Receiver levels - Supermarket rack systems

[tbowen]

I'm trying to determine what the optimum requirement would be for maintaining receiver levels to ensure most effiecient operation. We have 70 stores under a service contract with minimum receiver levels of 40% (25% in heat reclaim). We have aquired additional stores that will be put out to bid for contract. These stores were operating with near zero receiver levels. Can this contractual receiver level be modified to avoid a large cost in charging the systems to this level? The intent of maintaining the minimum levels is to be sure we have enough gas in the system to compenstae for swings in ambient conditions, splitting and unspliittting of condensers and full utilization of heat reclaim. We operate in the Northeast USA and have 90 degrees swings in annual ambient temperatures and sometimes as much as 40- 50 degrees in a single day.

[Magoo]

Hi tbowen.
your receiver should be big enough to hold total system charge when pumped down and a max fill volume less than 80%, and maintain a liquid seal in receiver for maximum system duty. With heat reclaim you may have a satilite receiver, both can be calculated for pump down volume capacity. I would think there should be a discharge gas balance line to top of receiver for low ambients. The trick is calculating the operational liquid volume and enough in receiver for a liquid seal, then allow the volume for pump down storage.

[Coorsman777]

I generally look at times when the system will use the most refrigerant and keep the reciever level around 15% on those days, with a low receiver level alarm at 10% with a 60 minute time delay. This is what I have found to ensure proper system operation and minimize refrigerant loss if a leak were to occur.

[THE DUDE]

I think that most racks have a "operating charge", by this I mean that there is a amount of refrigerant that the system needs to operate from the lowest to the higest ambient temps. Reciever sizing determines the amout of swing in reciever levels ( smaller reciever = larger swings in reciever levels)
It dosent sound cheap to get the store under a contract and then add gas to get it up to proper operating levels, but responding to repeat low reciever alarms in fall and winter isn't cheap either.

[MikeySq]

you could remove the reciever out of the flow of the system and float your head pressure like an "enviroguard" setup and run 0% receiver most of the year

Heat reclaim may be tricky or in effective though

you will also use less refrigerant and lose less on a leak when it does happen.

Mike