The Tank › AO Smith Model PCG-75
- January 5, 2016 at 11:10 am #22584
Hello all, I am a new user here and need help. I live in South East Michigan and three years ago I bought the AO Smith ProMax Plus High Recovery 74-Gallon Gas Water Heater Model PCG-75 because my old 40 gallon wasn’t enough. Within the first month of buying it we had issues, sometimes the water would not be hot early in the morning or not hot in the evening even though there was no prior hot water use.
I called AO Smith and their customer service informed me that I bought too big of a water heater for my use and that it goes into a sleep mode when it’s not in use for a long period of time and by long period of time I mean 6 hours or so. I told them that’s ridiculous and that no where does it state this feature. Every plumber I talk to says they never heard of such a feature. The next step was to have a drawn down test completed which it passed both times. Since it passed both times they said they can’t do anything about it.
After getting yelled at by my wife and kids about the hot water, I decided to call again about it. This time I was informed that there is no sleep mode on my water heater and that it’s probably just standby heat loss. I had a plumber come out and he replaced the gas control valve but it didn’t do any good.
Can somebody please help me!!!!
Thank you!January 5, 2016 at 12:54 pm #22585
You have a deadband issue. Using the link on the left side of the Tank topics index, go to Tanklets and click on
Temperature Fluctuations. My own tank does this, although not regularly.
Randy SchuylerJanuary 5, 2016 at 1:24 pm #22586
Thanks for the reply Randy. It’s not exactly the news I want to hear. I spent a $1,000 on a bigger water heater with the expectations of never running out of hot water and now I have to deal with a deadband issue. I have a call into AO Smith and I will mention this issue with them and see what they say.
Thanks again.January 5, 2016 at 4:08 pm #22590
Don’t expect too much. In the past, the manufacturers have not considered deadband to be an issue they need to solve. Still, it usually happens on older heaters, so you might get somewhere. If you can remember to run some hot water first thing in the morning to “wake up” the thermostat, it’s not so annoying.
RandyJanuary 6, 2016 at 12:05 pm #22594
They recommended raising the water heater temperature to 140 and adding a mixing valve. What do you think of that idea?
ThanksJanuary 6, 2016 at 1:24 pm #22595
I forgot to mention that he said “my model has the older gas control valve that isn’t as precise as the newer models”. It still doesn’t make sense to me because I didn’t have that issue with my previous water heater.January 6, 2016 at 6:41 pm #22596
They also recommended an insulation blanket.January 6, 2016 at 7:04 pm #22597
You have all the hallmarks of deadband, but there is one other slight possibility that ought to be checked. It won’t cost you anything but a few minutes. Again, go to Tanklets and click on Cross Connections and do the simple test described there.
A blanket might be worth it if the tank only has one inch of insulation. I’m not sure what to say about the 140/mixing valve idea, and will tell my friend Larry Weingarten to weigh in on that.
All in all though, it seems as if the tech mostly dodged the issue.
Randy SchuylerJanuary 8, 2016 at 3:05 pm #22598Larry WeingartenParticipant
Hello: The mixing valve approach can work, but it’s another moving part to fail, which happens a lot with hard water. I see it as a band-aid. One thing that could be having an effect here is the dip tube. If for some reason, there isn’t one, or if it’s on the wrong side, that could be showing some of the symptoms you have. Also, doing the cross connection test Randy suggested is good. Is there a recirc line? That also could play into this. Once all the possible “other” problems are covered, the control is the next thing to focus on. 😉
Yours, LarryJanuary 8, 2016 at 3:53 pm #22599
HI Larry, thanks for responding and no there is no recirc line. I had a plumber out yesterday to take another look at the water heater and of course it worked perfectly. He ruled out cross connection and a bad dip tube. He said it was either a defective water heater or just standby heat loss.January 8, 2016 at 6:39 pm #22600Larry WeingartenParticipant
Hello: Another sorta band-aid fix comes to mind :P. How about using a Grundfos pump? http://us.grundfos.com/products/find-product/comfort-pumps-up-10.html You would set the timer to come on, say 20-30 minutes before you plan on using showers. This would deliver a slug of cool water to the bottom of the heater, forcing it to kick on and recover before showering. The secondary benefit is that, done right, you would have quicker hot water as well. This is all to get around a control problem that you really shouldn’t have in the first place. 😕
ps. Not sure what your plumber meant by “defective water heater” … bad control?
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