Gatsby spa is out of business, maybe for this reason. This is the wiring design I need to change it. By this diagram the heater is on whenever the thermostat says it is cold and 24 volts are supplied to the relays. Note the pump is not on. This design relies on the High limit switch to kill relay power when water temp exceeds the limit switch (set to 119 degrees). Every other manufacture would use the limit switch as a safety protection circuit. Normally the heater would be on only when water was flowing across the heater coil. This is a flow through type heater design. The power supply generates 24 volts Dc. All other power is 240 V Ac.

Any help would be appreciated.

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Hay there mate,
Not sure exactly what you are asking but what I can see your heat is controlled firstly by your thermostat secondly by a pressure which is detecting water flow through your heater and would be mounted on your heater which if circuit is completed heater will turn on. I presume low speed pump is used for heating and is plumbed through heater barrel and is controlled via time clock? The high limit switch I presume would be located on metal heater barrel, this links in to cut out all 24vdc voltage by the looks on control side. Normally the high limit switch cuts out heater in all cases I hope this may help you in some way. Happy to help you further with some more information.

Hi Scott. I moved this to Electrical before I saw spa & pool doc's reply.

We'll leave it here for now so our electricians will see it promptly too.

Your right about the pressure switch. I had a friend redraw this diagram which helped show me what is really supposed to be happening. My pressure switch is stuck on. It has been that way for two years now. The tub temperature has been regulated by the on then off switching of the high limit switch and the thermostat. This explains why the buttons didn’t always work. When the limited switches killed the relays the pumps would not work. And the problem of uneven heating the thermostat being at the foot well but the heater located near the water level. I have lined up my replacement parts and this weekend maybe I can restore this beast to normal operation.

The pressure switch is extremely important and should be replaced asap because, now if your high limit fails you will have constant non stoppable heating occurring causing pipes to melt and distort. Most spa control units by law here in Australia have to have 2 hi limits, 1 set at 45deg C and the other set at 48deg C. If your pressure switch is stuck in the on position that means the heater will come on when there is no water flow (if the thermostat sensor is sensing lower water temperature than what you have the dial set to) and start to boil like a kettle inside the heater barrel until the over temp limit is reached then cut out everything.So really it sounds like all you need is a new pressure switch, which will cost you around $40USD at a good pool shop.

I have been very lucky that my high limit switch worked as well as it has. My switch acted like a relay in constant use. As the primary safety circuit it would not get any use in it lifetime. I have bought another high limit switch. I had planned on replacing my original limit switch. But now I like making it a backup to the primary. It is set to 48 C / 119 F. It is adjustable. I think I will install it in series with the primary limit switch as a backup. My pressure switch is adjustable. Right now I think it is set to 1 lb threshold to turning on. It has a range of 1-5 The heater core is 2 1/4 ID (57MM). What pressure value should I set the limit switch to?

The pressure switch should be adjusted in accordance with your spas plumbing system and pump pressure. It should be adjusted using a normal muti meter set on continuity.AFTER TURNING POWER OFF FIRST), Disconnect wires off pressure switch, connect muti meter to both terminals SAFELY and set to continuity 0 ohms, your meter should read open circuit. Then turn pump on which should close pressure switch making your meter read 0 ohms (closed circuit) and slowly turn anti clockwise until pressure switch clicks and you have open circuit again. Then turn clock wise until you get pressure switch to click again (closed circuit) and turn a further quarter of a turn passed that position. Your pressure switch should now be set!

Thanks for your help. I can't tell you how nice it feels to be on track. I almost gave up on the spa pack. The tub is almost 12 years old. The neighbors I bought it from had not used it in three years. It has a nice shell with seating for five. It has 19 jets and was top of the line in its day. I thought what could be wrong. The first day when turning it on my GFI blew. I noticed the water damage on the internal decking, below the blower. When trouble shooting the GFI problem I noticed water running down the 240V power line from the Blower. When I talked to my neighbors I determined that some electrical hack had wired the tub without a GFI. Well that was two years ago. Since then I have replaced a 2 speed pump, two heater cores, one thermostat controller, 3 relays, 4 air micro switches, switches, 24 volt power supply, one high limit switch, and now a pressure switch. Granted there is nothing left but I have gone through the school of hard knocks of hot tub service. I have had some 19 good months of use. Now I feel I can enjoy reliability. It has been a long road without having someone to ask questions of. Gatsby the manufacture is long gone. My probing of local resources says they can’t help. The say all hot tubs are different. Yes that is true but the principles of operation are the same and power behaves the same way on switches and relays. You can take the part number off a relay and get a hit on Google. The internet has helped me rebuild this hot tub. And you have given me the answers I needed. Thank You.
Michael Scott, Albuquerque ,NM [email protected]

Thanks Scotty glad I could help!