Water heater reset issue

[Tynee]

Evening gentlemen, I hope somebody can provide some insight on an issue I'm having with my water heaters. I've got (2) 50 gallon tanks plumbed in series and fed by a single 208V circuit on a 30A breaker.

My resets trip about every 6 weeks or so. Sometimes both, sometimes just the downstream unit. I've searched for potential issues, but I haven't found anybody else fighting resets this infrequently. Others I've seen trip in hours, not weeks.

I guess I don't understand why the 40A resets are tripping instead of the 30A breaker (other than the fact that the resets are in the crawl space, and the breaker is in the garage where it would be much easier to reset... my luck...)

Any advice on what could be causing this would be appreciated.

 

[zmaxmotorsports]

Try replacing the resets.
I'm wondering how/why you ended up with 2 gal water heaters on 1 30a circuit?

 

[Tynee]

If I remember correctly from last time I worked on them, the thermostats are about $30 ea. Would really rather know I'm fixing the issue before I drop $60.

Can't explain the thinking on the 2 tanks on a single circuit. Was that way when I bought the house. House is 11 years old, I've owned it for 4.

 

[ard]

If I remember correctly from last time I worked on them, the thermostats are about $30 ea. Would really rather know I'm fixing the issue before I drop $60.

Can't explain the thinking on the 2 tanks on a single circuit. Was that way when I bought the house. House is 11 years old, I've owned it for 4.

You left out the fact that you'd previously replaced one or both...

208v? What is each heater rated at? Volts and amps on the plate

 

[Tynee]

I haven't replaced them. Shortly after I bought the house, I had both lower elements replaced (IIRC) under warranty. Shortly after the warranty expired, the resets on both units tripped, but I didn't know that was the problem until after I bought a couple of new elements and a couple of thermostats, and hauled them down into the crawlspace with me. When I got down there and found the resets tripped, I believe I returned the new parts after a couple of weeks of steady hot water.

I'll have to get back in the crawl to investigate the plate ratings. They are matching units.

I think I may have just had a realization about one of my questions above. The 40A rating above was the 120-277V rating of the reset, 208V rating will certainly be less, so I'll have to get back in the crawl to investigate after work this afternoon.

More to come.

 

[Milton Shaw]

If the resets are tripping it's probably a thermostat stuck and overheating. Those resets should be set somewhere around 150-180 to cut power before the water could be boiling and building up pressure. You need to isolate which thermostat is bad by checking temps when they are operating. IF the tanks are in series then it could be any of the tanks thermostats. Get a temp gun and check temps around each thermostat to see which is too hot.

 

[Tynee]

That would make sense. I guess what's strange about it is the relative infrequency of the trips. Maybe having 2 tanks is masking an almost immediate trip on whichever one is the problem. Might just be time to replace them both as Zmax suggested above.

 

[larry4406]

Not sure I can help on the immediate issue, but you indicated you had the water heaters piped in series. This means that the first one does the main heating while the 2nd stews the storage.

My plumber puts them in parallel being careful to keep the pipe lengths equal to balance the flow. See attached sketch for concept. This results in near equal flow of the units and equal share of the heating burden.

 

[ard]

If they were in series, the first one would do all the heating...and the second one (the downstream one) would only kick on after the first one had been fully depleted, no?

You say they both trip? One more frequently?

 

[Tynee]

Yeah, there is discussion all over the place around whether series or parallel is the right way to go. People (plumbers) feel equally strong both directions about it.

Don't know if there's any way the series plumbing could be causing this issue. Doesn't seem like it. I'd think that if anything that would just affect efficiency of the system.

With three kids in the house we have some periods of pretty high water demand, and I've never once run out of hot water, unless a reset has tripped...

 

[Tynee]

208v? What is each heater rated at? Volts and amps on the plate

Plate below. 240, not 208. Also, rating of the reset. Still curious why it would trip so infrequently, and why the rest trips before the breaker

 

[Tynee]

You need to isolate which thermostat is bad by checking temps when they are operating. IF the tanks are in series then it could be any of the tanks thermostats. Get a temp gun and check temps around each thermostat to see which is too hot.

I'm not ignoring you, just don't have access to a temp gun. Got all next week off, but several higher priority projects. We'll see.

 

[Dagny]

The resets do not sense current only temp. As said one of the thermostats is sticking on. If Iwas called to your house I would recommend changing both thermostats in first heater.