exv

[bangoman]

Bn readin an article on electronic expansion valves .It says to check if the valve is functional you connect a step motor to the exv socket on the pcb.Wats a step motor,hw does it show the status of valve.Isnt there any other method besides havin to access the indoor unit pcb?Thank you all .

[Brian_UK]

A step motor is one that is rotated in steps, small movements, at a time.

The controls send pulses of power to it instead of a steady stream of on/off power.

For example, a valve may need 2000 steps to drive it fully open so giving it 1000 steps will only open it half way.

[Thermatech]

This is a common trouble shoot for service engineers looking at vrv / vrf systems.
If the indoor unit has no refrigerant flow or excessive refrigerant flooding through the indoor coil then you need to investigate the cause of this incorrect operation of the eev / lev.

But is the circuit board sending the correct d/c pulse commands to the valve ?
or is the valve step motor defective ?
or is the needle valve defective ?

To find the cause of the problem you need to investigate further.
A very easy way to proceed is to connect a new spare part valve to the indoor circuit board, hold the valve in your hand & watch to see it opens up when you set the indoor unit for test cooling & fully shut when you set the unit to off.
This test will indicate if the indoor circuit board is ok or faulty.
Next remove the suspect valve motor head from the indoor coil valve body & fit it onto the new spare part valve body.
Proceed as before & this will indicate if the motor head is faulty or not.

On some vrf systems you can get data from the outdoor unit or connect lap top computer which tells you what the opening pulse of each indoor unit is but it cannot tell you if the driver circuit on the circuit board is actually sending that command to the valve motor head or if the valve motor is responding to that command & actually moving the needle valve.
As most service engineers are not electronic experts & are unable to monitor the d/c pulse output from the circuit board this 'valve in your hand' trouble shoot test is an easy procedure which anyone can carry out.

[Grizzly]

This is a common trouble shoot for service engineers looking at vrv / vrf systems.
If the indoor unit has no refrigerant flow or excessive refrigerant flooding through the indoor coil then you need to investigate the cause of this incorrect operation of the eev / lev.

But is the circuit board sending the correct d/c pulse commands to the valve ?
or is the valve step motor defective ?
or is the needle valve defective ?

To find the cause of the problem you need to investigate further.
A very easy way to proceed is to connect a new spare part valve to the indoor circuit board, hold the valve in your hand & watch to see it opens up when you set the indoor unit for test cooling & fully shut when you set the unit to off.
This test will indicate if the indoor circuit board is ok or faulty.
Next remove the suspect valve motor head from the indoor coil valve body & fit it onto the new spare part valve body.
Proceed as before & this will indicate if the motor head is faulty or not.

On some vrf systems you can get data from the outdoor unit or connect lap top computer which tells you what the opening pulse of each indoor unit is but it cannot tell you if the driver circuit on the circuit board is actually sending that command to the valve motor head or if the valve motor is responding to that command & actually moving the needle valve.
As most service engineers are not electronic experts & are unable to monitor the d/c pulse output from the circuit board this 'valve in your hand' trouble shoot test is an easy procedure which anyone can carry out.
Thank you Thermatech.
Yet another useful and informative post.
Not my normal field of operation. But there is a definate trend towards acres of VRV's and VRF's instead of Chillers. So it is not going to be long before "we" will have to get some more training.
Personally I'D RATHER LEAVE IT TO YOU GUYS WHO KNOW!
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

[The Viking]

Thanks Thermatech,
That's sounds like a good way of doing it.


All we needs now is manufacturers that puts these valves where we can actually access them...

[Pooh]

And bigger vans to carry all the spares around in for all the different models each manufacturer makes, it would be so much easier if they used a standard valve and actuator would'nt it?

Ian

[Thermatech]

Pooh
Most of the major Japanese manufacturers buy indoor unit lev valves ( electronic linear control valve )from specialist manufacturer called Fujikoki in Japan.
The model code is EDM & has not really changed for more than 10 years.
I work mainly with Mitsubishi Electric, Daikin & Hitachi & they all use excact same lev valve.
Next time you replace one order two & keep one in the van to use as a service tool.
They dont last forever so lev locked open or shut is a common fault on older vrf systems.
But you will look a bit of a plonker if you return to site with a new lev valve but then find the circuit board is a duffer.
So its best to confirm correct operation of the circuit board on first site visit.

[Pooh]

Thermatech
interchangeable parts between manufacturers now theres a novelty. Most of the manufacturers kit I have worked on in the chiller field have had their own bespoke controls or even if the valves have been from another manufacturer there was usually something extra that meant you could not fit a standard part.

Were is the best place to get some training on VRV VRF systems as I have never had anything to do with them and I should really have more of an idea than I have.
I see them as a supermarket pack with hot gas defrost so you can heat and cool if you want however I may be wrong but the principle seems the same.

Ian

[nike123]

This could be of some help:
http://tinyurl.com/2lgm6w

[Thermatech]

Pooh
All the major vrf manufacturers in the uk do some training. But you might have to pay unless you buy lots of kit & qualify for some free training.
For example Mitsubishi Electric do a vrf basic for service engineers then a vrf advanced for senior service engineers & then a controls course for service & BMS engineers. Each is one day.

I think Mike Creamer at Business Edge is the only independant who does some vrf training.

[bangoman]

A great forum indeed I really feel am growin in the trade since my move frm Africa to Aussie befor then most of what I read used to be jargon at least now I can comprehend .Thanxs again guys!

[Thermatech]

Nike123

The valve link you have posted is for a typical 500 step lev valve. A lot of a/c manufacturers use this type of valve in resedential split systems & vrf outdoor units. I have only ever seen this type of valve fitted to a/c outdoor units.
vrf indoor units have historically used the 2000 step valve.
The needle moves less than 2mm fully open to fully shut. So for each one step command from the indoor circuit board the needle moves less than 0.001mm .
This gives very exact control of indoor coil SH & SC & is part of the reason why vrf systems are so energy efficent.
The 2000 step valve is a lot more complicated as it has a seperate motor head & a gear box which looks like the inside of a swiss watch. The head is screwed onto the valve body.