Electronic expansion valve, Eglehoff

[Jonc]

I am experimenting with an air source heat pump, and need something better that a mechanical TEV since I'm operating over such a wide range. (heating water from 20°C up to 60°C
I have a new (old stock) Eglehoff valve.
egelhof. escap p5 32 258 012 20. swis made xj.06.92
3/8, 1/2" rtc .05 VE

But I have nothing to drive it. Apparently the pulse voltages are quite tricky. Anyone know where I might get some specification on this. My guess is that this level of data is usually kept secret by manufacturers.
If I draw a blank, I will look for a proprietary electronic valve to try. Any suggestions of what make to try? I am talking small. 1/2 tonne or so.
thanks

[desA]

I am experimenting with an air source heat pump, and need something better that a mechanical TEV since I'm operating over such a wide range.

An interesting statement. Why should that be so?

[Jonc]

Why am I experimenting with an air source?
Maybe because I have less money than sense!
If I were sensible I might buy a new one. However, my experiment is to 'batch heat' hot water so that the average COP is high. This is all down to the cylinder, not the heat pump. However, to get a decent COP when the air is as warm as the water being heated, one needs a heat pump with a good refrigerant control. hence my experiment.
I like experimenting.

[desA]

Let me adjust the quote - my question was regarding the TXV.

...heat pump, and need something better that a mechanical TEV since I'm operating over such a wide range. (heating water from 20°C up to 60°C

Why will a standard TXV not suffice?

[Brian_UK]

The TEV will be operating the evaporator not the condenser side of the machine. Part of it's function is to protect the compressor from liquid slugging.

[Jonc]

Hard to get a mechanically controlled orifice to operate with such a wide range of pressure difference across it. One needs sufficient pressure across the valve to enable sufficient flow when condensing pressure is close to evap pressure. Conversly, at very high head pressures, the valve is likely to hunt. I understand that electronic valves do it much better

[chilled kiwi]

The voltage will be either 12 of 24 volt. The valve is a on/off type, so just experiment with the on/off times. As you get closer to the superheat setpoint the on times get smaller. From memory, when I had a Danfoss valve it seamed to be on for about 15s and off for about 30s on the particular system. Have a safety setpoint that prevents the valve opening on low superheat. Failing that go to a Carel EEV. They use a stepper motor rather than a pulse valve. On their webpage go to the KSA area and you will find a program to size the valve.

[Jonc]

Thanks for your thoughts. I had got around to thinking that the pulse method was the best way to go. I can probably cope with circuitry for controlling the pulses. It seems to me that the available drivers, like the Eliwell, are too complicated.

[lice to chill]

Let me adjust the quote - my question was regarding the TXV.



Why will a standard TXV not suffice?

danfoss hua tx element will measure superheat at compressor discharge if a mech/tev required.

[lice to chill]

danfoss txv have a thermal element measuring superheat at the compressor discharge oldy but a goody.

Let me adjust the quote - my question was regarding the TXV.



Why will a standard TXV not suffice?

Thanks for your thoughts. I had got around to thinking that the pulse method was the best way to go. I can probably cope with circuitry for controlling the pulses. It seems to me that the available drivers, like the Eliwell, are too complicated.