refrigeration compressor

[diyguy]

Is it okay to use a "hard start kit" on a compressor ,and if so, for how long?

[Repair-man]

Let's put it this way...

A hard start kit is a last-resort device. How long you use it depends largely on how long the compressor will continue to start on its own.

[Icehouse]

  RefrigerationCompressors come four ways.
1.RSIR = Resistance Start, Induction Run this unit comes with only a relay.
2. CSIR = Capacitor Start Induction Run this unit comes with a relay and start capacitor and has a higher starting torque.
3. CSCR = Capacitor Start, Capacitor Run this unit is equipped with a relay, start capacitor, and run capacitor and has a higher starting torque.
4. PSC = Permanent Split Capacitor no relay, but uses a run capacitor to make it more efficient (capacitor makes it act as a polyphase motor). Found on Air Conditioners mostly, however when problems evolve a hard start kit (consisting of a potential relay and a start capacitor) is recommended. The new solid state hard start kits eliminate the need for a potential relay.

[JWWebster]

Refrigeration is the key word here. Are you talking a simple domestic frig or a full blown walk in or reach in refrigeration unit?
On a small domestic yes, on a commercial unit hell no.never.

[Icehouse]

Then why are the new units (domestic) coming with capacitors ?

[shieldcracker]

Then why are the new units (domestic) coming with capacitors ?

Most new units come with capacitors to improve power factor and increase compressor efficiency. Also note that almost all refrigerators provide the option to add factory approved components to convert the PSC or CSIR motor-compressor in to a CSCR.  Most mfg recommed adding the additional components if the refrigeration system has to be opened up for service. The rationale is that in the field the refrigeration system is likely to have contaminants and it is unlikely that the serviceman can reproduce the controlled factory conditions during the assembly and charging at the field.
 

Is it okay to use a "hard start kit" on a compressor ,and if so, for how long?

Think about what I said. If the compressor has never been serviced it might just be  showing sings of aging due to wear (normal), a refrigerant leak or the begining of a more serious compressor faliure mode. However if the refrigerant circuit has been opened up the chance of contaminant intrusion is very likely and surely the source of the problem.
Now put all this in perspective... It is worth to open the refrigerant line in an attempt to restore the system to the original factory condition or replace a suspect compressor if the the unit is leak free?

If you decide to use a Hard Start try to use the one that goes by that name and avoid the solid state (PTC) models, or even better try to locate the capacitor start kit from the appliance or compressor mfg. Whatever you decide to install once you put it in leave there.

[Icehouse]

Hard Start:Consists of a Potential Relay and Start Capacitor. The purpose is to overcome high starting torque.
True with age, compressors start to develop characteristics of higher torque from age, and power factor problems the most evident is the so-called "brown-out" conditions from the electrical supply. (Con Edison,LIPA,PSE&G) for example.
PTC relays are now the norm from appliance manufacturers.
Unfortunately, this is the reason for so many problems as there is trace voltage present at the windings, even when the compressor is off.
The "Hard Start Kit" as being sold is a solid state device which incorporates the same principles of relay & capacitor. 

[shieldcracker]

Let me clear up what I said in the last paragraph.
Hard start is a generic term that will have two to three components depending on the model and brand; 1) capacitor. 2) starting device (starting relay or PTC). 3) overload (not on all models).
I try to steer away from hard start kits that use PTC's for the reasons Ice house state. Since it is very hard to get the exact capacitor switched in and out at the exact right time I recommend getting the components to do the conversion from the appliance maker or the compressor mfg. who has selected the right parts for the job.
I ll admit that this approach may not be feasable for the serviceman due to stock and time constraints, however there is an alternative I can recommend positively, Hard start kits made by Kickstart which use a potential starting relay that transistion remarkably well.