I need help dropping current though a water solenoid valve. I have a dauquiri machine that needs water running through it when the compressor is on. Rather than have to turn on/off water manually, I added a 110v water inlet valve that gets power only when the compressor is on. The valve is a generic one for refrigerators that has 2 spade plugs and a 110v coil. Perfect for my use. My problem is with direct 110v AC the 188ohm solenoid gets super hot after a few minutes. I shut it down at 250 degrees. I now realize the refrigerators must have a regulated circuit to power these with low amperage at 110v. My amp gauge shows about 600ma when directly powered (getting super hot), BUT I got it down to ~260ma by wiring a 6 watt light bulb in series and the coil buzzes but still seems to open enough and stays completely cold. I don't want to have a hot/fragile 6 watt light bulb inside my machine. Is there an easy way to use some kind of inductor to drop current without generating heat and wasting power? I know there is some way to calculate it with my known coil impeadance. I don't want to make a whole circuit just to power this thing. I am temped to find one that is 12v DC and use an old wall wart to power it but then that one may get hot too since I am sure a 12v one would have a very low impeadance anyway. Plus I already found & bought all the fittings to plumb this thing inside my machine.

 

I added a 110v water inlet valve

Do you have an info on that valve (data sheet, etc.)?

Since its for a refrigerator, it's likely designed for intermittent, not continuous duty.
So you either have to add a resistor to lower the voltage/current for continuous duty, or buy one designed for continuous duty.

The light bulb resistor is better than a fixed resistor since it has a low cold resistance which helps pull in the solenoid when power is first applied.
You might want to use one a little larger than the 6W you used so that it doesn't buzz.
A larger bulb will actually run cooler for this application.

You could add an inductor in series also, but they tend to be expensive.

 

Measure the DC-Resistance of the Coil.
Purchase a ~10-Watt Power Resistor with a value of approximately half of the DC-Resistance of the Coil.
Solder, and properly Insulate, all open Wires.
It will probably work for ever,
excepting the fact that an Appliance-Valve is automatically going to be relatively low-quality junk.
.
.
.

 

Obtain a 120v DC coil relay and a small bridge rectifier to feed it and cure the problem.

 

Do you have an info on that valve (data sheet, etc.)?

Since its for a refrigerator, it's likely designed for intermittent, not continuous duty.
So you either have to add a resistor to lower the voltage/current for continuous duty, or buy one designed for continuous duty.

The light bulb resistor is better than a fixed resistor since it has a low cold resistance which helps pull in the solenoid when power is first applied.
You might want to use one a little larger than the 6W you used so that it doesn't buzz.
A larger bulb will actually run cooler for this application.

You could add an inductor in series also, but they tend to be expensive.

I don't have any data on this since it was meant to be a standard part for GE/Kenmore, etc. refrigerators. I have an ice machine same kind of 110v water solenoid that runs a lot of water during cleaning cycle and it never even gets warm. I was thinking the same thing for the light bulb. I remember they rise in impedance when they heat up. I just can't trust one being inside this machines covers. I even thought of just mounting one inside but if it were to blow the water would stop, and I would quickly overheat the compressor. For reliability and low heat i even thought of a ~60watt LED light bulb, but then I would lose the variable impedance.

 

Measure the DC-Resistance of the Coil.
Purchase a ~10-Watt Power Resistor with a value of approximately half of the DC-Resistance of the Coil.
Solder, and properly Insulate, all open Wires.
It will probably work for ever,
excepting the fact that an Appliance-Valve is automatically going to be relatively low-quality junk.
.
.
.

Yeah, I have a grab bag with thousands of resistors and an assortment of capacitors, etc. but my resistors are all the standard 1/4 watt ones. I have had to parallel several before to increase wattage. I may even just try that if I have too.

 

Obtain a 120v DC coil relay and a small bridge rectifier to feed it and cure the problem.

I do have a bridge rectifier in my parts bin. I guess I could find out what current limiting resistor it would need and give it a try. I imagine this solenoid would work with DC. It works with an inline single diode, but buzzes at 30hz DC

 

don't have any data on this since it was meant to be a standard part for GE/Kenmore, etc. refrigerators.

If it is used to fill the ice maker or dispense cold water, it is not for continuous duty.

 

110v AC the 188ohm solenoid gets super hot after a few minutes.
I do have a bridge rectifier in my parts bin. I guess I could find out what current limiting resistor it would need and give it a try. I imagine this solenoid would work with DC. It works with an inline single diode, but buzzes at 30hz DC

Resistance of an AC solenoid is no indication of the final current.
Also, an AC solenoid that does not completely shift over to the engaged position will heat up excessively.
Do not use DC on the solenoid, the resistance is too low.

 

For reliability and low heat i even thought of a ~60watt LED light bulb, but then I would lose the variable impedance.

You said you used a 6W bulb and it worked but buzzed, which would indicate the holding current is marginal.
Try incandescent bulbs in the 10 to 20 watt range and see how they work to reduce the temperature rise of the coil while eliminating the buzz.

 

If it is used to fill the ice maker or dispense cold water, it is not for continuous duty.

I know, but my point is that they run for several minutes without issue. This thing is too hot to touch after 2 minutes. These must be meant to run though a current limiting circuit. I gave up and just ordered a 12v one that I will power with one of my 100 leftover DC wall adapters. I will probably run it with a 9v adapter. Some reviews of the 12v one said it also gets hot with 12v continous power, but can operate as low as 7v-9v and stays cool. I started with a 110v one to TRY and keep it simple to just power it off an existing 110v circuit. I have done this before with adding 12v PC fans to appliances using 9v wall warts so they run quiet. I will have to get some fittings and replumb and throw the 110v one in my parts bin.

 

they run for several minutes without issue. This thing is too hot to touch after 2 minutes. These must be meant to run though a current limiting circuit.

No.
If the are used in a refrigerator, that they do not need to be designed for continuous duty, since the water outlet is never activated for more than a minute or two at a time.

 

Resistance of an AC solenoid is no indication of the final current.
Also, an AC solenoid that does not completely shift over to the engaged position will heat up excessively.
Do not use DC on the solenoid, the resistance is too low.

I gave up and ordered a 12v DC solenoid. That resistance will be much lower according to a reviewer on Amazon but I will power it with a little 9v wall adapter.

 

I gave up and ordered a 12v DC solenoid. That resistance will be much lower according to a reviewer on Amazon but I will power it with a little 9v wall adapter.

The resistance of a DC relay coil is much higher compared to its AC counterpart for the same voltage level.
It is inductive reactance that limits the current on the AC version.
AC devices such as relay and solenoid coils possess lower efficiency than their DC counterparts.

 

AC devices such as relay and solenoid coils possess lower efficiency than their DC counterparts.

It's not clear to me why that should be true.
It would seem limiting the current with inductive reactance, would give lower power loss than limiting it by resistance.

 

It is generally recognized that the only time AC inductive devices, relays solenoids have the edge is at pull in time due to the very high current at this point.
But if there is any cause for the armature not seating properly or someone forcing an AC solenoid armature out of position, it usually results in a coil burn out.
A case in point, I did some major conversion of a manuf plant, i.e. convert relay logic panels to PLC, in the process, all the AC solenoids/coils were converted to DC.
(The factory maintenance dept Had a Very large inventory of spare coils !)
10 yrs on, they had not replaced one DC coil!
They should have got the hint, all the machines of European origin they had on the plant used DC coils, not one had ever been changed.
Incidentally in specifying control parameters for the company that were having some custom machines manuf by a 3rd party, I got some push back from their engineering dept who were reluctant.
By way of, "We have always done it this way!" (AC) ! ,

 

To be able to utilize the present solenoid, which is intended for only intermittent operation, it will need to cycle off and on. The efficient scheme will be to add a series thermostat to sense the cooling water temperature, and switch the solenoid off until the temperature in the heat exchanger rises some amount. This will also reduce water consumption. Or you can use a dual timer to run the valve for a few seconds out of every minute. That will be simpler and more efficient as well. And probably much easier to implement.