My AC system is getting very old and I was wondering if I should add a Hard Start kit and with what spec? Here is my AC spec included below and the existing Dual Run Capacitor is 440volt and 40+5MFD.
Which AC Hard Start kit capacitor I should use
air-conditioningcapacitorcoolinghvac
Related Solutions
If the outdoor fan comes on and the compressor does not, you need a "hard start kit" this is either a potential relay and start capacitor as in my diagram or a PTC thermistor solid state start assist device that piggy backs onto the run capacitor. This is assuming your compressor is cold to the touch and has not been starting. If your compressor has been starting and is off due to the thermal overload being open Then it is due to the capacitor being bad or refrigerant being low or the compressor is mechanically tight or electrically shorted to itself internally, this is not something a homeowner will usually be able to do unless walked through it step by step.
Nice chart. This looks like abnormally frequent triggering of the defrost cycle. Typically this will occur if the unit is severely low on charge or when the outdoor thermostatic expansion valve (TEV) has failed and is restricting flow of refrigerant through the outdoor coil so severely that the coil freezes in an abnormally short period of time, triggering frequent defrost cycles. You would have a similar problem if your outdoor coil was exceptionally dirty, but I assume you would have noticed that.
To positively diagnose this, a technician would connect a manifold to the service ports when the unit is heating, and verify that the subcooling of the refrigerant returning from the interior coil is at least 8 C to confirm the unit is not too low on charge. If the charge is adequate, then check the saturated suction temperature (SST) and also the superheat of the vapor in the suction line returning to the compressor. If the SST is much less than 6 C below ambient and the superheat in the line is much more than 11 C, then the outdoor TEV has likely failed in a closed position or become plugged. Depending on the unit this may be a fairly major repair. In a 29+ year old system it may not be worth it versus replacing the unit.
EDIT: Some defrost control boards have a manual setting that forces a defrost cycle at a programmed interval. If you have one of these control boards, you should verify that it has not been set to force a defrost cycle every 30 minutes. Also, someone should confirm that the "freeze-stat" that signals the defrost board when the outdoor coil needs defrosting has not become disconnected or damaged. You can eliminate these by looking at the outdoor coil after the system has been heating for 15 minutes. If it is covered with frost and really does need defrosting in that short a time, then this problem is not merely a control malfunction and is more likely a refrigerant charge / TEV problem.
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Best Answer
Should you just change a cap because your system is old? NO you don’t state there are any problems. Electrolytic capacitors do fail over time but we don’t know what you have. oil filled usually last the life of the unit but are much more expensive and not appropriate for all climates.
If you are noticing the lights dimming , hard starts blowing fuses if all the connections are good replace the cap with the same value.
As electrolytic caps age they loose their ability to hold a charge and or short out (note a bulged cap case has usually shorted, it may be working now but needs to be replaced). As caps loose their ability to hold a charge they can not get the motor started thus dimming lights and blown fuses, let this go in long and the compressor windings will be damaged.
There are lots of film flam guys out there if your system is starting hard the cap just needs replacing with the same size it is that simple (if the cap is the problem). If you could not find the same size +-10% will work but not as well as the manufacturers recommended size.