Sizing Hard Start
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
Serial # 4890 M2390 8620
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 ΅F
90V 277V 1/12 hp to 10 hp 1/3 hp to 2 hp 43 52 ΅F
90V 277V 1/12 hp to 10 hp 1/2 hp to 3 hp 88 106 ΅F
90V 277V 1/12 hp to 10 hp 1 hp to 4 hp 130 156 ΅F
SPP8E 90V 277V 1/12 hp to 10 hp 1 hp to 5 hp 189 227 ΅F
Can someone help me determine correct sizing and what the metod is if you do not have the HP stamped on the compressor anywhere?
Ask for a 5-2-1 at your supply house
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.
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.
Don't go away angry... Just go away.
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.
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,
Some Talk, Some Do
"keeping condensing pressures low and evaporator pressures high"
Comfort is my goal
I use the 5-2-1. That's the best drop in hard start kit on the market other than sizing up the components.
what is a 5-2-1 hardstart?
Originally Posted by second opinion
acfixr , i think there is a chart provided with every mars relay.
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.
Originally Posted by R123
"The only true wisdom is in knowing you know nothing" Socrates
I think you can't go wrong with this: http://www.kickstartoem.com
That's all we use.
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.
Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org