Daikin VRV coil target temp during heating

[mchild]

In the VRV training and service manuals the target temp (Tc) (as read and converted from the high pressure sensor at the outdoor coil) can be adjusted up or down 3*C from the factory setting. Under what circumstances would it be advised to make such an adjustment from the factory setting? Would raising the target temp by 3*C increase the effective capacity of the system?

Two of my four indoor units (FXSQ) are at their limit when it gets really cold outside and can not maintain the space at the set point temp on the controller. Would changing the target temp allow those two indoor units to produce a bit more heat on those really cold days? Is there a way to adjust the target temp of the indoor coils during heat mode?

Any help is greatly appreciated.

[nike123]

In the VRV training and service manuals the target temp (Tc) (as read and converted from the high pressure sensor at the outdoor coil) can be adjusted up or down 3*C from the factory setting. Under what circumstances would it be advised to make such an adjustment from the factory setting? Would raising the target temp by 3*C increase the effective capacity of the system?

Two of my four indoor units (FXSQ) are at their limit when it gets really cold outside and can not maintain the space at the set point temp on the controller. Would changing the target temp allow those two indoor units to produce a bit more heat on those really cold days? Is there a way to adjust the target temp of the indoor coils during heat mode?

Any help is greatly appreciated.

I am not Daikin expert, but generally speaking, if that setting have influence on air flow thru heat exchanger, compressor speed and superheat, then you could extract some additional amount of heat, but with aditional power consumption rise!

[mchild]

I am not Daikin expert, but generally speaking, if that setting have influence on air flow thru heat exchanger, compressor speed and superheat, then you could extract some additional amount of heat, but with aditional power consumption rise!

nike123,

Yes, I understand that each of those will have an influence on how much heat the unit can produce. And I know the additional heat will not be free but the power consumption is cheaper than having electric coils in the ducts to help when the system can not do it all.

So, by what you say I may be able to get some additional heat from the system by making the change.

Do those who are Daikin experts agree?

[nicolacozma]

Hello,

Changing Te and Tc parameters "in setting mode 2" have no effect during normal operation of VRV system.
Te and Tc value are using only during test run procedure in order to judge the lenght of the pipes and also to judge the quantity of the refrigerant(enough or not).

Kind regards,
Nicola

[mchild]

Hello,

Changing Te and Tc parameters "in setting mode 2" have no effect during normal operation of VRV system.
Te and Tc value are using only during test run procedure in order to judge the lenght of the pipes and also to judge the quantity of the refrigerant(enough or not).

Kind regards,
Nicola

Nicola,

Thank you for that explanation. Is there a way to change the target temp during operation of the indoor coil temp? If I could raise the target temp of the two indoor units that need a little more capacity then that might help. Can that be done?

Thank you.

[brunstar]

the best way to do that is to put a larger unit in and have it sized correctly from the start, is the return air ducted onto the unit and where are you sensing the return air from?

[puddleboy3]

I may have a setting can you tell me the full model number of your outdoor.

Also Te/Tc setting is NOT only for test run purpose

Te setting - Controls compressor capacity to adjust Te to achieve target value (TeS).
Te = Low pressure equivalent saturation temperature
TeS = Target Te value (Varies depending on Te setting, operating frequency, etc.)

Tc setting - Controls compressor capacity to adjust Tc to achieve target value (TcS).
Tc = High pressure equivalent saturation temperature
Tcs = Target Tc value (Varies depending on Tc setting, operating frequency, etc.)

Regards

[mchild]

I may have a setting can you tell me the full model number of your outdoor.

Also Te/Tc setting is NOT only for test run purpose

Te setting - Controls compressor capacity to adjust Te to achieve target value (TeS).
Te = Low pressure equivalent saturation temperature
TeS = Target Te value (Varies depending on Te setting, operating frequency, etc.)

Tc setting - Controls compressor capacity to adjust Tc to achieve target value (TcS).
Tc = High pressure equivalent saturation temperature
Tcs = Target Tc value (Varies depending on Tc setting, operating frequency, etc.)

Regards


puddleboy3,

Thank you for your response. I had read in the service manual the same as you said here and that is why I had thought some adjustment might be acceptable and possibly provide a little more capacity. It seems to me though that changing the indoor units would also be necessary.

My outdoor unit is a VRV-S RXYMQ48MVJU. Indoor units are FXSQxxMVJU.

Thanks again.

[nicolacozma]

Hi,

Also you have to take into consideration also that saturated evaporation temperature (cooling mode) or saturated condensing temperature(heating mode) could slightly be different for different indoor unit. The reason is the pressure loss on refrigerent pipes.
If you have a service checker registration observe the temperature of liquide pipe of each indoor unit.

Maybe the right solution is to increase the capacity of the indoor unit as you say before.

[mchild]

Hi,

Also you have to take into consideration also that saturated evaporation temperature (cooling mode) or saturated condensing temperature(heating mode) could slightly be different for different indoor unit. The reason is the pressure loss on refrigerent pipes.
If you have a service checker registration observe the temperature of liquide pipe of each indoor unit.

Maybe the right solution is to increase the capacity of the indoor unit as you say before.

Can you explain the method to increase the capacity of an indoor unit? And should I reduce the capacity of the units that now have excess capacity?

[Thermatech]

If the manufacturer openly provided information about how to get more duty out of systems for any body & every body to see

then

everyone & their dog would always purchase smaller than needed units & upgrade them on site with setting mode or dip switch to make them provide required higher capacity.

There are mainy fuctions on VRV & VRF systems for fine tuning which can be of assistance to get the best out of the systems for all sorts of different applications.

but

should we be trying to get something for nothing ?

or

should we be doing accurate heat load calculations & purchase the correct size units ?

[mchild]

If the manufacturer openly provided information about how to get more duty out of systems for any body & every body to see

then

everyone & their dog would always purchase smaller than needed units & upgrade them on site with setting mode or dip switch to make them provide required higher capacity.

There are mainy fuctions on VRV & VRF systems for fine tuning which can be of assistance to get the best out of the systems for all sorts of different applications.

but

should we be trying to get something for nothing ?

or

should we be doing accurate heat load calculations & purchase the correct size units ?


Thermatech,

I appreciate your concern.

Here in the U.S. we have limited choices and only have two capacities available 4 and 5 HP - the 6HP is not available for some reason. I have the 5HP version.

When the system was being designed (full heat load calculations were completed as part of the design process) we knew that the heat capacity would be close to or slightly less than needed (the cooling capacity is a little more than needed). Since the 6HP is not available, the only thing I could have done would have been to go with two 4 HP outdoor units which would have been significantly oversized and at a cost of about $4,500 more.

To make up for the heat shortfall I am having electric heat installed in the ducts but, I'm sure you know how expensive it is to operate.

In my research of these systems (very rare here in the U.S. so much of it was done on this forum and others around the world) I found that tweaking - as you say, was possible on VRV systems. Therefore, to help keep my costs to operate as reasonable as possible I hoped that some tweaking might provide a little more capacity and reduce my use of the expensive electric heat.

Thank you.

[nicolacozma]

Can you explain the method to increase the capacity of an indoor unit? And should I reduce the capacity of the units that now have excess capacity?

I mean to size-up the indoor unit. If you have a margine for the connection ratio of the outdoor unit then it`s ok.

Can you explain shortly, what means "tweaking", please?

Thanks in advance
Nicola

[nike123]

Thermatech,

I appreciate your concern.

Here in the U.S. we have limited choices and only have two capacities available 4 and 5 HP - the 6HP is not available for some reason. I have the 5HP version.

When the system was being designed (full heat load calculations were completed as part of the design process) we knew that the heat capacity would be close to or slightly less than needed (the cooling capacity is a little more than needed). Since the 6HP is not available, the only thing I could have done would have been to go with two 4 HP outdoor units which would have been significantly oversized and at a cost of about $4,500 more.

To make up for the heat shortfall I am having electric heat installed in the ducts but, I'm sure you know how expensive it is to operate.

In my research of these systems (very rare here in the U.S. so much of it was done on this forum and others around the world) I found that tweaking - as you say, was possible on VRV systems. Therefore, to help keep my costs to operate as reasonable as possible I hoped that some tweaking might provide a little more capacity and reduce my use of the expensive electric heat.

Thank you.

I am sure that manufacturer has tweaked unit for best performance. Further tweaking could only be at expense on unit life span.
Same thing as car chip tuning. It produce little more car power but at expense on motor well being.

[mchild]

I am sure that manufacturer has tweaked unit for best performance. Further tweaking could only be at expense on unit life span.
Same thing as car chip tuning. It produce little more car power but at expense on motor well being.


I have four indoor units in which two units only need about 60% of their capacity in heat mode while the other two could use more. So, I would not need to necessarily increase the total system capacity, more like shift it a little bit to the two units that could use a little more.

If I could tweak up the two units that need a little more heat, I could then tweak down the other two units and still have the system with well being.

[mchild]

the best way to do that is to put a larger unit in and have it sized correctly from the start, is the return air ducted onto the unit and where are you sensing the return air from?

As I mentioned in my post to Thermatech I have the largest VRV-S available here in the U.S. See my response to him with more details.

Each of the four indoor units have return air ducted to it. Each unit senses temp from a remote sensor in the area that it is supply air to.

[nike123]

I have four indoor units in which two units only need about 60% of their capacity in heat mode while the other two could use more. So, I would not need to necessarily increase the total system capacity, more like shift it a little bit to the two units that could use a little more.

If I could tweak up the two units that need a little more heat, I could then tweak down the other two units and still have the system with well being.

Sorry, I wasn't reading carefully that part in your first post and I see now that my answers are not addressing your problem.