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Thread: sundance sentry 724 heater help

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    sundance sentry 724 heater help

    I have a Sundance sentry 724 hot tub, yes I know it's a little outdated but I cant afford to buy a new one. Anyway, the heater on this baby stopped working for me a little while ago and I have been pulling out my hair trying to get it up and running again. I replaced the heater and the pressure switch; the pump, display, and temp sensors are working correctly. it was heating off and on kind of getting close and then not raising temperature for quite a while even with the new heater, I then replaced the pressure switch and instead of fixing the problem it made it stop heating all together. So, before I go any further into this pit of despair I thought it best to ask for some help, if anyone has any suggestions I would love to hear them. anything helps.

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    Mod Squad Jimrahbe's Avatar
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    Re: sundance sentry 724 heater help

    Happy,

    Welcome to TFP... A Great resource of all your pool and hot tub questions..

    I know nothing about your particular hot tub, but if this were my unit this is what I would do..

    1. Using a volt meter, I'd test the voltage going to the heater element. With the controls set to increase the temp, there should be 220 volts across the element. (Assuming this is 220 volt unit, 120 volts if only a 120 volt unit)

    2. If you have 220 volts across the element, and the spa is not heating then the element has to be open.

    3. If you do not have 220 volts across the element, then I'd test across the pressure switch. If the pressure switch is working (pump running of course) then switch would be closed and you should get zero volts across the switch. If you have 220 volts across the switch then it is not being closed.

    4. Your control panel must tell some relay to send power to the heater. You need to find this relay and ensure when the control panel calls for heat the relay is closing.


    That should get you started,

    Thanks for posting,

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

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    Re: sundance sentry 724 heater help

    So when you say crossed the element do yoy.mean the total voltage of both hot wires to the ground or around the coils loop itself

    - - - Updated - - -

    Attachment 58208
    Attached Images Attached Images

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    Mod Squad Jimrahbe's Avatar
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    Re: sundance sentry 724 heater help

    H,

    Assuming that is your heater... then between the white and black.. If that is a 220 volt input then between the two you should get about 220 volts. Each one to ground should be about half or 110 volts...

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

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    Re: sundance sentry 724 heater help

    it is my heater and I don't get any reading between the white and black wires at all. but I do get a reading of 118 volts per wire to the main ground

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    Re: sundance sentry 724 heater help

    I should also mention that my pressure switch is working properly. I get no reading acrossed it when it is running. If need be I can take a picture of my board and post it. If that will help at all. Its a pretty old hot tub so i know some of the stuffis goong to be tough to replace on it. Mostly the board is hard to find

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    Re: sundance sentry 724 heater help

    You must get 240v between the leads or the heater can not work.

    Testing each lead to ground does not work because power from one lead travels through the heater and back-feed into the other lead. 120v twice does not give you 240v, you must have 120v from each phase.

    You may have a bad relay on the control board or one of the safety devices not allowing the relay to close. You need to follow the circuit and test to diagnose the problem. Test each safety interlock to confirm that the high limit, flow switch or door interlocks are not the problem.

    How are you testing the pressure (flow) switch, testing for continuity? You say it has nothing across the leads, should it?
    Does it have continuity when there is no flow?
    Are you testing the switch with it disconnected so you actually confirm the switch is open when it should be, closed when it should be?

    On an older tub I would suspect a relay, they do eventually fail and sometimes create intermittent problems before completely failing.
    AGP 24' x 54" approx 14000 gal Full sun all day, Hayward 1.5 HP and EC50 D.E. filter
    Stenner 45MPHP10 10 gal/day fixed rate with intermatic ET1125C timer
    Dolphin E10 robotic cleaner, 330 gallon Tiger River Spa, Taylor K-2006C test kit

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    Mod Squad Jimrahbe's Avatar
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    Re: sundance sentry 724 heater help

    H,

    I am assuming your Spa runs off of 220 volts.. Is that correct?

    If so, and you measure 120 volts (118) between the white wire and ground, and the black wire and ground, and zero between the white and black wires, that means you are missing one leg of your 220 volts.

    I would follow the cable that has the white, black, and green wire back and try to find a relay of some type. I am assuming that the power to the heater only turns on when relay is closed. I also assume that this relay is controlled by some thermostat..

    So basically, the thermostat senses that it needs more heat, so it closes the relay, which applies power to the heater.

    You could have blown a fuse or circuit breaker in the 220 volt line, or the relay may be bad, or the thermostat is just not telling the relay to close.

    Thanks,

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

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    Re: sundance sentry 724 heater help

    I'm testing with a volt meter and a multi meter for all of these readings.

    It is indeed a 240v heater and system and each individual leg is running roughly 120v I'm jus5 not getting my accurate reading crossed the heater.
    The pressure switch is brand spanking new and has been tested by me while it's unplugged, running, disconnected and with the doors open at resting state. And I get voltage crossed it when the pump isn't running and it's still on when it is forced into rest mode since it will not stop pumping since it wont heat up.

    The board shows now burns or any real damage the breaker that it is hooked up to have been tested and reset but I have waited to pull my actual board out of it until I was sure I had to since I don't want to chance harming a piece that is so hard to find, But the relays on the board are not heating up and there is no arcing to speak of.

    I get a proper 240 across many other wires and combination but not across my two heater wires. Before the heater or at the heater.

    The only thing I am unsure of is if there is a way to test the hi limit and lo limit temperature sensors before I buy new ones to replace them. Since they are in the same clip with each other on the board it's hard to test just one.

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    Re: sundance sentry 724 heater help

    Attachment 58219
    Here is my control board I would assume the relays above the white and black wires would be the correct ones to check for this if that is where I am to go next. I know a good deal about computers and motherboards so I can check for damage to the actual board or capacitors but I am unsure of the correct way to test these relays, I'm assuming its similar to testing relays for cars though.
    Attachment 58220
    Just for posterity the tub is not running when I took these photos.

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    Re: sundance sentry 724 heater help

    Also if the red wire is tested with the white wire or the black wire I get 240v but not with each other

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    Re: sundance sentry 724 heater help

    So update on the tub, I still haven't gotten much further, but I think I'm going to replace the hi-limit sensor next.

    If that doesn't work I was hoping someone could point me to a place where I could get my motherboard refurbished for a decent price, since I am unsure if the replacement I am looking at will actually work for my system.

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    Re: sundance sentry 724 heater help

    I had the same problem with my sentry. Something shorted on the board. The coils for each leg were working but it wasn't getting 220v at the element. The main boards for this tub are hard to come by and very expensive! I used a jumper to power the dead leg after making sure all the interlocks still functioned.

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    Re: sundance sentry 724 heater help

    how did you jump it? From where in particular?

    I was going to try that but I was worried my heater wouldn't shut off if I did it from the wrong place, because that's an excellent idea before I order more parts.

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    Re: sundance sentry 724 heater help

    kill the power to the tub. Disconnect one of hot the wires to the heater. Power it back up and get the tub running so it's calling for heat. If your tub has open door switches you'll need to defeat them with a magnet in order for the tub to run with the doors open. Be very careful with the loose wire and don't let it ground. Once the tub is calling for heat test the voltage on the loose wire. If it has power the other circuit is dead. If it doesn't have voltage that circuit is dead. Trace the wires back to the panel and put a jumper on the dead circuit.

    Heres a a pic of it. The 4 silver terminals on the right are for the heater
    L1 and L2 are the inputs for the relays.
    H1 and H2 are the outputs to the heater.
    Find which one is dead and jump the correct one.
    If they're both dead don't jump both of them otherwise the heater won't shut off and the interlocks will not work.

    IMG_7937.jpg

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    Re: sundance sentry 724 heater help

    Make sure you have GFCI protection on the tub if you do this.

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    Re: sundance sentry 724 heater help

    This was extremely helpful. I can at least diagnose my problem now before I buy my next batch of parts

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    Re: sundance sentry 724 heater help

    Hooray!

    This did the trick but on the opposite heater and relay lead you have shown.

    Thanks a bunch everyone

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