HVAC TQ - Valve

it makes water cold

1) what is TQ valve? Electronically controlled expansion valve.

how is it operate????

It operates electronically.

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Looking at the Danfoss diagram on page 8, I don't see how superheat is measured. At least they are not showing it as an input to the controller. Maybe that's too much detail.

I worked with experimental electronic TX valves ~1979 from Singer (heat pump research). These were for small tonnage systems. It used a thermistor to measure superheat. And 24VAC was system voltage. I looked back a few years ago, and it looks like these never made it to market.

In one implementation I saw (quite some time ago) the superheat was measured by comparing the readings of two 1000Ω platinum RTDs, one where the refrigerant piping enters the evaporator and the other where the refrigerant leaves the evaporator. Low superheat (~2°C) could be maintained.

I would think they would integrate one of the thermistors in the valve. What really is confusing is the equalization pressure line, in the document say's to connect near the valve output, not where the superheat is measured at the evaporator output, this makes no sense. Which is probably why the OP is asking.

Does this valve control constant superheat, or is it controlling some full flooding of the evaporator, like a low side float system. The text indicates controlling real small superheat values. I would assume there is a suction accumulator to prevent liquid slugging the compressor.

The tech sheet doesn't show what is attached to the controller, such as possible temperature sensor(s).