I think it’s the heating element. Help me raise my confidence level.

[Caver01]

The quick facts:
Recently acquired a 3377 gallon Endless Pool.
Chemistry is all within targets.
Pump/filtration all working fine.
Heater (SpaPak electric ELS 552-2 5.5kW 240v) was/is tripping the breaker. No Heat.

Actions and observations to date:
High-limit switch is not popped or needing reset.
I can hear thermostat “click” as I adjust the heat level dial.
The heater turns on when the pump is running (properly detecting water pressure/flow). Light comes on.
Checked input power with a voltmeter: 240 definitely coming in. I can measure 240 right to the nuts on the heating element electrodes when operating—so power is definitely getting to the element connections.
Pulled the heating element to inspect for calcium etc. It‘s black (messy to touch), but otherwise visibly intact, no calcium encrustations anywhere on it.
Element tests 10.4 ohms resistance.
Inside heating tube where element goes looks clean. A few green specks on inner walls, but this is cast brass/bronze. Gasket seal is good.
Entire inside of heater is clean and dry, no corrosion.
I cleaned the switch coils inside the heater. No longer tripping the breaker immediately, but no heat.
Heater is probably 20 years old.

Ok, so this thing is not very complicated. It’s not a digital model, so no readouts or computer logic to deal with. I was expecting to see something wrong with the heating element but maybe I cannot visually confirm anything with these things.

My question is this—in spite of all of these facts, it’s not heating the water, even though I know that unit is delivering power to the electrode screws—Is the heating element still likely the culprit here, even though it looks intact and tests 10ohms? I would like to order a new element ($150 or so) if you think that’s the problem as I do. Thoughts? Suggestions? As a new owner of this house, it’s one thing after another, so trying to avoid spending $800 on a completely new heater + installation if I can avoid that. Thanks!

 

[ajw22]

Maybe @RDspaguy has experience with that heater and can say if 10 ohms says the element is good. That sounds low resistance for a heater element.

 

[Caver01]

I seem to recall reading somewhere 10 ohms was what you were looking for with this model but I don’t know.

 

[swamprat69]

A 10.4 Ohm heating element with a 240 volt supply Is ~ 5538 Watts and should draw ~ 23 Amps. This all seems correct for the heater you listed. Is the heating element drawing 23 Amps when it is powered? Be aware that the high limit is a manual reset. Does the high limit show continuity across both sides? The high limit protects both legs of the 240 volt supply. If the high limit tripped it may not be resetting fully.

 

[swamprat69]

Just looked at the manual for the heater Ladder Diagram; Schematic Diagram - Raypak ELS 552-2 Installation & Operating Instructions Manual [Page 5] . Does the "indicator light" light up when the heating element is powered? What size breaker is supplying the heater? Curious as to why the breaker tripped if the heating element is good ( 10.4 Ohms and no continuity to ground ) ?

 

[Caver01]

All good questions.
First, the breaker is pictured below:

 

[Caver01]

The pool heater is shown upper right, tripped.
It doesn’t always trip which is why I have been able to do some tests described above.
The light does come on when it’s supposedly working which I think means it is not blocked by rate limiter. That reset switch is not extended—I can press on it through a rubber cap on the outside, and it does not budge, so I think it means it is not tripped.

Finally, and this is why I am a bit stumped, is that when it is running, light lit, and supposedly heating, I can measure 238 or so volts AC across the poles of the heater. Is it drawing amps? I have no idea, but it’s not heating.

I did check continuity from each pole of the element while installed to ground and I don’t get any connection. I thought maybe it was making contact inside the brass tube, but no, it’s not making contact. I think it comes pretty close thoough.

 

[Caver01]

Thanks for the input to this mystery. I don’t want to buy an element I don’t need, but wondering if it’s still possibly bad given the facts. Any other tests I could try?

 

[Caver01]

I suppose feeling for a reset button is not exactly confirming the rate limit switch isn’t engaged. I can try probing it for continuity, but if the switch is tripped I would not be measuring 240 at the element, right?

<EDIT> Having looked at the diagram I can confirm that yes, I have already confirmed continutiy across the rate limit switch.

 

[RDspaguy]

If you have voltage at the element and continuity on the element then you have current flow.
What is the volume of the spa? Does it have a cover? What is the ambient air temp? Post pics.
The element should not leave black smears on your hands from touching it, but the o-ring might.
Based on your description I'd say your element has a ground fault and your gfci is bad or you lost your ground.

 

[swamprat69]

I see the breaker for the pool heater in the photo, but can't see the Amp rating on the reset lever? What is the Amp rating on the breaker? If it says 30A then you are under the 80% load limit. Since the breaker is GFCI it introduces another reason for it to trip other than over amperage. Just having voltage present at the load ( heating element ) does not insure that it is heating. Having the correct tools and being able to use them safely and correctly is essential when troubleshooting. A clamp style ammeter would let you check the amp draw for the heating element. Other things to check would be the voltage drop across any contacts in the circuit while under load such as the breaker, contactor or high limit switch as a voltage drop would show both voltage loss and a heat load at that point indicating poor contacts.

 

[Flying Tivo]

Just to rule out the breaker you can swap the breakers from the pool pump to the heater.

 

[Caver01]

Thanks for continued input.
For reference again, it’s a 3377 gal Endless Pool, about 17x9 and 4+ feet deep or so. It has a tight fitting thick vinyl security cover. I probed around again for ground faults I cannot find an issue. The heater, pump and water current motors are all tied together on a big ground wire and I get continuity to that all the way to the element mount plate.

Here’s a picture of the pool:


and here’s the breaker closeup . . . Given the hour, I was only able to share the photo I had of the breaker. Here you can see 30 amps:

 

[RDspaguy]

3377 gal

5.5kW

That's going to take about 1.5hrs to raise the temp 1 degree not counting heat loss to the environment. If that room is not heated I'd expect it to struggle to keep up in the winter. You really need a bigger heater on a tub that size.

 

[Caver01]

Good to know, but should I at least feel warmer water coming out of the jet into the pool? It‘s not warm coming out. Not even a little.

 

[Caver01]

The room IS heated, and it’s never going to hot tub temps—this is an exercise pool.

 

[RDspaguy]

Depends on the flow rate. Get a cheap multimeter and test the amps, they're less than $20 at harbor freight for a disposable. As I said, if you have voltage and continuity (ohms) then you have amps going somewhere. If that somewhere is the heater element (10 ohms or so) then it's making heat. I suspect it is heating, but it's going to take it a loooong time to get hot. You're trying to heat 8-10 hot tubs worth of water with one hot tub heater.
Does it have an autofill?

 

[swamprat69]

I think it works out to about a 1 degree temperature rise every 1 1/2 hours. With no temperature losses. That's if my brain is still working ( just go back from a week with my 2 granddaughters ) !

 

[Caver01]

We have a good news bad news situation. First, the good. I ordered a new heating element for $149. Figured it was worth the risk. Put it in and we have heat! For the first time since June, I actually have a pool that is delivering warm water. Estimates above were accurate. . . about 1 degree per 1.5 hours. The new element went in at 5pm and it was 72F. By 11pm we were at 76, and by 8:30am the pool was at 82. Took a nice swim then checked the thermostat.

I guess the challenge now, as it probably is with other Endless Pool owners with older analog heat controls is how to maintain a desired temp. The pump/filter needn't run 24/7, so it's an added challenge to optimize running the pump+heat to maintain water quality, while adjusting the thermostat to maintain temp, assuming it runs long enough to reach the dialed setting.

Now the not so good news: After my swim, I realized that 82 is plenty warm for a workout--perhaps even too high (but now I know what it takes to get there). So I decided to dial back the thermostat. Of course, once I turned it down past the current temp, it clicked off. . . but that threw the breaker.

Now that I have a working heating element, I have a new problem--it still trips the breaker when the set temp on the thermostat is reached. If I never run the pump long enough to reach the set temp, fine, but that's pretty unrealistic given the effort it takes to get me there. I need a working thermostat (or rather, a working circuit). Now, as has been suggested above, I am probably also troubleshooting the GFCI which is getting triggered when the heater shuts off.

 

[Caver01]

For anyone following along, I know it is nice to see outcomes of troubleshooting, so I am going to keep posting updates. Skip to the TLDR if you just want the current state:

After replacing the heating element as noted above, the pool continues to heat nicely. We are not actively swimming every day, so it is easier to maintain stability at this point. We run the pump/filter a few hours midday and again around midnight for several hours. My observations on temperature is that once it has reached a target after running continuously, I can go back to the timer-based filter intervals (twice per day for a few hours each) and it increases the temp about 1 degree per cycle. This aligns with the estimates posted above, but it also means my water is getting warmer and warmer now every day. The pool lives with the security/insulating cover on unless it is being used. This contains the humidity and prevents evaporation, but it also holds the temperature. It’s in the mid-50s in Portland, OR these days, but this being an indoor pool that is half in-ground and half inside a crawl-space, it is also wrapped in insulation down there, so it only loses about a degree per day with the heater off—maybe even less than that.

Today, the pool is at 85! I shut off the heater at the switch and we will run like this for a few days while I monitor heat retention without the heater on. This is also the only way to prevent the GFCI from tripping. Previously, any time the heater was turned off while running, it would trip the breaker. After cleaning the contactor coil again, the breaker survives when the heater shuts off due to low-flow sensor. In other words, it now reliably runs for the few hours while the pump is engaged via the timer. But, as soon as I adjust the thermostat to stop the heater at a given setting, that cutoff trips the breaker.

I have already swapped the 30-amp breaker with the labeled for use by my pump as suggested above with no change. Given some improvement resulted from cleaning the contactor, I decided to order a replacement conactor, as this is a relatively easy/cheap part. 20 years on the original contactor seems reasonable, so I figure it’s not a bad step to take. If that does not improve things, I may need to try replacing the thermostat I suppose. . . then bring in an electrician to help troubleshoot GFCI sensitivity or isolate where/why the heater is leaking current to ground when it switches off. . . but we are getting ahead of ourselves.

TLDR This is not quite finished, but improving. New heating element is working great, heater only tripping the breaker when thermostat shuts it off. New contactor coil replacement coming. . . will try that in the next day or so.