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I found on one P&I diagram from York(Johnson Controls), that they use bypass line from economiser to main suction line. Please look at attachment. I don't unerstand a purpose of using additional line.
We have a suction line from economiser to eco port of compressor. We have there an intermediate pressure. What is reason to make additional bypass line?
Thanks in advance!
The subcooling is obtained by using a small amount of liquid and evaporating into the flash tank. This causes an increase in volume due to the evaporation process in the flash tank. The extra volume is removed through the suction of the compressor.
Basicly this circuit removes the high side liquid receiver, and introduces a low pressure separator.
Usually, when slide valve is 70-80% solenoid to eco port will close. Bypass will handle flash load.Quote:
Originally Posted by Osar2007
Don't beleive everything you read. They will never give away there design criteria. Something will be left out of P &I
Yeah, but on P&I mentioned pilot valve which keep pressure difference between suction line and line to eco-port. We have an eco-port and economiser and evaporating temperature designed for some conditions.If design is ok, we will have enough capacity of eco-port and not necessary to have additional line. Thanks for your reply.Quote:
Originally Posted by NoNickName
Thanks for your reply! I think we can solve this problem by using pressure constant pilot valve and not necessary to use additional line.Quote:
Originally Posted by Segei
Sometimes economizer port has a maximum pressure recommended by manufacturer , so any excess can be bled into suction at this pressure point ?
Note they say: Side Port load not recommended....
On a screw, at low slide valve, the economiser port and the machine suction head to the same pressure. Most of the manufacturers shut off the economiser flow at 70-80% SV....But if the liquid delivery to the evaporator has been set up for subcooled or reduced pressure liquid, and neither is applied because the side port is disabled, the liquid is either not going to distribute or not going to be controlled, depending on the nature of the liquid refrigerant controls.
With a VFD machine, the VFD being the primary turndown: The functional envelope for the Side Port has been expanded.
This line will only be active during very low load conditions; so it is only required on circuits addressing highly varying loads....If the flash vessel were totally isolated from any suction pressure the accumulator controls would have to be tolerant of high temperature high pressure liquid make-up.
The control side of this thing is not entirely definitive: but many industrial 2-stage systems arranged for minus 40 or lower loads on the weekdays and nothing lower than Cold Storage temperatures on the weekends utilize something similar to ensure that the Intercooler remains at a pressure higher than the low stage suction....
I thought about it.I think it is a good thing, but why there is installed pressure difference pilot valve? For what reason?Quote:
Originally Posted by RANGER1
Thanks for reply. I understood your point of view. So, all liquid make up system and other control system on pump separator should be designed for both conditions( with economiser and without economiser)Quote:
Originally Posted by sterl
Osar2007
Your economizer is an open flash type & needs pressure above low side surge drum so it can maintain surge drum level through pressure difference .
Thats why pressure regulators are installed on both return to economizer port & suction line .
It is a good explanation! But we have pressure constant valve on suction line to eco-port. We can adjust this valve for intermediate pressure and if pressure in eco suction line goes down we will have intermediate pressure inside open economiser. What do you think?Quote:
Originally Posted by RANGER1
But if compressor unloads economizer port can be either open to suction pressure inside compressor or possibly port may close off altogether in some compressors .( this could also be why extra line into suction ) .
In case, when eco port is open and we have the suction pressure, our pressure constant valve (CVP) which is installed on menthioned line will keep intermediate pressure inside flash tank. I think, this line needs in case, when compressor works with low capacity and eco port is closed by solenoid valve and inside flash vessel is condensing pressure.In time, when compressor capacity goes up and solenoid valve is going to be open, when we can overload eco port. I think in this case bypass line will be usefull, for decreasing pressure to intermidiate pressure. What do you think?Quote:
Originally Posted by RANGER1
I would suggest to disconnect the solenoid and you don't need the bypass. Older models of Frick compressors don't have solenoids.Quote:
Originally Posted by Osar2007
I mentioned early at this forum that benefit of this solenoid is questionable. It will close at 70-80%, because at this load or lower port side will be exposed to suction pressure and benefit of this port will be lost. It can be useful only if other compressors will be able to handle the load of intermediate vessel. If other compressors won't handle the load, it will go to the suction through the bypass and efficiency will be lost anyway. Disconnect solenoid, open it manually and system will work fine.