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. 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.