What makes the Circulation Pump STOP running?


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Old 01-05-11, 05:57 PM
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What makes the Circulation Pump STOP running?

Hi I have a problem related but the exact opposite to what you've been discussing here. I have enjoyed learning the electrical process involved in the boiler operation, but my situation is:

I recently had an electrician do an overhaul of our circa 1970 hydronic heating system. He told me that two of the four end switches weren't working and they would cause my circulation pump to continue to run against the zones' CLOSED valves (which isn't good)
Indeed, you can hear the constant hum of the circulation pump and we have to switch the boiler on and off as the temp in the house requires (there's a light switch over the boiler to control power to the whole thing). Everything starts well and there is heat to all four zones; you just can't get the boiler to STOP pumping that water against the closed valves.

I have the Honeywell V8043G1018 valve on each of the four zones. I just took the valve head off to look at it. The yellow (and an orange?) go into the motor head and two red wires loop around under to what I assume is the end switch. It looks like I will have to unscrew the motor to get at the end switch and an added frustration is the screwhead design is unfamiliar (looks like a star - definitely not a philips)

First question is: Do you think it's the endswitch that tells the boiler's aquastat to shut down the circulation pump?

Second question: Is it easy to diagnose which two of the four valves has a faulty endswitch?

Third question: Is it easy to replace the endswitch?

Any help would be greatly appreciated!


Unrelated topic: When registering on this web page, it won't let you proceed without picking a State.... even if you live in Canada.
 
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Old 01-05-11, 08:12 PM
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Do you think it's the endswitch that tells the boiler's aquastat to shut down the circulation pump?
Can't answer that question directly because my answer wouldn't really relate directly... instead, let me try and explain how the great majority of systems are supposed to work.

Most moder boilers use either an 8124 TRIPLE aquastat, or an 8148 SINGLE aquastat.

There are terminals on these ( T & T ) or ( T & TV ) that will activate the burner if required and the circulator pump when a contact closure is placed across these terminals.

So technically, the answer to the question is : It depends on the controls (aquastat and zone controls) that your boiler is equipped with.

Tell us what boiler make/model, what aquastat make/model, what zone CONTROL panel you have (if any... you don't NEED one of these but some systems do have them).

Is it easy to diagnose which two of the four valves has a faulty endswitch?
Again... depends on who you are asking, and what their skill level is... if you ask me, I would say yes. If you ask my wife she would probably go deaf the second you started talking about boilers... put her hands over her ears and scream NO! NO! NO!

Is your real question: "How do I test to determine which endswitches are bad?"
 
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Old 01-05-11, 08:16 PM
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Is it easy to replace the endswitch?
Again... skill level. How can we know what you are capable of?

Let's say this: IF you can locate a suitable replacement microswitch, AND you have reasonable electromechanical skills, AND you are patient, AND you own a soldering iron and know how to use it... then, yeah, it's pretty easy.

In general, the zone valve head is replaced as a unit when the endswitch goes bad.

The MOTOR on the other hand is quite easy to replace.
 
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Old 01-05-11, 08:18 PM
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Here's the thing though...

If your electrician properly wired your system, and a zone valve had a bad endswitch, the boiler would not START... the burner would not fire, the pump would not pump.
 
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Old 01-05-11, 08:36 PM
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@ trooper.. they can get stuck shorted (heat call) too ..

I would disconnect the red wires and measure the switch for a short.

That screw might be a torx ? (6 pointed)

I dunno about honeywell zone valves.. I do replace the end switches in my Wirsbo ones.
 
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Old 01-05-11, 08:44 PM
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Yeah but he had a electrician there. He should call him back. Sorry to say he may have been taken......

Circ pushing against closed zone valves????


Mike NJ
 
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Old 01-05-11, 10:33 PM
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I could see that.. if no t-stat is calling for heat then the zone valves stay closed. If the end-switch is stuck in the on positon (shorted or closed), then the circulator is getting a call w/o the zone valves being open.

The hardest part of replacing the microswitch in a Wirsbo valve is the little tunnel-rivet that they use to keep the switch to the body. Have to hack it off and use a wee small bolt to put the new one in. A $0.50 switch is much cheaper than a $100 MVA for sure (if one is willing and adept). I dont recall anyone posting in here about working on a honeywell valve though.. its possible you ruin the valve trying to take it apart. Post steps and part numbers if you do go that route..
 
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Old 01-05-11, 10:56 PM
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The electrician said two end switches... Whats the chances????


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