Recently we've just installed Lochinvar NKC199N by a local contractor here, using liquid propane. Since this is a condensing combi-boiler, I understand that it will be running up to 95% efficient when the return water temperature is below Dew Point, which should be somewhere below 130F... the lower the better?
We have 4 zones, but mostly we use only it to heat just a concrete slab radiant floor. We setup the outlet temperature to ~120F and the return water from the slab is ~100F but because of the primary loop, the 100F return water ended up mixing with 120F (from outlet) and created a ~116F back into boiler inlet, so we ended up with only ~4F delta different.
So my question, Is "4F delta" good or bad for this boiler?
If we remove the primary/secondary loop, we would have it end up with 20F delta, will the boiler condense better?
So I am a bit caught up to either with or without primary/secondary, which one is more efficient in the long run?
