Heat Pump Low Pressure Faults

[frank]

During the past couple of weeks in the midst of the cold spell, we have attended several call outs to E4 (low pressure) faults on Daikin splits. Systems on R407C and in heating mode with the coils heavily frosting and not clearing fully on defrost.

Even the one recently fitted in our office was showing E4. I thought that the apprentice had not pressure tested correctly so I got him to recover and re-test, only to find that it was sound with a correct charge!!

Any one else been having these problems?

[Quality]

Not me personally but I do know a lot of engineers I associate with have had similar troubles during this recent cold spell

[marc5180]

Yes we have also had a couple with the most recent being on a Lennox packaged unit that trips as soon as the temperature drops.

I've got a post on here entitled "would a HGB work"

[nike123]

I think that is possible that during low temperatures R407C somehow fractionate partially (as oppose to R410A) and therefore low pressure alarm. I have that error frequently on air-to-water heat pumps of larger capacity with R407C and they are usually limited to -5°C outdoor air temperature working limit. I personally set them to use electrical backup heater when temperature is -2°C (which is rare in my location).

[DTLarca]

I think that is possible that during low temperatures R407C somehow fractionate partially (as oppose to R410A) and therefore low pressure alarm. I have that error frequently on air-to-water heat pumps of larger capacity with R407C and they are usually limited to -5°C outdoor air temperature working limit. I personally set them to use electrical backup heater when temperature is -2°C (which is rare in my location).

Internal fractionation causes higher pressures.

[Slim R410a]

During the past couple of weeks in the midst of the cold spell, we have attended several call outs to E4 (low pressure) faults on Daikin splits. Systems on R407C and in heating mode with the coils heavily frosting and not clearing fully on defrost.

Even the one recently fitted in our office was showing E4. I thought that the apprentice had not pressure tested correctly so I got him to recover and re-test, only to find that it was sound with a correct charge!!

Any one else been having these problems?

Not in work but when I've been at my gym one of the Daikin spits goes onto E4 on both cooling and heating. Think its R407c but didnt look into that far.

[frank]

Forgot to mention.....

We have also had this happen on a 3 pipe RSEYP8.

[frank]

Not in work but when I've been at my gym one of the Daikin spits goes onto E4 on both cooling and heating. Think its R407c but didnt look into that far.

If it's an E4 fault on both heating and cooling then it may have lost it's gas and be a genuine LP fault.

[Improver]

I have had a e4 fault code before on a sililar system but the charge was fine, The problem was a defective p.c.b on outdoor unit. I changed the p.c.b and got it back up and running again.

[jimmy wilkes]

could be lp sensor/transducer.get ur gauges on,run it and watch the gauge.if the comp starts to drive the back pressure to where u wanna be then goes into fault its ur faulty lp.check with "technical help desk!"on resistance readings before u change the pcb

[frank]

Looking at some of the replies to this thread, it's obvious that the main point has been missed.

The cold weather has caused the R407C to reduce in pressure below the set point of the LP switch/sensor.

Once the ambient has increased the LP fault goes away, without any loss of charge.

Please re-read the original post.

[DTLarca]

could be lp sensor/transducer.get ur gauges on,run it and watch the gauge.if the comp starts to drive the back pressure to where u wanna be then goes into fault its ur faulty lp.check with "technical help desk!"on resistance readings before u change the pcb

Voltage readings on transducers - resistance readings on thermistors.

[jimmy wilkes]

only known 407c systems struggle in cooling in low ambient.heating should b good or have i had too many knight riders.tis d wkend!!!!

[desA]

Looking at some of the replies to this thread, it's obvious that the main point has been missed.

The cold weather has caused the R407C to reduce in pressure below the set point of the LP switch/sensor.

Once the ambient has increased the LP fault goes away, without any loss of charge.

Please re-read the original post.

Heat-pumps tend to run a low suction pressure for some time directly after a cold start-up. Once the system gets itself moving towards equilibrium, the suction pressure will lift. Some manufacturers install a start-up timer which bypasses the LP trip until the system has stabilised.

It could be that the LP trip, or system setting, is actually a tad too high for prevailing conditions. Alternatively, there may be a start-up time delay function that can be modified.

[DTLarca]

Heat-pumps tend to run a low suction pressure for some time directly after a cold start-up. Once the system gets itself moving towards equilibrium, the suction pressure will lift. Some manufacturers install a start-up timer which bypasses the LP trip until the system has stabilised.

It could be that the LP trip, or system setting, is actually a tad too high for prevailing conditions. Alternatively, there may be a start-up time delay function that can be modified.

A good point I am working on too. I have been drafting an article on the matter of HP operating characteristics in colder seasons to publish in the industry magazine currently publishing my thoughts. Like most articles I write - I write them because it is something I want to undertsand better - not because I already understand