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justplumducky 05-10-2013 11:08 AM

Approxiimate compressor amp draw, old Sears packaged unit (cooling only)
Only thing I could get from data sticker is Model Number RN _ _ _ 30, then a space followed by 807819331. Nothing on serial number. Here's the only pic Google could find that matches the cabinet style:
Attachment 70639
Tonnage and other info on data sticker not legible, but's it's on a 14' x 70' mobile home, which is maybe a 3 ton unit?

What I measured was 18 amps on both 240v legs feeding comp. I didn't know that a compressor would start up with a 40 uF run cap (single, not a dual run cap) that measured only 10 uF. Is 18A possibly a high amp draw because of the bad run cap? Blower wheel was loaded with gunk on its blades, and it's run cap was only 2.5 uF (5.0 uF new) - it wouldn't start. Forgot about giving the wheel a spin to see if it would start. It wasn't locked up however. The 18A draw was measured without blower running.

Condenser fan was running, but air wasn't coming out/up vertically (at all) from fan - was coming out mostly horizontally from around the perimeter of the opening. Forgot to amp check fan motor and check for a run cap.

There was a slight overheat spot on the disconnect box's pullout T-handle and it's corresponding spot on the T-handle's receptacle in the disconnect box. Compressor terminal connections ( posts and quick disconnects on wire-ends) were clean. Didn't see any overheat spots anywhere else in wiring or on components. Contactor points were decent- not overheated.

Fuses in disconnect box were new - maybe one of the old ones caused a problem.?

yuri 05-10-2013 11:16 AM

4 a old school 3 ton unit 18 amps does not sound 2 high. A new 2 ton may draw 8-10 and a 3 ton 10-15 so that old bird may be right on. Hard 2 believe it starts with that capacitor, R U sure your tester is OK. Try it on a new cap.

justplumducky 05-10-2013 11:32 AM

It's a new Fluke Yuri ( not that it couldn't be bad), but I tested about 4 new run caps same day before testing that one. That compressor started right up, no hesitation, no rough running. An ohms check on comp. was close (numbers adding up) and no shorting of case to ground.

I might have been editing my post when you replied. Could you please speak to air coming out of the condenser fan horizontally, not the usual up/more vertical direction?

yuri 05-10-2013 11:45 AM

Listen VERY VERY carefully and write this down for future reference.

Your cond fan is now running backwards which could be due to a faulty capacitor. OR you may be getting a short in the compressor. If it shorts to the shell then the fan can run backwards and you can also get ZAPPED or killed if you touch the unit as you become the ground. This happens a lot with older units and WHENEVER you see a slow running cond fan or going backwards DO NOT touch the unit. Shut off the high voltage and remove the comp wires and check from the terminals to the suction line NOT the shell as it can be painted and work like a insulator. Suction line is best. Sounds like you need to test it and replace both capacitors and yes a weak cap can cause high amps but usually it just sits there and hums and overheats and cuts out on the internal thermal overload.

justplumducky 05-10-2013 11:48 AM

Ok, was editing my last post about ohms checking compressor while you were replying about backwards fan. Gotta finish reading your post about that.

justplumducky 05-10-2013 12:10 PM

Ok, I did scratch up real good the comp. case (to clean bright metal) before testing from terminals to case (wires removed), but I'll do it to suction line in the future, and when I get back there.

I had to put a new 50A circuit breaker (if that's the correct one - that's what was in there I was told, and some googling had a breaker for 3 ton units at 50A breakers also) in their service panel temporarily to run this unit, but removed it when I left - had to use it same day for a kitchen range (community action peeps (installed a new furnace for them) told them to scrap this old AC unit and took their 50A breaker with them when they left). I'll tell them not to reconnect power till I get back.

Can't thank you enough for the warning and life-saving info - maybe it would be a good idea to keep a non-contact voltage detector handy when I approach future units, if they're reliable enough, or maybe even use my Fluke VOM to test cabinets when approaching.

This comp. was definitely running (buzzing) and suction line started to get wet, but didn't let it run too long cause blower wasn't running - figured that wasn't good for system.

yuri 05-10-2013 12:39 PM

The non contact tester is a VERY good idea and especially for attics and crawlspaces or anywhere there is old dubious skanky wiring but a proper tester is also necessary to confirm. Twice I had a unit with a shorted comp and it ran for 10 seconds with the cond fan slow and then it blew the fusite plug where the comp terminals are (fuse ite, google that fusite name for more info on them). Then hot oil and burning oil and phosgene gas (Freon breaks down in a fire) which is like mustard gas came shooting out at me. VERY dangerous if you see any slow running fan or funny condition like that. Techs have been burned, gassed, electrocuted etc. Falling off ladders comes next.

yuri 05-10-2013 12:54 PM

2 Attachment(s)
Yur Welcome

Plus I am an environmentalist and after watching those Dove dishwasher soap commercials I want to

justplumducky 05-10-2013 01:05 PM

I don't know if I've seen the Dove soap commercials yet, but I'll be remembering the fusite plug warning for a long time, in addition to putting safety glasses on my list.

Not too excited about being burned, gassed, etc. Maybe I could come up with a shield to temporarily put in front (over?) of, around the fusite side of comp.? Anything that would keep the blowout from getting at me. Maybe that's not practical?

Kudos on your environmentalist status. You have a web site associated with your environmental status? I don't want to build you/sell you one - just curiosity.

Okay, I better leave you alone for now - thx so much for all your time and help today. Have a great weekend.

yuri 05-10-2013 01:27 PM

There is a cover on the fusite plug but when it blows there can be 250 or more PSI on a R22 and even higher on a R410 so very high pressure gas is shooting out. After many yrs of being burned by gas and oil furnaces backfiring you learn to keep your face/nose away from dangerous locations. Always stand back if something seems weird, wear rubber soled shoes or better yet leather work boots and safety glasses if you don't mind. Us old fart Journeymen never grew up in a safety oriented biz so our bad habits are hard to break but you young guys should know/do better. Actually I wuz a duck hunter when I wuz 16. True story = went duck huntin with my Dad and Uncle in a boat at dusk. Saw a fast movin Mallard comin towards us with me in the middle of the boat. Duck I yells to my Uncle, swings around and lets one fly over hiz head with my 12 gauge. Came so close he said he felt the heat from the shot cross his scalp. OOPS, he didn't duck but thank God lived.:laughing:

Now I shoot em with a camera.:yes:

justplumducky 05-10-2013 05:43 PM

:) Was your uncle a little ticked off at you for trying to give 'im a new hairdo with your shotgun?

I couldn't be more grateful for all the safety information (and I don't mind the safety glasses a bit), and along that line, how far from the fusite plug would you say is a safe distance?


Us old fart Journeymen never grew up in a safety oriented biz so our bad habits are hard to break but you young guys should know/do better.
I'm a bit of an ol' fart myself - maybe even older than you - but as far as I'm concerned, you can keep talkin' at me like I'm one of those younger guys. Scold me, chew me out, cuss me out - no problem :thumbsup:

yuri 05-10-2013 05:58 PM

That Uncle is one of my favorites (actually is my God Father) and is pretty cool so no he did not get too excited. Dumb things happen when you get a bunch of good ole boys in a boat with guns and some ducks and we were not even drinkin.:no:

I have had so many apprentices over the years and they were always younger so I assume most guys who don't know the biz are young and startin out but hey even a older guy with good mech skills can get into it and do well.:thumbup:

There is no need to get alarmed but recognize that with any machine, furnace or AC you want to stand back a foot or 2 or 3 if it starts doin something weird. ALWAYS know where the disconnect switch is in case of emergency. Especially with furnaces you want to be back at least 2 feet from a burner and NEVER at eye level. Tanned or burnt face / eyebrows is livable. blindness is not. If the AC is doing something unusual or sounds bad then back up and shut it down and start over. Don't just jump in with your probes and elec meter as that is when bad things can happen.:whistling2:

justplumducky 05-10-2013 06:04 PM

Cool beans Yuri, thx for all your advice.

yuri 05-10-2013 06:08 PM

I tell my apprentices that the best way to learn the biz is to document readings and pressures at different outdoor temps and indoor temps and loads and age of machines and start seeing trends of what they do. Along with listening you will start to recognize sounds and when things are going wrong. Most of them want to be parts changers and collect a paycheck but the real techs in this biz listen and can tell when things are going wrong and know when to step back. Think before rushing in.

justplumducky 05-10-2013 06:13 PM

I"ve been keeping a sheet on each job (just tearing it off a legal pad), but not as thorough as your suggestions. I'll get a "log book" tomorrow.

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