VRV expansion devices.

[Markie]

Another theoretical question thats bugging me.
On the Daikin vrv's ive been installing it seems that the expansion devices are at the indoor unit. I havent really taken an indoor apart to have a look as I never have the time but i assume there is some kind of electronic expansion valve at the indoor unit that allows refrigerant to flow when the unit is calling for duty.
Thats pretty obvious and all fine and dandy etc but what i want to know is this. When you are pressure testing or evacuating the system with no power to the units this expansion device restricts the flow of gas but does not shut of completely.
So why is it that when the condenser is running but you may have a particular unit or group of units turned off that there is not refrigerant passing through those expansion devices causing the refrigeration effect.
I.e. if you turned the power off to one particular unit and left the system running, why does this unit not start to ice up?

[Lc_shi]

it's an interesting topic which I'm not familiar with . As I know the VRV‘s compressor is VFD type and can accomodate the indoor unit on /off load change.

Let Marc say more about it:)

rgds
LC

[DALO]

Im not certain because its a long time since i worked on a VRV but dont the expansion devices open just 2% in an off cycle for oil return purposes??
Surely this tiny amount wouldnt be enough to provide a cooling effect.
Also on the Mitsi Y series system if i remember correctly i pressure tested a system once which held 300psi on the high side but lost all nitro on the low side. Hence the valves were fully shut. Cant remember if power was on or off.

[frank]

You are correct about the EEV being on each indoor unit. This is how the outdoor unit is able to ramp up and down to suit the load.

The basic operation of the VRV is this:

The outdoor unit has one or more inverter driven compressors (depending on which series) and so has a wide capacity control.

On the outdoor unit is a suction pressure transducer which monitors the returning vapour pressure. This is what adjusts the compressor speed. High suction pressure - high compressor speed etc.

If all indoor units have a high demand for cooling then all of the indoor EEV's will be pulsed fully open (2400 pulses).
As each individual indoor unit approaches control set point then the EEV pulse signals are reduced and the valve starts to close (0 pulses).

As the indoor units start to shut down because they are getting satisfied, the suction pressure drops and the outdoor suction pressure transducer picks up on this. The compressor speed is then reduced to try and maintain a high suction pressure.

As you can see, when there is no load on the indoor unit the valve receives 0 pulses and so remains closed.

This is the reason why the indoor unit does not ice up when the rest of the system is operational.

Also, if you cut the power to one of the indoor units, as you suggest, then after 20 seconds (the control loop time) the whole system will stop under fault conditions (U9 fault).

When installing VRV you must never apply power to the indoor units until all pressure testing and vacuum proceedures have been carried out. The indoor units are sent from the factory with the EEV fully open. The moment you apply power then the EEV is forced 100% closed effectively isolating the indoor unit from the system.

If you inadvertantly apply power to the indoor units before you have completed all the pipework operations then you will need to attach a Service Checker to re-open the valves.

[aeb200]

If you inadvertantly apply power to the indoor units before you have completed all the pipework operations then you will need to attach a Service Checker to re-open the valves.

not necessarily!! - as the LEV is a stepper motor you can reverse 2 wires to drive it back open (standard daikin LEV reset).

If you swap the yellow and White cables in the jumper that plugs on to pcb LEV drives out.

[Andy]

Im not certain because its a long time since i worked on a VRV but dont the expansion devices open just 2% in an off cycle for oil return purposes??
Surely this tiny amount wouldnt be enough to provide a cooling effect.
Also on the Mitsi Y series system if i remember correctly i pressure tested a system once which held 300psi on the high side but lost all nitro on the low side. Hence the valves were fully shut. Cant remember if power was on or off.

The oil return is carried out as part of an oil scavenge cycle. I assume the units are force run on cooling to return the oil.
Frank will know the answer to this:)

Kind Regards. Andy

[Markie]

.


When installing VRV you must never apply power to the indoor units until all pressure testing and vacuum proceedures have been carried out. The indoor units are sent from the factory with the EEV fully open. The moment you apply power then the EEV is forced 100% closed effectively isolating the indoor unit from the system.

If you inadvertantly apply power to the indoor units before you have completed all the pipework operations then you will need to attach a Service Checker to re-open the valves.


Thanks for replies, I think this answers my question Frank.
BTW what is a service checker?

[frank]

The oil return is carried out as part of an oil scavenge cycle. I assume the units are force run on cooling to return the oil.
An oil recovery is done 2 hours running time after commissioning and then every 8 hours running time. The system control (set points) is suspended, the indoor valves are forced fully open, indoor fans switched off and the compressor is ramped up to full speed for a short duration (off the top of my head I can't remember the exact time in minutes). This causes maximum velocities around the system which returns the oil to the compressor.


BTW what is a service checker?
It's a bit of Daikin kit that attaches to the laptop and the F1 F2 connections. It lets you see/log/control the whole system. Everything going on in the electronics is shown, compressor frequency, oil temp, suction pressures - too many things to list :)

Very helpful for fault finding.

If you are reclaiming the charge from a VRV there is a recovery button sequence that can be used on the outdoor PCB. What this does is force all the indoor valves fully open then you must switch off the power while you reclaim. There's no way of knowing if all the valves are open though without a Service Checker.

[Markie]

An oil recovery is done 2 hours running time after commissioning and then every 8 hours running time. The system control (set points) is suspended, the indoor valves are forced fully open, indoor fans switched off and the compressor is ramped up to full speed for a short duration (off the top of my head I can't remember the exact time in minutes). This causes maximum velocities around the system which returns the oil to the compressor.


It's a bit of Daikin kit that attaches to the laptop and the F1 F2 connections. It lets you see/log/control the whole system. Everything going on in the electronics is shown, compressor frequency, oil temp, suction pressures - too many things to list :)

Very helpful for fault finding.

If you are reclaiming the charge from a VRV there is a recovery button sequence that can be used on the outdoor PCB. What this does is force all the indoor valves fully open then you must switch off the power while you reclaim. There's no way of knowing if all the valves are open though without a Service Checker.


Thanks for info Frank. You must be well into your Daikin VRV as Ive worked with quite a few people who've been putting it in for years without this kind of knowledge. On the install side its not generally necessary I guess but I kind of like knowing the ins and outs of the cats arse with whatever Im doing if you know what I mean. :)

Also regarding the service checker and reclaiming, I presume there is no problem with reclaiming even if you dont know if all expansion devices are open as long as you are connected to both sides of the sysytem?

[frank]

I presume there is no problem with reclaiming even if you dont know if all expansion devices are open as long as you are connected to both sides of the sysytem?
Would you be happy recovering from a cellar cooler not knowing if the SV was open - what if the tev was closed? the pipework between the SV & TEV would contain trapped refrigerant :eek:

With the VRV (it differs, I know :rolleyes: , between 2 pipe and 3 pipe) you could end up with trapped refrigerant between the BS box and the indoor unit even if you make sure you are connected to both the high and low side.

I'm not saying you can't recover without a Service Checker - you can if you follow the correct proceedure - but having the correct tools makes for an easy job ;)

Ask the boss to get you on a training course.

Ive worked with quite a few people who've been putting it in for years without this kind of knowledge

Frightning :eek:

[Andy]

Ask the boss to get you on a training course.


Frightning :eek:

But normal. I don't even work at A/C, but I can see that their is a lack of knowledge out their. In fairness Dakin are a bit secretative. The company I work for sold Dakin for, well a lot of years, all the manuals are there in hard copy, but we found them very hard to approach when you had a problem. We now sell Toshiba and find then very good for back up, technically speaking. There is a few differences, main one being, we now call it VRF:D
Rotary compressors on the condensing units, variable speed control on all the compressors (not one fixed and one speed control) and from memory the BS Box is now called a ref net.
Also all units are 410a which cuts down on size at bit and saves a bit on piping and install times.

Being rotary compressors less oil is carried over so the there is less need to scavenge oil back.

In all we think Toshiba are ahead of Dakin.

They also claim to have created the VRF system eairlier than Dakin too, I have my doubts:D

What do you think Frank;)

Kind Regards, Andy:)

[frank]

Hi Andy

They also claim to have created the VRF system eairlier than Dakin too, I have my doubts
Daikin have the patent on the name Variable Refrigerant Volume so all other manufacturers have to use variable Refrigerant Flow - same thing really. Have a look here - scroll down to 1987 http://www.daikin.co.uk/about/milestones/default.jsp


from memory the BS Box is now called a ref net.

The BS or Branch Select box contains the solenoid valves for cool/heat switch over. The Refnet is a pipework joint.


In all we think Toshiba are ahead of Dakin.


:D :D

[ric]

I myself have worked on all range of a/c units and have found daikin and mitsubishi electric to be at the top.Older toshiba units are not made for service and repair in mind as to get to the compressor you have to take most of the panels off.Not to sure of new models for servicing.

[Markie]

[QUOTE=frank]Would you be happy recovering from a cellar cooler not knowing if the SV was open - what if the tev was closed? the pipework between the SV & TEV would contain trapped refrigerant :eek:

Themostatic expansion valves dont fully close do they? If you reclaim for both side of a cellar cooler with tev its quicker if you lift the solenoid with a magnet but not essential is it?:confused:
:(
With the VRV (it differs, I know :rolleyes: , between 2 pipe and 3 pipe) you could end up with trapped refrigerant between the BS box and the indoor unit even if you make sure you are connected to both the high and low side.

I was talking about about 2 pipe but didnt make that clear.:(

I'm not saying you can't recover without a Service Checker - you can if you follow the correct proceedure

I know, the book tells you how to prepare system for reclaim. ;)


Ask the boss to get you on a training course.

I am the boss :rolleyes:


Frightning :eek:[/QUOTE

If you think thats frightning I think you might be suprised by the amount of ac installation thats done by people with no real knowledge about how the damned stuff actually works. Service and installation are almost two different trades and Ive worked with a lot of plumbers , duct workers and semi skilled guys who can actually do good installation work with commissioning being done by someone with a bit more knowledge. Thats pretty common in the world of us install subbies :D

PS how do you do the "quote thing" where you quote bits of peoples posts in those bubbles??

[phil68]

Themostatic expansion valves dont fully close do they? If you reclaim for both side of a cellar cooler with tev its quicker if you lift the solenoid with a magnet but not essential is it?:confused
Yep, I'm sure you're correct, if anything the TEV will be wide-open if the system's been turned-off for a while prior to reclaiming as the suction pipe that the sensing phial is attatched to will have warmed-up.
I do however remember being taught when I was an apprentice to always activate the solenoid valve when reclaiming/evacuating as they can retain a pocket of gas within the valve body when closed, although I've never understood why, but it's been proven when I've run a vac-pump on a system & then activated the valve to find the vacuum reading decay momentarily:confused:

[frank]

Themostatic expansion valves dont fully close do they?

I think you will find that like all mechanical things, a TEV can breakdown and stick in the closed position.

It's very rare I know but it can happen and should not be discounted when working on a system


To use quotation marks highlight the text you want, right click and copy, then click the little text ballon at the top right hand corner of the formatting bar (next to the picture of a mountain button. Place your cursor between the [quote] marks and paste.

Alternately. click the "quote" button at the bottom righthand of the post and delete all of the text you don't want in your reply.

[Markie]

I take your point about a faulty solenoid, Frank.
And thanks for info on how to you quote thing.
Cheers,
Markie :)

[puddleboy3]

Think we need to go right back to the start, on Daikin VRV when shipped from the factory the expansion valves on the indoors are 50% open. To allow pressure testing and evac. Problem being that as soon as the power is applied the valves close fully down. The best way to solve this problem is turn the power on to the full system and allow to initalize and enter mode 2 setting 21 at the outdoor unit and hey presto all expansion valves on the indoor fan coils will open, also the SV valves on the outdoor will open hence the name of the setting recovery/evac setting. Its in the K series service manual and the new VRV 11. So dont waste time swapping wires at valves READ THE MANUAL.

P.S Cooling mode and indoors start to go thermostat off the exp valves close completely. Heating mode and thermostat off the expansion valves close down to 10%. Hence problems with stratification. Oil recovery is every 8 hours accumulated compressor running time.

[joel]

Another theoretical question thats bugging me.
On the Daikin vrv's ive been installing it seems that the expansion devices are at the indoor unit. I havent really taken an indoor apart to have a look as I never have the time but i assume there is some kind of electronic expansion valve at the indoor unit that allows refrigerant to flow when the unit is calling for duty.
Thats pretty obvious and all fine and dandy etc but what i want to know is this. When you are pressure testing or evacuating the system with no power to the units this expansion device restricts the flow of gas but does not shut of completely.
So why is it that when the condenser is running but you may have a particular unit or group of units turned off that there is not refrigerant passing through those expansion devices causing the refrigeration effect.
I.e. if you turned the power off to one particular unit and left the system running, why does this unit not start to ice up?

I THINK THAT PARTICULAR EXPANSION VALVE IS SHUTTING OFF FULLY...??? THATS WHY ITS NOT EXPERIENCING ICE FORMATION...