Why two fuses for a 5 ton residential AC?

Hi Bruce,

The entire plate on the compressor:

RHEEM MFG CO MODEL RAFD-060 JBS MFD 1-90 SERIAL NO xxxxxxx OUTDOOR USE Volt 208/230 1ph, 60 hertz COMPRESSOR, R.L.A. 30. 8/30. 8 L.R.A. 178

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nomail
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snipped-for-privacy@noplace.org fired this volley in news: snipped-for-privacy@4ax.com:

running load amps (at both the stated voltages) 30.8A locked rotor amps 178A

It sucks roughly 6X running current when starting; that's the reason for time-delay fuses or HACR style breakers.

Technically, the fuses are redundant. But fuses tend to more reliably open under load than breakers do. If you're more interested in protecting your AC than the inconvenience of servicing the fuses every

8-10years, then leave them in.

The reason one should not bypass fuses (even if they are not required) is because by doing so, you have modified the function and purpose of an approved electrical device. Doing so clears all bets off the table in case of a fire.

LLoyd

Reply to
Lloyd E. Sponenburgh

RLA - Running Load Amps - How much it draws at 208V /and 230V

LRA - Locked Rotor Amps - How much it draws on initital startup, or if it can't start because there is still pressure in the system (short cycling) or the compressor goes bad mechanically and jams.

You need to know these amp ratings to design the power feed circuit and (if you are making your own electricity) to size the transformer or generator plant feeding the unit.

Note that generators meant for Recreational Vehicle use often say things like "Will start a 7,200 or 13,000 BTU Air Conditioner" in the paperwork.

It says "Fuse or HACR Rated circuit breaker" so the fuses aren't absolutely necessary. Either will do. Get out a magnifying glass to read the breaker label for the HACR rating, which won't be on old-stock breakers.

But I would still leave the fuses in, because circuit breakers DO fail to trip occasionally - or they do trip, but after far too long of a time delay that allows compressor damage.

It's cheap insurance, so big deal if you have to replace the fuses every 10 years or so.

So don't let it crap out!

When it's running, check that the big suction line headed out to the condensing unit is still frosty cold - that's the quick and dirty test that there's enough refrigerant in the system. The "leftover" cold in the system is how the compressor motor gets cooled - the incoming cold gas goes through the windings. If the refrigerant charge is too low, you start slowly cooking the compressor motor to an earlier failure.

If it's low on refrigerant you WILL need to call someone to fill it up, because you need a Refrigerant Technician License to buy the refrigerant (Multiple Guess Test, simple once you grasp the principles) and $1500 to $2500 worth of gear on hand to do it legally. (Must have a refrigerant recovery machine and an empty recovery tank on hand if a big leak starts, so it doesn't leak into the environment. Silly, but I didn't write the laws I just try to follow them. And when the EPA can fine you from $10,000 up to a Half-Million Bucks for each violation, you have an incentive to follow the rules...)

Everything else, you can do.

Get some Non Acid condenser coil cleaner and a pressure washer, and clean out the bugs and dirt from the condenser core outside. Let the soap soak then pressure wash out the crud.

Get a can of self-rinsing evaporator core cleaner and get the gunk off the inside coils. You can't use a pressure washer, so it rinses off with the normal condensation.

Get a case of good High Efficiency air filters, and change them every couple of months, or as they get filthy.

And make sure the condensate drains are clear, and the secondary drip pan is under the unit if it's a horizontal in the attic, and a general once-over.

Oil the fan motor bearings with non detergent 10W Turbine Oil, and change the belt if the blower is belt drive. Same thing with the condensing unit fan if it's oilable - look for the little black plugs and OIL markings on the oil holes, and plug them again when finished to keep the rain out.

Spin the fan and feel the bearings, if they are getting lumpy buy a new motor. Not too hard to change, not worth the trouble to fix.

No you don't - window units are far less efficient, and give more trouble. And depending on where you are, natural gas heat is a LOT less expensive than electric or heat pump. Propane and Oil heat are more, but still cheaper than electric. That old furnace and central air is still worth keeping.

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Reply to
Bruce L. Bergman

Why would you change fuses "periodically"? Until they blow, they're in place indefinitely.

They're slo-blo, to let the compressor start, and if the compressor gets stuck, they blow before the short burns the house down.

Cheers! Rich

Reply to
Rich Grise

The SquareD breakers are almost 30 years old - so I guess no dice.

I agree - but I regard myself as just lucky this time. Prior to that a service person did and explained the cleaning of all parts. It only worked when I redid it myself.

This time I have avoided operating the ON OFF handle since if it is corroded to a good connection - don't mess with it. Is this incorrect thinking?

What are current reasonable prices for a service call? What if one has to have freon added?

I have never looked at the inside or compressor. Thought it was all sealed and no lubrication needed.

You and others have given some or many of us a real helpful education in AC.

I would keep the gas for heating - zoning the AC would be valuable. The heating blower fan and motor is one unit and I believe sealed with no lubrication points. Should one attempt this anyway?

Reply to
nomail

"Frosty cold" I read that as dry and with frost where a finger would stick like glue. I have what I would call 'very cold' but wet or damp with condensate.

Does this unit past the test or is there some refinement?

Mike

Reply to
nomail

Very cold will do. When it hits "lukewarm" then you worry.

Reply to
Bruce L. Bergman

Andrew VK3BFA

Regardless, the fuse sustains some minor damage each time the current exceeds its rated current, the CB does not. It might take the CB

60-1000 seconds to open for overloads, in that time a fair amount of damage can occur to the fuse, without yet clearing it. As this happens start after start, eventually the fuse fails, without tripping the breaker.

jk

Reply to
jk

Very.

NOTHING ever corrodes TO a good connection jk

Reply to
jk

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