Water temp will not go above 140 but will run.

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  #1  
Old 11-29-18, 05:07 AM
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Water temp will not go above 140 but will run.

I can not find anything specific to my problem. I have an old Weil McLain CG-5 series boiler. As of this year the temperature gauge will not go above 140 maybe 143 degrees. The psi is settled around 20. The boiler will run according to the thermostats demand. The reduced water temperature has reduced the btus coming out of each radiator so the system now struggles to heat the house on the bitter cold nights, Iím talking below ten degrees outside. If I turn the aqua stat down to the 140 mark while the boiler is running it will shut off as if it reached a high temp cut off. The boiler will run continuously on the colder nights because it cannot keep temp on these cold nights. I have no clue what could be wrong. Please help!! Iíll be out of work Eleven hours after posting this. So I canít post pictures for that long. Thank you!
 
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  #2  
Old 11-29-18, 05:31 AM
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The aquastat or whatever controls the temperature may have become clogged with sediment so as not to function properly.

The burner nozzle(s) may have become clogged with rust or sediment so as to reduce the flame. If a gas boiler kicks on with a loud "woof" or banging sound that often means the burner nozzles need cleaning. The nozzles nearest the pilot light being clogged, more raw gas flows before ignition and then the ignition is more explosive.

Incidentally if the boiler is running continuously and the radiators are not giving enough heat then the boiler may not have enough BTU capacity for your house at that outside temperature. Sediment or damaged/worn/burned internal parts could have contributed to this reduced capacity.

Do you have your boiler "serviced" every year or two? During the servicing session, an oil burner will often have its nozzle replaced due to clogging.
 

Last edited by AllanJ; 11-29-18 at 05:48 AM.
  #3  
Old 11-29-18, 05:50 AM
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It is a cold start boiler with only a high limit shut off. Is there any way I can remove sediment from my system?
 
  #4  
Old 11-29-18, 05:53 AM
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This is a natural gas boiler that needs a good servicing. Last year we bought the home and had an intermittent pilot light system and new gas valve put on the boiler. This year it is not keeping temp. We had a home energy audit done and the measured the boiler at 83% efficient. As far as a know the boiler has not been cleaned internally is a very long time. Would an aqua stat replacement fix it?
 
  #5  
Old 11-29-18, 11:18 AM
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PD,
Were you in the home last winter and if so was the boiler able to keep up with demand.

Does the boiler shut off at 143 and then cycle back on when the water temp drops or just continuously run and never get any higher due to the heat demand.

Did you try raising the high limit to see what happens. The cap. tube might have lost some sensing abilities.

What you can try, depending on your abilities, is to remove the aquastat from the well so the bulb senses nothing and turn on the boiler and see if the temp. climbs to set point.

Bear in mind that since the bulb is not installed in the well and sensing temp it will not shut the boiler off on limit so you must do it manually. This is only for testing purposes and to narrow down your problem.

Pics of the boiler and controls would be helpful if possible.
 
  #6  
Old 11-29-18, 06:12 PM
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The boiler easily kept up with demand last winter. It reached the set point of 180 degrees. Right now it will run continuously until the house reaches the thermostats set temperature. The water temp however will not go above 140 degrees. So the system as a whole struggles to reach the thermostats set temperature. I will try your procedure with the thermostat tomorrow as well as uploading pictures.
 
  #7  
Old 11-29-18, 07:20 PM
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While your checking your boiler did you happen to notice your gas flame. Does it look like it's burning at full pressure or does the flame look low maybe not enough flame to heat the boiler water to limit.

Possibly something happen to the gas pressure or restriction in valve. Make sure all gas cocks are fully open

Did the boiler work right after you had the gas valve installed or is this the first year your using it with the new equipment. Maybe the gas valve needs to be adjusted.
 
  #8  
Old 11-30-18, 05:46 AM
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You need a good service company come and check the gas input and the gas burners. If the boiler heated fine last year and the only change to the system was the intermittent pilot system then the installer did not due a good job and set the unit up for the correct gas input. If they can't do it or don't know how, throw their phone number away and hire a better service company. It ain't rocket science.
 
  #9  
Old 12-04-18, 03:33 PM
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I have not had the boiler serviced professionally. I took the aqua stat out and the temp remained at 140 and running. I did fully open my bypass valve and this has allowed the water temp to reach 180.
 
  #10  
Old 12-05-18, 10:51 AM
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What by-pass valve are you referring to. Are you referring to gas or water.
 
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