How well is my heating working at lower water temps?

giantsean

Hi. Now that the cold has really hit, I have been trying to really stress my heating system to max efficiency. A little background. I have a pretty leaky 1950's cape renovated about 10 years ago, improved insulation, air sealing etc. During this time changed to forced hot air w/ hydro air handlers. In the beginning it really struggled to keep up on very cold days even with supply water set from 165-180. Eventually the old Navien CH NG combi gave way to new Navien NCB-E two years ago. There are three zones (one up, two down) run with two Ecobees and one Alexa stat.

The other night I experimented w/ a 140 degree supply. I was getting return air of around 110-120 (was aiming for under 130 to get condensing) but it struggled to hit 69-70 set points. I tried dialing in 145 which it's still on, and getting about 125 return. Below is the run graph for the upstairs stat. Just at a glance, how does it look in terms of number of cycles and cycle time?

Thanks for any feedback!

hot_rod

it’s hard to tell the time duration of the blocks? Is it on setback thermostats? It looks like a long non stop run starting at 4:00 AM

Knowing the output of the air handlers compared to the heatload might be useful.

bjohnhy

Initial glance on that graph, you can go down on the supply temp if you so desired. Even at the coldest part of the morning (6F?), your system not only maintains but brings up the temp. It doesn't seem to be struggling at all in that 24 hr period. Lowering the supply temp will minimize the cycling frequency but won't necessarily improve your overall energy efficiency as those air handlers can use a good amount of energy for delivery. I've seen many at 500 watts or more. Do you know how much your's pulls?

Do you know your btu/h output during that long 0400 run?

What design temp you are targeting?

This is from ecobee Thermostat? What equipment settings do you have it set for?