Hot tub heater troubleshooting issue

Rig84

Member
Location
Maryland
Occupation
Electrician
Hello, first time poster here, I'm hoping someone can help me out. I have a hot tub heater (watkins no fault 240v 6kw) that isn't heating. The odd thing is most of the information I have found online, as well as the hot tub manufacturer tech support, claim that this heater will work at 120 volt at 1500 watts. That's the way it currently wired. I have 9.6 ohms resistance through the heater, 119 volts, and it's drawing 11.75 amps. Yet it still isn't heating. Tech support said that it sounds like the heater is bad, but it doesn't make any sense to me that all the electrical values are in acceptable range. I'm curious if the heater is only good for 240 volt installation, as that is what the tag says. Tech support told me it would work either way. Do any of you guys have any thoughts on this? Also, the circuit board and relays appear to be doing what they should. the indicator light is on that calls for heat and I have power where it should be. Any input will be greatly appreciated! Thanks in advance!
 

kwired

Electron manager
Location
NE Nebraska
Hello, first time poster here, I'm hoping someone can help me out. I have a hot tub heater (watkins no fault 240v 6kw) that isn't heating. The odd thing is most of the information I have found online, as well as the hot tub manufacturer tech support, claim that this heater will work at 120 volt at 1500 watts. That's the way it currently wired. I have 9.6 ohms resistance through the heater, 119 volts, and it's drawing 11.75 amps. Yet it still isn't heating. Tech support said that it sounds like the heater is bad, but it doesn't make any sense to me that all the electrical values are in acceptable range. I'm curious if the heater is only good for 240 volt installation, as that is what the tag says. Tech support told me it would work either way. Do any of you guys have any thoughts on this? Also, the circuit board and relays appear to be doing what they should. the indicator light is on that calls for heat and I have power where it should be. Any input will be greatly appreciated! Thanks in advance!
Sounds like it is working to me. Maybe a little low on amps, but still well within likely tolerable ranges.

It will take some time to heat the entire tub, as in maybe 24 hours or more to reach set temp. If you starting out with pretty cold water you probably won't even be able to feel any heat in the discharge side of heater, but that kind of current is making heat somewhere and if not in the element then some really bad connection shouldn't last long at all.

Other thing is to make sure you don't have the jets "on". The pump on high speed (or the separate jet pump) will draw too much to be able to handle the heat at same time, many these are designed they won't heat while jets are on for that reason. They only heat during down time, there may be a delay before it will start heating so be patient. It will automatically kick on heating pump or if only one pump will kick it on at a low speed while heating.

As far as using the 240 volt element on 120 - simple Ohm's and Watt's laws apply. If you only apply half the volts to a fixed resistance you get half the current but 1/4 the power.
 

Rig84

Member
Location
Maryland
Occupation
Electrician
Sounds like it is working to me. Maybe a little low on amps, but still well within likely tolerable ranges.

It will take some time to heat the entire tub, as in maybe 24 hours or more to reach set temp. If you starting out with pretty cold water you probably won't even be able to feel any heat in the discharge side of heater, but that kind of current is making heat somewhere and if not in the element then some really bad connection shouldn't last long at all.

Other thing is to make sure you don't have the jets "on". The pump on high speed (or the separate jet pump) will draw too much to be able to handle the heat at same time, many these are designed they won't heat while jets are on for that reason. They only heat during down time, there may be a delay before it will start heating so be patient. It will automatically kick on heating pump or if only one pump will kick it on at a low speed while heating.

As far as using the 240 volt element on 120 - simple Ohm's and Watt's laws apply. If you only apply half the volts to a fixed resistance you get half the current but 1/4 the power.
Thanks for the reply! This thing is driving me crazy!
It's been running for about 24 hours and still no change in temperature. The heater itself and the water lines going in and coming out of the heater are cool to the touch, I don't feel heat anywhere. The jets are off, only the circulation pump is on, which I believe needs to be on to distribute the heat. As far as the connections go, all connections that I can access are good, and it is drawing a continuous load of 11.75 amps. Do you have any other thoughts?
 

Rig84

Member
Location
Maryland
Occupation
Electrician
The current is close enough to correct, unless you are including the circulating motor in that amperage as well.
Heater amps via ohms law would be 12.5 amps @ 120 volt.
Hot tub covers are all on?
Thanks for the reply!
The circulation pump amperage isn't included, the 11.75 is strictly on the heater. The cover isn't on, something I really didn't consider. The person who has this tub bought it used and without a cover. They wanted to get it running before investing in one. Does the cover have that much to do with the heat? The heater itself is cold to the touch as well as the water coming out of the heater.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Is the current identical on both ends of the element? Is there a GFCI involved?

It's possible that the element has an internal leak to ground, the water, etc.

Perhaps disconnect one end at a time and check for current on the other wire.
 

Rig84

Member
Location
Maryland
Occupation
Electrician
Is the current identical on both ends of the element? Is there a GFCI involved?

It's possible that the element has an internal leak to ground, the water, etc.

Perhaps disconnect one end at a time and check for current on the other wire.
Thanks for the reply!
Yes, the current is the same on both wires 11.75 and it is coming from a 20 amp GFCI
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Then it should be heating, even if very slowly. Curiouser and curiouser.

I wonder if an element could have an internal break that is arcing without heating. :unsure:
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
The cover is extremely important to reduce heat loss, also make sure all air jets are closed so no cold air is being inserted into the water.
 

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician Semi-retired
I believe it is heating, but so slowly that the heat is lost right away. You need either better insulation and cover, or a 240 volt circuit.
 

Rig84

Member
Location
Maryland
Occupation
Electrician
The cover is extremely important to reduce heat loss, also make sure all air jets are closed so no cold air is being inserted into the water.
I could try closing the jets, I suppose. But I'm still confused as to why the heater itself is cool to the touch. I'd think that the heater and/or the water line leaving the heater would at least be warm, but it isn't.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
Should the heater be warm? Or at least the water leaving the heater?
Depends on how cold your water is entering the heater and the length of piping before it enters the tub. Have your tried using a non contact thermometer instead of your hand?
 

Rig84

Member
Location
Maryland
Occupation
Electrician
Depends on how cold your water is entering the heater and the length of piping before it enters the tub. Have your tried using a non contact thermometer instead of your hand?
I haven't tried a thermometer, I was just feeling by hand. Where the water immediately leaves the heater it feels cold, so that just seems wrong to me. I will try with the laser though to see if there is a difference.
 

Rig84

Member
Location
Maryland
Occupation
Electrician
Most heaters are connected to a flow switch that won't allow the heater to work if there is no flow. I don't know about the heater the OP has.
This particular heater doesn't have a flow switch, at least not that I can tell. But the circuit board is calling for heat and the relays are operating properly and the voltage and current are both present at the heater wires. So even if it did have a float switch, it would seem to be working. Otherwise, I don't think it would call for heat, but I'm not too sure. This one really has me stumped.
 
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