AO Smith GVR-50-300 Water temperature very unstable

[AzJazz]

Hi - I have an AO Smith GVR-50-300 Natural Gas Water Heater (About 18 months old). It has a more modern Honeywell thermostat with an occasional flashing red LED that I believe indicates everything is working OK. I live in Arizona and the tank is in my garage.

 

I have had a problem where the hot water temperature from the tank changes drastically throughout the year. For example, last week my hot water temperature was about 125 DegF.

This morning, the temperature was 102 DegF (Of course, I hadn't changed the thermostat between the two readings).

 

It seems like the hot water temperature actually goes down as the exterior temperature goes up.

Shouldn't the temperature be more consistent? I have to adjust the thermostat about 6 to 10 times throughout the year to keep the temperature in the 120 => 125 DegF range.

 

Thanks,

 

AzJazz

[BryanS]

You shouldn't have to change the setting at all to get a constant temperature year round. Typically the gas valve has a temperature probe built in, so I would try changing that first. Nothing else comes to mind that would impact the temperatures. When are you taking these readings? Obviously, the temps will go down the more water you use until it heats up again. I will say most of the gas water heaters I worked on were manual controls. I did change maybe one with the newer type digital valve. When I get more time, I will look over my manuals, and see if I have one on this model. I wanted to give you some sort of an answer for now.

Edited August 12, 2014 by BryanS

[m_west5]

If you are in Phoenix metro especially (or anywhere else in our state for that matter), I highly recommend draining and flushing your water heater at least once per year due to the water hardness and high mineral content. You will be surprised by how much sediment (from every water company) is in the tank. Especially after 18 months.

Here's how:

Hook up a garden hose to the drain near the bottom. Run hose out to driveway.

Open drain valve.

Examine drain water. You will see ALOT of very fine tan sediment.

Let it flush until sediment clears. Close drain valve.

This sediment build up will affect the holding tank's thermal conductance properties, which in turn affects the thermostat's performance.

Also due to the nature of the typical gas water heater, the temperature in certain situations may vary by up to 30 degrees F higher or lower at the bathtub, shower, sink, etc. A flakey, really out of spec thermostat will allow more variation.

This model should have a draft test port at the top of the water heater. This could affect the temp swings. Check the manual on how to perform this test if you still have it. Check your flame too. A properly operating burner should produce a soft blue flame. Blue tips with yellow inner cones are satisfactory. Anything else is bad. Also verify nothing is obstructing the rooftop flue pipe vent cap.

Unfortunately, AO Smith does not rate very good when in comes to water heaters imo. If after completing the above, and you still have issues, you will probably need a new thermostat and/or manifold assembly. Most likely thermostat. Check which one you have, Robert Shaw or WhiteRogers.

Good luck.

Edited August 13, 2014 by beam current

[AzJazz]

You shouldn't have to change the setting at all to get a constant temperature year round. Typically the gas valve has a temperature probe built in, so I would try changing that first. Nothing else comes to mind that would impact the temperatures. When are you taking these readings? Obviously, the temps will go down the more water you use until it heats up again. I will say most of the gas water heaters I worked on were manual controls. I did change maybe one with the newer type digital valve. When I get more time, I will look over my manuals, and see if I have one on this model. I wanted to give you some sort of an answer for now.

 

Hi, BryanS - I always take the readings throughout the day, usually across multiple days. I also try to take the temperature when the flame is off, since the temp should be near the current set point. For this current situation, the water temperatures were really low in the morning when I got up, but I didn't make any temperature measurements until later in the day. I then tested the temperatures over a 4+ hour period, constantly raising the thermostat when the flame was off but the temperature was still low. I moved the dial almost 1/4 of the full dial circumference before the temps were around 120 DegF again.

 

If you are in Phoenix metro especially (or anywhere else in our state for that matter), I highly recommend draining and flushing your water heater at least once per year due to the water hardness and high mineral content. You will be surprised by how much sediment (from every water company) is in the tank. Especially after 18 months.

Here's how:

Hook up a garden hose to the drain near the bottom. Run hose out to driveway.

Open drain valve.

Examine drain water. You will see ALOT of very fine tan sediment.

Let it flush until sediment clears. Close drain valve.

This sediment build up will affect the holding tank's thermal conductance properties, which in turn affects the thermostat's performance.

Also due to the nature of the typical gas water heater, the temperature in certain situations may vary by up to 30 degrees F higher or lower at the bathtub, shower, sink, etc. A flakey, really out of spec thermostat will allow more variation.

This model should have a draft test port at the top of the water heater. This could affect the temp swings. Check the manual on how to perform this test if you still have it. Check your flame too. A properly operating burner should produce a soft blue flame. Blue tips with yellow inner cones are satisfactory. Anything else is bad. Also verify nothing is obstructing the rooftop flue pipe vent cap.

Unfortunately, AO Smith does not rate very good when in comes to water heaters imo. If after completing the above, and you still have issues, you will probably need a new thermostat and/or manifold assembly. Most likely thermostat. Check which one you have, Robert Shaw or WhiteRogers.

Good luck.

 

Hi, beam current - I drained my tank about 6 months ago, and there was absolutely no sediment in the tank (I was pleasantly surprised!).

 

I'll try draining again in the next few days. I'll also get on the roof to see if the vent cap is blocked. I will also do a draft test this weekend.

 

I noticed this problem immediately with this WH. I had a similar problem with my previous WH, too - but not as frequent. I was hoping that the more modern tank/thernostat/thermopile designs would have helped, but it doesn't look like it now. Maybe something common - like a blocked vent cap - is causing this issue.

[m_west5]

Hi AzJazz,

 

"I drained my tank about 6 months ago, and there was absolutely no sediment in the tank"

 

Not the issue then.

 

"I'll also get on the roof to see if the vent cap is blocked."

 

Still a good thing to check.  Gas appliances need correct airflow to operate correctly and safely.  Intake and exhaust airflow is extremely important.  More to follow below.

 

"I noticed this problem immediately with this WH. I had a similar problem with my previous WH, too - but not as frequent."

 

You've had this problem since new, for 18 months?  Did you contact AO Smith right away and seek some sort of resolution? Or the place you purchased it from?  Did you install it, or someone else?  Did you replace the old WH for this similar reason?

 

Side note: You state it has a Honeywell tstat. Sorry, just saw that. I'm not 100% sure, but I believe AO recently went with the Honeywells because of the numerous issues they had with the other brands. Is this newer design time tested? Not sure yet, but AO Smith will know.

 

So, some things to check:

 

1.)  What is the blinking light status when it is, and more importantly, is not heating properly?  You will have to monitor it closely and frequently in case it throws an error and then resets itself.  You state "occasional flashing red LED that I believe indicates everything is working OK". How is the light blinking and what does the chart say when it is not heating properly?

 

2.)  You stated this WH is in your garage. Is your dryer also located in the garage?  If so, it creates even more dust and "fluff" in an already dirty environment.  Are you cleaning the 360 degree air filter regularly?  It is very important you clean this for proper combustion chamber operation whether the dryer is in the garage or not.  Here"s why: When the thermopile initiates a burner on command, and then senses insufficient air intake, it will not stay lit long enough to achieve the desired water temperature setting. It's doing what it is designed to do . To protect you.  And say your garage daytime ambient temperature is 130 - 140 degrees F (common for AZ summers) and your your tstat is set for 120 degrees F.  It's not going to heat the water until the tank temperature is below 120 degrees (night time), and then perhaps it gets caught up in this error cycle again.

 

3.)  Take a look through the view port and see what the pilot looks like.  Is it blue?  Staying lit all the time?  Is it in constant contact with thermocouple?  What does the burner flame look like while operating?  It must look like what I described above.

 

4,)  Is the gas shut-off valve functioning properly?  Have you checked the flex gas line for kinks and leaks? Use dish soap/water solution, looking for bubbles.  You can contact your gas company and request them to check the gas pressure to your home.  Probably free also.

 

5.)  It just seems odd you had similar problems with the old WH. Is there other information you can add here? 

 

There really isn't much to the WH.  It may have a flakey TCO.  Try resetting the button several times.  Check all the wire connections.  Simple, common sense stuff. If after all that, try contacting AO Smith.  This should still be under warranty at only 18 months old.

Edited August 15, 2014 by beam current