carrier 30rap and hot gas
Hello all, question regarding adding hot gas bypass to a Copeland digital scroll. Unit has a low load in winter time and satisfactory load in summer. Problem is freeze protect alarms due to compressor starts at 100% capacity for a short time before it starts to unload. During this time LWT takes a nose dive and it's hit or miss if an alarm comes up. Once it starts to unload, it's fine.
There is a buffer tank.
Unit is configured for max unloading.
Thinking of adding HGB to be separate from the Carrier chiller controls to load evap during these times. But am wondering if that will create other problems?
This is a 10 ton air cooled chiller.
Thoughts and thanks!
Re: carrier 30rap and hot gas
Hi daneel
If you fit a HGB valve you will most likely need some sort of de-superheating valve as well ,as scrolls are notorious for failing due to high superheat.
So you can fit an HGB plus a liquid injection valve ,or you could fit a Danfoss CPCE valve with an LG Mixer ,this way then both the hot gas and the de-superheating is satisfied.
The CPCE Valve uses a 1/4" signal line for the control set point ,you can fit a solenoid valve in this pilot line and via a timer or pressure stat you can control when the hot gas is used and for how long. I think unless you control the hot gas then you will interfere with the digital scroll unloader and the system will suffer with most likely a compressor failure
Re: carrier 30rap and hot gas
Looking at the manual for this unit Carrier only seem to have HGBP option on the larger units.
You mention a buffer tank is fitted do you know what the capacity is for it also is this comfort cooling or process.when on full load what delta t do you have. What is your setpoint.
Re: carrier 30rap and hot gas
Quote:
Originally Posted by
Glenn Moore
Hi daneel
If you fit a HGB valve you will most likely need some sort of de-superheating valve as well ,as scrolls are notorious for failing due to high superheat.
So you can fit an HGB plus a liquid injection valve ,or you could fit a Danfoss CPCE valve with an LG Mixer ,this way then both the hot gas and the de-superheating is satisfied.
The CPCE Valve uses a 1/4" signal line for the control set point ,you can fit a solenoid valve in this pilot line and via a timer or pressure stat you can control when the hot gas is used and for how long. I think unless you control the hot gas then you will interfere with the digital scroll unloader and the system will suffer with most likely a compressor failure
Thanx for the reply....don't think I need a desuperheater, there is a place to tap into right after the EXV. And I only want hot gas for a limited time..perhaps 10 minutes max. The timer idea intrigues me. I looked up the Danfoss CPCE valve but didn't readily see one for R-410a. Sporlan makes one though.
Considering this system has a micro channel coil and no receiver and no pump down, it's a critical charge system. Adding extras may open a can of worms.
Re: carrier 30rap and hot gas
Quote:
Originally Posted by
Gibbo
Looking at the manual for this unit Carrier only seem to have HGBP option on the larger units.
You mention a buffer tank is fitted do you know what the capacity is for it also is this comfort cooling or process.when on full load what delta t do you have. What is your setpoint.
Hi, Carrier does not have HGBP with digital scrolls at all (according to manuals). This unit is fitted with factory CW pump, flows are correct. NOt sure of the size of buffer tank but it's appears to be large enough for a 10 ton unit. BT is located in return water.
This unit serves an ice core lab on campus here. We have a year round chilled water loop, but in case of a loop hiccup this pony chiller comes on to serve the lab. In the winter time they mostly use it for a process loop for their helium compressors and minimal comfort cooling...I would estimate about 2 tons worth total. While requirement for the helium compressors can be about 65F, the AC needs are lower. System does have OSA dampers for free cooling but are located near street and car fumes (not allowed).
