VRV Outdoor Unit - Standby
VRV Outdoor Unit - Standby
(OP)
Hi everybody,
i want ask if there is any way to make standby unit to duty VRV outdoor unit, is it possible?
what i need as piping accessories?
what i need for outdoor data connection? for example interface module?
please i need advice.
The Picture below showing outdoor connection
thanks
Mohammed
Mechanical Engineer





RE: VRV Outdoor Unit - Standby
vrv units of most manufacturers can sustain about 130% of nominal load without trouble, so you already have 30% standby if you design for nominal capacity. if you specify unit with at least two compressors, if one compressor burns out you still have 65% capacity, and for commercial applications usually you can temporarily rearrange priorities until repair is done.
RE: VRV Outdoor Unit - Standby
the problem that the owner want 100% backup, so i have to make my design with 100% back up.
this backup required for maintenance and emergency not for drop in cooling load.
another question. if one of compressor burns out from group or module shall we stop all group and clean out refrigerant pipes?
Mohammed Sulieman
Mechanical Engineer
RE: VRV Outdoor Unit - Standby
if you are in design phase, design outdoor unit with 100% provision and you are well, you need to check whether unit is large enough to contain at least two compressors, and to check minimum acceptable load, comparing it with occupancy schedule.
of course, you will run at efficiency bellow optimal almost all the time, but your client likely knows that when posting such demands.
RE: VRV Outdoor Unit - Standby
for example , if you have one module 36 HP (10+10+16) outdoor, if there is damage in one of three units, what will happen??
we lose this group until make the maintenance , so my question i want to add one more 16HP as stand by unit with this group
it will be (10+10+16)duty + 16HP standby connected to same pipe with isolating valve normally close and open if there is one unit is blackout.
RE: VRV Outdoor Unit - Standby
RE: VRV Outdoor Unit - Standby
even if you connected all the units to one circuit, one leak will take them all out and you have difficulty meeting ASHRAE 15 and 34 with that much refrigerant.
RE: VRV Outdoor Unit - Standby
RE: VRV Outdoor Unit - Standby
Maybe other manufacturers have different options. but really the next person to talk to should be manufacturers.
RE: VRV Outdoor Unit - Standby
It is exactly redundancy why it should be designed as one system within installation limits - if some of outdoor modules fail, others are still working and in most of commercial applications you can easily reset cooling priorities during repair so that most of customers don't even feel lack of capacity.
it is solution offered by manufacturers, their refrigerant piping system are proprietary as a rule, they offer/impose all branch fittings together with calculation/specification software.
everything op wants can be specified within proprietary manufacturer's system - there is no other approach available currently - i would like if it would exist, but it doesn't - dy piping hydraulics is much related to compressor oil which is circulating within system together with refrigerant, and each manufacturer uses own oil.
RE: VRV Outdoor Unit - Standby
I don't know why the system wouldn't be able to do something like this, but close coordination with the manufacturer will be needed. Probably be a very heavy and expensive controls system. Hopefully there's an option.