Subject: Re: Wanted: Professional Opinions

From: [email-masked] (George Goble)
Date: 29 Jul 1995 22:06:29 GMT

In article <[email-masked]> [email-masked] writes:
 >
 >Paul, as you may know, converting R-500 a/c systems to R-22 is not an
 >uncommon practice nowadays.  Consider the following problems when one
 >has to service an R-500 unit: (1) try finding R-500 refrigerant.  It is
 >doable, but not easy.  Then try paying for it.  :-) (2) try finding a
 >'drop-in' replacement for R-500.  Perhaps refrigerant R-401B (MP66) is
 >as close as you are going to get but, IMHO, R-401B doesn't solve your

R-406A has also been used by quite a few as a drop-in for R-500.
No oil or metering device changes.

--ghg
http://worldserver.com/R-406A

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From: [email-masked]
Date: 29 Jul 1995 15:45:58 GMT

One of my employers was a contractor with those home insurance companies.
The policy cost about $300 circa 1985. The homeowner pays $25 per service call and
the service company does the work on a fixed rate basis. The homeowner makes a 
call to the insurance company, generally has no choice about service companies.
Callbacks are the responsibility of the service company. 
	If there are no unusual problem, unlike the one we are concerned with, all
can go well. The insurance company takes the hit. The service company is likely to 
cut corners since the margin is small, or condemn rather than repair. 
	I found a leaking, corroding evap on an older home, was not approved for 
replacement. Corrosion was deemed "normal wear and tear." Not a covered failure.
Homeowner was not pleased, but it was an insurance question, not service problem.
	Anyway, I fully agree with Paul's posting. The service person probably never
saw a 500 system. I've worked on 3 in 13 years. I still have about 10 pounds of 500 from
1987. 
	Jim Sullivan

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From: [email-masked]
Date: 29 Jul 1995 15:56:38 GMT

In <[email-masked]>, [email-masked] (paul milligan) writes:
>~~>In early July 1995, the air conditioning failed. The same air conditioning
>~~>repair company  was dispatched by the Home Warranty company.  Upon
>~~>diagnosis, the HVAC company stated that the evaporator coil was designed
>~~>for R500 refrigerant and the condensing unit was designed for R22
>~~>refrigerant.  Therefore, the evaporator coil and condensing unit were not
>~~>compatable.  The HVAC company also stated that they were sure the
>~~>condensing unit that they replaced the previous summer was engineered for
>~~>R22 refrigerant.
>
>	SO they admit their error  ?  By their own statement they say that
>they installed a condensing unit that is incompatible with the evap they left
>in ?  Are they trying to say that repeating what they claim to be someone 
>elses mistake excuses their own ?  Homey don't think so ! 
>

Paul, as you may know, converting R-500 a/c systems to R-22 is not an
uncommon practice nowadays.  Consider the following problems when one
has to service an R-500 unit: (1) try finding R-500 refrigerant.  It is
doable, but not easy.  Then try paying for it.  :-) (2) try finding a
'drop-in' replacement for R-500.  Perhaps refrigerant R-401B (MP66) is
as close as you are going to get but, IMHO, R-401B doesn't solve your
evaporator coil problems any better than R-22.  The expansion device will
have to be change in either case.  Refrigerant velocities in the evaporator
will be significantly lowered (compared to R-500) using either alternative,
which tends to degrade coil performance.  And R-401B has a large temperature
glide one must consider.  R-22 doesn't have this problem and, of course,
it is much cheaper.

The *ONLY* reason one should convert an R-500 a/c system to R-22 (or
R-401B, or whatever) is simply to extend equipment like.  With a residential
a/c unit, it makes no sense to change the condensing unit to an R-22 type
and save the R-500 evaporator.  C'mon! what are you saving here?  A
residential sized evaporator is not that expensive in the grand scheme of
things.

On commercial equipment, trying to save R-500 air handlers may make
economic sense.  Here, I've seen many R-500 to R-22 conversions.  I
recommend to servicemen doing this work to change out the TEV and
resize the refrigerant distributor to improve refrigerant distribution
in the coil with R-22.  Then hope for the best.  Oil return doesn't
seem to be a problem--R-22 is a fairly reactive refrigerant and tends
to drag oil along in the suction line pretty well at low velocities.

BTW, you think placing R-22 condensing units on R-500 coils is
'challenging', just wait till you see the new condensing units using
R-22 alternative refrigerants make it to market.  These units, with
their polyol ester oil, will likely be hooked up to old, beat up R-22
evaporators. Expansion devices *WILL* have to be changed for the unit
to operate properly.  And the ester oil may create moisture and foreign
material problems not seen before in the residential a/c industry.

Isn't this a great industry????!!!!!!

Andy Schoen
[email-masked]

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From: [email-masked] (George Goble)
Date: 28 Jul 1995 15:12:35 GMT

In article <[email-masked]> [email-masked] (FryinBryan) writes:
 >The following scenario involves a client of ours that is experiencing
 >difficulty with a Home Warranty. The warranty was purchased when our
 >client purchased the home.  The home is at least 25 years old.  Our
 >company has already advised the client of our opinion. However, we would
 >appreciate any opinions from HVAC professionals.  Please be advised, your
 >opinion or statement may be used to support the homeowner in their
 >arguement with the Home Warranty Insurance Company:
 >
 >The residence in question is a single story, ranch style home.  The
 >original air conditioning consists of a split system, Carrier, R500
 >refrigerant air conditioner.  The air handler and evaporator coil are
 >located in the attic.
 >
 >During the summer of 1994, the air conditioning failed.  The Home Warranty
 >company was notified by the homeowner and a HVAC service company was
 >dispatched by the Home Warranty company to fix the air conditioning.
 >
 >Shortly thereafter, the HVAC company condemned the condensing unit for
 >unknown reasons and a new, R22 refrigerant condensing unit was installed. 
 >No work was performed on the air handler or evaporator coil at the time of
 >condensing unit replacement.

Proper service after a compressor failure (was it that?), especially
if it was a motor "burnout", requires a proper cleanup of the
whole system.  Acids and other debris left over from the motor
burnout will lead to early failure of the new compressor,
or plugging of the expansion devices on the inside coils or both 
in a few weeks to a few months.
Power flushing with R-11 or other solvent is the best way to
clean up the lines and inside coils..  Other methods are
installing driers and suction filters (look like orange juice
cans installed in the refrigerant lines).  After a burnout,
return trips are needed to change these devices out one or
more times along with a compressor oil test for acids to
ensure the cleanup is complete.. Failure to do this will result
in new compressors failing.

--ghg (Inventor of R-406A, drop-in substitute for R-12)
http://ghg.ecn.purdue.edu
http://worldserver.com/R-406A

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From: [email-masked]
Date: 31 Jul 1995 03:36:50 GMT

>No oil or metering device changes.

George, expansion device sizing wouldn't seem to be a problem going
>from  R-500 to R-406A.  But in the case of a TEV, I doubt you would have
enough adjustment range in the valve to compensate for the differences
in pressure.  The dew point curve of R-406A (from the last publication
I have on the refrigerant) shows it to be significantly below that
of R-500.  A 'power head' change would be in order.

Andy Schoen
[email-masked]

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From: [email-masked] (George Goble)
Date: 31 Jul 1995 18:27:43 GMT

>of R-500.  A 'power head' change would be in order.

Although the static pressures of 406A are higher than 12 (82psig @ 70F),
things come right down when the system is started up.  Due to the glide,
the head pressure on 406A is sometimes lower than R-12.  I have never
put 406A in a R-500 system, these are just reports I got back
>from  users.. Most of them were in cap tube systems.. the users
seemed happy.  We have even had users change out R-502 systems
(cargo reefers) to R-406A! (after we told them not to)  All they changed 
was the TXV and the pressure controls.. no compressor change!  One would 
think the compressor displacement would way low for this.. but they
were happy and I didnt argue with them.

Purdue just lost chilled water campus wide.. valve broke and the whole 
loop dumped into the holding pond.. going down now
--ghg

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From: [email-masked]
Date: 3 Aug 1995 03:11:42 GMT

In <[email-masked]>, [email-masked] (George Goble) writes:
>seemed happy.

With systems using TEVs, the dew point curve of a refrigerant blend
must be considered, not the bubble point curve.  At 15F, the dew point
of R-406A runs approx 7 psi lower than R-12, and 12 psi lower than R-500.
Under ideal circumstances, the TEV adjustment would compensate for the
7 psi difference between R-12 and R-406A.  A 'power head' change would
be safer than depending upon the range of TEV adjustment.  The 12 psi
difference between R-500 and R-406A, however, would likely present problems
for any R-500 TEV.

Fortunately, cap tube systems are dependent on pressure drop, and the
refrigerant's density and net refrigerating effect.  Not the refrigerant's
saturation/dew point curve.

Andy Schoen
[email-masked]

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From: [email-masked] (FryinBryan)
Date: 3 Aug 1995 01:45:45 -0400

Thanks a bunch for the thread guy's! Just what I needed.

Sorry about the delay getting back to you.  107DF heat wave has kept me a
little busy!