Zone valve question


  #1  
Old 12-11-18, 08:59 AM
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Zone valve question

One of three baseboard zones is not giving off heat to the entire loop. Only the first half of the first radiator gets hot, then everything gets progressively colder. This zone serves the 4 bedrooms upstairs. When the stat calls for heat I sometimes hear a gurgling sound for like a second or two then nothing.

I have already replaced the old Honeywell t-stat with a Lux.

I checked the 3 zone valves, and I can move the lever on the 2 that are working and it returns slowly. On the zone that is not working, the valve lever is completely free. No resistance whatsoever.

I am thinking the motor failed but somehow the valve is slightly open allowing a little bit to get out?.

Could it be an electrical issue ?. Visually, the wiring looks fine on all 3 valves.

Any suggestions on what else to check, before I attempt replacing the valve.
 
  #2  
Old 12-11-18, 10:49 AM
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F,
The valve having no resistance means that the valve is open and you should be getting water circulating through the loop. A guess would be the valve is open because the stat is calling for heat and with everything cold it's not being satisfied.

Turn down your stat all the way to see if your valve closes and you get resistance like the others. That will tell you that your stat and zone valve are working properly to a point.

The use of ZV's means you only have 1 pump, so if the other zones are heating that eliminates the pump and the boiler since they are common to all 3 zones.

When the stat calls and the ZV opens on the troubled zone does the pump and burner come on. If not the end switch on your ZV is not making and although the ZV is open you will only get gravity feed to the zone without the pump being on.

What you can try is to open the troubled ZV and turn on one of the other working zones. The pump and burner should come with the good ZV but will circulate water through both zones.

If the troubled zone heats when you do this then your ZV head is bad and should be replaced.

If you have a Taco ZV term #1 & 2 open the valve and term #2 & 3 start the pump and burner. If you have a Honeywell the 2 yellow wires open the valve and the 2 red wires start the pump and burner, so if the valve opens it can still be defective if it doesn't start the pump & burner.

I'm not eliminating an air problem but with the limited info given I would try this first.

Pics would be very helpful if this doesn't work. Hope this helps a little.
 
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Old 12-11-18, 02:36 PM
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I will check again but pretty sure that when I checked the lever, the stat was not calling for heat.

Additionally, I do hear a quick gurgling sound when the stat calls for heat so that switch may be the cause. Maybe it makes contact for a split second and then it opens the circuit again.

Yes it is Honeywell valve.
 
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Old 12-11-18, 03:37 PM
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f,
If your stat is not calling but your valve is open you either have a short in the wire from the stat to the ZV or something is wrong at with your stat.

If that's the case remove the stat and the valve should close. If it doesn't check your wire. If it does close jump your 2 stat wires together, there is no danger, it's 24V, and the valve should open and the pump and boiler will start.

If it does your stat is the problem. If it doesn't, it would point to the ZV head.

The only thing that activates the ZV is the stat if everything is in working order.

It's a simple series circuit. Starting from a 24V trans to the stat, from the stat to 1 yellow wire on ZV, then from other yellow wire back to trans. The 2 red wires go to TT on the aquastat at boiler to start burner & pump.
 
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Old 12-14-18, 12:27 PM
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I have already replaced the stat, but will retest this weekend. I will shut off the stat, and check the valve is closed. Just to be sure on the wiring: RH and W if 2 wire - correct ?. There is a jumper from RH to RC, so i don't think it matters either way, but the old stat was RH and W.
 
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Old 12-14-18, 01:12 PM
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Remove the wires from the stat taking it out of play and then just jump the 2 wires together and see if valve operates properly. Wires apart, valve should be closed. Wires together, valve should open and boiler and pump should start.

This should narrow down the problem.
 
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Old 12-14-18, 04:02 PM
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OK I will try that, but I also tried this........

Tstat OFF resulted in valve closed.
Tstat ON resulted in valve open. Pump running but no heat.

I then fired up another zone and manually moved the lever to the open position. The pipe downstairs got hot, but upstairs was about the same.

So now I'm thinking two possibilities: air lock in the line ?. is that even a thing ?

or

The circ pump lacks the power to raise the water 3 floors and run the length of the loop.

I don't have the specs of the pump, but it is the smallest pump I have ever seen.

I will try to bleed the line tomorrow and also post pics and maybe try to get a model number for the circ pump.

This is a weird problem.
 
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Old 12-14-18, 04:20 PM
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The pump is probably fine for your application...they make 'em small these days. What is the make and model number of the pump? Pictures of the entire "near boiler piping" would be even better.

The fact that "only the first half of the first radiator gets hot" on the upstairs loop to me sounds like it could be an air issue.

What does the boiler pressure gauge read?
 
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Old 12-14-18, 06:05 PM
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It's not only the pump that moves the water to the third floor...... it's the system pressure too.
Many times you have to increase the boiler pressure to near 25psi to bleed the third floor. After finishing the bleeding.... you can let water back out to arrive at normal pressure.
 
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Old 12-15-18, 11:29 AM
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When running the gauge shows between 20-30 depending on how long it runs
 
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Old 12-15-18, 01:49 PM
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Update: finally got around to bleeding the line and a whole bunch of air came out......let’s see what happens going forward
Also, it looks like due to low water pressure in the house it is pretty hard to get the air bubbles to come all the way down to the basement.
 

Last edited by fxcarden; 12-15-18 at 02:48 PM.
  #12  
Old 12-15-18, 05:57 PM
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F,
Thanks for the update. Good luck.
 
 

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