Zone issue: Basement zone only heated when other zones call for head

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Old 12-20-13, 07:12 AM
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Zone issue: Basement zone only heated when other zones call for head

Hi all,

I've been having issues with heating in my basement apartment for quite a while now. A plumber has come twice and replaced both the thermostat and the zone valve for the basement zone. The heating system is baseboard heating boiler system, with 3 Taco zone valves to separate Basement / 1st Floor / 2nd Floor.

What is currently happening is that my heat appears to be controlled from another zone. When my thermostat is on and set to a temperature, it is ignored and the temperature instead fluctuates between seemingly random temperatures (e.g. 68 - 71). When my thermostat is off, the same thing happens - the temperature is going between seemingly random numbers. What I suspect is happening is that either 1st floor or 2nd floor thermostat is the one which is actually kicking on the boiler and heating my apartment.

So the past two days, the other tenants have been out of town and I assume turned their heat off. And so now, I have no heat no matter what I do. If I manually open my valve, doesn't do anything. If I turn my thermostat to max temperature, doesn't do anything.

One interesting note: If I turn my thermostat on, I can hear a click happen. Also it heats up the top of the zone valve. If I turn my thermostat off, I can hear another click, and after a few minutes the top of the zone valve is no longer heated (no longer warm to the touch). I don't have a multimeter to test if my zone is actually opening, but the heating up/down in response to tstat seems to be a good sign.

I suspect a wiring problem since it seems another zone is controlling my heat.

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I've attached a rough sketch I made of the wiring. Some of my terminology may be off, as I don't understand this stuff too well, but the basic idea should be communicated. I've found wiring diagrams online and this wiring seems to be correct, but again I don't have much expertise in this area.

Could it be the wiring? Is there anything else I can try? As I wait for a plumber to come out, is there any manual override I can do to make the boiler turn on?

Thanks!
 
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Old 12-20-13, 07:53 AM
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The wiring diagram appears to be correct to me...

You say that the zone valve for the basement has been changed, and that is strange because it would be my first suspicion. So if the valve itself is good, it would tend to make me want to trace the wiring and do some tests with multimeter to track down the problem.

Here's what is SOUNDS LIKE is happening to me, and a little theory of operation:

Each zone valve has a 'motor' (in the case of the Taco valves, it is called a heat motor) that opens the valve when the thermostat calls for heat. This 'motor' is wired to terminals 1 and 2 on your valves.

The thermostat itself is not 'directly' connected to the boiler. All the thermostat does is open and close the zone valve.

Each zone valve also has an 'ENDSWITCH' which closes when the valve opens. This endswitch is wired to terminals 2 and 3 on your valves.

It is the ENDSWITCH that signals the boiler to fire after a valve has opened. So, in effect, the zone valve 'passes on the heat call' from the thermostat to the boiler.

If the endswitch in the basement zone valve is not working properly, what will happen is that the valve will OPEN, but the boiler will not be signalled for heat by the endswitch.

The valve will REMAIN OPEN because the thermostat will not satisfy.

As long as that valve remains open, anytime that ANOTHER zone calls for heat, the hot water will also flow through the basement zone because the valve is already open. This is why it seems as though a different thermostat is controlling your heat... because in a sense, it IS.

Here's something you can do as a test:

Turn your basement thermostat all the way up to call for heat.

Take a short piece of wire and while the zone valve is open, carefully touch this wire between terminals 2 and 3 of the valve. This will 'simulate' the endswitch in the valve calling for heat and the boiler should start up and you should get heat in the basement.

If this does fire the boiler, and you get hot water through your baseboards, it's a pretty closed case that the endswitch is not making contact and not signalling your boiler to fire.

If it does NOT fire the boiler, it would be an indication to me that there is a bad connection or a broken wire somewhere in the 'jumble'.

Note that the three valves have terminals 2 and 3 wired in parallel. This allows any ONE or combination of valves to 'call' the boiler for heat.
 
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Old 12-20-13, 08:28 AM
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NJTrooper, you seem to be exactly correct. When I used a wire to touch between terminals 2 + 3 on my basement zone valve, the boiler comes on right away. So I guess this means the end switch in my valve is bad?
 
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Old 12-20-13, 08:40 AM
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I guess this means the end switch in my valve is bad?
Pretty conclusive. I don't understand why a new valve has a bad switch, but, poop happens I guess!

You can use this 'trick' to temporarily get heat into the home, but do not leave it unattended. Place the jumper under the screws only AFTER you've got the valve open from the thermostat, and remove as soon as the valve closes.
 
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Old 12-20-13, 08:43 AM
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It's only down to about 64 in here with no heat, so I can totally live with that for now. Good to know I have the jumper option in case it gets too cold, but I'll probably wait for the "real fix".

Thanks for the great explanation and troubleshooting steps!
 
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Old 12-20-13, 08:48 AM
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You know those taco valve heads are extremely easy to change out...

Label and disconnect wires, twist head a quarter turn (can never remember if clockwise or counter-clockwise) and head pops off valve.

Pop new head on, reattach wires.
 
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