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Daz man
14-12-2012, 10:52 PM
Hi blokes,

i have come across this expansion valve (metering device) on an air to water chiller.

with out sounding stupid, can somebody explain how it works?

More so with the pipe connections on top of the device. I've never seen one like this before.

Obviously you have in the device & out the device, the bulb on the end of a capillary. But what are the other two connections for, what is there purpose?

The piece of pipe that comes out of the top of the device (NOT! the pig tail piece) this bends 90 degrees and enters back into the liquid line straight after the expansion valve??

Not your every day run of the mill TEV!

Thanks

Tayters
14-12-2012, 11:01 PM
Does the pipe which goes back to the liquid line have a solenoid valve in it? If so I think this solenoid is opened to get liquid pressure to close the valve up when you don'e need cooling anymore.
Where does the other small pipe go?

Daz man
14-12-2012, 11:07 PM
Will check on your second question, can't remember exactly. But there is no solenoid on the other piece of pipe, just straight into liquid line!

is this type of expansion valve got a specific name/type?

RANGER1
15-12-2012, 03:01 AM
Danfoss PHT pilot operated main valve.

one connection on top external equalizer, the other they call "pilot connection".
Used on bigger eqipment usually with solonoid valve on external equlizer to close valve off.

You can also get electronic ones with the pilot PHTQ.

Daz man
15-12-2012, 08:29 AM
Appreciate that! There's always some body on this forum that comes up trumps! Cheers Ranger1

Grizzly
15-12-2012, 08:34 AM
Hi Daz.
Following on from rangers excellent answer.
http://www.danfoss.com/Products/Categories/Group/RA/Thermostatic-Expansion-Valves/Thermostatic-Expansion-Valves-Exchangeable-Orifice/PHT/0c79a379-7572-48fe-9cfd-e62a160b2e5d.html
Grizzly
PS that looks like an old York of some description?
**HP by any chance?

hookster
15-12-2012, 10:16 AM
As per Grizzly and Rangers answers on a larger TEV

I just wanted to add a basic understanding answer for the why of the extra porting arrangement, by using a pilot valve, pressure is used to provide the larger force required to shift the valve while keeping the size of the components to a more manageable arrangement. The valve should be considered as two separate units a pilot valve and a flow valve the manufacturer has combined both into a single body arrangement.

Pilot valve operation is as per a standard TEV where bulb pressure and its spring pressure need to be overcome for valve to open.

http://www.acr-news.com/masterclass/news.asp?id=652&title=Masterclass%3AExternally+Equalised+Thermostatic+Expansion+Valves+%2D+Part+11

The flow valve is balanced by the extra port connection and the higher pressure after the evaporator to reduce the force required from pilot signal to overcome its main closing spring pressure and the larger forces generated by the larger flow valve. The balanced flow valve piston line also provides surge control.

RANGER1
15-12-2012, 06:28 PM
There would still be a lot of these valves out there in air con chillers, would'nt there?

Or maybe its a sign of my age!

Daz man
15-12-2012, 07:00 PM
Blokes! Tar very much for the feedback! I've cut my teeth for 15 years now on mainly AC. Splits, VRV's etc etc over my short time I've worked on the odd Trane chiller but now I need to earn my stripes and start being classed as a proper fridge engineer by working on and more importantly fixing chillers!!i find that's where the dollar is!