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Thread: Remote condenser + heat recovery
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29-03-2006, 11:46 AM #1
Remote condenser + heat recovery
Two Bitzer screw compressor on R22 conected with heat recovery and then to air heat exchanger (Condenser).
I calculate thet i need pipe NO 50 from two comressors and heat recover.Calculate for 250kW each circle,Tcond=55 C,Tevap=0C,liquid subcoling = 10C,superheat at suction=12C
2 oil traps
20m horizontal
5m vertical distance
4 elbow
In this case I woul have 11m/s in discharge line and 0,8m/s in liquid line.So I thinking about reduction in discharge line to get 17m/s.
This is all for full load but what when compressor start to unload I dont know steps.(25%,50% or 75% etc.)
So you see I am afraid that due the unload I would hawe problem with velocity (oil return) to compressor.
Althaugh Bitzer screw have oil separator inside.
What is your sudgestion??
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29-03-2006, 12:16 PM #2
Re: Remote condenser + heat recovery
You can't have a full canister and a drunken wife at the same time.
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29-03-2006, 12:40 PM #3
Re: Remote condenser + heat recovery
Yes but I dont wont to have past out wife.
Renato
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29-03-2006, 01:03 PM #4
Re: Remote condenser + heat recovery
Set the microprocessor to a very short maximum time for unloading, in order to make sure it won't work for long at reduced capacity. This will negatively affect temperature stability, but will positively affect reliability.
Please note that 25% on bitzers is normally only used for starting and not for thermoregulation, otherwise you will most probably end up with a liquid injection request.
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29-03-2006, 02:01 PM #5
Re: Remote condenser + heat recovery
I have liquid injection on compressor.
Renato
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29-03-2006, 10:16 PM #6
Re: Remote condenser + heat recovery
Originally Posted by Renato RR
Kind Regards. Andy
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29-03-2006, 10:42 PM #7
Re: Remote condenser + heat recovery
Yes, bitzers have 4 steps, that is 100% plus 2 unloaders (75 and 50) plus the 25 which should only be used for starting.
I actually use just the 75%, no solenoid on the 50% and one solenoid for the intermittent oil injection.
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30-03-2006, 02:42 AM #8
Re: Remote condenser + heat recovery
Originally Posted by Renato RR
rgds
LCI hear...I forget;I see...I remember;I do...I understand
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30-03-2006, 07:20 AM #9
Re: Remote condenser + heat recovery
Yes you are right about 25%.This compressor have oil separator inside housing so that will give me some time until unload stops.
Anywone have idea how much will oil separator slow the reduction of oil on suction line.
Some sors claims 4-5 working hours.
Should I instold ICS Danfoss pilot ventil to make bypass in case that heat recovery takes all heat from sistem?
Renato
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30-03-2006, 07:26 AM #10
Re: Remote condenser + heat recovery
bitzer has a very good demister on discharge, so I wouldn't worry, unless refrigerant owns a low isoentropic exponent (low discharge temperature, like 404).
Try to keep the oil as warm as possible, and connect the oil switch level sensor, just to be sure.
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