Transport ref. unit TXV regulations.

[Edvin]

Hi Guys,

Reading this forum, puting the theory together with my expierience I have some serious questions.

If it is a stationary unit(not transport), usualy the heat transfers and compressor rpm are constant.
As I have a lot of work with direct drive units I have question at what parameters should the TXV be regulated? (compressor rpm, condenser heat transfers) because as I noticed that the higher the compressor RMP are - the higher the superheat is, on the other hand when the car ir moving the with increases the subcooling so the superheat lowers.

And not always the more rpm the car has the faster it goes (this is not linear - nope You understand what I mean)

I think there are no problems with trailer units, because thay have constant engine speeds and almost constant heat transfer throu condensser.
Truck units have constant rpm, but the heat transfer changes

But in direct drive units all values change.

So the final question is at what rpm (idle or caompressor max capacityor middle) and subcooling value (theoreticaly) should the TXV be regulated.

Sorry for the novel, but I think this is very serious and everyone had broken compressors on direct drive units without any obvious resons.

Best regards, Edvin.

[moggy66]

the TXV is set at factory so it should never have to be adjusted,if you think you have to adjust the txv there is usually another fault somewhere, the only time i have had to adjust a txv on a transport unit is when sombody messed around with it....usually direct drive units have a condensor fan cycle switch to regulate the condensor pressure..............but i can see the reason behind your question

[Edvin]

As we are mounting new direct drive units I see that regulations are completly wrong. As I have worked for carrier dealer carrier training people said that the unit should be regulated when mounted, but not always thats done and I very doubt that our competitors do it.

[moggy66]

Thats very interesting...i must make some inquires

[Edvin]

Few days ago we maunted a new Alex original unit, I didn't touch the superheat regulations, but i see that in the factory superheat is set quite large(I would say 10-15K at 0C in the box) - I usualy set 7-9K.