Rheem Power Vent HW Heater - Intermittent Lockout

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  #1  
Old 03-06-18, 11:04 AM
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Rheem Power Vent HW Heater - Intermittent Lockout

Woke up this morning to no hot water. I have a 75-gallon Rheem PowerVent LP water heater. The "A" and "B" lights were lit up indicating a lock-out. I unplugged it and plugged it back in. It ran for a while and eventually locked out before the water reached the set temperature.

So I've been monitoring it all day. I unplugged it and plugged it back in again. It's working in cycles of 3:
1) The power vent comes on, ignitor glows and the burner fires. It will run for 5-10 minutes and then shut off before the water reaches the set temp.

2) The power vent will then immediately come back on, ignitor will glow but the gas valve does not open. Power vent runs for a few more minutes and then shuts off.

3) The power vent immediately fires back up, ignitor glows and on this 3rd attempt the burner fires up. It sometimes continues to run until the set temp is reached. Other times, after this last of the 3 cycles, it will shut off before the set temp and show the lock out code.

If I unplug it and plug it back in, it will work in these cycles of 3 until either the set temp is reached or it locks itself out.

Any guesses as to what's going on here? I'm guessing a failing thermocouple but don't want to throw parts at it without some other opinions.
 
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  #2  
Old 03-06-18, 03:02 PM
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Starting to wonder if it's an LP gas issue. The flame on the burner has a lot of orange in it. I'm cooking on the grill (hooked up to the same 1,000 gallon tank) and it's barely getting up to 400 degrees. It should be getting a lot hotter.
 
  #3  
Old 03-06-18, 04:06 PM
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I'd need the model number of the water heater to check further.

It could very well be a propane pressure issue. Is your tank low ?
 
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Old 03-07-18, 09:28 AM
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I got 200 gallons a couple of weeks ago so low propane shouldn't be an issue. That would leave one of the regulators. After cooking some chicken last night, I'm wondering if the gauge on the grill is off. It's definitely reading lower than in the past but I burned the crap out of the chicken thinking it was only 400 degrees. But I digress...

If I rule out propane pressure, it looks like other possibilities are:
- Clogged air intakes. They're on the sides and look ok
- Thermocouple

Reading the manual, the only things that would cause it to stop mid-cycle is:
- an overheat scenario where the glass thingy would melt. In this case, it would not come back on until it's replaced
- combustible gas is detected. Also will not come back on once this happens (at least that's my interpretation reading the manual)
- thermocouple shuts it off because it's not detecting enough heat. I'm leaning toward this because it's sometimes not detecting that the ignitor is lit and doesn't open up the gas valve. It also shuts the burner off mid-cycle possibly for the same reason

Reading the manual, I've eliminated anything to do with the power vent. The ignitor won't light if it doesn't sense the change in pressure from the vent fan. But the ignitor is behaving as it should.

It's model #42VP75PFW
 
  #5  
Old 03-07-18, 10:23 AM
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Based on the error code (6) you may need to clean the flame sensor rod and confirm its location near the burner. The rod can be cleaned with a scotchbrite pad or steel wool.

Intellivent-gas-control-troubleshoot.pdf
 
  #6  
Old 03-08-18, 07:19 AM
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Thanks! I'll give that a shot.
 
  #7  
Old 03-10-18, 07:26 AM
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Well that didn't work. There's no way to adjust the flame sensor rod but it appears to be where it should be. I cleaned it with steel wool. I ordered a new hot surface ignitor which comes with a flame sensor rod. Hopefully that will do it.
 
  #8  
Old 03-15-18, 03:41 AM
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I replaced the HSI and flame sensor rod with new parts from Rheem. It behaves exactly the same way. It will cycle multiple times (anywhere from 3-6), sometimes igniting sometimes not, until the temperature is reached. Once it reaches the temp, or very close to it, it will show the lockout code.

I'd call someone but my fear is that they'd just throw parts at it until it works. I can do that without the labor costs.

For now I have it plugged into a WiFi switch that resets it daily at 4:00 am (so I don't wake up to cold water) and noon. This simple hack ensures I always have hot water until I can figure this out.

The flame is a little orange, but the flame sensor is glowing red hot.
 

Last edited by turbojimmy2; 03-15-18 at 05:29 AM.
  #9  
Old 03-15-18, 11:21 AM
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The flame rod just needs to be engulfed in the flame.
It's glowing because it's hot but it doesn't rely on heat to work.
 
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Old 03-15-18, 02:36 PM
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Ok - it's pretty well engulfed. It's the 7/16" away from the burner per the troubleshooting manual. The old one was actually a lot closer, but they both appear to be working. The behavior is exactly the same with the new parts. Something else is causing it to shut off and lock out.
 
  #11  
Old 03-19-18, 06:53 AM
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Well I bit the bullet and called a technician today. I should have went with my gut and just ordered a new gas valve, but it cost me $150 for the tech to tell that it needs a gas valve. It's $176 (it's on the way to my house now). He wanted $400 to install it but I'm just going to do it myself. He said that I went down the path that he woud have: flame sensor/HSI first. Since that didn't work, that only leaves the valve. It's not a fuel delivery issue because the gas valve is not opening on the second attempt.

So, it looks like the valve is threaded into the tank (it's a thermostat/valve assembly)? I assume I need to drain it or is it in some sort of dry well?
 
  #12  
Old 03-23-18, 08:50 AM
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Well the family finally got tired of playing Russian roulette with cold showers. I replaced the thermostat/gas valve today. That fixed it. The old one had a lot of scale on the thermostat probe. I don't know if that was the issue or what. But it's fixed now.

And in case you were wondering it takes forever to drain a 75 gallon water heater through a garden hose.
 
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