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

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')
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Have seen them overcharged and heard of a couple having a 'double' charge...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Whats your subcooling??

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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

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 .

You sure about that??

Not with a 55 degree ODT

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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)

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.

The other variable is air flow.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

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

That will exhibit additional symptoms, and cause other problems.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why?
--
Respectfully, Bob

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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 20 ambient but failure at 50 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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

text -

We all know we charge by SC on a TXV system, but knowing the SH is valuable data for troubleshooting.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ever see something other than the charge cause bad pressures????????
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

what method of charging did you use to add exactly 21 oz of gas?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I say you have a restriction and the problem (lack of cooling) will show up come summer.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Then why would a restriction magiclly vanish with a slightly lower refrigerant charge?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.