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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 Bud on March 7, 2007, 9:39 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')- 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.

Yep, maybe I need to go back to school but Rheem's documentation says
to use their chart. For heating mode use indoor dry bulb and suction
PSI then measure liquid PSI. If it's above that value recover. If
it's below then add.

(ex: 40 low, 70 indoor ambient = 196 PSI high side)

>
> > 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 connser coil or outdoor
> > TXV had problems.
>
> You sure about that??

What scenario other then overcharge would do that. Wouldn't
restrictions result in low suction pressure in heat mode since most
everything that would create a restriction is upstream from the
compressor's suction service post.

>
> > 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

The other variable is air flow.
>
> > 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.- Hide quoted text -
>
> - Show quoted text -



Posted by Noon-Air on March 7, 2007, 10:55 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')- 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.
>
> Yep, maybe I need to go back to school but Rheem's documentation says
> to use their chart. For heating mode use indoor dry bulb and suction
> PSI then measure liquid PSI. If it's above that value recover. If
> it's below then add.
>
> (ex: 40 low, 70 indoor ambient = 196 PSI high side)

According to the manufacturers charging chart, and the numbers provided by
the OP, the system is *STILL* a bit over charged. Without the actual LLT,
there is no way I can be sure that the subcooling is within normal range.
The model number of the air handler would be helpfull also to make sure that
it is a correct match for the heat pump. When doing the initial charging on
a R-22 Rheem heat pump, its a good idea to break the vacuum on the lineset
and inside coil with refrigerent vapor to approximately 50psig, open up the
service valves, then start up the system and balance the charge with
subcooling and superheat.

>> > 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 connser coil or outdoor
>> > TXV had problems.
>>
>> You sure about that??
>
> What scenario other then overcharge would do that. Wouldn't
> restrictions result in low suction pressure in heat mode since most
> everything that would create a restriction is upstream from the
> compressor's suction service post.

It depends on exactly where the restriction(s) are, and what mode the HP is
operating in.

>> > 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
>
> The other variable is air flow.

That will exhibit additional symptoms, and cause other problems.

>> > 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.- Hide quoted text -
>>
>> - Show quoted text -
>
>



Posted by Bob_Loblaw on March 8, 2007, 10:02 am




>When doing the initial charging on a R-22 Rheem heat pump, its a
> good idea to break the vacuum on the lineset and inside coil with
> refrigerent vapor to approximately 50psig, open up the service valves,
> then start up the system and balance the charge with subcooling and
> superheat.


Why?


--
Respectfully, Bob

Posted by Rob on March 12, 2007, 9:28 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')- 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.

We have faced this problem also, I'm need to go back to the info we took at
the time to see if there was a blatant issue but it seems that Rheem may
have an issue with these, even if the issue is just no tolerance for
*slightly* reduced indoor airflow, what is this system going to do when the
homeowner goes 2 months with a dirty filter? My questions for Rheem are,
why the wide variance from their chart due to operating conditions i.e.
perfect reading at 20º ambient but failure at 50º ambient, why good readings
in cooling and catastrophic head pressure in heat mode, what is the function
of the 'charge compensator' they've installed and how can we troubleshoot
something that isn't described in any of their technical literature?

- Robert



Posted by Noon-Air on March 13, 2007, 12:19 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')- 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.
>
> We have faced this problem also, I'm need to go back to the info we took
> at the time to see if there was a blatant issue but it seems that Rheem
> may have an issue with these, even if the issue is just no tolerance for
> *slightly* reduced indoor airflow, what is this system going to do when
> the homeowner goes 2 months with a dirty filter?

If the ductwork was correctloy designed, sized, and installed, then airflow
isn't an issue. If the customer doesn't change the filter(s) like they are
supposed to, then they are going to end up with a frozen evap in cooling
mode, or a tripped HPS in heat mode. Rheem doesn't have any more issues with
improper ductwork or dirty filters than any other manufacturers do.

> My questions for Rheem are, why the wide variance from their chart due to
> operating conditions i.e. perfect reading at 20º ambient but failure at
> 50º ambient, why good readings in cooling and catastrophic head pressure
> in heat mode, what is the function of the 'charge compensator' they've
> installed and how can we troubleshoot something that isn't described in
> any of their technical literature?

The answer you seek is 2 words grasshopper....

Subcooling and Superheat

You can have the specified pressure gauge readings, but without a good
thermometer(preferably digital) and a PT chart, your pissing in the wind.
If you can't charge by subcooling and superheat, you're fixin to replace a
compressor on your dime.
If you had attended all the training put on by the Rheem Tech Rep, you would
have a much better understanding. Sufice it to say that some manufacturers
equipment is a lot more tolerant of being installed by "Billy-Joe-Jim-Bob"
than others. Rheem and RUUD are much less tolerant of bad installs and
incorrect refrigerant charge balance.




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