# Variable Refrigerant Flow (VRF) systems



## PDSH (Jul 15, 2016)

Installation safety:

IMC 2012 appears to not have any section to address this system’s installation safety issues:

Per IMC 1104.2 there is a limitation for refrigerant charge for all refrigerant containing components inside the building and outside of machinery room- Table 1103.1.

Section 1104.4 has guidelines for volume calculation to check compliance with table 1103.1 requirements. However, this guideline is not clear in reference to communicating spaces through permanent openings and HVAC ducts. Specifically, it seems that 1104.4 does not address VRF systems:

It does not appear to be a clear definition for permanent opening and its size requirements in the code.

Section 1104.4.1 refers to spaces without any HVAC ducts and permanent openings to adjacent rooms. Generally VRF systems are not being installed in such rooms as there should be an auxiliary system to provide ventilation for such a space.

Additionally, 1104.4.2 clarifies the communicating spaces through HVAC ducts for conventional HVAC systems where an evaporator or condenser is located in an air duct system, which is not the common case for VRF systems installation. Generally, there is a safety issue with VRF system when the refrigerant containing parts are located outside of duct system and installed directly in a small room.

Although, this section refers to communicating spaces, there is no reference to permanent openings in its criteria.

Section 1104.4.3 is only applicable whenever VRF cassette is installed inside plenum and there is no refrigerant containing part inside the room space.

In conclusion, it appears that IMC 1104.4 guidelines for volume calculation does not cover VRF systems characteristics.

# Problem:

For installation of a VRF cassette connecting to a large circuit of refrigerant inside a small room, in case of a disastrous rupture in system, the whole system’s refrigerant charge will be discharged into the room.

How big should be the permanent openings size or how much ventilation (provided by an alternative source) is enough to prevent occupants in this room do not experience refrigerant concentrations above the allowable limits per table 1103.1?!


Considering this problem, the question is

“How different AHJs are regulating VRF installation all over the country?”

How do you define communicating spaces for the case of VRF systems which are different from conventional HVAC systems?

Your inputs will be appreciated.


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## steveray (Jul 15, 2016)

Never seen a VRF system I guess, but if the refrigerant is in side the building, it needs to meet the requirements...


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## north star (Jul 15, 2016)

*$ = $ = $*


PDSH,

Welcome to The Building Codes Forum !

Have you contacted a manufacturer to discuss ?


*$ = $ = $*


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## north star (Jul 19, 2016)

*@ ~ @*


PDSH,

Continuing with your scenario & questions........Here in
my current position, we install the "city-multi condensers"
outdoors......We do not have any or install any of the
condensers indoors........Also, each of the city-multi
systems have separate refrigerant circuits with linear
expansion valves to control the amount of refrigerant
being supplied to each zone.

Do you have the resources to install the main condensers
and install only the cassettes indoors ?


*@ ~ @*


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## PDSH (Jul 25, 2016)

north star said:


> *$ = $ = $*
> 
> 
> PDSH,
> ...


Thank you,
I have checked with few of manufacturer's representatives. They did not assure us that there is any safety measurer integrated into the system to stop catastrophic leakage into small rooms, if any.


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## PDSH (Jul 25, 2016)

north star said:


> *@ ~ @*
> 
> 
> PDSH,
> ...


For most cases that I have seen, condenser will be installed outdoor. But as VRF system is a direct system, if any leakage happen in any part of circuit, specially in the cassettes which are installed inside the rooms or at ceiling, the whole refrigerant load can be discharged into the room. It's not assured if the linear expansion valves are capable of sensing  sudden pressure drops and stopping refrigerant flow into different zones in case of leakage.


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## north star (Jul 25, 2016)

*@ ~ @ ~ @*


PDSH,

If you have discussed the VRF Systems with their reps.,
what do they recommend ?......Are their reps. the same
as their engineers ?........Can some type of sensing
valves or sensors be installed to contain a catastrophic
release [ i.e. - an aftermarket sensor  ] ?

If none of these are a viable solution, do you HAVE to
use these type of systems ?......Other ?

Shirley, this isn't the first time these questions have
come up to the manufacturers...


*@ ~ @ ~ @*


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