Reverse Cycle Air Conditioning

Technical discussion on converting internal combustion to electric
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AirAg
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Reverse Cycle Air Conditioning

Post by AirAg »

I am installing a reverse cycle airconditing switch in my Corolla as a requirement to be able to demist the windscreen. I purchased the switch from EV Works and had it installed by an AirCon tradesman. It works fine in cold mode but will not heat. My tradie thinks it is because of the TX valve not working in reverse. We are talking about putting another TX valve on the heat exchanger side to give the pressure differential to allow for cooling in the heat exchanger.
Has anyone used one of these switches and what other mods were needed to be done?
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gmacd33
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Reverse Cycle Air Conditioning

Post by gmacd33 »

I'm planning on doing this for a couple of the vehicles that I'm working on. I haven't done it yet, but the advice I have received is as follows:
"Many cars have a TX or thermal expansion valve - does not work with reverse cycle, need to replace with orifice valve."

On another note, the NCOP14 requires a heat source, OR an alternative method of demisting the windscreen. Therefore I believe that if you have A/C cooling working, that will demist the windscreen and thus satisfy the legislation requirement.

Although heating might be nice at this time of year - how cold does Goondiwindi get?!?
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polo-ev
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Reverse Cycle Air Conditioning

Post by polo-ev »

I had a good look at these but decided it was too fiddly for a car.
TX valves only work in one direction so you would either have to have a second one installed going in the other direction close to the outside condenser. You will also possibly need 2 bypass valves across each TX valve to bypass the TX valve not being used.
There are bi-flow TX valves available but you would need to find one the right size.
Alternately, you could replace the TX valve with a capilliary tube. These will work in either direction but they are a fixed orifice unlike a TX valve. TX valves can open & close to regulate the refrigerant flow & are more efficient than a capilliary tube.
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AirAg
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Reverse Cycle Air Conditioning

Post by AirAg »

Thanks for the replys. This is basically what my Air Con guy has come up with. He says that the orifice is not as good as the TX valve and will let liquid through whereas the TX valve can adjust to atomise the liquid better. This means he will have to put a collector tank prior to the pump to capture any liquid. Depending on the cost and practicality of all this I may go back to an electric heater element.
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Reverse Cycle Air Conditioning

Post by mcudogs »

If it's just for demisting the windscreen it should work ok in cooling mode.
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