Sizing Hard Start

[hvacpb]

I am a Electrical Engineer who does primarily controls work and I know the electrical side of systems in good detail.

I need some help with sizing a hard start for a condenser unit. The info is

Brand. Ruud
Model. UPFB-036JAS
Date. 06/90
Serial # 4890 M2390 8620
Volts. 230
Phase. 1
HZ. 60
Compressor RLA. 18.9 / 18.9
Compressor LRA 100 / 100
Fan FLA 1.3
Circuit Ampacity. 25 / 25
Design PSI High. 300 PSIG
Design PSI Low. 150 PSIG
Factory Charge. 94 OZ R22

The kits at my local supply are supco eclass and i need to determine the compressor HP to get the correct kit. The above information is thats left on the unit. Can a compressor size in hp be determined from this information?

If not what would be the next best method?

These are the supco sizes i have access to.

SPP4E 90V – 130V 1/12 hp to 1 hp 1/8 hp to 1 hp 88 – 106 µF
SPP5E
90V – 277V 1/12 hp to 10 hp 1/3 hp to 2 hp 43 – 52 µF
SPP6E
90V – 277V 1/12 hp to 10 hp 1/2 hp to 3 hp 88 – 106 µF
SPP7E
90V – 277V 1/12 hp to 10 hp 1 hp to 4 hp 130 – 156 µF
SPP8E 90V – 277V 1/12 hp to 10 hp 1 hp to 5 hp 189 – 227 µF

Can someone help me determine correct sizing and what the metod is if you do not have the HP stamped on the compressor anywhere?

Thanks

[mechanix]

Ask for a 5-2-1 at your supply house

http://five-two-one.com/

[Ford3517]

You could use this rule of thumb in the future.

1hp per ton for A/C

2hp per ton for medium temp coolers

3hp per ton for low temp freezers

so by judging from the model number I think it is a three ton unit so possibly 3hp. Although I would verify this but I think the "36" in the model number indicates BTU output and that converted into tons is 3 tons.

[HoneyDo]

See if you can get info off of pot itself.
Sometimes it's stamped or labeled.
Or look in the electric cover sometimes.
If you can't actually read it... I've snuck my cell phone to take pics in cramped places. Works well.

When coolers are backed right up to the walls where you can't read the labels... Sneek my cell back there and take some pics.

The HVAC Paparazzi.

[post time]

to size a custom start kit you need to measure back emf voltage. measure voltage between common and start wnen the compressor is running . mars gives you a relay guide with voltage ratings. every potential relay has different ratings so you need this chart to size the particular compessor your working on. your coil must be equal to or above to handle this voltage. then you take 80% of this voltage and it must fall between the pick up min and max of the relay. the size of the start cap is up to you. i use large if its locked , medium if its above 50% rated LRA, and small for others.

[ACFIXR]

Thanks post time. Where did you find that chart? Can you post a link?

I have found that it is better to properly size start components than to just drop in a ready made kit. The kits may be fine 70% of the time,

[R123]

I use the 5-2-1. That's the best drop in hard start kit on the market other than sizing up the components.

[second opinion]

what is a 5-2-1 hardstart?

[R123]

what is a 5-2-1 hardstart?

http://five-two-one.com/

[post time]

acfixr , i think there is a chart provided with every mars relay.

[mgenius33]

http://five-two-one.com/

What is the difference in their potential relay that makes it multi-positional? Makes me wonder if it's calibration and sensitivity is as precise as say the Tyco.

[Qualitair]

I think you can't go wrong with this: http://www.kickstartoem.com
OEM approved
That's all we use.

[Paul Bee]

Or you could order the factory start assist kit from Ruud and Install the kit designed just for your compressor and approved by Ruud for your unit.