stuck on reversible ac system question in kotza book

[moondawn]

hi there,

i am reading the kotza book which i am studying at home at night and have a question. i am reading about reversible A/C system so just a split system as the example is.

it says in my book that the liquid reciever is used when systems have 4way reversing valves and that in cooling operation mode the condensor is full of liquid. this bit i understand.

but then says when the cycle is reversed in to heat mode and the condensor changes in to an evap, this means a large quanity of liquid is being drawn into the compressor hence the liquid reciever being fitted to the suction side of the compressor.

please could someone explain why large quantities of liquid would be in the Outdoor Unit which has then become the evap?

i thought on heat mode that would mean the indoor unit would have the large quanity of liquid inside it.

struggling to get my head around this bit?:confused:

cheers lee

[Brian_UK]

Firstly splits normally have a suction accumulator not a liquid receiver to protect the compressor.

Now back to your headache...

Think about the system in cooling when the evaporator is gas and the condenser is liquid; the gas is returning, via the reversing valve, through accumulator to the compressor.

Now, when the unit changes over into heating mode it starts with the liquid in the outdoor coil; what was the condenser is now the evaporator. The liquid gets sucked, via the reversing valve and accumulator, into the compressor. The liquid is held in the accumulator with the gas being taken off the top to the compressor.

Once the system has stabilised the liquid has relocated to the indoor, condenser, coil and the evaporator is feeding gas back to the compressor.

If you now change back to cooling the liquid has now got to be moved back to the outdoor coil so it will go via the accumulator again.

Clear as mud now? :)

[moondawn]

hi brian
thats great that i understand now the book is not being clear for me, so on startup from a mode change ie cooling to heating this would mean the liquid gets sucked back towards the compressor then when the cycle is working how it should the liquid will then be in the indoor unit on heating.

i am on the right track now aint i mate?

[Brian_UK]

That's it, you've got it.

Cooling: Wet outside/dry inside
Heating: Wet inside/dry outside.

Simple graphics here...
http://www.copper.org/applications/plumbing/heatpump/geothermal/gthrml_main.html