I have a 6 year old Richmond (made by Rheem) power vent water heater. The burner will not stay lit for longer than a second or two. If I disconnect the vacuum tube that goes to the vacuum switch and provide a small amount of suction the heater seems to function properly. I have noticed a bit of condensation in the vacuum tube where it comes out of the case on top but before it connects to the blower motor. If I disconnect the vacuum line at the switch and blow it out the unit works for a cycle or two then needs to be blown out again. I have disassembled, cleaned and lubricated the blower motor and it all seems to be functioning properly. Model # for this unit is 5VP40E-IP A. Any suggestions?
Thanks

Check the pvc vent pipe for any restriction since this could be allowing the condensation to build up.

Additionally, check the pressure switch for moisture contamination. Remove it and give it a shake. If water comes out, replacement will be necessary.

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Originally Posted by hvac1000

Check the pvc vent pipe for any restriction since this could be allowing the condensation to build up.

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I checked the vent pipe when I disassembled and cleaned the blower unit. I found it to be clear. Do you think it is likely that the vacuum switch could be leaking enough to let air through and create condensation but still be tight enough to allow the unit to run?

Thanks

First unplug your unit. Now open the panel and disconnect the two wires going to the vacuum switch. Connect those two wires together (you can use a very small alligator clamp) and make sure they DO NOT TOUCH anything. Put a wrap of electrical tape on if you are in doubt. Now plug your unit back in. If it starts and runs without clicking on and off you have found your problem. They will not tell you to do this on the consumer hotline because the vacuum switch is a safety device and you have now rendered it non-functional. You must investigate further if the switch is bad, and/or your exhaust is restricted, and/or your vinyl tube connection is leaking so you can fix it permanently and enable the vacuum switch to operate as designed.

Two other vacuum issues to check... rubber hoses for cracks or loose fits on joints, and power-vent fan blades for being thickly coated or caked with dust.

One more thing- hose fitting on power-vent fan: the orifice on mine is small, like 1/16" (with 1/4" hose). Orifice could be plugged with dust.

Burning natural gas gives off h2O and cO2. This moist vapor makes dust and particulates want to stick and cake over the years. I have blown-in cellulose insulation in my house, so it is a dust nightmare.

If you have any or all of these issues, you are operating on the edge. The thing may start, then once the moister/thicker exhaust air finally hits the fan it starts to bog down a bit. When you are on the edge to begin with, "a bit" can be all it takes make it start to founder and/or quit.

-Matt Starbuck, Port Huron, MI