Stopping outdoor unit VRV-S

[mchild]

In order to use the indoor ducted units for emergency heat when the outdoor ambient drops too low or when there is a failure of the out door unit I would like to be able to stop the outdoor unit from operating.

I understand that to stop the outdoor unit you need to short terminals A and C on the PCB. What is the best way to do that? Could a simple switch work?

[Krondor]

Why would you like to do so? First of all the system will simply stop working whether there is a malfunction (you don't have to stop it manually). Second, it is supposed to work up to -15 degrees C below zero. Do you get any lower then that?

[mchild]

Why would you like to do so? First of all the system will simply stop working whether there is a malfunction (you don't have to stop it manually). Second, it is supposed to work up to -15 degrees C below zero. Do you get any lower then that?


Yes, on occasion it does get lower than that. That is not my main concern though. I thought if there was a fault with the outdoor unit it would shut the entire system down including indoor air handlers. If not, then I would not need to stop the outdoor unit in order to still have indoor units running. I need the indoor units to continue to run because I will have electric heat in my ducts in case of emergency or on those occasions that it does reach -15C.

[frank]

To stop the electric heat from operating when the indoor fan coils switch off, I would recommend that you install a pressure differential switch across the fan in your heater control circuit.

I am not aware that you can force the indoor fan coils to run when the outdoor unit is held off by using a KRP add on pcb.

[mchild]

To stop the electric heat from operating when the indoor fan coils switch off, I would recommend that you install a pressure differential switch across the fan in your heater control circuit.

I am not aware that you can force the indoor fan coils to run when the outdoor unit is held off by using a KRP add on pcb.

The Daikin document I have simply shows shorting A and C on the outdoor if you want the outdoor to not run while still having use of the indoor unit fans to distribute the heat from the secondary source. It does not show exactly how to short the two terminals. In the document there is a vague reference for the use of a third party ambient temp t-stat. I guess this is want they are suggesting be used to force off the outdoor unit.

[Krondor]

Well, as far as i remember, shortening A and C connectors will force the system to enter "Fan mode". In that case you can operate the indoors in fan mode. But then, how will you control the temperature of the electrical heaters? are you going to use another thermostat? It seems like a very complicated system you are building there....

[mchild]

Well, as far as i remember, shortening A and C connectors will force the system to enter "Fan mode". In that case you can operate the indoors in fan mode. But then, how will you control the temperature of the electrical heaters? are you going to use another thermostat? It seems like a very complicated system you are building there....


Yes, I will have simple t-stats to operate the in-duct electric heat that will be used primarily for supplementing the VRV system when the ambient temps drop to the lowest point and will also be used in case of a VRV system default.

The electric heat is needed to provide about 10-15K BTUH at the coldest ambient conditions but it is sized to provide sufficient heat to use in case of a VRV fault. If the outdoor unit has a failure, it may take some time to get repalcement parts as these systems are not yet widely used here in the U.S. Hopefully, that may never happen, but I will be prepared just in case it does happen.

If Daikin had a VRV-S system with more heat capacity then I would have gone that route but here in the U.S. we do have all the sizes available to the rest of the world. 5HP is the largest available.

[Krondor]

We have a similar work with electrical heaters for heating. However, we did it with only one thermostat, that will control both VRV and electrical heating using CoolMaster with Coolex for control.

[mchild]

We have a similar work with electrical heaters for heating. However, we did it with only one thermostat, that will control both VRV and electrical heating using CoolMaster with Coolex for control.


I had looked into Coolmaster, but could not see how it would allow one set of controls. I sent Coolmaster an email through their web site and they said it could not be done. Posted questions here on this board asking how it could be done- did not get a response. Can you provide me with more details on how it works?

The Daikin KRP1B add on wiring adapter board has a switch (YC-Y1) that closes at 4*C below the Daikin controler temp setting and reopens when it has risen 2*C. That would work great except 4*C is too much below the set temp. It needs to be closer to 1*C it closes and repopen at .5*C. Daikin says the 4*C value can not be changed.

[Krondor]

Well, the logic of operation is as following:
1. You use communicating thermostats instead of the original Daikin.
2. CoolConverter (which is a modification of CoolMaster that can communicate withthe thermostats by Modbus or Maxinet protocols) is chained to each themostat and to the CoolEx.
3. CoolEx provides the controls for the electrical heaters.
4. When there is a demand for heating, the thermostat sends "heat" command to the CoolConverter and to the CoolEx to start operating the Electrical heater of the requird indoor unit. In paralel, it turns that indoor to a fan mode.

This is how it works in general.

Moreover, speaking to the company that provides that stuff i have been told that they are about to release (2-3 month) a new thermostat. This themostat will speak directly with Daikin and will be also able to provide control to the Electrical heater

[mchild]

Well, the logic of operation is as following:
1. You use communicating thermostats instead of the original Daikin.
2. CoolConverter (which is a modification of CoolMaster that can communicate withthe thermostats by Modbus or Maxinet protocols) is chained to each themostat and to the CoolEx.
3. CoolEx provides the controls for the electrical heaters.
4. When there is a demand for heating, the thermostat sends "heat" command to the CoolConverter and to the CoolEx to start operating the Electrical heater of the requird indoor unit. In paralel, it turns that indoor to a fan mode.

This is how it works in general.

Moreover, speaking to the company that provides that stuff i have been told that they are about to release (2-3 month) a new thermostat. This themostat will speak directly with Daikin and will be also able to provide control to the Electrical heater


All good information. Thank you.