Same flood different problem

[GPster]

This time it's electrical and Hot tub related. The control panel for our hot tub is powered off a transformer, Don't know what the secondary voltage is supposed to be ( the only identfication on the transformer is Made in Mexico ) but it primary voltage is 120.  Now this hot tub is 240 Volts with a neutral so it has 120 volts in there also. This transformer is not shorted to ground but there doesn't appear to be any resistance across the windings. There is no continuity between the primary and secondary windings but my cheap little tester shows full continuity across the primary windings and accross the secondery windings. This should be reading something other than full continuity in the windings of a transformer, right. The ground-fault breaker didn't want to stay. It was tripping as soon as you turned it on. The pump was wet and I blew it out and by itself  the breaker will stick. The blower reads on my meter the same as the wet pump did. I haven't figured out how to blow it dry yet. I may set a resistant heater next to it, but with it unplugged the breaker will stay. The control system (printed circuit) showed continuity through it to ground and I checked each component separately and the only one that showed to ground was the transformer. With the transformer out of the circuit the breaker will stay. When I checked the transformer it wasn't grounded to its case but it does show full continuity accross it's primary winding. Now because this transformer is 120 volt primary it is taking one side of the 240 volts to neutral  and as best as I can tell the neutral is grounded so I'm showing direct continuity from that one side of the 240 to ground through this transformer. There should be resistance through the windings of a transformer shouldn't there? This transformer was under water and it is not the encapsulated kind so I'm hoping I've found the problem. I'm just not sure of the idiocyncracies of electrical components. My wife has Fibermyalgia and the hot tub would help her comfort but I don't want to electricute her. GPster

[MrMopar64]

I can't help you with the readings..... but could you get this tranformer out and say put it in an oven with low heat and maybe dry it out inside then see how it acts...

Just a thought

MM64  

[enjenjo]

Yes, a transformer should have resistance across the primary winding. But with an AC transformer, you may need a pretty sensitive meter to measure it. It may only be 5 or 10 ohms.

[GPster]

Resistance and ohms is the part that confuses me. If I touch the probes of my meter together I get the same reading that I get when I go accross the windings of the transformer. I am electrically savy enough to read that as a dead short but knowing the design of a transformer I wonder, should/shouldn't it be? With a computor controlled furnace and no door bell I'm at a loss for having another transformer around to compare readings (checking a 12VDC ignition coil might throw too many variables into the equatin). I do have an oven with a 170 degree warming section and I know how to work it. I probably should go to the library and educate myself but I'm plumb out of work clothes and I'm doing laundry. I could go past church on the way to the library and pray for it but the bishop will be here Friday. Oh yea, I won't we're headed to Fort Wayne. To complicate matters even more I need to take our Jeep to the dealer for survice before the trip. GeeeeeeeeePster

[Cword]

The primary side of your transformer can look as if it's shorted, ie very low resistance. Transformers resist curent flow with "inductance" rather than resistance.  There should be no continuity between primary and secondary windings.

I've grabbed a few transformers off the shelf here at work, primary winding resistances vary from 1 to  26.7 ohms depending on the type of transformer.

GFI breakers open when they detect trace current leakage from the circuit to ground.  Essentially what they do is compare the current being supplied to the circuit on the hot(black) wire to that returning on the Neutral(white) wire. If the current on both wires is not identical the breaker opens.  That discrepancy in current is usually caused by moisture or a person in the circuit presenting a leakage path for current to go to ground rather than returning via the wiring.

mike

[GPster]

Comparing what people know to what I think I know the transformer is probably not the problem. Reading what I wrote last night with all this new found knowledge the problem is probably still moisture between the white wire that was pulled in for the 120 volt circuit and the ground. I was hoping to get this thing running because everything I might gain by circulating air with a fan during the day is lost to condensation at night and the fog til 10:30. There seems to be a differance between being retired and being dis-abled retired. Boy, I'm glad I started driving again. Thanks all! I wish I could get back to thinking I'm helping rather than asking for help. GPster

[Bruce Dorsi]

Here is another instance where someone has already answered your question, Joe!  ......While I was down in my basement measuring the resistance of some transformers, Mike was posting a reply.


I have some new 120v/24vac 100VA transformers as spares for carwash equipment.  They test as such:

Resistance across Primary leads = 4.3 ohms

Resistance across Secondary leads = .9 ohms


Do you have a schematic of the hot tub?  .....Maybe that will indicate the secondary voltage of the transformer.    .....Can you call the tub manufacturer/dealer?

Many HVAC transformers are 24vac, but if the transformer is powering just solid-state circuitry, the voltage may be less.  ....Solenoid valves or relays are usually powered by 24v.

Does your transformer have 4 leads coming out, or does it have screw terminals?  .....If it has screw terminals on a fibre strip, sometimes the VA rating and Sec voltage is embossed into the fiber strip.

[GPster]

And the answer seems to be. If you take a water logged transformer and put it in the oven at 170 degrees for one hour and then let it cool to room temperature ( which is 72 because the furnace and central airconditioner are working OK) it will check exactly the same. But because you have spent this time typing instead of working on it, it will have fixed itself. The blower still kicks the GFI But maybe with the hot tub working that action will happen some other way GPster