Boiler Tripping on High Limit

Thursday85

Hello all:

I was doing a walk around on some equipment at work late friday afternoon and noticed one of my boilers was tripped on high limit. I didn't get a chance to look too much at it and I'm pretty new at boiler systems and there operation. I figured I would look here for some pointers for what to check out on Monday morning. It's a Raypak Xtherm boiler. Natural Gas. The temperature directly out of the boiler was about 160, but so was the return temperature going right back into the boiler. It appeared as though the water pump in the boiler was operating. The hot water system in this building runs off of 2 circulator pumps. One was running, but one wasn't and seemed to be down. Would that effect the unit going off on high limit?

Thanks for any assistance for what to look at come Monday

4Johnpipe

Water Flow. The heat exchanger needs to be flushed / cleaned and or one of the pumps is faulty or fouled.

aircooled81

4John is correct, water flow is far more likely than other issues.

If 1 pump was primary for the boiler, and the other was secondary for the loop, than you can trip on high limit if the secondary pump is not running or moving enough water. My experience has been you need atleast 50% of your system flow with these raypaks to prevent high limit trips. Raypak says you need 110% of your primary flow in the secondary loop for correct operation.
If your two pumps are for the secondary loop, is one for redundancy? They might lead lag and thats why one is off. If the secondary pumps are operating normal, then you can look into the boilers operation.
I would want to know what the heat rise through the boiler was. what were the amps of the boiler pump (ie the boiler pump's not working), was there a restriction like stuck check valve or closed 3-way valve causing short cycling.
Just cause the pump humms doesnt meen its moving water.

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boilerguy101

Check your strainer.

pecmsg

boilerguy101 said:

Check your strainer.

I think after 6 1/2 years that's been done!

At least I hope so.

pedmec

Check to make sure that the internal circulator for the boiler has not failed. The circulator is located under the cover. It just serves the boiler to maintain minimum flow thru boiler

mattmia2

pecmsg said:

boilerguy101 said:

Check your strainer.

I think after 6 1/2 years that's been done!

At least I hope so.

2016 was 6.5 years ago?

pecmsg

mattmia2 said:

pecmsg said:

boilerguy101 said:

Check your strainer.

I think after 6 1/2 years that's been done!

At least I hope so.

2016 was 6.5 years ago?

May 2016 yes.