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Discussion Starter · #1 ·
3 yr old Nutone/Nordyne 3 ton Heat pump, system has a slow leak, after two years needs recharge, just got bottle of 410A, have means to weigh bottle as I go. Can I just add liquid 410A into low pressure fitting and go by feel and gauge set. Or do I really need to read high side temp differential and add vaporized 410A? Don't have ready access to a Multi meter with temp or a vaporizer, guess I could source them. Thank you.
 

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Take this as a grain of salt as I am a layman. I don't know what you mean by going by feel. But I would exit the R410A bottle as liquid (to eliminate fractionation) and then throttle my low side gauge set so that it enters the system as vapor. I do this by reading the low side pressure and then throttling so that the pressure does not increase by more than 10 psi as refrigerant is entering the system. Otherwise, there is risk of liquid entering the compressor and liquid cannot be compressed, so damage could occur. Does your nameplate show typical operating pressures and a target sub cool? What metering device does it use?
 

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The PSI readings on the nameplate are just test pressures, not what the system is supposed to be running at.
If your unit lacks a low pressure switch, and the suction line was allowed to go into a vacuum, then the remaining refrigerant should be removed as there is a high chance non condensables were drawn into the system.
 

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1st pressures are going to be different with different temps..

2nd, you want to feed in the R410a as a liquid.

3rd, if you don't know how to use a manifold gauge set and do SH/SC, you can use the old beer can cold method. Beer can cold will get your AC working, but it won't be be most efficient.

4th... depending on how bad the leak is, until it's fixed, you're going to be doing this over and over again...

5th..... a 3yo unit should have a warranty.. who installed it and why might you not be using the warranty to get the leak fixed 1st?
 

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You really should fix the leak.

Yes you should be monitoring the high side while you do this. Measuring the temperatures of both lines are highly advisable, but with experience can be skipped. (not recommended though)

You should have an amp probe to measure current draw while you charge.

Low pressure or loss of charge (LOC) switches are generally optional. They ate usually included with the wiring diagram so that the manufacture has less stickers to worry about, but not every unit will include it.

Everyone else have also mentioned good points.

Cheers!
 

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Discussion Starter · #18 ·
Wanted to thank everyone for all the helpful advice, received gauge and manifold set yesterday. Took a couple hours but got both lines within spec. took 7.5 lbs of R410. Seems to be cooling like a champ, cycling as it should.
Leak seems like it may have been in Schrader valve. Time will tell...
 
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