emitters doesn't change much with the flow. High flow lower delta, low flow higher delta heat output doesn't change much