Rheem gas furnace RGDC-10nc-jr


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Old 10-23-09, 06:10 PM
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Rheem gas furnace RGDC-10nc-jr

Have above furnace with new pressure switch. Draft motor running fine, producing .30 in vacuum but will not activate pilot. New exact pressure switch installed, will activate pilot if I pull off vacuum hose while running, but not enough vacuum to activate switch when furnace starting. Any suggestions? Thanks, Chuck
 
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Old 10-23-09, 06:24 PM
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That's not much of a vacuum. I'd expect between .6" and 1" wc untill ignition occured, which might drop you to as low as .55"wc. You might inspect the inducer blower wheel and inspect your venting for a restriction. What is the amp draw of your inducer? Is it much over 1.5A?
 
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Old 10-23-09, 06:45 PM
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The fact that your furnace starts when you pull off the vacuum hose makes me wonder if you have miswired it. Are you using com and normally open contacts on your pressure switch?
 
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Old 10-23-09, 07:00 PM
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I agree with Houston --- it sounds like something in the furnace or venting system is plugging up the works.


The real cause of global warming is all the unneeded pressure switches people install on furnaces when the problem is elsewhere. I generally find that 90-95% of the time, the problem is NOT the pressure switch.

But it seems that 90-95% of the time DIYers (and 'way too many repairman) replace the pressure switch rather than measuring the pressure to see what's actually going on.
 
 

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