temporary removal of indoor units off a VRV

[rbartlett]

We have to remove some 5 cassettes off a 24 indoor VRV in order for the owner to carry out some refurbishment works. However we must set the rest of the system up and running before we leave.

I have in my mind a method but would love to hear from a few here as to what they would do and any pitfalls to avoid or any short cuts to take

Cheers

Richard

[puddleboy3]

Hi there can you tell us the make and model of the VRV system?

[rbartlett]

Yes sorry about that..

It's a Daikin on 407c -I don't know the actual model.


Cheers

Richard

[frank]

Hi Richard

First, put the system in to recovery mode then switch off. Close the outdoor valves and recover from the indoor circuit. Take out the 5 x cassettes and cap off the pipework for future use.

If you want to have the system in operation without these 5 cassettes then you must make sure that the index of the remaining indoor fan coils add up to above the minimum index of the outdoor unit.

If they do then you can electrically isolate any indoor BS boxes to the 5 cassettes so the system does not see them, measure the remaining liquid lines, calculate the new charge, subtract from the original charge and put the gas back in (minus the differrence)

Open the valves, press the reset button, wait 12 minutes and it should run

If the remaining indoor fan coils do not add up to more than the minimum outdoor index then I wouldn't recommend running the system.

[KISS KISS BANG]

If it's a "K" or "L" Series Condensing Unit then you may need to hold the RESET button down whilst turning the power back on until you hear a click (about 5 seconds). To check if your System is "seeing" the correct No. of Fan Coils press the MODE button once then press the SET button five times then press the RETURN button, the No. of Fan Coils is then displayed in binary from right to left....1st LED=1, 2nd LED=2, 3rd LED=4, 4th LED=8 etc etc. Press the MODE button to get back to start.

[rbartlett]

many thanks thus far ;-)

However why bother to remove any refrigerant if the system is designed to run from 1 -24 indoor units operating?

This alone factors for far more refrigerant circulating (or not as the case may be) than 5 units effectively in the off position...

Cheers

Richard

[frank]

However why bother to remove any refrigerant if the system is designed to run from 1 -24 indoor units operating?

Hi Richard

The systems are not designed to run with 1-24 units. They are designed to operate with upto 48 indoor units but the indoor index count must be matched to the outdoor index capacity. The outdoor units have a minimum and maximum index limit.

You cannot operate them outside of these limits without unexpected results.

If you have the system at present with a refrigerant charge to match the indoor unit capacity and then remove a proportion of that capacity you end up with a system overcharged. This will result in liquid returning to the compressor and you know the result of that

[rbartlett]

Hi Richard

The systems are not designed to run with 1-24 units. They are designed to operate with upto 48 indoor units but the indoor index count must be matched to the outdoor index capacity. The outdoor units have a minimum and maximum index limit.

You cannot operate them outside of these limits without unexpected results.

If you have the system at present with a refrigerant charge to match the indoor unit capacity and then remove a proportion of that capacity you end up with a system overcharged. This will result in liquid returning to the compressor and you know the result of that

So how comes it doesn't get liq back when only one indoor unit is running instead of the full 24??

Cheers

Richard

[frank]

So how comes it doesn't get liq back when only one indoor unit is running instead of the full 24??

Cheers

Richard

Because the liquid charge is held in all the indoor units that are not working

[puddleboy3]

So how comes it doesn't get liq back when only one indoor unit is running instead of the full 24??

Hence the name of the system VRV variable refrigerant volume, with only one fan coil running the inverter compressor will tick over just enough to maintain constant superheat through the fan coil. Going back a few threads, it is correct that you have to press and hold the reset button on the outdoor but there is no need to do it whilst turning the power on. Turn on power then press and hold reset button BS5 for 15 seconds to ensure that the outdoor board starts a fresh looking for the indoor fan coils.

[rbartlett]

Because the liquid charge is held in all the indoor units that are not working

this is interesting -how is that then-is there a sol on the suction outlet of each indoor unit?

Cheers

Richard

[rbartlett]

Hence the name of the system VRV variable refrigerant volume, with only one fan coil running the inverter compressor will tick over just enough to maintain constant superheat through the fan coil. .

I think you should be addressing this to Frank not me ;-)

I'm confused how the indoor units can 'hold liquid'

cheers

richard

[puddleboy3]

The indoor fan coils dont actually hold any liquid when in a thermostat off condition or switched off the indoor expansion valve will close and prevent any flow through the indoor fan coil.

[rbartlett]

The indoor fan coils dont actually hold any liquid when in a thermostat off condition or switched off the indoor expansion valve will close and prevent any flow through the indoor fan coil.

Which brings me to the point -why remove any refrigerant.?

These things have a huge receiver and given that 1 -24 can be operating can only mean they are high charge tolerant machine



Cheers

Richard

[Dan]

this is interesting -how is that then-is there a sol on the suction outlet of each indoor unit?

Heck, Ron, I don't know a thing about these units; I am paying attention just so I can learn. But if you are using suction solenoids, would that not explain that the indoor coils are storing liquid refrigerant?

[rbartlett]

Heck, Ron, I don't know a thing about these units; I am paying attention just so I can learn. But if you are using suction solenoids, would that not explain that the indoor coils are storing liquid refrigerant?

are you sure you're paying attention ??

cheers

richard

[Andy]

are you sure you're paying attention ??

cheers

richard

Would the BS box be the suction solinoide then

I was going to up load a schematic of the BS box but it's too big

Kind Regards Andy

[Peter_1]

.... This will result in liquid returning to the compressor and you know the result of that

Are these systems then not throttled by a SH controlled EEV?

[puddleboy3]

Even with power off to the BS Box there is a constant path through the BS Box, so refrigerant flow is only prevented by the liquid line expansion valve. The older Boxes had three SV's the new VRV II BS Boxes have a four way valve and a SV that is only energised when the system goes to heat recovery mode. So there is no way of holding liquid up in the fan coil.

[frank]

Are these systems then not throttled by a SH controlled EEV?

They control by suction pressure. The inverter ramps up and down by the measured returning suction pressure and the indoor EEV throttles by temperature control.

In cooling, every 20 seconds the control loop measures the difference between set point and return air temperature (or room temperature in the event where the return air thermister is replaced by a room thermister). As the return air temp approaches set point then the EEV is pulsed closed. This way, the EEV is able to vary the amount of liquid entering the coil and so the amount of cooling duty is varied and is able to control down to 0.5C of set point. If all the indoor units are close to set point then the compressor(s) are ramped back to minimum waiting for a call without switching off. The last thing they want to do is switch off . It is only when all indoor units do not call for a set period that they system cycles off.

On a 3 pipe heat recovery unit where some of the indoor units are heating and some are cooling, the outdoor coil is used to balance the system. Say that the system has 8 indoor fan coils. With 4 fan coils in heating and 4 in cooling where the duties are balanced then the outdoor coil will only be used to reject the heat of compression. As the indoor load swings either to a majority of cooling or heating the outdoor coil is used proportionally as a condenser or evaporator. This is where the 3 pipe VRV/VRF differs from acting just like a glorified multi split system (heating or cooling).

With all the fan coils calling for cooling but being satisfied on stat then the refrigerant is stored in the outdoor unit and liquid line. By removing some of the indoor fan coils you effectivly are un-balancing the system (large condenser with small evaporator). There will come a point where the unit will be overcharged.

Richard has not said what the system is, only that it operates on R407C. We have to make assumptions that the fan coils he proposes to disconnect total a significant proportion of the system. Maybe more information would help to give better advice.

The manufacturers of these systems publish guidelines as to what number of indoor units can be safely connected to the appropriate outdoor unit. If you want to operate outside of these guidelines then unexpected results will ensue.

[Dan]

this is interesting -how is that then-is there a sol on the suction outlet of each indoor unit?

are you sure you're paying attention ??

I misread what you wrote. I read it as "how is it then that there is a solenoid in the suction outlet of each unit?" Let me rephrase: I think I am paying attention.

[Andy]

On a 3 pipe heat recovery unit where some of the indoor units are heating and some are cooling, the outdoor coil is used to balance the system. Say that the system has 8 indoor fan coils. With 4 fan coils in heating and 4 in cooling where the duties are balanced then the outdoor coil will only be used to reject the heat of compression. As the indoor load swings either to a majority of cooling or heating the outdoor coil is used proportionally as a condenser or evaporator. This is where the 3 pipe VRV/VRF differs from acting just like a glorified multi split system (heating or cooling).


Thanks Frank

So the outdoor unit on a three pipe has a reversing valve. But how does it know when to change from cooling to heating

Kind Regards Andy

[Peter_1]

Frank, the way the VRV is working (like you described in your post 23) is excatly how we control a pack with different cold-rooms connected to it.

We've done it once this way for flower storage. The more we reached set temperature, the more we reduced fan speed.
Reducing this fan speed resulted in an decreased evaporator capacity so the EEV's decreased automatically refrigerant flow.
Due to this reduced refrigerant flow, the VFD on the compressor automatically reduced compressor speed.
We could maintain a stable temperature of +/- 0.2K and a suction pressure within a margin of 0.1 bar (1.5 psi)

As soon load increased, everything increased automatically.

[rbartlett]

On a 3 pipe heat recovery unit where some of the indoor units are heating and some are cooling, the outdoor coil is used to balance the system. Say that the system has 8 indoor fan coils. With 4 fan coils in heating and 4 in cooling where the duties are balanced then the outdoor coil will only be used to reject the heat of compression. As the indoor load swings either to a majority of cooling or heating the outdoor coil is used proportionally as a condenser or evaporator. This is where the 3 pipe VRV/VRF differs from acting just like a glorified multi split system (heating or cooling).


Thanks Frank

So the outdoor unit on a three pipe has a reversing valve. But how does it know when to change from cooling to heating

Kind Regards Andy

it doesn't

cheers

richard

[rbartlett]

what about the wiring?

cheers

richard

[Peter_1]

With Mitsubishi Electric, you only need 2 pipes

[Peter_1]

So the outdoor unit on a three pipe has a reversing valve. But how does it know when to change from cooling to heating

Never thought about this Andy.
I should say, as soon the system monitors what will be the greatest efficiency on that moment.

Can't be that difficult to calculate with the proper software in the CPU with the information of all the sensors and electronics that are in these systems.

[Andy]

With Mitsubishi Electric, you only need 2 pipes

Yes but can some rooms be on cooling and some heating,
Daikin and Toshiba all have two pipe systems also, but they don't heat and cool together, if the majority want cooling, you get cooling on the ones that want heating just run fan only.

Kind Regards Andy

[Andy]

it doesn't

cheers

richard

Then how does it work

Each outdoor unit has two reversing valves and two outdoor coils to control, so how does it know when the coils should be condensers or evaporators

Kind Regards Andy

[Peter_1]

Yes but can some rooms be on cooling and some heating,
Daikin and Toshiba all have two pipe systems also, but they don't heat and cool together, if the majority want cooling, you get cooling on the ones that want heating just run fan only.

No, no Andy, Mitsubishi Electric is a complete heat recovery with only 2 pipes! Seems it's patented.


http://www.bdt.co.nz/citymulti/od_r2.asp first link I found

http://www.bdt.co.nz/citymulti/how-2-pipe.asp

[Andy]

No, no Andy, Mitsubishi Electric is a complete heat recovery with only 2 pipes! Seems it's patented.


http://www.bdt.co.nz/citymulti/od_r2.asp first link I found

http://www.bdt.co.nz/citymulti/how-2-pipe.asp

Now thats quite a nice looking piece of kit. Robust looking control valves and some good technology

Kind Regards Andy

[frank]

So the outdoor unit on a three pipe has a reversing valve. But how does it know when to change from cooling to heating

Its all down to the electronics. The indoor units change over on command from the local controller. The outdoor PCB interrogates the indoor units every 20 secs and looks at their status and responds accordingly.

Every time the systems changes over it stops the outdoor unit then restarts. This can lead to a lack of close control under certain operating conditions.

[Andy]

Its all down to the electronics. The indoor units change over on command from the local controller. The outdoor PCB interrogates the indoor units every 20 secs and looks at their status and responds accordingly.

Every time the systems changes over it stops the outdoor unit then restarts. This can lead to a lack of close control under certain operating conditions.

Frank,
thank you

Truth be known we have a problem with such a senario, I am going to look at it Monday.

NOISY BS BOXES
Now I am sure you have never heard this before

Its a Hotel, a retrofit with the BS boxes in the rooms. When the main group is on heating and a few units are on cooling, the noise problem is there. A running water noise, the liquid on bypass. But it's more than that, it happens at change over on low ambient.
Again there is more to it than liquid on bypass and the unit changing over, the units are all in an under ground car park and the noise only occurs when the ambient is low, but only on two out of 14 systems.

As the man says, I will know more on Monday

Kind Regards Andy

[rbartlett]

Frank,
thank you

Truth be known we have a problem with such a senario, I am going to look at it Monday.

NOISY BS BOXES
Now I am sure you have never heard this before

Its a Hotel, a retrofit with the BS boxes in the rooms. When the main group is on heating and a few units are on cooling, the noise problem is there. A running water noise, the liquid on bypass. But it's more than that, it happens at change over on low ambient.
Again there is more to it than liquid on bypass and the unit changing over, the units are all in an under ground car park and the noise only occurs when the ambient is low, but only on two out of 14 systems.

As the man says, I will know more on Monday

Kind Regards Andy

it's courteous not to hijack other peoples threads with your own problems . this was directed at those who know about daikin vrvs not those who don't

cheers

richard

[rbartlett]

what happens when the system is on a intiligent controller? how can a hard reset of the outdoor unit re-set the controller.
In this case do we have to re configure the IC to remove the 'missing' units?

Cheers

Richard

[Andy]

it's courteous not to hijack other peoples threads with your own problems . this was directed at those who know about daikin vrvs not those who don't

cheers

richard

What gives Richard

I can start another tread if you want

Or I can have a pop at you knowledge too

Kind Regards Andy

[frank]

what happens when the system is on a intiligent controller? how can a hard reset of the outdoor unit re-set the controller.
In this case do we have to re configure the IC to remove the 'missing' units?

Cheers

Richard

The Intelligent Controller lets you remotely access each individual indoor fan coil and perform certain functions, i.e. lock out remote controller function, adjust set points, set mode etc. What it can't do is assign Group Addresses. This function must be set from the local remote attached to the fan coil/coils.

Pressing the outdoor Reset button (yes I know you have to hold if for 5 secs ) clears all memory and starts the outdoor unit looking at the connected indoor units and assigning new addresses. If you just change a pcb for instance on a fan coil you must do a reset of the system as the new pcb won't be recognised until it has been addressed.

The Intelligent Controller will now show the new Addresses of all connected indoor units. The Grouping has to be done manually as it is you or the client that determines which fan coils to Group together - it's not that "Intelligent"

[rbartlett]

What gives Richard

I can start another tread if you want

Or I can have a pop at you knowledge too

Kind Regards Andy

I started this thread with a specific job in mind and I was asking for advice. Therefore it's courteous to keep within that, keep out or start another thread 'noisy bs boxes' 'Mitsubishi 2 pipe systems' etc

if 'd started with 'hey lets talk about VRV' then sure everyone is welcome to partake

cheers

richard
'

[Andy]

I started this thread with a specific job in mind and I was asking for advice. Therefore it's courteous to keep within that, keep out or start another thread 'noisy bs boxes' 'Mitsubishi 2 pipe systems' etc

if 'd started with 'hey lets talk about VRV' then sure everyone is welcome to partake

cheers

richard
'

OK I will give you soom advise on your problem

If you remove indoor units you need to adjust the charge or you will have damaged compressors. The extra refrigerant charge may be contained in the outdoor, or the indoors maybe on heating, bypassing the liquid back into the main liquid line. The indoors (on heating) will keep feeding the liquid into the liquid line until the excess is fed back into the suction line and you end up with low suction superheat.
Earlier you stated that that there may be only one unit of say 24 calling. Normally they will be modulating not pumped out, this is the way the excess liquid is controlled in this situation

In my experience refrigerant charge is the most important part of any VRV system set up, along with the index value calculations to match the indoor to the outdoor setup.

In this instant you need to look at both these before proceeding.

Then what would I know, I don't work at A/C, but I have had occasion to read the Daikin manuals recently

PM me if you need them and I will email them to you

Kind Regards Andy

[Josip]

Hi, rbartlett

Then what would I know, I don't work at A/C, but I have had occasion to read the Daikin manuals recently

PM me if you need them and I will email them to you

Kind Regards Andy

The same is with me I have also some Daikin VRV manuals in pdf but I need the type of VRV to send it to you

Best regards,

Josip

[rbartlett]

do you have the correct setting pdf for the IE controller -not the users manual BTW.

cheers

richard

p.s I still do not believe that VRV's are that charge critical. ANY system with a receiver is not critical and has by it's very nature a high tolerance.

If I had all 24 systems running on full cooling and then shut down 23 of them then the excess would be backed up in the receiver. This factor alone tells one that there is a very high float with regard to charge.

I once had a conversation with Toshiba who was extolling the virtues of the 'excess charge' sensor. I mentioned that in that case there was no need to weigh in the refrigerant as it was a simple case of charging to excess and removing 10%. He hummed and har'ed but basically couldn't come up with a single answer apart from 'can't'

The correct charge is to g.tee the minimum for correct operation under full load conditions -that's all in my view.

I remain to be convinced otherwise


Cheers

Richard

[puddleboy3]

If your system has an I controller connected and you remove some indoor fan coils from your system. Your I controller will still have the group numbers registered and if it can not communicate with the specific group numbers it will display a UE fault code, so you will have to go in to the service mode and un register the fan coils you have removed. Hope this helps! Im with you on the charge doesnt have to be so accurate for it too work. But what i will say is that if you run a system with for instance 8 fan coils on it and there is only one in the thermostat on condition the outdoor unit will tick over at 30Hz just supply enough liquid for that one fan coil! As for the outdoor unit it will work to maintain discharge superheat by opening the liquid injection to lower the discharge temp rather than worry about the suction superheat, especially on the VRV II as the windings for the compressor are in the discharge side of the compressor not the suction.

[rbartlett]

If your system has an I controller connected and you remove some indoor fan coils from your system. Your I controller will still have the group numbers registered and if it can not communicate with the specific group numbers it will display a UE fault code, so you will have to go in to the service mode and un register the fan coils you have removed. Hope this helps! Im with you on the charge doesnt have to be so accurate for it too work. But what i will say is that if you run a system with for instance 8 fan coils on it and there is only one in the thermostat on condition the outdoor unit will tick over at 30Hz just supply enough liquid for that one fan coil! As for the outdoor unit it will work to maintain discharge superheat by opening the liquid injection to lower the discharge temp rather than worry about the suction superheat, especially on the VRV II as the windings for the compressor are in the discharge side of the compressor not the suction.

That's exactly what I did.
Besically I did your reset thing which I presume told the outdoor unit to looksee and then went inside and just deleted the numbers for those missing on the IC list 1-10to 1-15.(I may have done this the other way round it was quite fraught on Sunday)

We still have UE as there are still 6 icons blue but -luckily for us- 18 are red I can live with this...;-))

If you have the set up manual I'd love it BTW ;-)))

However many many thanks for all those who shed some light on this and look out for the 'replacing 6 indoor units into a VRV system' thread coming soon !!

Cheers

Richard

[rbartlett]

Guy's

we got the system all back up and working. last Friday I re-connected the units electrically and re-set the condenser. Then I set those 6 to 'fan only' as the piping wasn't meant to be done till Saturday.I know that all 6 were red a-okay on friday evening

Sat comes and the works are completed by our guy's and the units are all up and running.

Today tuesday we get a call saying that 3 of the 6 have changed colour from red to yellow and show a UF fault but the indoor fans are still running.

i told the guy to switch off the condenser and turn it back on and see if it re-configures.

The client phoned back and said that this did not work..

Why should these systems suddenly UF fault?

Any idea's??????

Cheers

Richard

[puddleboy3]

When you turned the outdoor unit back on after connecting the six units back up did you do a hard reset on the PCB BS5 reset button for 15 seconds. The PCB should pick up the new fan coils by just turning the power off and on but doesnt always work. Ive had systems that ive turned the outdoor off and in one instance taken three hours to display U4 faults. Can only assume this is the problem or power related problems! Hope this helps

[rbartlett]

When you turned the outdoor unit back on after connecting the six units back up did you do a hard reset on the PCB BS5 reset button for 15 seconds. The PCB should pick up the new fan coils by just turning the power off and on but doesnt always work. Ive had systems that ive turned the outdoor off and in one instance taken three hours to display U4 faults. Can only assume this is the problem or power related problems! Hope this helps

Yes i did this several times as I got each unit online. I also did it again once for luck. As I say I know it was all red on friday when I left but now they have gone yellow??

I wonder if another reset of the condenser will be needed...It's such a pain as the site is a long old way away..

Cheers

Richard