Who has a Supco Hard Start on their A/C unit?

j-d wrote:
It's 5-2-1 and from what the website says...

Oops, fat finger syndrome! :)

BillyW wrote:
So.... It appears there is consensus that a hard start kit, or OEM equivalent, improves the performance and reliability of our RV air conditioner compressors. And as a direct result, our generators and shore power connections would also benefit from the reduced load requirements. This thread is almost worthy of "sticky" status!

Agreed but understanding whether or not your A/C unit already has the components you're thinking of adding is worth noting and/or finding out.....

I think the Dometic A/C unit is the most commonly seen A/C on RV/trailers (at least for what I've seen) and my Dometic seemed (per the advice of members on this forum) to already have what I thought I needed to add. I learned a lot on this thread but other than the valued knowledge gained, the attempt was a waste of time.

So.... It appears there is consensus that a hard start kit, or OEM equivalent, improves the performance and reliability of our RV air conditioner compressors. And as a direct result, our generators and shore power connections would also benefit from the reduced load requirements. This thread is almost worthy of "sticky" status!

It's 5-2-1 and from what the website says, it's a Potential Relay type device. Every Start Assist needs to get its Start Cap out of the circuit as the Compressor comes up to speed. The bare-bones Start Kit uses a Positive Temperature Coefficient Resistor (PTCR). It works on a built-in value that's supposed to match the compressor's needs. SPP6 works that way. SPP6e has electronics that adjust somewhat to what the compressor's doing. The OEM Potential Relay assists are supposed to do a better job. It seems 5-2-1 is meant to do that better job aw well.
I'd love to see somebody here evaluate 5-2-1 against the basic PTCR types and the SUPCO SPP6e that usually come up here.
EDIT - Looks like Craig may have done just that...

I went to a seminar in 05, put on by the coinventor of the "5-2-1" kit and the guy was then working for Harris welding products which were also covered that day. It was the best seminar I've ever attended! I only remember his first name was John. They named their hard start kit after the 3 potential relay terminal numbers that connect to the compressor terminals. It's so easy to remember how to install their kit. 5-2-1 = common, start and run. That one and the comparable kit made by Hardstart are very good kits and use a potential relay. I've put the 5-2-1 kit on EVERY AC I've installed since that seminar, including my own. They add life to a compressor. John and his partner researched 230v residential single phase compressors and came up with a good cap size and relay pickup/dropout voltages for each tonnage. Johns speech got pretty technical but the keys point were... a potential relay isn't limited by cap size or current draw like a PTC relay. A compressor w/o a hard start kit builds up more internal heat because of the long start process than a compressor with a proper start kit. It's better (less heat and stress) to give the compressor a HARD kick and get the rotor up to speed than to let them start w/o the extra assist. A PTC is also no good for rapid cycling machines cuz they require a cooldown between cycles. A potential doesn't care.
After 10 year in a service truck, I took a plant maint. job in 85. That plant had some single phase RTUs with long wire runs and the compressors sucked the voltage down so low on startup, they would cycle on the OLs til they finally started. Someone before me replaced the compressor after they burnt up and put buck n boosts on the two worst units and they weren't working much better. I pitched the buck n boosts and got the right hard start parts from the comp. mfgr. and they never gave me another problem. Craig

I've never had much love for those band aid fix PTC/cap kits. I've tried them since the 70s when they first appeared. They are fine if a system is flawless or only has a VERY minor problem with starting. I had a customer in the 70s and their 3T home AC kept blowing fuses. Most of those old houses didn't have the service for add-on AC so they got put in with minimal sized circuits. This one only had the run cap and the system wasn't fully equalizing before the next stat call for cooling. I put on a PTC/start cap kits and watched the gauges. The pressures had to be within 20psi or that kit still wouldn't start the compressor. I called the compressor mfgr and they had pt. #s for a real hard start kit w/potential relay. I put those mfgr designed/approved parts on that compressor and it would immediately restart after a shutdown even with 175psi differential and not blow the fuses. To make the rest of the story short... I always check with the compressor mfgr for the correct hard start parts first cuz they are by far the best. A lot of compressors don't have any mfgr approved hard start parts. I've tried to find better start parts for RV ACs and hit a dead end. The oem ptc/cap is all there is. If a bigger one works.. more power to you and your compressor. Craig

When I worked for the School District as a Facilties Manager, we had literally hundreds of air conditioner units to service. Our Maintenance Dept. used the 5-3-1 Compressor Saver which is a 3 wire.

It wasn't my department so I don't know exactly why. Is a 3 wire better than a 2 wire?

Point taken.

Katoom, a point you may be missing here is that many rooftop RV A/C units do NOT have a hard start/start assist device. Only Run Capacitors. Going from NO start assist to ANY start assist can make a huge difference. Trying to upgrade from one type of assist to another, not so much.
You already have an assist setup so the improvement would be marginal, as compared from adding one where there was none originally.

I do not own any A/C units that have not had starting cap and run cap upgrades.

Not only in uf capacity for starting, but in voltage tolerance (run caps).

The penalty is in size (and price). The advantage is (higher voltage) dramatically increased capacitor lifespan.

Capacitor selection should be done by experts.

This usually means substantial modification to capacitor mounting brackets.