Water Recirculating Pump Tripping Thermostat on Water Heater

[TonyN]

My water heater works fine, except when I run the Watts recirculating pump I have installed in the system and then it trips the thermostat after working and doing what it should do for a short time. I have already replaced the thermostat on the water heater. This pump has been working fine for the last three years with no problems. It is still recirculating water as it is supposed to do, but now all of a sudden it is tripping the thermostat on the water heater after working for a little length of time. What could be wrong? I really need this in my system as it takes a ridiculously long time to get hot water at my kitchen sink without it.

 

[MicEd69]

What do you mean, "it trips the thermostat"? Do you mean it trips the circuit breaker to an electric water heater?

 

[TonyN]

What do you mean, "it trips the thermostat"? Do you mean it trips the circuit breaker to an electric water heater?

It does not trip the main circuit breaker feeding the water heater, but a thermostat near the top of the water heater that has a red button you push to reset. If I don't run the recirculating pump, it doesn't trip. When I do it does, though the pump is still doing what it's supposed to do.

 

[MicEd69]

Where does the return water from circulating loop connect to your water heater? At the drain valve, at the cold-water inlet, other?

 

[Twowaxhack]

Move the return from the bottom to the top/cold water inlet and install a check valve upstream of your return connection. You’ll need an expansion tank downstream of the check valve.

It’s “ stacking “. That means it’s causing the thermostat to cut on and then it over heats before it cuts back off. The lag between on and off is too great. The thermostat is not in the water. The heat must transfer to the thermostat by convection. It’s a slower process.

Another option might be to increase the temp of your water or increase the speed of circulation if it’s too slow.

 

[TonyN]

Move the return from the bottom to the top/cold water inlet and install a check valve upstream of your return connection. You’ll need an expansion tank downstream of the check valve.

It’s “ stacking “. That means it’s causing the thermostat to cut on and then it over heats before it cuts back off. The lag between on and off is too great. The thermostat is not in the water. The heat must transfer to the thermostat by convection. It’s a slower process.

Another option might be to increase the temp of your water or increase the speed of circulation if it’s too slow.

If you're familiar with that system, it has a bypass connected between the hot and cold feeds at the connections to the faucet. IT HAS BEEN WORKING FINE FOR THE LAST THREE YEARS THE WAY IT IS NOW!!! Why is it suddenly not working the way it should?

 

[MicEd69]

Move the return from the bottom to the top/cold water inlet and install a check valve upstream of your return connection. You’ll need an expansion tank downstream of the check valve.

It’s “ stacking “. That means it’s causing the thermostat to cut on and then it over heats before it cuts back off. The lag between on and off is too great. The thermostat is not in the water. The heat must transfer to the thermostat by convection. It’s a slower process.

Another option might be to increase the temp of your water or increase the speed of circulation if it’s too slow.

Twowaxhack, I'm a gas water heater person, so just was wondering, could it be that his bottom element is bad? Or it has a mineral buildup making the top element work "overtime"? Just wondering.

 

[Twowaxhack]

It’s probably causing the bottom to fire on and off due to the temp drop of the recirc loop. Then the lag between on and off is over heating the tank. The upper thermostat has a high limit switch that cuts the heater off if it gets too hot.

Of course I’m not on site to verify the heater is working perfectly and there’s no other issue mimicking what I’ve described as stacking.

 

[TonyN]

Twowaxhack, I'm a gas water heater person, so just was wondering, could it be that his bottom element is bad? Or it has a mineral buildup making the top element work "overtime"? Just wondering.

No, I've checked everything on the water heater, elements and everything else and it's working fine except when I run the recirculating pump, which is still doing what it's supposed to do, but eventually trips the thermostat on the water heater. It was working fine for three years until just lately.

 

[TonyN]

It’s probably causing the bottom to fire on and off due to the temp drop of the recirc loop. Then the lag between on and off is over heating the tank. The upper thermostat has a high limit switch that cuts the heater off if it gets too hot.

Of course I’m not on site to verify the heater is working perfectly and there’s no other issue mimicking what I’ve described as stacking.

It's been working for 3 years with this recirculating pump, but is just now tripping the thermostat, which I've already replaced thinking that was bad. Everything else checks out on the water heater.

 

[Twowaxhack]

It's been working for 3 years with this recirculating pump, but is just now tripping the thermostat, which I've already replaced thinking that was bad. Everything else checks out on the water heater.

Are the thermostats tight to the tank ? Insulation in place under the access panels ?

What’s the water temp getting to in tank ? What’s the returns water temp ? There will be a temp drop after it circulates

Is your water hotter or cooler than it use to be ?

You could try adjusting the temp up or down 10 degrees. If you’ve replaced the thermostats, they can differ about 10 degrees. So something has changed in your system, you claim it has worked for 3 yrs. That’s something that could’ve changed.

 

[TonyN]

Are the thermostats tight to the tank ? Insulation in place under the access panels ?

What’s the water temp getting to in tank ? What’s the returns water temp ? There will be a temp drop after it circulates

Is your water hotter or cooler than it use to be ?

You could try adjusting the temp up or down 10 degrees. If you’ve replaced the thermostats, they can differ about 10 degrees. So something has changed in your system, you claim it has worked for 3 yrs. That’s something that could’ve changed.

Yes, the thermostats are tight to the tank and the insulation is fine. I don't know the water temp into the tank, but I'm on the same water the whole time both in summer and winter.

Are the thermostats tight to the tank ? Insulation in place under the access panels ?

What’s the water temp getting to in tank ? What’s the returns water temp ? There will be a temp drop after it circulates

Is your water hotter or cooler than it use to be ?

You could try adjusting the temp up or down 10 degrees. If you’ve replaced the thermostats, they can differ about 10 degrees. So something has changed in your system, you claim it has worked for 3 yrs. That’s something that could’ve changed.

I finally backed off the temperature and got everything to work now, though my water is not as hot as I like it. I kept it at the maximum temperature as I don't have children in the house and I think it's more efficient to keep it hotter as you use less hot water from the tank when you do use it. I also like it really hot water for washing some items like towels and underwear and for the dishwasher. I don't know why it suddenly wouldn't work at the temperature I had it at previously.

 

[MicEd69]

I'm assuming your circulating line is insulated throughout. Not that that would cause a sudden change in the way your system works, just wanted to confirm that.

If a system that has worked for three years is now not working, something broke/changed. If the thermostat that has tripped was replaced, and it is still not functioning as before, assuming the thermostat replacement is like the original, then running change Managerial Analytics process, you need to look at all the other components in the system.

Water supply = no change.
Bottom element = working, no change.
Circulating pump = working, no change.
Circulating pipe = no change.

The only component in the system that I can think of that could break or change is the sensor/crossover valve.

I'm not sure how you can check them, and $85 to replace them just to find out that is not the problem is a little steep. But maybe someone can suggest a test or a cleaning method that may resolve your issue. Just a guess using MA.

 

[Twowaxhack]

If I buy 4 electric water heater thermostats I might get 4 different temps if I put them all on the same setting.

For example, If I set them all at 130 degrees I might get 120, 125, 130 or 140. They’re not accurate.

So you changed your thermostats and that likely changed your water temp which would affect the return water temp.

If the return water is too cool when it’s piped into the bottom of the heater it will trick the heater into thinking it needs to turn on. This will make the thermostat overshoot the thermostat setting.

To stop this the manufactures recommend piping the return to the top of the cold side and letting the dip tube of the water heater introduce the return water.

In the early 90’s I believe, the manufacturers started making the dip tubes shorter. With long dip tubes and short draws of hot water it would do the same thing as having a bottom return with the return water being too cool. It’s called “ stacking “.

 

[Twowaxhack]

Also circulating water over 140 degrees will accelerate mineral fall out. It’s not advised.

 

[MicEd69]

If I buy 4 electric water heater thermostats I might get 4 different temps if I put them all on the same setting.

Understood. However, TonyN's problem began before he changed out his thermostat. So, while the thermostat was apparently not actually broken, it would be quite unlikely that the problem would remain with a replacement thermostat that may be not as accurate or calibrated like the original thermostat.

So that is why I thought just perhaps the sensor/crossover valve was the issue. Is there a way to test those valves?

 

[Twowaxhack]

Understood. However, TonyN's problem began before he changed out his thermostat. So, while the thermostat was apparently not actually broken, it would be quite unlikely that the problem would remain with a replacement thermostat that may be not as accurate or calibrated like the original thermostat.

So that is why I thought just perhaps the sensor/crossover valve was the issue. Is there a way to test those valves?

Who knows now ? That’s why people shouldn’t be parts changers without troubleshooting.

If he has a return line there shouldn’t be a bypass valve.

Simply having a return piped to the bottom can cause his issue. Especially with a high thermostat setting. I don’t care how long it worked, it’s a known problem to the industry that’s why most of not all advise a top fed return.

If I were in the job and his heater checked out, I’d pipe it to the top and see if the problem went away. I’m pretty sure it would. If you turn the thermostats up all the way and circulate the water, you’re asking for trouble.

 

[Twowaxhack]

If he has a bypass valve then it could be defective. I can’t make heads or tails out of some peoples posts. Convoluted crap and half the info is probably wrong. I get it from customers on the phone. They make statements then when you get to the house it’s totally different.

 

[Twowaxhack]

Twowaxhack, I'm a gas water heater person, so just was wondering, could it be that his bottom element is bad? Or it has a mineral buildup making the top element work "overtime"? Just wondering.

Elements can ground out and create a complete circuit to the element 24/7 and cause the tank to over heat. Each element has 120v at all times.

Mineral build up wouldn’t cause any issue on the elements like he’s having. I suppose it could if it were on the walls of the tank acting as an insulator. I’ve never seen it.

 

[Twowaxhack]

If you're familiar with that system, it has a bypass connected between the hot and cold feeds at the connections to the faucet. IT HAS BEEN WORKING FINE FOR THE LAST THREE YEARS THE WAY IT IS NOW!!! Why is it suddenly not working the way it should?

Then you don’t have a return line I’ve been speaking of.

Did you check the amp draw of the elements ? It shouldn’t have any amp draw when the thermostats are not calling for heat.

Watts divided between volts gives you amps. Check the elements for proper draw.

Does your pump run 24/7 ?

If you turn the cold water off to the heater and open a hot water faucet, does the water stop after you bleed the pressure off ?l

This is a hot water bypass system not a traditional recirculating system.

Forgive me for not trusting your description of what’s happening. You say that the heater trips out when the pump is running. Is that possible correlation without causation ? I get that all the time.

Example: lady calls up,

“ ever since you repaired my toilet my washing machine won’t spin “