1 of 5 zones not getting hot. Taco zone valve head replaced but no difference.

yoyotogblo

I have a Burnham Revolution boiler with 5 zones (4 rooms and 1 hot water). There are 2 circulation pumps (1 in the boiler and 1 just outside the boiler in the supply). It also uses a taco valve control and there are 5 taco zone valves (1 for each zone).

4 of the 5 zones get very hot (touching the pipe from the taco zone valve for a second is scalding). However, the main upstairs zone valve pipe gets pretty hot but not scalding. Because it's upstairs and needs high pressure for the water to make it up, the upstairs baseboard heater never actually gets hot. For a contrast, the master bedroom is its own and does get hot despite also being upstairs.

I've replaced the main upstairs taco valve head but that didn't make any difference. I've also manually opened the valve but no difference either. I'm beginning to think there might be something wrong with the zone valve.

Any thing else I can try to single out the issue? Thanks

jesmed1

The number one reason for lack of heat in a zone is air in the pipes/rads. Air will stop water circulation. Find the bleeder(s) on the radiators for the zone that isn't heating and open them slightly, one at a time, with something underneath to catch any drips. You may or may not be able to get all the air out that way. If you can't, you'll need some more advance air purging that the pros here can help you with.

Meanwhile, check the water pressure gauge on your boiler and report what it says. 12 psi or so is typical for a 2-story house. Lower pressure than that can allow air to leak into the system, resulting in circulation problems. So if your pressure is too low, that's something else that will need to be adjusted.

hot_rod

Which Taco valve do you have? Most zone valves allow you to push them open manually. That would rule out a bad ZV.

If you push it open while other zones are heating, it should flow and get hot quickly at the valve.

If not an air lock or frozen pipe are possibilities.

Grallert

You might not be able to bleed air at the radiators/emitters. If that is the case you will have to bleed that zone somewhere near the boiler. Pictures will help us help you accomplish that if you're willing.

yoyotogblo

https://forum.heatinghelp.com/discussion/comment/1879940#Comment_1879940

I have the TACO 555-050RP. I already opened it up manually and it didn't get as hot as the other zones. I also had it as the only zone on and it still didn't get as hot as the other zones. I have bled that zone a few times recently (most recently about 3 weeks ago for about 40 minutes) so very much doubt it's an air issue. But even if it was an air lock, won't the supply pipe from the zone valve still be expected to get very hot? It's weird that that's the only pipe that doesn't get super hot when they all seem very connected.

yoyotogblo

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Here are some pictures. It's the pipes leading out the valve Im checking to get for the temperature and all of them except the one for upstairs scald my hand once I touch it.

jesmed1

@yoyotogblo said " I have bled that zone a few times recently (most recently about 3 weeks ago for about 40 minutes) so very much doubt it's an air issue. But even if it was an air lock, won't the supply pipe from the zone valve still be expected to get very hot? It's weird that that's the only pipe that doesn't get super hot when they all seem very connected."

Some air pockets can be very difficult/impossible to "bleed" out. That's when you need to "purge," which involves forcing fresh water into the system in such a way as to induce flow through the loop that isn't heating, with a drain valve open, and the forced water flow needs to be fast enough to "drag" the air pockets with it, out through the drain valve. Use the search function on this site to search for "purging" and you'll find dozens of threads about situations like yours where someone had to purge their system to get the air out of one loop.

EBEBRATT-Ed

I suppose it could be something internal to the valve but its doubtful.

I know you already tried this but shut the other zones when your working on the sluggish one.

It looks like you have enough water pressure in the system.

Do you have purge stations and air elimination at the boiler? Take a few pics standing farther away so we can see what you have.

yoyotogblo

I do have purge statioins and air elimination at the boiler. When I said I bled the system, that's what I was referring to. My radiators don't have a way to bleed them. I use the service valves to bleed the system. I have replaced the circulator pumps since then so maybe air was introduced as was suggested. I'll purge again.

https://forum.heatinghelp.com/discussion/comment/1880030#Comment_1880030

This is what I did. Sorry, I called it bleeding but I guess that's considered purging.

I have pics of the system in this thread. I purged using the return side of each zone. I saw another thread that also suggested using the supply side. Can try that if worth it.

https://forum.heatinghelp.com/discussion/comment/1880023#Comment_1880023

yoyotogblo

Some more pics of the system. Please ignore the hardwiring. The mixing board needs to be replaced so have hardwired the circulator pump for now.

yoyotogblo

Yeah, just started purging the upstairs zone again and there's a ton of air (water barely coming out actually , mainly air) and the water is very dirty. Must have introduced a lot of air when I changed the circulator pumps. Going to purge all zones now.

hot_rod

If it has worked in the past, a good purge, zone by zone should get it heating. Check to see the brass air vent above the boiler is working by pressing down the tire stem valve at the top. You should get a shot of air followed by water.

Plenty of room to upgrade the system on some warm day. A better air purger, pump to expansion tank switch, clean up some wiring at the pump and relay box. Odd to see those extra relays on the relay box?

yoyotogblo

https://forum.heatinghelp.com/discussion/comment/1880112#Comment_1880112

Purging did the trick. Now the house is warming up very nicely and upstairs gets warm. Thanks guys!

The brass air vent is actually new. Replaced that recently as part of my trying to fix this issue. But tested it and works fine.

That's a TACO zone valve control. Not sure if it's meant to have relays. The 2 relays are for downstairs and upstairs. There are no relays for the basement or the master bedroom. Both zones don't have c wires. I would love c wires so I'm not stuck with using a nest that only has batteries.

jesmed1

Your ceiling/floor joist bays are open. Can't you just plug a 24V transformer into a basement outlet and run power up through the wall into the Nest? That's how I powered our ecobees.

yoyotogblo

They are open in the unfinished basement but I'll need to pass those wires all the way to the Master Bedroom. I regret not having done that when renovating. I didn't realize then that there was no c wire as I had just bought the house and renovated before moving in

yoyotogblo

https://forum.heatinghelp.com/discussion/comment/1880112#Comment_1880112

I still can't figure out why they used the RIB2401B for the thermostats. I also think one of the relays is bad (the upstairs one). At times, when the thermostat stops calling for heat, the relay stays on and I keep getting heat. I'm tempted to disconnect the relay and connect the thermostat directly to the zone valve control but concerned about causing any damage.

Zone 1 and Zone 2 are the zones that use the relay and they also are connected to the AC (heat pump) so not sure if that could provide a reason for the relay. The C wires and Rc for both zones are provided by the air handler as opposed to the boiler.

Zone 3 and Zone 4 use Nest 3rd Gen thermostats, have no extra relays and also have no C wires so use battery). Both zones frequently complain about no power in the Rh line. Since it's getting power from the transformers, I don't understand why it frequently loses power in the Rh line thus losing connection to the boiler. Any thoughts on how to fix that also?

hot_rod

Well the nest t-stats add some complexity to wiring. Perhaps that is why there are RIB relays for isolation?

You need to be sure you have adequate transformer size to run all the components. Many of the zone pump relay boxes only have a 15 or 20Va transformer. Although that looks like a zone valve relay with two transformers?

yoyotogblo

Yes, it has two transformers so enough to run the 6 zones. All 4 zones use nests and only 2 have the extra relays.

For the one where heat keeps coming out, I think I'll skip the relays and wire directly and see if it fixes it. I already exchanged the thermostats in case it was due to a faulty nest and the same issue occurred so I expect the relay is the issue.

yoyotogblo

I just figured out why the relay exists. We recently replaced our AC units with heat pumps and so our boiler is now connected to the aux heat of the Nest thermostat. The aux heat (W2) gets energized using the Air Handler and it's connected to the C wire from the Air Handler. So if those terminals get connected to the transformer, there'll be 2 power sources on the same circuit. So instead of that, they are using the relay.

It appears the relay is bad. I'll get that replaced and that should fix the issue I'm having.

Thanks