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 Posted: Fri Oct 19th, 2018 08:42 pm
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alvin
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Hi,Just checking if anyone has ever had this issue and how they resolved it.  Frequently, my rheem power vent HW heater, manufactured in 1995, has been found to be venting for extended time lately with the burner off.  I resolve this by cycling the power switch.  The fan comes on, the igniter lights and then the gas comes on is lit per normal.  It works fine the rest of the day, and at some point I notice that the vent fan is once again running too long and find the burner off again.

I've used this HW tank continuously since installed back in 1995.  I remember this happening a long time ago, but have forgotten what I did to fix it.  I may have replaced the igniter - I believe the igniter also functions as the flame sensor, perhaps the 'sensing' capacity of the igniter is failing?  I've had this igniter in service for going on 10 years if memory serves, which is a record in my experience.  I've never had a 'pressure' issue, my vent pipe is screened at the end and was clear as of yesterday when I inspected it. Any advice or questions are appreciated.

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 Posted: Fri Oct 19th, 2018 11:54 pm
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eleent
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Hello,  There probably is a troubleshooting flow chart for your heater someplace... possibly with Rheem tech support.  But, the first thing I'd look at is the pressure switch.  It sounds like it's sluggish, not freely moving. It should be fairly easy to check it with an ohm meter to see how well it's reacting to pressure changes. :cool:  This link from tanklets might help also: http://www.waterheaterrescue.com/Troubleshooting/Tanklets/power-vent-heater-issues.html

Yours,  Larry

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 Posted: Sun Oct 21st, 2018 03:07 pm
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alvin
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Thanks.  Another factor I keep thinking about is the thermostat.  I replaced the thermostat just before this issue came up, maybe something is going on with it or perhaps I bumped or dislodged something while replacing it.  I do know that since this has been going on, it has started properly each and every time I cycle the on off switch, so that's why I find it difficulty to believe its a sticking vacuum switch, but I'll try tapping it the next time.  To properly use the ohm meter on it, I'll have to remove the power, so it will open anyway, so how can I test it with an ohm meter, when voltage is applied to it?

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 Posted: Sun Oct 21st, 2018 05:34 pm
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eleent
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Hi,  The vacuum switch is sensitive, so you can just blow or suck a little on the tube that comes from it and that will activate the switch. :cool:
Yours,  Larry

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 Posted: Fri Oct 26th, 2018 02:35 am
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alvin
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Well, I've been monitoring my WH, and it hasn't failed to operate normally for the last 3 days.  I have been adjusting the thermostat, just to get it to shut off at a proper temp - it had been too hot, even set slightly less than "MED" on the dial.  The water is still a little hot for my liking, but I can live with it this way.  Since I've been adjusting the temp downward, I haven't had any problem with the fan running and the burner not, nor had I ever been without hot water. Thanks for the help.

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 Posted: Tue Oct 30th, 2018 11:38 pm
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alvin
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It didn't take too long to start acting up again.  I took off the  vacuum switch and  checked it - it seemed fine and registered continuity with a small amount vacuum pressure, I checked it several times.  I reinstalled it with new tubing as the old was stiff at the ends and may have been leaking. 
Then today I was restarting it, just switching it off at the switch and  turning it back on.  blower starts, after a minute  the igniter came on, then  a small click, but no gas.  I did this about 3 times, never lit.  I got my multi tester out to see if the controller was sending voltage to the  gas switch, yes it was but this time, the valve opened and it lit, so I still don't  know  which part is failing, the  controller or the valve.  I didn't have time to keep trying it. Maybe I'll investigate it further tomorrow, or just buy both the  controller and the valve?  The controller is easy to change out provided they have a direct replacement, just 2 screws,  one of them operates as the ground.

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 Posted: Wed Oct 31st, 2018 05:07 pm
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alvin
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I finally caught it, the voltage just comes on for a split second, then shuts off.  When it lights, the voltage stays on for at least 1 second.  So am I looking at a new controller, or is there some other condition that could cause this?  Again,  the igniter comes on.

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 Posted: Thu Nov 1st, 2018 04:36 am
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eleent
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Hello,  The only other thing that comes to mind is the possibility of "messy" power; that is low or high voltage, not operating at 60 cycles, voltage spikes etc. However, it's good you found a problem. :cool:
Yours,  Larry

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 Posted: Thu Nov 1st, 2018 12:04 pm
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alvin
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I just ordered  an ignition control from Rheem.  I talked to them yesterday, first guy for 5 minutes and their secondary unit guy for about 10 minutes, they sent me the troubleshooting guide.  Basically, If you have 24V at the vacuum switch wire on the ignition control then it's either the gas valve or controller.  Subsequent testing identified the control, as the gas valve fires when 'hot wired' to the vacuum switch wire.  That was the test on the troubleshooting sequence. 
As a note, the first thing they ask to check after checking for voltage from the vacuum switch, is the igniter.  Check it with an ohm meter, check it while its both hot and cold.  Cold it should read 70-100 ohms between the two wires and hot it should be 30 ohms or less.  They say use a torch to heat it, but since mine was firing, I just let it fire and quickly removed the wires and checked it while still hot.  Another note - on a unit this old, he said I could check the vacuum switch by taping the 2 vacuum wires together, bypassing the switch.  I asked him about the controller needing to 'see' an open condition first, but he said that was on later models - mine was made in October of 1995.  We talked a little about the age of the tank, I guess it pays to simply filter the incoming water as I do.  
I am concerned about the voltage as well - I'm reading 30V AC most of the time, when it should be 24V, but it's not even listed as a part or even to check the transformer - I don't see where it could be, it's inside the heater jacket somewhere; I guess it's not serviceable?

Last edited on Thu Nov 1st, 2018 12:13 pm by alvin

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 Posted: Wed Nov 7th, 2018 07:08 pm
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alvin
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I  received and installed my new ignition control yesterday.  The HW  tank is working normally again. One modification had to be made to the ignition control unit - a small piece of the plastic housing must be removed to accommodate the double 2 wire bayonet connector in the bottom slot, my old one appears to have been made without the plastic piece.  This must be done because there just isn't enough room for both wires and the double bayonet connector in the hole.  I scored the plastic deeply with the saw on my multitool and snapped it off with the pliers. Then bent the male bayonet on the control slightly so the wires and connectors would fit the space. I looked at the old one and that modification was made on it as well. The ignition control was $132 delivered from Rheem.  They always seem to send a FedEx return sticker in case the part needs to be returned.

Last edited on Wed Nov 7th, 2018 07:18 pm by alvin

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