In my earlier post I learned what a "Hard Start Kit" is and how it is used. To summarize briefly, all Basement AC come with a Hard Start Kit (HSK) and most roof top AC also come with one. However, the roof top AC has a smaller compressor and therefore a roof top AC uses a smaller Start Capacitor vs. the 2-Ton Basement AC used in may RVs from 1996~2010. (After 2010 only Roof Top AC were used.)
So what is a Hard Start Kit and why do you need one?
Here's my answer:
* In RV terms a HSK consists of a start capacitor and WSX7 Motor Starter, which is a PTCR-thermal type switch. In residential terms a HSK consists of a start capacitor and a 5-2-1 relay.
* A hard start kit is used to help to start your compressor for split seconds, then it the PTCR drops the start capacitor of the circuit. (I will not explain why, but this is the desired effect.)
* You also should know, that prior to the compressor reaching 75% full speed, the compressor coils behave like a heater. And the start winding not only has more ohms vs. the run winding, it also has thinner gauge wire. Therefore, your start winding is typically more susceptible to heat-fatigue and failure over time. And if at any time the PTCR fails you could damage your compressor.
* Luckily, the PTCR does not fail that often, but it is susceptible to melting-down when you use your AC in RV parks with low voltage. However, it is a very reliable, and cheep device. ...But is it the best device for the job?
WHAT IS THE DESIRED AFFECT?
* First let me say, the run capacitor is specified by the compressor manufacture and you should only use the right micro-farad run capacitor matched to the compressor. In the case of a my 6535-671 Basement AC this is a 45uF run capacitor, but some other models that came with Tecumseh compressor they call for a 35uF capacitor. (Just be sure the use the one matched to your compressor.)
* The compressor manufacture does NOT specify the type or size of a HSK. But if you look at your OEM start capacitor you will know. ...But what about the relay?
* What about the relay? How do they create a time-delay so the start capacitor remains "in the circuit" for a estimated period of time... and then the relay trips to take the start capacitor "out of the circuit?"
* Answer: All RV manufactures install a a small, cheaper start capacitor; and all RV manufacture use a cheaper WSX7 Motor Starter (PTCR) to put the start capacitor "in" the circuit... until it heats up, and the the PTCR takes the start capacitor "out" of the circuit at an estimated 75% of full power.
* But all this is just PTCR is doing is acting like a time-delayed switch, which is a crude estimate at best. (...but proven reliable, nevertheless.)
REVIEW
The RV industry is smart. They build reliable products for a cheap as possible. Ergo, our Basement ACs and most roof top AC will last 10+ years without any maintenance or they could fail in 5 years.
Owners, don't think of doing Preventative Maintenance (PM) on their ACs, but they should. And it's so easy and cheap do to! So why haven't you heard about this subject until now? ...Good question? ...And now that you have, when are you going to PM your AC?
The problem is that these electrolytic capacitors typically leak and are not within spec after 5 years. (My estimate.) So the first thing you should do if you have never checked your run and start capacitors is to properly check them and replace if necessary. This will do wonders to extend the life of your compressor and avoid huge repair cost. Plus these capacitors only cost ~$10 each so the parts cost is cheap! What you lack is the knowledge on how to replace your AC run and start capacitors! ...But it's easy! Anyone with half a brain can do it.
* SAFETY PRECAUTION: Be sure to short the top of your capacitor (between pins) before pulling any wires and watch a YouTube video on how to do this. (Piece of cake.)
SO WHAT IS A 5-2-1 HARD START KIT AND WHY SHOULD I UPGRADE?
* As stated above, your coach manufacture builds a quality product, but unfortunately for owners they sometimes care more about profit margins over building the best product they can. And I'm thinking if that was their goal, they would have used a 5-2-1 relay instead of a WSX7 Motor Starter (PTCR).
* A 5-2-1 is a relay. The 5-2-1 represents the pin numbers on the relay so you know how to hook it up. The 5-2-1 replaces the WSX7 Motor Starter (PTCR-Switch) in an RV application; and in residential AC it is standard equipment.
In fact, when residential ACs undergo a repair, the tech, often uses 2-wire Supco SPP6 (with PTCR) to diagnose the system; and then they typically only leave this cheap device installed for only as long as it takes to get OEM parts replaced. I.e., the 5-2-1 is always preferred to the PTCR device.
* Here's the challenge: In order to use a 5-2-1 relay you are supposed to know the right "Pickup Voltage" for the Back-EMF of the compressor.
* The problem RV Basement AC owners have is that the Panasonic compressor manufacture (and AirXcel-Coleman) does not provide technical support. So we don't know what the "Pickup Voltage" is.
* Replacing the start capacitor is no problem. We do know what type of start capacitor to use since it's marked on the outside case. And in most cases, the OEM start capacitor for a 2-ton Basement AC is 88-108uF.
* However, my research suggests that you can use a 135-162uF Start Capacitor in place of your OEM 88-108uF start capacitor and when you do you should not only get a faster and smoother start-up... as evidenced by listening to your compressor start... this upgrade should extend the life of your compressor, because those start coils in your compressor will not get a hot... if the PTCR or the 5-2-1 is "tuned" to take the start capacitor "out" of the circuit when the compressor reaches 75% of full power. (TBD)
At this point you can refer to this thread for more details on how I arrived at this conclusion; and I would recommend you jump to the last few thread entries to skip over my learning curve in the beginning:
https://www.winnieowners.com/forums/...de-359467.html
HOW TO "TUNE" YOUR 5-2-1 HARD START RELAY?
So now we need to talk about how to optimize the relay that takes the start capacitor "out of the circuit" after an unknown period of time.
This is currently being accomplished by a 22-ohm, WSX7, PTCR type, Motor Starter, but I wonder if using an adjustable 5-2-1 relay is a more efficient solution for the same amount of money or for just a few dollars more?
* 5-2-1 relays are supposed to me matched the the "Pick-up Voltage" specified by the compressor manufacture. However, as mentioned earlier, Panasonic/Matsushita will not answer my emails requesting this information. So what can we do?
ANSWER: Supco makes an adjustable ARP5 Relay that can be "adjusted" to match your compressor "Pick-up Voltage." ...And Supco recommends an adjustment between 180-190 on the trim-pot to achieve this. However, this is just another estimate.
HVAC TECHNICAL QUESTION: When you adjust the "Pick-up Voltage" on the APR5 (5-2-1 relay) between 180-190... can you discern the best setting by listening to the compressor start?
===> SO IS THERE ANYONE OUT THERE WHO HAS USED A SUPCO APR5 RELAY AND "TUNED" IT FOR OPTIMUM PERFORMANCE?
If so, please let us know how your experiences... pro or con... using one of these devices, because in theory, a "tuned" relay will drop out at ~75% maximum compressor power/rotation... and I would like to know from the HVAC professionals if they recommend using a APR5 over a Motor Starter (PTCR)?
Additionally, you owners in the desert states, who are finding your AC has trouble starting in 105+F weather, you would benefit from installing a 5-2-1 since it works on the principles of a coil switch and is not affected by outside temperature like a PTCR, WSX7 Motor Start is affected in hot weather.
Attached is a circuit diagram I created that shows how you wire a 5-2-1 relay to your Basement AC.