Top floor baseboards warm but circulator has been off for days

Hi all,
I've done a lot of searching this forum and haven't yet found a problem similar to this.

I recently had some work done on water parts around the boiler. They replaced a flow check valve, fast fill valve, backflow, and a couple air purgers, checked the expansion tank, then they bled the system. The baseboards have been silent since then. We have 3 zones (1st floor, 2nd floor, finished basement).

However, the top floor zone is throwing heat and we've had the thermostat set all the way down for days. It seems to be throwing heat on one side of the house only, in one room the baseboard is very warm and it gets cooler in the rooms down the line. So it seems perhaps convection is causing the hot water to rise, I'm guessing the warmest baseboard is at the start of the loop.

Question is, how can I prevent this from happening? It's causing some of the upstairs rooms to be uncomfortably warm and it's wasting my hot water. We've also noticed that the shower can't sustain hot water like it used to, perhaps related?

Checking the pressure just now (with all thermostats off), 18psi at 175F.

Thanks for any tips.
Brett

 

Do you have individual zone valves?

 

or do the zones have individual circulators?

I'm presuming that since you mentioned domestic hot water that your boiler has a tankless domestic coil in it... and is set up as a warm start.

Yes, I agree that it's gravity flow... but why? ... let us know how the system is zoned.

 

I don't believe I have individual zone valves, I have 3 circulator pumps on one side and 3 flow check valves on the other side. I'm attaching a picture. Yes, it's a tankless domestic coil, I assume warm start, not sure exactly.

Thanks,
Brett

 

More info: in the pic above, the zone giving problems is the middle one with the black circulator. Part of the work I had them do was replace the leg of copper immediately above that black pump. It previously was two small pieces scabbed together and the union showed signs of seeping in the past so I wanted it cleaned up. As part of that, they also replaced the flange just above the pump (or at least half the flange). I should have mentioned this before but I figured they are no moving parts here, and no apparent air leaks, but perhaps some debris fell into the circulator during the work...

Thanks again,
Brett

 

Most flow control valves have a manual open bypass on them.
Make sure it isnt partially open. I think i see them in the back or the picture looks like taco with a thumb screw on top . Then i would tap on it lightly with a hammer to free the check.
Below is from Taco
.
Why does my Flo-Chek leak by?
Typically this is caused by debris accumulating on the disk or seat. This would be the case if the valve worked fine when it was first installed. You will have to take the valve apart and clean the seat, disk, and stem to bring the valve back to original. The stem should be vertical.

The bypass knob should be turned clockwise all the way for normal operation. For bypass mode, thurn the knob counterclockwise until you have reached the position desired.

 

OK, let's see if I have this right. Heating loop water is pulled through the check valves, through the baseboards and back to the circulator pumps where it returns into the bottom of the boiler. The vacuum created by the circulator at the exit of the flow check valve would cause it to open for normal operation. The flow check valves would normally be closed if circulators are off, but we think debris may be stuck in the seat of one of them, causing hot water to percolate up to that zone.

Sounds like even if I freed the debris this time, it'd just return to clog this or another check valve in the future? So I could either attempt to flush the system by opening the bypass(?) and bleeding the zone(s), trying to get fresh water to push out any debris, or as Taco suggests disassemble the valve.

I just tapped on it while running the circulator, turned it off again, we'll see if it cools down.

Thanks,
Brett

 

You've pretty much got the story correct Brett...

Of course, the first thing to check is that the valve is in the correct position... maybe the installer turned it and forgot to turn it back...

Sometimes opening and closing the valve is enough to dislodge any 'debris' that might have gotten in... it's very possible that once the valve is working again that there won't be further problems... probably what happened is during the course of refilling after the work was done, some debris got pushed out and it ended up in the valve...

I wouldn't try flushing anything just yet... do all the easy things first, obviously!

 

I verified this morning that all the bypass knobs were tight.

Report from my wife is the baseboard is still warm, so we're on to plan B.

When I get home, I'll open up the bypass, then turn on the circulator and do some tapping. This morning I didn't open the bypass, so that'd be the difference here. Then I'll close it up and wait for results.

Thanks,
Brett

 

Brett, not sure what you mean by "bypass" ? Technically a 'bypass' is a whole nuther animal... and I think you are actually talking about the knobs on the top of the flo-check valves... so if that's what you mean, that's fine, just so's we all know what you are talking about.

 

I think I would close the return valve ( and ensure that the pump does not cavitat ) and make sure that stops the unintended flow.
After that turn the zone on and quickly find out what rad heats first, then let it cool and see what rad heats first when the unintended flow begins again.

I have a hunch, may not be a good one, that the placement of the expansion tank may be helping to cause the migration.

It's definitely at the wrong spot.

 

Yes, you're right. I was using the terminology LukeP put in post #6. I meant manually opening them with the knobs on top.

Thanks,
Brett

 

Good news, cycling the flow check valve's manual open knob, running the circulator, and tapping seemed to do the trick. Outlet pipe and baseboard are now cool.

Thanks for all the info and help here, my first experience on this forum was a great one!

-Brett