Condensing unit switching off after a few minutes and give error code P8. Also the suction is very low at 300kpa but when charging with gas suction ices back from indoor unit to compressor. Filters and evaporator is clean and fan is running. Phases are ok. Mitsubishi PUH6yksa

There is several possible causes. The most probable cause is wrong charge. Many units have a low suction safety on the low pressure side of the compressor. There is often a high pressure swithch to guard against over pressure also on the high pressure side. If your unit has the condensing fan stop in mid cycle, the compressor has inherent motor contacts inside the compressor to help guard the compressor from overheating. I just recently had to replace several customers main contactor because the contactor contacts were severly burned and sometimes could pass current and sometimes could not. I also had a few customers whose condensing unit was so dirty that the compressor was overheating causing the inherent motor contacts to open. Hope this gives you some ideas to look.

Hi,
The orifice or the expansion valve are for a three ton unit and you only have a 2ton...so too much gas is going through causing low discharge and high suction... install correct orifice or TXV and you'll be okay...

heatman101

P8- Abnormal temp of out door. If new unit, check gas pressure, may be over charged. Release some gas. If existing a/c, check condenser coil- dusty- clean it. Check f.motor- less rpm-replace capacitor. F.motor mechanism locked- replace motor. If above all o.k., non-condensate gas inside. Release all gas, flush out, replace filter drier and vacuum. And do gas charging. Thanks, helpful.

Code P8
Error detail Abnormality of pipe temperature.
Inspected unit Indoor.

Check may be icing in your indoor coil due to evaporator coil /air filter blocked- Clean it.
Short of gas or gas leak. Call repairman to find out the leak & arrest to recharge gas.

Helpful?

E4 Outdoor activation of low pressure switch/ less suction pressure.

Check back pressure, which should be 60 PSI when ambient temp 98 degree.If not Short of gas- find leak and arrest. And do gas charging. Even due to indoor coil dust blocked also e4 arise. Clean the coil and reset it.

Code P8
Error detail Abnormality of pipe temperature.
Inspected unit Indoor. Due to non condensable gas/over charged/condenser dust blocked.
For non condensable gas, remove gas and flush out and then recharge gas./remove over charged gas/clean condenser coil

Add 404A to system. It is low on gas. But kep an eye on the TXV for ice buildup. Make sure unit is free of ice before you charge it. It is difficultr to charge a refer system when itis iced up. Rus

P8 error is abnormal pipe temperature indoor. If you are running it on heating P8 error will appear because the disc pressure is too high. It could be overcharged.

Look for any refrigerant leaks - no or low refrigerant can cause problems in both modes. The unit may be going off on low suction.

-OR-

The unit may be stuck in the heating mode.

Make sure the system is calling for the correct mode (cooling or heating) - some systems are auto, but if you can, select cooling since that is the requested mode. Check for power at the reversing valve inside the condensing unit. If power exists, then the reversing valve is stuck. It could also be the reversing valve solenoid coil, so make sure that isn't bad. There should be a strong magnetic field at the solenoid coil.

If you can hear the reversing valve clicking (moving), check the T-stat and make sure it will switch modes. Also check the reversing valve relay (those can be located in either the indoor unit or condensing unit).

The 3 beeps indicates that the freeze cycle is longer than 60 minutes. with the suction pressure at 20, it sounds like low on charge (freon). I believe this is an R 404-A unit. Other things to look for are: Stuck float switch (in the up position), Water valve leaking, hot gas valve leaking, txv not feeding properly, weak compressor. Look at high side pressure too. It should not go below 210 psi during the freeze cycle. Low pressure should be in the middle to upper 40's psi.

Let me know if you need more.