Heat will not shut off in one zone.

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Old 03-05-14, 09:09 PM
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Heat will not shut off in one zone.

Hi all

I have a water baseboard heating system and I can't seem to get it to turn off in my basement. I have an old style analog honeywell mercury thermostat in the basement and digital everywhere else. I have no issues anywhere but the basement.

If I move the dial above or below the temperature gauge I do hear a clicking noise but the heat remains on. I have tried cleaning it with a brush and using a can of air to clear dust. I will go out an buy a digital thermostat tomorrow to see if that helps. Does anyone have any other suggestions before I do this?
 
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Old 03-05-14, 11:32 PM
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Q: 1) You hear the clicking coming from the boiler room?
2) We need to see the other side of the boiler where the pump/thermostat wiring is connected.

A: Most likely the problem is miss-wiring or the relay controlling the pump to that zone or defective/dirty flow-check valve causing ghost-flow.
 
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Old 03-05-14, 11:55 PM
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Q: 1) You hear the clicking coming from the boiler room?

Yes from the boiler room.

2) We need to see the other side of the boiler where the pump/thermostat wiring is connected.

This thing? It was covered and no sign of corrosion/rust. (green light is on)

If it's not an easy fix is it possible to just disable this zone safely, I don't need the area heated...
 
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Old 03-06-14, 02:46 PM
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You show 3 pumps and 2 connected to the control. Where's the other one connected.
Take the t-stat off the wall & see if it stops the heat.

Does your pump run when t-stat is off. If pump is off problem is elsewhere.
If pump is running, see if it stops with t-stat removed. If pump still runs it's not stat.
Could be shorted wiring or relay, what you have the pump connected to.
 
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Old 03-06-14, 05:25 PM
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Okay So I took the thermostat off the wall and I still got heat....

I found what the 3rd one is connected to and it looks like it took some burn damage (2nd pic).

Soo what to do next...
 
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Old 03-06-14, 06:47 PM
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Soo what to do next...
You'll need to replace that aquastat.

Surprised that you didn't smell that. Burning G10 circuit board is NASTY smelling!
 
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Old 03-06-14, 07:06 PM
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Lo,
It looks like you have room on your relay for one more pump.
That 3rd pump looks like it's on C1 & C2. Remove those wires and use the last zone on your relay.
Tie your pump wire into the 3rd set of terminals on the relay and your t-stat wires also and try that.
If that control works OK other than that it might get you through but it should be replaced at some point.

Echo Trooper. Surprised you didn't realize something earlier. DOA.
If this doesn't work it's a new one.

Good Luck,
 
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Old 03-07-14, 05:19 AM
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Lokril,

#3 This thing? It was covered and no sign of corrosion/rust. (green light is on)
A: Yes, That thing. This is a Taco SR502 See the missing resistor, Relay & socket on the right? [Spot take note]
Your contractor monkey should have used A SR503-4 ( One relay for each zone pump.) Instead they connected the basement zone pump to the relay on the boilers' aquastat, so now that pump is connected as if it were the boiler pump, running on all calls for heat. Then they connected the basement thermostat to the boiler aquastat (TT). then cranked-up the Low limit to 180F and maxed-out the differential on the boiler. [Unless I'm just cranky today?] I bet this is the same goof that did all the piping work too?

I think this should work; based only on the Taco Wiring diagram instruction sheet.

Corrective action: [Example only]
Inspect and replace as needed boiler aquastat. Relay points maybe welded closed, other damage.
Replace SR502 with SR503-4 (OR SR503-EXP-4) and connect all pumps & thermostats to SR503-4 (1)
Remove jumper ZR ZC from SR503-4.
Connect ZC on SR503-4 to ZC on aquastat (R to ZR.)
Connect XX on SR503-4 to TT (thermostat) on aquastat (XX to TT.)
Lower Low limit on boiler.


Lokril,
#3 Q: If it's not an easy fix is it possible to just disable this zone safely, I don't need the area heated...
A: The pump needs to be exercised 2-4 times a month to keep the bearings from seizing.
You could disconnect the pump from boiler' aquastat C1,C2 then connect it with one of the other pumps for now. Or just close the registers in the basement and lower the thermostat : (

Q: Am I seeing the aquastat settings correctly, High limit 200F, low limit to 180F, and differential set to +30F?



Notes
1) you can install missing resistor, relay & socket on SR502 -->> SR503 BUT:
SR503 NOT EQUAL SR503-4, as SR503 shares X2/ZR so that will not work.
SR503-4 http://www.taco-hvac.com/uploads/Fil...ry/102-379.pdf
SR503-EXP-4 http://www.taco-hvac.com/uploads/Fil...ry/102-387.pdf
SR503 http://www.taco-hvac.com/uploads/Fil...ry/102-167.pdf

See: Taco Wiring diagram instruction sheet -- Tankless Coil Boiler Application (Alternative Wiring) -- SR503-4 Switching Relay

That is all for now. HW
 
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Old 03-07-14, 12:49 PM
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Thanks HW.
Was looking @ terminals & never noticed the missing cube.
Late night, old tired eyes.
Picked up new specs today, opens up a whole new world.
 
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