How much is too much?

[jrc2905]

I got a call from a homeowner who had obtained an EPA card and he decided to buy himself a set of gauges and a tank of R22 to charge his own system. He was having a problem with the system showing 375lbs on the low side before he shut it off. When I got there I first told him he had his gauges on the wrong sides, he did have 375lbs but it was on the high side.
To make a long story short, I removed over ten pounds of refrigerant on a 2.5 ton system.
When I left the system was running ok, but I was wondering how much refrigerant do you need to put into a system to kill it? I do have a new found appreciation on how tough they make these compressors.

[grodan1]

What a great post.I'm new to the field and I'm always so worried about overcharging a unit.I did'nt believe a thing like what you describe is even possible.I can't wait to see some of the replies to this one.

[Jultzya]

At least this was a homeowner and not someone in the business... like the one I had to do!

After, they condemned the compressor do to noise!
(I wonder why?) :(

[jacob perkins]

Originally posted by jrc2905
but I was wondering how much refrigerant do you need to put into a system to kill it?

Hell,I would like to SEE it being done.

Write a letter to Copeland.Tell them you have a sales gimmick.

[Edited by jacob perkins on 06-30-2005 at 11:28 PM]

[Jultzya]

If you don't already know what SH & SC are, learn. This will help aid in the prevention of over charging a unit.

Also, don't assume every system that is not cooling is because of a low refrigerant charge.

[airworx]

subcooling and superheat. txv will have 10 to 18 degrees subcooling and superheat will be around 20 usually (residential usually has axv and not txvs)
orfice or cap tubes you will need a charging chart because tempertures determine the superheat. but you can check subcooling on orfices also and anything over i would say 15 degrees is overcharge.

[grodan1]

Here's how I've been checking and charging.I hook up gauges and check high side's saturation temp off of gauge.If it's not 20 to 30 degrees above ambient I get the refrigerent and start charging.Then I get a temp probe on the suction line and watch my superheat.If its low on refrigerent-regardless of the load- it's usually high and steady.I keep charging til I get about 25 to 30 above ambient on the high side and then I keep my eye on the superheat,keeping in mind my load and humidity level.As soon as I see my superheat start to dive I stop charging and let the system settle down because I know I'm within a few oz of the proper charge.Then I go inside and do another temp split between the supply and return.If I have about a 20 degree split with not too much humidity I pack up.If I have very high humidity I settle on a lower split.If I don't like the split and my pressures look good I start looking for other problems like air flow--like yesterday in a trailer their fresh air intake from outside was pointed dead into a-coil and blowing 95 f air into it and that explained my unsatisfactory 67 f supply.Is OK?

[grodan1]

I know the above post can be picked apart,but if I covered every aspect needed to keep it from being picked apart by professionals it would have been a book.It was just a brief overview of my normal fixed oriface residential unit without going into all of the normal details I check for also.