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-   -   Intermittent pressure switch problem (http://www.houserepairtalk.com/f8/intermittent-pressure-switch-problem-15024/)

homeowner123 11-03-2012 10:29 AM

Intermittent pressure switch problem
 
Here's my problem. York Diamond furnace, heat turns on but after running for a while, turns off with 6 flashes indicating pressure switch opened 5 times after normal operation. Here are some observations.

1. Pressure switch is about 2 years old.
2. The tube from draft inducer to the pressure switch is clean.
3. The pressure from the draft inducer to the pressure switch seems low.
4. I can hear the draft inducer running and it sounds pretty strong.

so I'm thinking either one of these.

1. Bad pressure switch
2. Bad draft inducer
3. Clogged vent.

My questions are as follows:
1. How much suction should I expect from the draft inducer to the pressure switch? I feel some suction coming from the inducer when it's on but it's not so strong. Should it be really strong like it's sucking air strong or should it be slight?
2. How do I verify if I have a clogged vent??

Your help is appreciated. Thank you!

Joe

Wuzzat? 11-03-2012 12:57 PM

1. How much suction should I expect from the draft inducer to the pressure switch?
>What are your pressure switch spec's?

Should it be really strong like it's sucking air strong or should it be slight?
>You may be able to feel 0.5 PSI (14" of water column?). You can test this - fill a soda straw with water, block the top opening and see if you feel the pull of this many inches of water.

2. How do I verify if I have a clogged vent??
>Pressurize it, measure static pressure with a homemade manometer and compare the inches of WC with what is normal back pressure for a vent.

homeowner123 11-03-2012 06:45 PM

Quote:

Originally Posted by Wuzzat? (Post 79525)
1. How much suction should I expect from the draft inducer to the pressure switch?
>What are your pressure switch spec's?

Should it be really strong like it's sucking air strong or should it be slight?
>You may be able to feel 0.5 PSI (14" of water column?). You can test this - fill a soda straw with water, block the top opening and see if you feel the pull of this many inches of water.

2. How do I verify if I have a clogged vent??
>Pressurize it, measure static pressure with a homemade manometer and compare the inches of WC with what is normal back pressure for a vent.

Thanks for your response. The pressure switchis rated at 0.5" w/c. I guess thats really slight. I also checked the vent and there was no obstruction. I will try a new pressure switch and report back.
Joe


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