Suction line T

[monkey spanners]

Hi guys,

I'm quoting on a job for an farm ice builder system, on one of the options they have asked for they want the same condensing units to run a direct expansion milk tank also (tank during milking, ice builder over night).
The system has an 1 3/8" suction line. I've never really liked 't's from a flow point of view, what i had in mind was to fit a 1 5/8" t with fitting reducers to help lessen the restriction of changing direction sharply. Also with a similar set up with the liquid lines.

Any views would be welcome:)

Cheers Jon

[Peter_1]

Good idea, I only have to add but you knew this perhaps already, slope the suction line towards the compressor and make that the main suction line has enough speed at it's lowest cooling capacity.

Face the T for the suction upwards and the T for the liquid downwards.

How will you manage the different evaporating temperatures? Will you fit a suction evaporation regulator on the milk tank?

[monkey spanners]

Thankyou Peter,

I had planned to bring the tank suction in from the left and the icebuilder suction from the right and drop out the bottom of the t with the main suction line and then back up forming a p trap, but thats why i'm asking for opinions:D Whats the reason behind your suggested method?

The system (Packo) only runs either the tank or the icebuilder at a time, with the tank having priority. The units are on pumpdown, with liquidline solenoids selecting the desired evaporator. I'm fitting checkvalves in the suction line to the icebuilder to stop refrigerant condensing in it when the system is running the tank. There are no evaporation regulators on the tank.

I'm only installing the pipework and commissioning, the tank, icebuilder and units are being supplied by the milking parlour agent as these are the people who have the Fullwood/Packo agency. The pipework sizes are to Packo's specification.

[Peter_1]

What a coincidence: I can see the Fullwood/Packo factory out of my window right now.

Your suggestion with the P-trap is good but I shouldn't install one. It can't harm anyway but as long as your lines doesn't rise more then 3 to 4 m, you don't need those.
Same remark for the NRV's, they don't harm but you don't need those to let it function properly.
At least, that's my opinion.

Sloping suction lines towards the compressor is a must to ensure oil return.
A T for suction lines is also a must to be sure that the oil doesn't falls back once it it is in the main header.

Don't bother too much about the friction in the T. What capacity do you have? I suppose they use R404a with U.H. compressors or Maneurop.

[Brian_UK]

I have no expertise with these systems but will you be creating any problems having an open evaporator on the non-duty side when the other side is running?

I ask because you say that you are using the liquid line solenoids to select which side runs.

[monkey spanners]

I belive they will be using Copeland scroll units, on R404A, either two ZB75KCE's with a 20m pipe run to the icebuilder and a further 20m run to the tank, or two ZB11ME's with a 20m pipe run to the icebuilder and chilled water to the tank. The icebuilder feeds a plate heatexchanger in the milk line to the tank. Its a rotary milking parlour so it needs to be well sized to keep up with it, 34,000L every other day.

The reason for the check valves in the icebuilder suctions is that when the icebuilder is full of ice and its coil is around 0c and the system is running the tank and is evaporating above 0c i've found that a quantity of refrigerant will condense in the icebuilder evaporator causing symptoms of being short of refrigerant at the tank, and causing the ice to melt from the pipework from the inside.

Jon

[monkey spanners]

Yes Brian i think you are right hence the check valves on the icebuilder as its (almost) always colder than the tank. The check valves are not in the manufacturers specification. The trouble i have is convicing the customer that these things are necessary, all they can see is the purchase cost and not the benefit.
Last year when i quoted them for a similar set up at the same site they got as far as dropping a pipe size and not bothering with insulation to try and get the price down :mad: I'd like to be able to walk away from jobs like this but i get about 25% of my income through this company and i simply could not afford to do without it:(

Jon

[monkey spanners]

Peter, what is the idea behind the different liquid line and suction line connections to the main pipework, one into the bottom and the other out the top? I had planned to mount the suction T the opposite way to that you suggested:eek: my idea being that any oil that is running along the bottom of the pipe would just drop into the main suction line and carry on to the compressor. I was a bit concerned that if i oversized the T for flow reasons it might stop the oil making it out of the T on low load conditions, hence dropping out the bottom.

Cheers Jon

[Peter_1]

Jon, download once the Trane paper on this link http://www.megaupload.com/nl/?d=9PBD792J
A picture tells more then 1000 words.

[monkey spanners]

Thankyou Peter, that will keep me amused for hours and hours:)

Cheers Jon:D