Where Do I Locate a Buffer Tank?

[Jethro Bush]

Hi, I am a first time user but I think I will become a regular user!
We look after a new hospital that has just had the mechanical services come out of warranty. Thank god we didn't do the installation because it is shocking. The main Rhoss heatpump chiller has now lost 2 compressors due to liquid slugging. There is no buffer tank in the circuit and the supplier is blaming this as the reason for liquid slugging. If we are to install a buffer tank would it be positioned before the pumps or after them but before the chiller?

[Brian_UK]

Hi Jethro and welcome to the forum.

According to this...
http://www.cemline.com/CWB_piping_diagram.pdf
the circuit would be - chiller - load - buffer tank - pump - chiller etc etc

[wambat]

This heat pump should have a liquid accumulator in the suction line right before the compressor to protect it from slugging but if you mean the chill water line and an air seperator then in a closed system where are you taking on air?

[The MG Pony]

Accumulators are cheap and sure shot at helping to stop slugging, better then that is do an audit of the whole operating system and tune it properly and get the best capacity sequencing of the compressors.

Any thing short is patching, and thats a nasty never ending game, Only way to win it is not to play in the first place.

[US Iceman]

I think what he is looking for is a "water" buffer tank. From his description of the problem the water volume for the system is too small and allowing the system to short cycle on low load conditions.

I remember seeing some statement about this in Trane chiller brochures as something very important to pay attention to.

An accumulator is secondary protection for the compressor in light of not having the water tank to add system volume.

[Jethro Bush]

The heatpump chiller is a RHOSS aircooled twin circuit machine. During normal operation it runs fine but as soon as a defrost cycle is completed one compressor starts to slug and the crankcase oil foams enough to drop the compressor out on oil failure. The second compressor on the machine doesn't experience the same problem. Any suggestions?

[nike123]

The heatpump chiller is a RHOSS aircooled twin circuit machine. During normal operation it runs fine but as soon as a defrost cycle is completed one compressor starts to slug and the crankcase oil foams enough to drop the compressor out on oil failure. The second compressor on the machine doesn't experience the same problem. Any suggestions?

Increase superheat on TXV!

[Andy]

The heatpump chiller is a RHOSS aircooled twin circuit machine. During normal operation it runs fine but as soon as a defrost cycle is completed one compressor starts to slug and the crankcase oil foams enough to drop the compressor out on oil failure. The second compressor on the machine doesn't experience the same problem. Any suggestions?

Hi Jethro

it has been known for Rhoss to position the TXV bulbs in the wrong position, we normally move the bulb on the heat pump chiller models to the main compressor suction on the compressor side of the 4 way valve.

Also check the operation of the outdoor fan if you are in heating and the refrigerant charge.

Kind Regards Andy