Insuff heat - circulator pump issue?


  #1  
Old 12-27-04, 02:55 PM
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Insuff heat - circulator pump issue?

Greetings everyone ~

I have been trying to get answers at alt.home.repair, and thought I would give DIY a try...

I abe a 10 year olf Weil Mclein Gold FHW single zone system feeding 8 radiators in a 100 year old two story colonial, 1300 sq feet in NE.

All 8 rads have been bled, no air, only clear water. Boiler temp usually between 160-190, pressure usually 20-25psi.

My question is what specifically starts a circ pump (mine is a
Taco) located on a return line? Is it water temp? I popped off the honeywell aquastat controller and aside from the elec connections from the thermo and the
circ pump, there is a only a single dial set to 190. I thought there should be low limit and high limit dials, by there is only one, set at what looks like 190. Is there an adjustment I can make to have the heat circulate more frequently?

I have luke warm heat in 3 of the 8 radiators for the 1st time this year and I think short cycling is the issue. When it long cycles (when I get home from work and go from 62 to 72) the sytem cranks for a good while and has time to get hot and
circulate properly to a point where the house gets nice and warm.

(When the thermo is set at say 72 and the temp drops to 71, the burner
will fire, but only enough to get the outgoing pipes hot - once it get
to 72, that's it...the hot water never has a chance to return to the
circ pump and make it do its thing.)
 
  #2  
Old 12-27-04, 04:44 PM
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Thank you for the clear concise post--it really helps us help you

Your circulator and gas valve are controlled by a relay, which is powered by a 24 volt step-down transformer in your boiler. Your room thermostat closes the circuit when it calls for heat. The circulator comes on, along with the burner. When the stat is satesfied, the circuit opens, thus shutting the burner and circulator off. There is also a hi-limit switch that shuts the burner off when the water temp. reaches a predetermined limit--that's the control you found that's set for 190.
Are you sure your pump is working? Is it an older three-piece style or a wet-rotor style? (Taco makes both kinds.)
Have you recently replaced your thermostat? It sounds like the differential is set too close.
Also, your water pressure seems a little high. You only want about 12-15 pounds in a two story house.
I can't really give you a definitive answer to your problem, but those are a couple of points for you to chew on.
 
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Old 12-27-04, 05:49 PM
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If you don't use the boiler for domestic hot water, you don't have (or need) a low limit aquastat. As soon as your thermostat calls for heat, the burner and circulator will start. Water temp will increase all the way up to the high limit (190) setting unless the thermostat is satisfied first. You may have a radiator that is close to the boiler that is short circuiting too much of the flow. You can partially close the valve and balance the flow through all the rest. Especially if the hot one is near to the thermostat.

Ken
 
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Old 12-28-04, 08:02 AM
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Hi Guys ~

Thank you for the replies. My system is heat only, which makes sense there is no 2nd control dial for the circ pump).

My taco is a black cylinder on the return line - not sure of the type, but I it is less than 8 years old - this sytem was installed just before I bought the house in 97.

This morning the house was cold again. (oustide temp around 10.) boiler was at 200 degrees, only stopping when the aquatstat shut it off, but heat is only getting to 5 of 8 radiators. It does not appear the circ pump is working. I have an oil tech coming today to check the circ pump, the relay, and the connection to the thermo., (Thermo was not replaced, same one since 97).

Any thoughts are appreciated, I will keep you updated. My gut says circ pump.


Bluesman
 
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Old 12-28-04, 09:57 AM
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I've never seen a black Taco circulator--all I've seen are green. Hmmm...
I think your gut is right about it being the pump, although Ken's idea about the short circuiting is quite plausable.
Let us know how it comes out!
 

Last edited by Andrew; 12-28-04 at 10:00 AM. Reason: Added info
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Old 12-28-04, 12:47 PM
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** It is fixed !! **

It was the Honeywell Aquastat Controller. The C1 connection to the circ pump was dead. I knew the pump was not working properly!! (I asked the tech so many questions he asked if I wanted a job.)

It was covered 100% by my service plan - and i got a hell of an education on my heating system as well.

Thanks again - Although this was my 1st post to DIY, it will not be my last - I appreciate the help.


Bluesman
 
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Old 12-30-04, 07:42 AM
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The Taco 007 pumps are durable and quiet... perhaps a bit too quiet. Any tricks on how to tell if they actually are working?? The B&G 100 pumps are so much easier to tell when they are working but they seem to love to leak by the bearing assmebly.
 
 

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