Water flow in zone

greasy

On my four zone system, setting back the temp 10 degrees causes one of the zones not to heat up in the morning when there is a call for heat. I'm assuming the cooling of the water in the zone is blocking hot water flow. All the other zones work fine. I'm using four pumps, pumping away. In order to re-start flow in the blocked zone I have to inject DHW pressure water into that zone each day when I get up, then it runs fine for the rest of the day. What gives?

Timco

Bad impeller, air bound, bad pump motor, may be a few things. When you setback the t-stat?

T

greasy

Pump has been changed out once. I'm pretty certain it's OK. Temp is setback at night. I bleeded the air out of the loop. But it is a rather long one. Seems weird it would heat all day with no problem and then, refuse to heat up in the morning...

[Deleted User]

Got check valves?

Could be a sticky check valve. Your boost purge in the AM unseats it and lets it do its thang.

I had a spring check on a job recently that wouldn't unseat. Endned up going from a 1542 all the way up to a 2664 and it woulnd't work. Finally pulled the check, replaced it and put the 42 back in . Works fine now.

The check valve is a paper weight/reminder on Jims desk..

You also mentioned that this is the longest loop. THere's a real possibility that the other shorter loops have enough residual head at the return so as to cause flow issues. John Siegenthaler wrote an article on this called Dueling Circulators.

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,150683,00.html

ME

greasy

Good suggestion Mark. I'll check the check valve. I don't think it's dualing pumps caue I've got a primary/secondary arrangement with closely spaced tees and don't think pressure drop would be a factor.

greasy_2

Well this is weird

After trying all the solutions mentioned above, with no luck, I fiddled around with the thermostat setback timing. For some reason, not understood by me, this has solved my problem.

Maybe one of the pros can explain it: I previously had my thermostats set so that the basement zone called for heat in the morning before the 1st floor zone, which came on an hour later at 6:00 a.m. But that arrangment would not circulate water or produce heat in the first floor zone (which draws water from the second nipple on the supply header), although the other 2nd floor zone (the third nipple on the supply header) would heat. So I made the first floor zone, the first morning call for heat before the basement came one and that seems to have solved the problem. Very weird.