hot tub circuit board

[1hunt2fish]

I am troubleshooting a 240V hot tub circuit. The problem is (I think) that the heater is getting about 30V when it is supposed to be off, and tripping the overheat relay, after a few minutes. When the heater is on, I see 240V across the leads, at the heater. When the overheat is tripped, I see 0V across the leads. When it is supposed to be off, I see 30V across the leads, and going from each heater lead to the neutral supply wire, I see 120V on one, and 90V on the other. I already replaced the relay, feeding the heater. Where else would this voltage be coming from? I do not have a schematic.

 

[davenn]

hi there
welcome to the forums

You may have to try and draw out a circuit as accurately as possible
else its pretty difficult for us to see what is going on
a couple of good sharp photo's of each side of the circuit board would be a great help too
and some labling to show power in/out connections etc

Dave

 

[1hunt2fish]

a little more info

here is a pic of the front. Not a lot of help, I'll see what else I can come up with. Kind of hard to work on, because I need to keep it running, so it won't freeze.

 

[KJ6EAD]

Have you checked the price/availability of a replacement board yet? If the problem can be isolated to the board and not some other fault, that may be the best option since the board has some liquid/corrosion damage. Usually, where there's some visible corrosion, there's more hidden.

The 90V seems like it could be the drop through the heater element. It looks like you have a separate relay for each phase. There could be a problem with the other relay or a driver transistor that controls it.

 

[1hunt2fish]

Another picture

I can't find a board, and even if I could, they run $3-400, and I can buy a new control pak for about the same price. I'll attach a schematic of a 240V heater circuit. It should be pretty much the same as this circuit.

 

[AffordableHotTubRepair]

Looks like a Balboa circuit board. If you can provide the number on the white label on the chip I can provide you wiring diagrams (schematics are not available). I can also tell you if a replacement board is available.

One side of the heater will always be hot (120V). When the heater relay closes, the other leg of 120V connects to give you 240V across the element.

With power to the heater, check between the water in the tub and a known good ground. (Literally stick one probe in the water and one probe in the ground if necessary) If you have voltage in the water you have a grounding problem and should address that before anything else.

30V across the heater is most likely not causing the high limit to trip. If your problem is an error message such as 'HH' or 'HL' you should be looking at water flow through the heater or at the high limit sensor or the circuit board itself.

You can avoid freezing by keeping the pump running on low speed and hanging a 100W light bulb or other heat source in the equipment area until you resolve the issue. Alternately, you can winterize the tub by draining it completely and sucking/blowing the residual water out with a shop vac. You should also disconnect any plumbing you can in the equipment to completely drain all components.

 

[1hunt2fish]

thanks

Thanks for the reply, that info is helpful. I'll check those things you suggested. The error message is OH and the reason I think it is the heater on when the pump isn't running is because if I run it constantly, it will not error, or even if I sit in it, with the cover off in standard mode (comes on every few minutes to maintain temp), it runs often enough that it will not OH. Also, ever since this problem started, when you are sitting in it and it kicks on, you can feel a short burst of extra-hot water about a second after it starts running, which is the water sitting in the heater area while it is off. The time it OH errors is after it shuts off, and sits for more than 10-15 minutes.

 

[AffordableHotTubRepair]

The picture shows the system uses a pressure switch to detect flow through the heater (two prong connector on the left side). The pressure switch should prevent the heater from coming on when there is no water flow through the heater manifold.

If the pressure switch is stuck closed or adjusted incorrectly, it can cause the heater to come on when the pump is not running and will cause the problem you describe. If the pump is set to run continuously, the problem will not trigger an error.

The pressure switch should be open when the pump off and closed when the pump is on. More specifically: open when there is no water flow through the manifold and closed when there is water flow.

Be certain to remove the filter while troubleshooting. A dirty filter can allow enough water flow to activate the pressure switch but restrict water enough to cause OH (overheat) errors.