Spa does not heat water

I have an old 120v spa. It had trouble previously, which I fixed by replacing GFCI outlet a couple of years ago.
It developed a new problem, which is t hat it does not heat water.
The pump, the timer etc, all work, but the water stays lukewarm (we have warm days). I set thermostat to the highest position, but it does not help. I am a reasonably electrically handy person (plz do not suggest to "hire a pro", at least yet), but I would like to know what typically goes wrong.
thanks
i
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Heating element.
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On Tue, 06 Jun 2006 02:21:13 GMT, Ignoramus11409

Could be the heating element.
Beacuse the heating element can be easily damaged in a matter of seconds by a lack of water flowing over it, most spas have a flow sensor that detects of the water is not circulating properly. This sensor will keep the heater element off if it detects little or no water flow. Could be as simple as cleaning the filters.
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Mys Terry wrote:

Some heaters have a little red pilot light on the end that tells you when they are on. And some heaters have a thermostat of their own, seperate from the temp sensor of the spa. These are set to high, as a back against overheating.
Basicly, you need to find out if power, 120V in your case, is getting to the heating element. In small spas, the heater is frequently located under the power pack, with the end accessible. They do fail from time to time. To replace it requires draining the spa, disconnecting the power, unhooking the wires from the heating element, and then unscrewing it. To replace, use teflon tape on the threads and reassemble.
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wrote:

thanks, will check it out, maybe tonight.
i
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Thanks. I will drain the pool, check the filters and will also check the heater with an ohmmeter.
If the heater is bad, and if there is enough room for a 220V heater (as opposed to a 115V heater that I have), perhaps I can put a 220V circuit to the spa and rewire it to use 220V heating. The issue that must be resolved before it is whether the flow of water from my current pump is enough to keep the 220V heater cool.
i
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Ignoramus8339 wrote:

I'm sure the water flow on the circulation setting is adequate if you did switch from 120V to 240V for the heater. It will heat 4X as fast, but that still amounts to a very small temp delta of the water flowing through the heater. The water coming out is barely noticeable as being warmer than the water going in.
However, I don't think I would fool around with trying to rig up the heater to work at 240V That typically would require going into the power pack, running 240V to the relay (assuming it's rated for that), etc. Unless you're 100% sure of what you're doing, you could create a lethal hazhard. It may be possible to get a whole new power pack for the spa that is designed for 240V.
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wrote:

That is overwhelmingly likely to be the case.

Well, surely it is important to either do it right, or not do it at all.
I could add a GFCI 20A circuit for 240V, and use the 120V output from my control (that used to feed the heater) to be the input to a appropriately rated contactor, that would switch 240V.
The only issue with this is that instead of one breaker going to the spa, there will be two (120V and 240V). So an unsuspecting person may think that by disconnecting one of the breakers, the spa is no longer powered, which would not be the case.
i
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Ignoramus8339 wrote:

Don;t know what other heating elements are available, but mine which can support either 120V or 240V uses 25 amps at 240V, 12.5 amps at 120. Would suspect yours is similar, as using 12.5 for the heater at 120V, leaves the remaining amps on a 20 amp circuit for the pump, blower, lights, etc., so somewhere around 12.5 amps for the heater at 120V makes sense. So, if it pulls X at 120V, it will pull 2X at 240V, meaning you would need a 30 amp 240V circuit to support just the heater.
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On 6 Jun 2006 10:20:49 -0700, snipped-for-privacy@optonline.net wrote:

You have things backwards. The higher the voltage, the lower the current. Ohm's Law.
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That is so when you have two circuits producing same power, but it is not true when you compare current going through the same resistor at different voltages.
I = V/R
i
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Mys Terry wrote:

Oh really? So if I put 240 volts across a 10 ohms resistor, I get half the current I would at 120V? They must have changed OHMS law and not bothered to tell me!
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OK, I think -- I hope -- that I have my answer.
I inspected the control system and heater tonight.
To my surprise, a 10 ga (at least) wire leading to heater was HOT to touch. (and carried voltage and current) I measured current, it was about 7-8A.
I found that the crimped connection of a 10 ga wire leading to a ring terminal screwed on the heater, worked itself loose.
I recrimped the connection (kept original ring terminal, just crimped it harder).
After that, the measured current increased to about 12A, which, I think, is about where it ought to be.
If that turns out to be the solution, I may replace the existing cheap wires with my beautiful 10 ga nickel plated, 200 degrees C rated military aerospace wire, of which I have a big spool.
i
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wrote:

IIRC, my spa on a 15 amp circuit. (and yes, I think that it is too little). There is both the pump, as well as the heater on this circuit. My spa is very old, it was actually not working well when I moved into the house due to malfunctioning GFCI.
I will check these heaters, I think that they are rated for 20A at 240V, not 25, but I am not sure.
i
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