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Pre-charged heat pumps - ever see one over charged???

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Pre-charged heat pumps - ever see one over charged??? Kettering 03-05-2007
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Posted by Kettering on March 5, 2007, 10:45 pm
Did an install on a Rheem 4T RPNE. Factory says to add .6 oz/ft. over
15'. OK, I pulled her down to <500 microns and added exactly 21 oz
gas. (ie 50-15 X.6 oz)

Now I fire her up and she runs about a minute of two and shuts off
while AH continues to go. "Y" remains hot.

Now I hook up the guages and low is about 65 PSI and hi goes upwards
of 300 PSI!!!.

OK now I recover the refrigerant and add enough back in to to bring it
to the Rheem chart. Now it's about 40-45 PSI low/200-210 PSI hi at
about 50 ambient and 65 IDB. It's producing about 25-30 heat rise
over the coil.

Have you ever seen the factory charge this far off?? Does elevation
affect factory charge that much? (site is at 1500')







Posted by on March 5, 2007, 11:31 pm
> Did an install on a Rheem 4T RPNE. Factory says to add .6 oz/ft. over
> 15'. OK, I pulled her down to <500 microns and added exactly 21 oz
> gas. (ie 50-15 X.6 oz)
>
> Now I fire her up and she runs about a minute of two and shuts off
> while AH continues to go. "Y" remains hot.
>
> Now I hook up the guages and low is about 65 PSI and hi goes upwards
> of 300 PSI!!!.
>
> OK now I recover the refrigerant and add enough back in to to bring it
> to the Rheem chart. Now it's about 40-45 PSI low/200-210 PSI hi at
> about 50 ambient and 65 IDB. It's producing about 25-30 heat rise
> over the coil.
>
> Have you ever seen the factory charge this far off?? Does elevation
> affect factory charge that much? (site is at 1500')


Have seen them overcharged and heard of a couple having a 'double' charge...



Posted by Noon-Air on March 6, 2007, 7:12 am

> Did an install on a Rheem 4T RPNE. Factory says to add .6 oz/ft. over
> 15'. OK, I pulled her down to <500 microns and added exactly 21 oz
> gas. (ie 50-15 X.6 oz)
>
> Now I fire her up and she runs about a minute of two and shuts off
> while AH continues to go. "Y" remains hot.
>
> Now I hook up the guages and low is about 65 PSI and hi goes upwards
> of 300 PSI!!!.
>
> OK now I recover the refrigerant and add enough back in to to bring it
> to the Rheem chart. Now it's about 40-45 PSI low/200-210 PSI hi at
> about 50 ambient and 65 IDB. It's producing about 25-30 heat rise
> over the coil.

Whats your subcooling??

> Have you ever seen the factory charge this far off?? Does elevation
> affect factory charge that much? (site is at 1500')



Posted by Bud on March 6, 2007, 5:44 pm
>
>
> > Did an install on a Rheem 4T RPNE. Factory says to add .6 oz/ft. over
> > 15'. OK, I pulled her down to <500 microns and added exactly 21 oz
> > gas. (ie 50-15 X.6 oz)
>
> > Now I fire her up and she runs about a minute of two and shuts off
> > while AH continues to go. "Y" remains hot.
>
> > Now I hook up the guages and low is about 65 PSI and hi goes upwards
> > of 300 PSI!!!.
>
> > OK now I recover the refrigerant and add enough back in to to bring it
> > to the Rheem chart. Now it's about 40-45 PSI low/200-210 PSI hi at
> > about 50 ambient and 65 IDB. It's producing about 25-30 heat rise
> > over the coil.
>
> Whats your subcooling??
>
>
>
> > Have you ever seen the factory charge this far off?? Does elevation
> > affect factory charge that much? (site is at 1500')- Hide quoted text -
>
> - Show quoted text -

Subcooling isn't valid for a HP running in heat mode. He could use the
Lennox method of heating the home with aux. heat then blocking off the
condenser and running it in AC mode to get his subcooling reading.
Superheat won't tell him anything either since his indoor coil has a
TXV.

For a HP in heating season the only accurate charging methods are the
manufacturers chart for heating mode and recovery/weighing it in.

I don't see any scenario on why a new HP would show both a high
suction and liquid line pressures unless it was overcharged. A bad
TXV or indoor coil restriction would cause high vapor line pressure
but low suction pressure. Same thing if the condenser coil or outdoor
TXV had problems.

It sounds like his system is now performing normal. 25 degrees heat
rise over the coil sound about right given his ambient. Low of around
40 and high of around 200 also sounds in the ballpark.

He should double check against the manufacturers chart and then come
back in cooling season and measure subcooling.



Posted by Noon-Air on March 6, 2007, 8:41 pm

>>
>>
>> > Did an install on a Rheem 4T RPNE. Factory says to add .6 oz/ft. over
>> > 15'. OK, I pulled her down to <500 microns and added exactly 21 oz
>> > gas. (ie 50-15 X.6 oz)
>>
>> > Now I fire her up and she runs about a minute of two and shuts off
>> > while AH continues to go. "Y" remains hot.
>>
>> > Now I hook up the guages and low is about 65 PSI and hi goes upwards
>> > of 300 PSI!!!.
>>
>> > OK now I recover the refrigerant and add enough back in to to bring it
>> > to the Rheem chart. Now it's about 40-45 PSI low/200-210 PSI hi at
>> > about 50 ambient and 65 IDB. It's producing about 25-30 heat rise
>> > over the coil.
>>
>> Whats your subcooling??
>>
>>
>>
>> > Have you ever seen the factory charge this far off?? Does elevation
>> > affect factory charge that much? (site is at 1500')- Hide quoted
>> > text -
>>
>> - Show quoted text -
>
> Subcooling isn't valid for a HP running in heat mode. He could use the
> Lennox method of heating the home with aux. heat then blocking off the
> condenser and running it in AC mode to get his subcooling reading.
> Superheat won't tell him anything either since his indoor coil has a
> TXV.

Time for you to go back to school there sport. Subcooling is the PREFERED
METHOD of charging Rheem heat pumps down to 40F ODT.

> For a HP in heating season the only accurate charging methods are the
> manufacturers chart for heating mode and recovery/weighing it in.

Manufacturers chart is based on subcooling. The subcooling for that
particular heat pump should be between 10 and 14 degrees with the
RBHK-24J18SFG or RHLA-HM4821JA air handlers .

> I don't see any scenario on why a new HP would show both a high
> suction and liquid line pressures unless it was overcharged. A bad
> TXV or indoor coil restriction would cause high vapor line pressure
> but low suction pressure. Same thing if the condenser coil or outdoor
> TXV had problems.

You sure about that??

> It sounds like his system is now performing normal. 25 degrees heat
> rise over the coil sound about right given his ambient. Low of around
> 40 and high of around 200 also sounds in the ballpark.

Not with a 55 degree ODT

> He should double check against the manufacturers chart and then come
> back in cooling season and measure subcooling.

Checking the refrigerant charge balance in cooling mode, once there is
enough of a heat load is a good thing.
However, if it was done right in the first place(even in heat mode), the
charge balance shouldn't change.



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