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Old 09-27-2012, 06:31 PM   #1
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Boiler shuts off


This is New Yorker CG-A series gas boiler about 10-20 years old. I recently refill the system, bled all radiators, open all valves and see clear water coming out.

The unit fires up normally, but it shuts down after 1-2 mins when the temperature reaches 80-100 C. The water pressure was around 12-15, just below the red arrow, but it didn't drop when water was drained from the unit. The pump continues to make sound after system shuts off, temperature drops slowly, but can't restarts for hours.

The supply pipe above boiler is hot, but not too far away from the boiler. I took out the TACO cartridge circulator pump, it looks fine, and I test it by inserting wires into outlet. It spins, and air comes out from one end. So it seems that the pump works. I decided to put it back on to try my luck. i refill the system, drain a bucket of water out from under the pump, and turn on the unit again.


One thing to note is that the water pressure indicator didn't drop when the water was drained! Maybe something wrong here. It fires up as before, the temperature goes up to about 80C and the system shuts down again. The temperature continues to rise to just above 100C/220F, the pump continues to make noise after the boiler stops, and I can hear water flowing thru the pipe. The return pipe remains cold thru this time, so I think the pump is working (but not sure how efficient). The supply pipe gets hot quickly, but not much beyond the expansion tank. I am going to wait for the system to cool down while letting pump continues. The pump feels hot again, and pipe around it are getting warm too. The temperature is dropping slowly from around 100C.

After about 20 mins, the pump continues to make sound, the temperature drops to about 80C, but pipe above the pump starts to get warm, and supply pipe doesn't get hotter, and it actually cools down. This seems to indicate that the hot water is not circulating out of the boiler. The pump also feels extremely hot. Perhaps the pump stops working when temp goes up?
It's about 30 mins past, the pump still makes sound and is hot. The return pipe above the pump is hot, while supply pipe above boiler feels cold already. It seems the pump isn't circulating water at all. I turn off the unit! So, is the pump the problem? What could be possible reasons and what can be excluded? I need your professional help. Thank you.


Last edited by oh'mike; 09-28-2012 at 05:26 AM. Reason: Added some spaces
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Old 09-28-2012, 04:24 AM   #2
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Boiler shuts off


Moved to HVAC forum.

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Old 09-28-2012, 04:33 AM   #3
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Boiler shuts off


Either pump is not working, or a flo check is stuck closed.
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Old 09-28-2012, 06:11 AM   #4
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Boiler shuts off


Thx beenthere. But I have checked the pump and it spins while I plug it into a wall outlet. Also, what is " flo check" and how to resolve that? Thanks.
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Old 09-28-2012, 07:45 AM   #5
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Boiler shuts off


How do you fill the system with water? Is there an automatic fill valve, or are you manually adding water to the system?
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Old 09-28-2012, 08:01 AM   #6
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Boiler shuts off


There is a dome shape regulator with a lever switch right after the water inlet switch

[ATTACH]58067[/ATTACH. I assume it is an automatic fill valve to regulate water pressure, right? The picture shows it is in an open position when I can hear water flowing into the system.
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Old 09-28-2012, 08:06 AM   #7
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Boiler shuts off


After the system is drained from here (see picture) with pressure relief valve open, I open the water inlet switch, and then bled all radiators.

Boiler shuts off-image-3075117060.jpg
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Old 09-28-2012, 08:11 AM   #8
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Boiler shuts off


A plumber came in and told me the pump not working. I took it off, and check it on an electric outlet. The propeller spins and I can feel air came out from one end. When the system starts up, the return pipe before the pump vibrate, indicating water flowing thru the pump, and the temp before the pump remains cold. However, after the system shuts off due to overheating, the pump still makes sound but the pipe around it starts to get hot, indicating that the pump is probably not circulating water anymore, although it still making grounding sound.
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Old 09-28-2012, 09:08 AM   #9
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Boiler shuts off


Jacki..Te pump may be spinning however, the impeller (propeller) could be worn down resulting in wider gap between impeller and housing so will not pump water. You may need a new pump . You can purchase just the pump housing and propeller assembly and replace it. Otherwise you seem to have filled and bled the system properly. Could also be an air lock in top of boiler. You can check this by bleeding water/air from relief valve, if it is located on the top of the boiler.

More pictures of all piping would be helpful.

Also..very concerned that pressure gauge did not drop when system drained. Picture of gauge also helpful. Usually the gauge is a combination temperature and pressure design with 2 indicators..one for temp and one for pressure.

Further NOTE: The pump could be cavitating (spinning in air), due to air stuck in housing or top of boiler. This causes heat build up in pump and adjoining piping.

Try draining the system once more . Make sure water feed and power is turned off..open drain then remove/open air vent at highest point in system (this depends on type of air vent..if float type with cap like tire valve then remove it if just a bleed valve with little spout then just open it. This will allow all water in system to drain out. Check gauge after draining to make sure it drops to zero. Also make sure supply and return vakves are OPEN.. One could have been shut off then stem broke when opened and the valve did not actually open.

If all drains and gauge drops to zero then open feed line until water comes out of opening at top of system then close the vent. If gauge pressure does not go to zero ..loosen/remove it to ensure all water did actually drain or to see if gauge is defective.

MORE PIC PLS
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Old 09-28-2012, 09:45 AM   #10
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Boiler shuts off


Thank you so much. The plumber who replaced the pump, control panel and a thermostat last fall refused to tell me anything specific except warning me not to touch anything and pay him to come out again to give just an estimate! So, I am determined to solve the problem this time, and I thank people like you who are willing to help here. Attached here are more pictures. The first is the gauge showing high temperature when the burner turns off (with pump continue to make sound). The second picture is the same gauge showing water pressure remain unchanged after the water is drained from the system. Also, I followed your advice and opened the relief valve and drain out a bucket of water from there. The water is still warm from last night trial. There seems to be air in there at the beginning. One question, what would be the problem when the water pressure didn't drop to zero when the system is drained? How to fix that and how to remove the gauge? Many thanks.

Boiler shuts off-image-2160544900.jpg



Boiler shuts off-image-1828400229.jpg
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Old 09-28-2012, 10:05 AM   #11
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Boiler shuts off


jacki....pump could work while not under a load....as soon as its installed with the weight of water pushing down on it could not be doing so good with moving water....there not that expensive ...its pointing to the pump as the source of trouble.....replace it...just my thougth....
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Old 09-28-2012, 10:20 AM   #12
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Boiler shuts off


A frozen tridicator limits your diagnostics but causes no boiler problems beyond this. A pressure guage attached to the drain valve will confirm that you have enough pressure 12 - 20 psi to allow the water to circulate. If you find that it's below that psi, it could cause your problems and you could then manually over ride the water feed valve to test that theory out. If your real PSI is fine then your back to
replacing the pump assy.
Remember that all you know is that the water isn't circulating.
A faulty Pump Assy/ stuck zone valve ball (if you have more than one thermostat)/ too low a water pressure/ an air lock/ or a gate valve that has been accidently turned off will cause no circulation.
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Old 09-28-2012, 10:52 AM   #13
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Boiler shuts off


Thanks. indeed, I have two zones (two thermostats). In prior tests, I didn't raised temp on the second thermostat. I manually turned the zone valve to open position, and it then got stuck there. I have then increased temp setting in that second thermostat, and it indicates "heat on", then the zone valve can be moved! I also am emptying the system from pressure relief valve, and the water is a bit brown. I guess there are rust inside the boiler. It is getting clearer now. i think I will retest it again with both thermostats set to the highest temp, open water supply, and perhaps temporarily release the pressure relief valve while the system is heating up? Any suggestions how to correctly test it again?
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Old 09-28-2012, 10:53 AM   #14
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Boiler shuts off


To remove gauge ..press in boiler panel behind gauge and you will see gauge fitting. Use properly sized spanner/wrench and turn counter clockwise to remove.


First Tap the gauge to see if it is stuck and might return to zero. If not Should be able to get them same at big box / hardware/plumbing store. Buy some teflon tape or pipe dope to put on threads when reinstalling gauge. Tighten snugly but do not over tighten could distort gauge. Refill boiler. NOTE: also keep boiler relief valve open until water starts flowing from it when you are refilling..this will help to get rid of any air at top of boiler. Close it when pail half full then continue refilling system Don't forget to leave the vent open at top of system until water comes out with no air.

Last edited by techpappy; 09-28-2012 at 11:01 AM.
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Old 09-28-2012, 11:11 AM   #15
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Boiler shuts off


Did you mean the pump was replaced just last year. They usually last many years so, if it was replaced it should be OK Leading me to believe you have an air lock in the system. Air locks are common and are some times difficult to get rid of. AND A WATER CAN NOT BE CIRCULATED IF THER IS AIR LOCK. Just keep venting the top of the boiler.top of system until you can't hear or see any air spitting out. Try turning on boiler and pump again after all air is out.

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