COLD hot tub!!!

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  #1  
Old 02-11-06, 09:36 PM
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COLD hot tub!!!

Hello,
I recently had a used Morgan Hot tub (circa 1999) placed in my back yard. The unit appeared to heat ok prior to shipment but now the heater does not work (ran for 8 hrs with low pump on and no temp change). The jets appear to be providing adequate flow for the pressure switch and I checked the OHM's on the heating element itself (~11 Ohms). All of the other functions (jets and blowers) work just fine, just not the heater. There are no signs of a "dry burnout" condition as the heater shell appears "clean".
I measured the voltage on the heater from one contact to the shell and got ~120V, measured approximately the same with the other contact. So.. Just for grins, I disconnected both of the leads to the heater (which run into a circuit board) and checked the voltage at the circuit board leads which was approx 40 volts.
I also took the liberty of adjusting the screw setting on the pressure switch (2 turns out... or towards less pressure required), but this had no effect on the heating element (still did not heat).
Is there something else I can test/check? There does NOT appear to be a physical high limit reset, as the high limit switch appears to be a thermocouple (bound to the heater) that is connected to the circuit board via 2 wires. The spa panel also indicates that it is "heating"...
Any help is greatly appreciated!
 
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  #2  
Old 02-12-06, 04:59 AM
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There is usually a ThermoDisc somewhere on the high voltage wires, and usually the last connections prior to the heating elements. It should have a red button in the middle of it. Press it. If you hear a click the elements likely just came on. The amount of movement is so slight you would never know it moved so listen for the click sound. *Carefull around live wires.*

Using your ohm meter you can check the continuity on the pressure switch without messing around with the setting. The switch is set to as little a 2 pounds so small adjustments can have a huge detrimental effect. Use the ohm meter (disconnected) or a voltmeter (while connected and in use - careful.)

You also have a thermostat probe somewhere from the tank to the circuit board, or maybe to the thermostat dial itself, if it is a manual thermometer. Be sure it is intact. Without knowing the make/model of heater that's about as much as I can offer.

It's just a matter of tracing the voltage through the switches until you find the one not closing.
 
  #3  
Old 02-12-06, 08:44 AM
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Thanks for the reply md!
OK.. A little more info. The heater assembly is an RMF Related (flow thru) model # C2550-0802ET. The only connections directly to the heater assembly are 2 large wires that run directly from the circuitboard (Gecko Model # MAS-MSPA-4-P12-P21) and a ground wire. There is a pressure switch with two relatively small wires that terminate into the circuit board and a connector labeled "high limit" that also runs to an element (thermocouple?) that sits on top of the heater and is covered with a sheath.
I looked all over the electrical control area and could not find a red button (I would be jumping for joy if I found one). Could this switch be located by the spaside contol display? It is a digital unit and appears to display the actual water temp (59F) along with the desired temp (100F). There is an icon on the display that looks like a vertical squiggley line that I believe is an indicator that the spa is "heating".
If there must be a high limit switch somewhere I guess I'll have to remove the CB and look behind it...and also trace the circuit.
Does this new info help in diagnosing my problem? Thanks for your time!
 
  #4  
Old 02-12-06, 02:25 PM
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Some closure...
Removed the circuit board and voila... there was a burnt spot on the back side. It was on a power relay AZ2150-1a-24DEF. I'm going to get a replacement clean up the board (light filing) and then solder the new relay in and see what happens...
Tracing the circuit back from the heater worked for me.
 
  #5  
Old 02-12-06, 06:29 PM
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Glad you are making progress. I should also mention that the thermodisc with the red button could be older, and instead of a red button in the center there is a small spade like peice of metal to push. Sometimes it is situated where it can be reset without opening the unit.

But, it sounds like you are on to something. Keep us posted.
 
  #6  
Old 03-03-06, 10:02 PM
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Md,
-First of all- thank you for aiding me in diagnosing this issue (tracing the circuit was great advice, abeit semi-painful). I have since had a few enjoyable 102F dips in the tub... but...let it be known that sometimes there are NO mechanical resets. I am posting this for people who may be somewhat befuddled when asked to look for a switch or reset... sometimes they simply do not exist. When there are no red buttons or disks to reset, readers may be interested in the following:
Most of the details of my tub are listed in this thread and I will not delve on those... but here is what I did to correct the heating problem...
After searching the Internet for replacement parts (a $2 relay) I found that most of the suppliers had a minimum order requirement ranging from $25 to $35 (this is fair enough given that it's a unique relay)... so I thought I would check the relay myself to see if it actually needed replaced. I found the specifications via Google/Internet search and discovered the relay was a 24 Volt DC switch. I had the means necessary to run a low voltage power supply @ 24 volts across the switch (according to the spec) and it "clicked".
IF YOU DO NOT KNOW WHAT THE PREVIOUS SENTENCE MEANT, THEN DONT TRY IT! You may have to replace your Circuit board (heck, if it's burnt... replace it). All facets of your tub should work just fine after you have a certified spa guy replace the board.

Anyhoo, I knew the switch worked but did not know how it would operate under load...
Long story short, I soldered solder wick to the circuit board to complete the circuit. In a rush I pulled a trace from the board (this really leaves you with that.. uh-oh feeling...how am I going to fix this???), I resoldered the trace, and the dern thing has been working like a champ ever since! (I will do the proper thing and replace the board prior to the Southern winter). :-)

So...
1) Sometimes there are no mechanical switches that fix problems!
2) Do yourself a favor and have patience... Trace the circuit back but BE CAREFUL! 240V CAN KILL YOU! If you choose to diagnose your board then remove the power to it... ensure you have removed the power to it... and then trace the circuit back (through the circuit board) using the OHM function on your multimeter and checking for continuity... Again, IF YOU DO NOT KNOW WHAT THE PREVIOUS SENTENCE MEANT, THEN DONT TRY IT!

Hope this helps someone...
 
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