HELP - Power Vent Not Tripping Vac Sensor

TimPa

on my sons hot water heater - reliance 606. i can activate it by sucking on hose. i don't have a manometer so gonna' rig one with plastic tubing and water to see if fan is pulling -0.85 pv as best i can. going to try blowing out filter on bottom of firebox with air gun. see if that improves fan op. any other suggestions? vent is open, about 7' long with about 4 ells and a 45 3"pvc. i'll have to cut it to get the blower assy out.

BCConstruction

Perhaps a faulty pressure switch. I have never worked on one or seen one so im not much use.

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TimPa

so i made a u tube manometer with plastic hose and water, and measured the fan to be pulling about 2.5" w.c., sucked on the hose to the pressure switch and it required about half that. put it all back together and it started working. i hate that.

BCConstruction

I used to service combi boilers and system boilers and they used to do that all the time. Pretty common to open them up and mess with connections then the things fire back up when you put them together. Pressure switch may have just been stuck and you lossend it up a little.

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Plumbermurrieta

Check the vent pipe where it exits the house. If you can shine a flashlight into the pipe, look for obstructions such as wasp nests etc which can reduce the air flow enough to prevent the switch from tripping.