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  #1  
Old May 31st, 2004, 10:30 PM
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Default Goodman piston changes

Goodman is the only manufacturer that is still rating piston metered coils with high efficiency systems. Goodman is able to do this because of the physical size of the coils.

Some of the new condensing units and heat pumps are being changed from recip compressors to scroll compressors that require a different piston. If you have a standard Goodman piston chart it should be used to determine the correct piston size for the indoor coil.

If you get a piston with a new outdoor unit that is different than the piston noted on the piston chart it is because the compressor has been changed in that unit. The change will be noted in the last letter of the model number. A CPLJ030-1 for instance may become a CPLJ030-1A when a scroll compressor is used.

Whenever you get a piston with a new outdoor unit, use that piston over the one that is shown on the piston chart.
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Old June 1st, 2004, 07:34 PM
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Default Re: Goodman piston changes

Now you tell me, all that flood back for no reason..

I did not know it made a diffrence between a tin can and a scroll, thanks bubba...
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  #3  
Old June 1st, 2004, 09:08 PM
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Default Re: Goodman piston changes

Not too worry Robo. The only Goodmans I work on are the ones I am ripping out. And it is against my religion to sell Goodman.
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Old June 1st, 2004, 10:50 PM
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Default Re: Goodman piston changes

No problem Sarge, we all gotta eat

The smaller piston makes little difference except for a possible compressor noise which can also be lessened by lowering the charge a hair. You will notice that all of the new pistons for the scrolls are just a bit smaller than the older ones.

Hell, there are thousands of these things installed without ever changing the pistons at all and they are still running. Not very efficiently, but running none the less.
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Old June 2nd, 2004, 12:30 AM
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Default Re: Goodman piston changes

Thanks for the info.


That's what we've been doing though it's nice to know for sure. We figured they wouldn't send the piston if we weren't suppose to use it.


A couple of quesions too if don't mind.

How much longer until Goodman gets into 410A?
And...
Are they working on a unit with the new Scroll 2 stage, unloading compressor yet? I really could sell some of those.


Goodman sales is good here. I have the installer going full throttle, hell, I'm even going to help tommorrow......installing a/c with a coil blower and all the duct work in a high school fitness room, some good scenery there .
I have sold 2 heat pump systems, one furnace, and 3 a/c systems in the last couple of weeks. With only one dedicated installer, that's not bad...and we aren't even into busy season here yet.
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Old June 2nd, 2004, 02:42 AM
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Default Re: Goodman piston changes

The Amana line has a full range of R410a equipment including the two stage systems with the Copeland scroll unloading compressor. If need be, all Goodman has to do is label the Amana unit. I assume that will be for next year but that is only an assumption.
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Old June 2nd, 2004, 08:41 PM
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Default Re: Goodman piston changes

I got a goofy question?

Can you "pump down" a scroll compressor ?? being an American Standard dealer I rarely get into 'scroll' compressors, all though I'm slowly switching from American Standard to Rheem equipment.
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Old June 2nd, 2004, 09:02 PM
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Default Re: Goodman piston changes

Yes, it's not recommended to go below 15-20 psi though.
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Old June 2nd, 2004, 09:48 PM
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Default Re: Goodman piston changes

I sure hope so, why would they have pump down valves on them if you couldn't. Of course if the system is a bad match up and or long freon lines I would blow some in recovery tank before shutting down LL Valve.
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Old June 2nd, 2004, 10:01 PM
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Default Re: Goodman piston changes

I just ask because I hear the scroll can get into vapor lock pretty easy, I think I have installed 2 scroll units in the last couple of years.
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Old June 3rd, 2004, 12:15 AM
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Default Re: Goodman piston changes

It is very bad to pump down a scroll compressor. Scrolls that go into a vacuum can be damaged very quickly by the arcing of electrical current in the casing with nothing in it and scrolls will go into a vacuum very quickly. By the time you read 20 psi on your gauge the compressor could already be in a vacuum.
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Old June 3rd, 2004, 06:06 AM
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Default Re: Goodman piston changes

Quote:
Originally Posted by RoBoTeq
It is very bad to pump down a scroll compressor. Scrolls that go into a vacuum can be damaged very quickly by the arcing of electrical current in the casing with nothing in it and scrolls will go into a vacuum very quickly. By the time you read 20 psi on your gauge the compressor could already be in a vacuum.
oops
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Old June 4th, 2004, 01:52 AM
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Default Re: Goodman piston changes

OK, I may have a bit of a goofy one too.


I have been doing sales a lot lately and haven't got to go help on much lately. I have helped on 2 installs very recently and this is what I notice....BTW, both units had very short linesets and needed some refrigerant removed ....

When recovering the refrigerant I let the pressures stabilize for a while and take superheat. When I hit the correct superheat I notice that you can then hear flash gas going into the evaporator piston. To me this says it is a bit undercharged but my superheat is right on, subcooling looks good too. It isn't a constant sound of flash gas, you just hear it for a couple of seconds or so every 20-30 seconds.

Am I right that this is tell tale of undercharge or should I trust that the superheat is correct?

Maybe I am paranoid, but I'd like to know.


I had to add this other question.
Would insulating the liquid line help, you know to keep it from extracting heat from the air on it's way to the evap coil?
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  #14  
Old June 4th, 2004, 06:08 AM
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Default Re: Goodman piston changes

if your superheat is correct, then you have the correct charge.


as indoor & outdoor temps change, so will the volume of r-22, the best I can explain it is this way:

If you install a site glass, and then fill the system ( on a 90 day ) so there are no bubbles in the site glass, and then go back a couple days later when it's 75 you WILL see bubbles in the site glass, it's not under charged, you don't have a leak, you just have differant conditions. I can't tell you the number of times I have gone on a job on a 'cool' day and have some goof add r-22 just because they see 'bubbles' in a site glass.

so if you hear "flashing" or bubbles don't worry about it, if you have clean coils and the SH & SC are correct theres not much else you can do.

as for insulating the LL, if the design engineers wanted the line insulated they woulds have sent it to you that way.
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Old June 4th, 2004, 06:47 AM
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Default Re: Goodman piston changes

If I may add to Jeff's most excellent post; can you be 100% positive that what you are hearing is flash gas and that it is actually coming from where you are hearing it?

We all have been fooled by the sounds that travel so well through copper tubing, pvc venting and ducting.
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Old June 4th, 2004, 08:37 AM
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Default Re: Goodman piston changes

Yeah, the old lady in the house may have been farting! That's some flash gas you don't want to mess with!
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Old June 4th, 2004, 11:19 AM
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Default Re: Goodman piston changes

What an image Peg......thanks a lot.
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Old June 4th, 2004, 05:39 PM
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Default Re: Goodman piston changes

Yeah, I'm 100% sure that is what I am hearing and it is right before it passes through the piston.

I know having a little flash gas here isn't hurting anything and I realize that it will change as conditions change. I was just curious because the noise is a little annoying to a perfectionist like me .

Thanks for the responses though, now I can sleep at night.

BTW, sold 2 more Goodman HP's and an a/c today .


TGIF y'all!!
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  #19  
Old June 4th, 2004, 09:29 PM
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Default Re: Goodman piston changes

Sarge, I thought all you sold was Janitrol/Goodman!





j/k



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