Testing low water cutoff
#1
10-25-10, 07:01 AM
Testing low water cutoff
Is it possible to test a Guard Dog model RB-24 lwc? The company I'm arguing with says it can't be tested it just needs to be replaced to see if it was the problem with boiler. Being an electrical component I imagine it should be able to be tested . If so what contacts would I test on. Thanks for the help.
#2
10-25-10, 10:17 AM
Push the 'TEST' button...
while the burner is running.
The burner shuts off and the red LED on the LWCO lights.
Release the button,
The burner starts and the LED goes off.
Remove and clean the probe every 5 years.
Replace the unit every 15 years.
The burner shuts off and the red LED on the LWCO lights.
Release the button,
The burner starts and the LED goes off.
Remove and clean the probe every 5 years.
Replace the unit every 15 years.
#3
10-25-10, 12:34 PM
There is no test button. The end of cutoff has a red light, green light and wiring harness connector. I know cutoff is fried, I just need to know if it could have been tested before the tech fried it. They say you can't test you just replace it and see if that works. Thanks
#4
10-25-10, 02:34 PM
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My GuardDog RB-24E has the two LEDs, a cable connector, and a test button. Perhaps earlier versions didn't have the test button?
Without a test switch, you could temporarily jumper between the two yellow wires, bypassing the LWCO contacts. If the boiler then operates correctly, you know that the LWCO is interrupting the control circuit. But that is a DIY, Rube Goldberg type of procedure - I wouldn't necessarily expect a plumber to try that. Or, with a voltmeter, see if there is 24-V across the contacts during a heat call - if there is 24V, then the LWCO is open. Or, if the red LED is lit, the cutoff contacts are open. If the green LED is dark, then there is no voltage getting to the cutoff.
Personally, I would want a LWCO with a test switch.
Replacing the LWCO is a simple DIY job, although all or part of the system may need to be drained. $64 from PexSupply.
How did they fry your LWCO?
Without a test switch, you could temporarily jumper between the two yellow wires, bypassing the LWCO contacts. If the boiler then operates correctly, you know that the LWCO is interrupting the control circuit. But that is a DIY, Rube Goldberg type of procedure - I wouldn't necessarily expect a plumber to try that. Or, with a voltmeter, see if there is 24-V across the contacts during a heat call - if there is 24V, then the LWCO is open. Or, if the red LED is lit, the cutoff contacts are open. If the green LED is dark, then there is no voltage getting to the cutoff.
Personally, I would want a LWCO with a test switch.
Replacing the LWCO is a simple DIY job, although all or part of the system may need to be drained. $64 from PexSupply.
How did they fry your LWCO?
#5
10-25-10, 02:40 PM
I have no idea. Boiler stopped working , tech diagnosed as bad aquastat. During hooking up aquastat he shorted out a transformer ( I saw this) and somehow fried LWC. Wiring harness where it connects to cylinder is blackened and you can smell burnt elec. They say both components were bad before they replaced aquastat, but they couldn't miss burnt connector and where did burnt smell come from?
