I have an older Eastern gas furnace and 3 zones of baseboard hot-water heat. Recently I've been having a problem with one zone for the upstairs. The other two zones work fine. The problem with the one zone is that I call for heat and I hear the pump kick in for that zone. The furnace, however, does not get the call to light. But the water must be circulating because if I call for heat in another zone, the furnace will light and my problem zone will get hot water.

The problem zone goes through it's own temperature regulating relay. Is this what I need to look at replacing?

 

That sounds like a reasonable hypothesis.

The problem is that you need to confirm your guess by analyzing what is actually happening. Boiler systems can be wired up in lots of different ways.


I'd start by taking a careful look at how the zone valves operate when someone else turns the thermostats up and down. See if you can identify a difference in the way the one is operating. Ideally, you'd be measuring the voltages controlled by the zone valves and determine whether they are turning on the pump and/or boiler directly, and measure what the apparently defective valve isn't doing.


Assuming it's a bad zone valve, the good news is that the electrical controls to open and close the valve can often be replaced without opoening up the piping. The bad news is that even if you get a similar model valve, the wiring of the valve may be different, which means you have to figure out how to wire it up properly.


Thaink about whether that's a task you want to try.

 

Strange as it may sound it could be stuck, just hung there. Or it could be air bound. Both fix for free. Try tappin on it with a hammer when its calling for heat. Otherwise try burping it by draining it some off the drain at the bottom of the boiler to get it by the bubble. Both of these were told to me by my plumber. If it's airbound at the zone pump you can feel it by putting your hand over the pump itself and feeling it gently pulsating under there. That means burping it. He said it was a common problem with boilers set up with the pumps pulling from the cold return end. Pumps always push way better than they pull but they were set up that way in the theory that they would last longer with less heat on them. A theory that was pretty much disproven he said and that it caused a lot of simple problems like this.

 

If another zone is heating do you get heat in the problem zone? If no, how much pressure is on the boiler?
Pictures of the boiler, controls, & nearby piping are always helpful. You can post them for free @ www.photobucket.com or similar site & provide a link here.