Adding a Run Capasitor to older Frige compressor?

[g3bill]

In a previous thread I was told that some newer compressors than mine are more efficent because of the use of a RUN capasitor? Question is Can I use a older compressor with just the start cap. and add the RUN Cap. or must I find that particular type compressor? I found this writing below that leads me to think I might be able to add a RUN Cap. If I can figure out the mf value, Right or Wrong? Seems like the run cap. can just be spliced in the start wire near the 3 prong plug into compressor?

["The run capacitor is used to improve the running efficiency of a compressor’s motor. The run capacitor is placed in series with the start winding of the compressor and will remain in the circuit as the motor operates. As current flows through the run capacitor and the start winding, it causes a phase shift of the motor’s current, thus improving the power factor of the motor"]

 

[cfz2882]

could reduce power usage some-would have to experiment a little to find one that gives a reduction in running current without causing adverse effects to the motor,probably something around 10-15 uf.I was going to experiment with adding a run capacitor to my '80 GE fridge,but inspection revealed adding the capacitor to the compressor with it's plug-on start relay would take more work than i wanted to do on a fridge that only pulls 2.7a anyway.My '77 kelvinator has a 1/4 hp compressor and that fridge pulls ~4.2a:if i place this fridge into DD use,will investigate adding the capacitor(i work in a motor shop so have lots of caps to experiment with)to see if i can get an amp or more of reduction in current use.

 

[g3bill]

THANKS FOR THE REPLY

I have the start and relay remote in front of frig on the '73 frigidair, too bad you didn't try this out already to make it easy for me Can you figure the run cap size by the start cap size, would hink they'd have to be kinda parallel in values like 2 &4 or 4&8 or percentage diff? just thinking out loud

I wonder if the cap needs to be between motor and start relay or before start relay if this makes sense.

So I dont know my horse power or even amps? can't see anything on the motor. guess you'd need a amp meter to see which size cap is best? Phil said his ('77 sxs frigidaire I think) is a 1/3rd hp so mine might be also?

Wonder what combo52 thinks?

 

[g3bill]

I was trying to find a diagram showing hook up to add a run capasitor, this was clearist I could find. I thought though in series meant spliced in one line. guess I don't understand the hook up just right? looks like just connecting to start coil and main coil before motor? See lower (cap. start / cap. run) diagram: http://ijyam.blogspot.com/2011/05/single-phase-capacitor-start-and.html

Any feed back appreciated...

 

[travis]

From what I understand, the value of a run cap is entirely dependent on the windings of the compressor.  Typically, run caps are now value, like 20 mfd or less.

 

Honestly, I am not really sure why you're trying to modify your fridge.  It's 40 yrs old.  Leave it alone.  I can understand trying to fix something, but you're trying to improve it.

 

[g3bill]

Adding a run capasitor is an easy fix to save some on electric current use on older friges I'm told, that simple. A capasitor costs a few bucks but just want to be sure I connect it properly for the use. U want your old style kitchen and I want my good old frig

 

[travis]

Bill,

 

I wish you the best.  Maybe John or his brother will chime in here with a suggestion.  I think the best someone will do is guess at a value.  My caution is that unless you know what you need, you're likely to harm the fridge that you're wanting to save.  I don't think that anyone is going to be able to give a certain answer.  Repair of something is entirely different than engineering of something.

 

If it were me, I would turn off some lights and let the fridge have some electric. 

 

[cfz2882]

run cap

the run cap is connected across the start switch contacts(either relay or mechanical)so that current flows trough the start winding and run capactor when switch contacts open-if a start capacitor is also in circuit,added run cap should be connected so start cap is out of circuit when switch is open.Another way to reduce power usage of the fridge is to modify the defrost intervals,disable any mullion or other small heaters that are not needed(these low wattage heat strips are to reduce chance of condensation forming under certain conditions)ON my '80 GE,i added a switch to disable the automatic defrost untill defrost is actually needed-a plexi window was added to back panel so frost buildup on the evap coil can be observed and defrost activated as needed-about once a month Door gasket fit can be checked and door insulation checked/improved as needed.If fan motors are worn and need replaced,they can be replaced with more efficient styles VS original inherently inefficient shaded pole originals for a few 10ths of an amp reduction in current.As suggested upthread,keeping uneeded lights,etc. off will probably save more on the bill than the fridge improvements/modifications,but if you like to play with old fridges...BTW,if this unit has a condenser fan is it an old Delco "inside out"external rotor style?

 

[g3bill]

Thanks for clearing up my mine?

Question mark after the condenser fan, not sure,,, its a heavy thing for its size, I've removed it a few times over the years to oil and runs fine. Looks like it was built to last 100 years...

I was searching for the power saving units they used to have at Home Depot, plugs in wall outlet and large appliance plugs into it, supposed to save something like 25-30% on current used but can't find it to read info. They were around $35-40 a few years ago. I don't know if they lowered the power output of a motor? They used to have a disply with a motor and the powersaver with switch, flip switch and motor got very quiet?

 

[g3bill]

Lower value safer than higher?

OK , Travis said I might damage the frige if perhaps I use the wrong value capasitor, I guess he means too large of one saying dont go over 20uf. Sounds inline with what cfz2882 said, he thought 10-15uf. Once I know the compressor HP and Amp draw then can maybe get a closer figure on the uf number without causing damage to frige. With some info my cousin might be able to get it close being a electrical enginner but sometimes I wonder Thanks for all the help.

 

[combo52]

Adding A Run Capacitor To An Older Refrigerator

This is a good question Bill, I have often thought of trying this myself, basically I would take an initial amp reading and see if it goes down with the capacitor, it is very unlikely that it would hurt anything unless the amp draw goes up.

You should also replace that nasty old condenser fan motor, older CFM usually had a amp draw of around .39 amps, newer High Efficiency motors draw .o4 amps or about 1/10 of the power and do the same job as the orignal power hog and last longer to boot because they run so cool.

If you are clever you can also replace the evaporator fan motor and go from about 30 watts of power draw again down to about 4 watts, and with the evaporator fan you really save because the waste heat from the EFM causes the compressor to run that much more.

You may also be able to change the defrost timer and make a real savings on power consumption by reducing how often the ref defrosts. Living in a dry climate this ref has always been defrosting at least four times more often than it really needs to especially when you consider that only your Mom uses it anyway.

 

[cadman]

Start Capacitors

It may take some searching, but there use to be Starting Capacitor Selection Units that were used to find just the right cap value for the motor at hand. It consisted of an ammeter, aligator clips and a series of toggle switches. You would flip each switch in succession until the motor kicked over, then you'd tally up the value. -C

 

[cfz2882]

just for kicks,experimented with a 1/6hp split phase motor:hooked a 15 uf capacitor across the start switch-no-load current went from 3.9 without the cap to 3.1 with the added capacitor-pretty impressive reduction!Though my '77 kelvinator is not in a good position to play with right now,a 1991 GE/kenmore is and i might check that one and see if it will be decently easy to add run cap and reduce amps from 2.5 down to perhaps less than 2 amps

 

[cadman]

Slippery Slope...

I guess the one thing we haven't touched on is what the cap is really doing. The idea is to offset the inductive load by making the phasor closer to "true power" (like a resistive load) rather than a reactive load where current leads or lags voltage. At the end of the day there's no free lunch in terms of energy consumed, only how out of phase the load is.

The real question should be do you have a "smart" electric meter that also captures your Power Factor? Your V*A meter in series shows less current, but will your electric meter? This is a pretty good question for us collectors of motorized equipment...-C

 

[g3bill]

My inquiry is based on what I think John brought up that some newer friges have a run capasitor which made them more efficent and might save a few hundred watts? I lov taking in all this info and saving it to hopefully see a reduction in energy used and other might benefit also?

John How is this possible? "replace the evaporator fan motor and go from about 30 watts of power draw again down to about 4 watts" and maintain the same CFM? 4 watts is a dim night light? Your right I'm sure that cond fan must use alot of amps. As for the evap fan I already bought a new one so will use it.

["You should also replace that nasty old condenser fan motor, older CFM usually had a amp draw of around .39 amps, newer High Efficiency motors draw .o4 amps or about 1/10 of the power and do the same job as the orignal power hog and last longer to boot because they run so cool."]
So how would one find these motors if anyone knows? I suppose the HP needs to be same or you'll get less CFM.

I hate to give it to myself but, I bought a evap fan motor from ApplianceZone, not knowing there very unreliable, they sent the wrong motor then I asked for a full refund, still haven't received it, they said well it takes up to 7 days to process my refund, emailed them after 8/9 days and said well it could take up to 10 days. Not the place to shop imo. Going to contack paypal in a couple days if no refund They did say keep the universal motor, no need to return plus I get the refund but when? The universal motor uses a bit les amps than the original but not a big amount, think it was something like .26 compared to .31 for original motor, might be off some...

 

[kb0nes]

What Cadman said

You can alter the relationship between the current and voltage phasing (the power factor) with a series run capacitor, but in the end you aren't changing the system efficiency. I'd suggest barking up a tree that might make a difference. I'm also not convinced that you can add a cap to a motor designed to run without one to get proper results, there was a reason it wasn't added originally.

If you really want to try to save power, trim the other excesses. Replace lamps with LED bulbs. Replace fans with new high efficiency electronically commutated motors. Finally swap the defrost timer (if there is one) for one that runs less frequently.

Be sure to get some sort of a power consumption meter so you can quantify your efforts.

The question that begs being asked is "why" though. If you are concerned with consumption a vintage refrigerator is probably not going to compare well even with tweaks.