Solenoid coil ????'s

[SS MAYFLOAT]

The company I work for installed a rebuilt shake/sundae machine that was in my shop. I never got to fully check out everything on it before my unscheduled surgery.

These machines are somewhat complicated. Freon freezes the barrel in which the mix is frozen. Around the barrel is a coil in which glycol circulates. On top of the machine is the hoppers in which the mix is stored in until it is pumped into the barrel when the product is served. Simple as mix in equals mix out.

The hoppers are kept cool by the glycol that circulates around the barrel and then circulated around a coil for the hopper. Just a simple way to transfer heat/cool. Each side is independent of each other, but is controlled by one mother board and control.

Everything was going good up until the sundae side hopper kept raising in temp. Shake side is okay. There is a liquid line solenoid for the glycol that opens when calling for cooling or shuts off when temps are satisfied.

I have 208 volts going to the solenoid. I pulled the wires and checked continuity, I have resistance. Here is my problem, when I put my amploc on the line to measure the current draw, it is "0". No draw at all.

I've been doing service work a long time and have never encountered a electrical coil that measures out okay, but does not show a current draw. I'm thinking (hoping) that the coil has broken down and not providing the proper current to fully open the solenoid.

My main question is shouldn't I get an amp draw when that coil is energized? I do get a reading on the other side of .3 amps. The resistance on both measures the same??

 

[Splat]

Re: Solenoid coil ????'s

208 volts AC or DC?

If your reading dc voltage your amploc may not be able to read DC current. Just a thought.

And yes I would expect to see a draw when the coil is energized. Dumb question have you tried tapping on the solenoid lightly with a blunt object? Perhaps it's stuck or frozen closed?

Can you plug the wires from the working solenoid into the one of question just to see if it opens?

Bill

 

[jlinder]

Re: Solenoid coil ????'s

Something sounds very odd. You say you have voltage on the coil and measure resistance. Some thoughs:

1. Try putting a screwdriver by the solonoids to see if you get any magnetism when energized. Just another piece of info.
2. I assume the resistance is the same on both solonoids.
3. What about swapping solonoids?
4. Could the current draw be so low your meter does not register?

 

[SS MAYFLOAT]

Re: Solenoid coil ????'s

Right after I posted this, my boss called me back up and told me that the machine went into its heatmode which is a pasteurization process that happens when the store is closed. The worker that went by my list of perimeters to set times, temps, and viscosity settings. He made the mistake of setting it on the right AM or PM.

The machine in 40 minuets in heatmode had already heated the mix up to 160*F, even in the hopper I'm having trouble with. This sorta surprised me as why would the solenoid let the heated glycol through to the hopper.

At this point, I'm thinking I have a bad thermistor that is out of calibration and is out about 6*. The mix in the hopper would not rise to room temp but only hover at 43 to 44. Set point for the solenoid to cut out is set at 36 and cut in is at 40.

Yes, I put my screwdriver up beside the coil and could feel the draw of the magnetic field. Line power is 208ac 3ph.

I'm released to go back to work Monday (Yahooooo!!) so I can actually work on it without breaking docs rules on the restrictions. Thanks for the help, but I still don't know why my meter will not pick up the amp draw on the one and not the other. Gremlins must be the cause

 

[Splat]

Re: Solenoid coil ????'s

Good luck, and remember not to let the magical smoke out of it, electronics don't wirk without the magical smoke.

BIll

 

[stevenj]

Re: Solenoid coil ????'s

Besides putting a screwdriver to the coil stem to check for magnatism,
take your amp meter and open the jaws then put the open jaws in the vicinity of the coil ,the magnetic field created will cause a noticable reading
on your amp meter, Note that the reading does not indicate the amp draw of the coil but shows there is magnatism. This method has not failed me in the
27 years I have been in HVAC/R,

add on; check with your hvac suppliers, If they sell danfoss, they should be able to get you a little tool that goes on your key ring , is a little pinwheel
indicator that spins, when layed on top of a coil stem

 

[SS MAYFLOAT]

Re: Solenoid coil ????'s

Today was my first day back to work and that machine was the first thing I tackled. The machine was in heat mode when I arrived. I took the stores pyrometer and probed the mix and compared it to the reading on the machines display. It was of 2 degrees. I then aborted the heat cycle and put the machine in to the standby mode. As the temps came down, there was an increase in difference between the pyrometer and the machine. Once it got to 43* it stopped, but he pyrometer continued to go down.

I put a new thermistor in the hopper and the display now reads the correct temp. When you have so many different systems that work together, you can't get stuck on thinking it has to be that system. Even the factory tech kept saying it had to be that solenoid. I did take another reading with the amploc with a different meter and got a reading.

The machine that was taken out was condemned by the factory distributor for a leak in the barrel. I pulled the panel off and removed the filter. The condenser coil is 95% clogged. The service valve caps still have the dirt and fuzz on them where they were never removed. So how can he say there is a leak when the coil is clogged? Geeeesh a kid out of tech school would have seen that one. No wonder it didn't freeze down in its allotted time.

Thanks again the machine is working great. Now to rebuild the one we just replaced this one with.