(-)P20B Inverter Heat Pump
What can I help you find?
Charging
Are you looking for the charging chart?
Please familiarize yourself with the process before consulting the chart links.
Factory Charge Values
| Size | Weight |
| (-)P2024B | 210 Ounces |
| (-)P2036B | 212 Ounces |
| (-)P2048B | 222 Ounces |
| (-)B2060B | 228 Ounces |
Charging Process
Charging an inverter system requires a skill level above that of an entry level service technician, but is otherwise pretty straight forward. You surely noticed these are not 8 or 10 SEER units with pistons or capillary tube metering devices, so we can’t treat them as such. The details are crucial to achieve proper charge. First and foremost a technician needs to understand is that there must be a specific load on the coil in order for pressures to line up with the ones on the chart. We’ve all seen in the past, on a high load, the suction is higher than it is on a low load, right? In other words, an 80 degree home will have a higher suction pressure than it would if it were 70 in the house, no?
So how do we ensure we have a load similar to that used in the development of the charging charts? It is safe to say, we don’t have control over the outdoor temperature, so the charts are made to accommodate various outdoor temps. We do however have the ability to control the indoor temperatures. After all that’s what we do for a living.
Airflow, or the quantity of air that carries heat, is also crucial to achieve a proper charge. This may mean turning off any airflow adjustments and de-humidification to provide design airflow. You can turn all that back on after you have completed the charging task at hand. None of those were in play when the charts were developed for the sake of consistency.
Finally, since these are variable speed units, it is important to have the compressor running at the designated speed. For the (-)P20**B Models, this speed is known as charging speed. Below, we will provide that speed by model number.
The following criteria must be achieved in order for charging to work.
• For Charging in Cooling, the Outdoor Temperature must be between 55 and 99 degrees.
• Indoor temperature must be 80 degrees F +/- 2 degrees.
• For Charging in Heating, the Outdoor Temperature must be between 40 and 60 degrees F.
• Indoor temperature must be 70 degrees F +/-2 degrees.
• The system must be matched.
• The coils and filters must be clean.
• Airflow Adjustments must be turned off.
• Compressor must be running at high speed.
o (-)P2024B – 3000 RPM for Cool – 3000 RPM for Heat
o (-)P2036B – 2800 RPM for Cool – 2800 RPM for Heat
o (-)P2048B – 3750 RPM for Cool – 3750 RPM for Heat
o (-)P2060B – 4100 RPM for Cool – 4100 RPM for Heat
When applied with an EcoNet thermostat (601 series, rev 90 or later, or 700 series). You may go to the menu and find the service icon, and select OD checkout. You may set the variable speed test to charge cool, or charge heat depending on the mode you are going to charge it in. You may still access the status screens. Once the compressor RPM’s are at high, verify airflow.
Charge mode will temporarily disable de-humidification mode so airflow will not be reduced during the charge process. Be sure to turn off any airflow adjustments in the thermostat as well.
• Verify Airflow is where it needs to be for the equipment.
o 2 Ton – 800 CFM
o 3 Ton – 1225 CFM
o 4 Ton – 1575 CFM
o 5 Ton – 1700 CFM
If the system has been wired legacy make sure both Y1 and Y2 are calling. The outdoor unit, when wired legacy will only operate at one speed but the air handler doesn’t know that having been wired legacy. The legacy single stage operation is the correct RPM for charging.
Allow the system to operate on the factory charge for a while. I would love to say 15 minutes, and while that may be the case occasionally, it won’t hurt to go 30 or 40 minutes before attempting to adjust the charge.
Measure the outdoor temperature (the temperature of the air going into the outdoor coil) and plot this on the charging chart. It’s important to remember all the key bullets listed above.
As for the indoor condition, it needs to be 80 degrees, plus or minus 2 degrees entering the indoor coil. If its not, then the load on the indoor coil does not match the conditions used to develop the chart and you cannot expect the pressures to line up with the chart.
If the head pressure is lower than the chart add refrigerant. If it’s higher, remove some refrigerant. Wait for a period of at least 15 minutes before making additional adjustments. Once you have pressures similar to those on the chart, allow the system to stabilize and then you can look at the subcooling. Do NOT go straight to subcooling. You must allow the system to stabilize and redistribute the refrigerant you added or removed. None can be left in the accumulator and the metering device must have settled as well.
Subcooling is used to overcome a pressure drop in the liquid line. The smaller or longer the line, the more pressure drop the subcooling must overcome. The subcooling will be displayed on the 700 series thermostat outdoor unit status screen during charging mode. If you have a short line set, chances are you can be a little short on subcooling and be just fine. Overcharges can cause failures related to high discharge pressures such as envelope faults, overcurrent and others. Do NOT overcharge the system. The old adage of “If a little is good, a lot is better” does not, and never has applied to refrigeration.
Superheat may be viewed as well at the thermostat but you must look in the right place depending on the mode. For cooling mode, use the status screen for the indoor air handler. You cannot get superheat from a cased furnace coil. For heating mode superheat, go to the outdoor unit status screen.
If you are commissioning the system in temperatures below 40 degrees or above 99 degrees, you will most certainly have to get it close and plan a return trip to finalize the charge when conditions are suitable. There is data in the charging chart for conditions outside of these ranges, but they are not going to be 100% correct, especially in heating below 40 because the accumulator may be storing some of the refrigerant and above 100 degrees, it’s too easy to overcharge the system.
One of the biggest challenges the author sees is technicians slapping gauges on an installed system and looking at a chart. There is no room for this type of service without the system being in charge mode. It will most certainly lead to adjustments to the charge that should not be needed.
