R22 to MO29(R422d)

Hi Guys

Would like to run through a system that i've converted from R22 to R422D.
Equipment is for a potato store that holds 2000T of potatoes. It has been in production since 1990 running on R22. Carrier 6 cylinder compressor with 3 fan air cooled condenser with fans being controlled with pressure switches. The evaporator is 3 fan floor mounted with fixed spiral ducting going to ceiling blowing across product and air returning to cooler. Off cycle defrost. Defrost every 6 hours for 1 hour. I have a list of pressures/temperatures that i have obtained

Suction Pressure 3.0Bar(g)
Suction Pipe temp at expansion valve bulb +8DegC
Suction Pipe temp at compressor +8DegC
Suction Pipe Length 6Mtrs
Superheat 13.6K

Discharge Pressure 15.5Bar(g)
Discharge Pipe Temp at Compressor +70DegC
Discharge Pipe Temp at Condenser In +65DegC
Liquid Line Pipe Temp at Condenser out +33DegC
Liquid Line Pipe Temp entering Expansion Valve +32DegC
Liquid Pipe Temp directly after Expansion Valve +11DegC
Air On Cond 12DegC
Air Off Cond 24DegC
SubCooling 8K


Ambient Temperature is 12DegC.
Air On Evaporator 11DegC
Air Off Evaporator 6.5DegC
High Pressure Receiver showing 10% Liquid Level However sight glass at expansion valve flashing.

Im guessing that the system is still under charged due to high superheat and low subcooling....would anybody be able to comment on this? I can also see frosting on about 3/4 of the evaporator. Thank you in advance

Hi I have been involved with many companies in the potatoe storage industry. Many of these systems have been retro fitted with R422D. many have caused problems due to a large drop off in capacity. Some systems show a loss in capacity by up to 20%.
Many of these units use electronic expansion valves to try to keep the superheat of the system as low as possible to stop the crop being de hydrated.
With the use of electronic expansion valves the controller can be re-calibrated to work with R422D.
When using R22 Thermostatic expansion valves, normally the system runs with a higher static superheat and the capacity drop off can be severe as the valves element charge is not designed to work with other refrigerants due to the variances of the refrigerants pressure /temperature and glide.
This usually causes the systems suction condition to run at a lower temperature/pressure, again reducing the systems capacity. On many of these systems using this refrigerant we have had to fit a larger orifice into the expansion valve to bring the system duty back up to somewhere near design, both Electronic and Thermostaic.
Also I have experienced poor oil return with this refrigerant on several systems even though it is supposed to work with the original mineral oil, most companies replace the oil charge during the retrofit to a POE type as this works with this gas no problems. I know of systems with this gas where engineers have mixed some POE with the mineral to encourage oil return
From the info you supplied the system looks almost charged as it looks like you have some subcooling at the Expansion valves inlet, but the suction superheat at 13degK is very high . Depending on the type of expansion valve fitted try to open the valve to reduce the s/heat to 4 to 6 K with an EEV , and 5 to 7 K with a TEV.
8K of subcooling if that is correct is not low as expansion valves are rated at nominal capacity at 4k .
If you are struggling for temperature in the store you need to get the expansion device to reduce the superheat in the evaporator, either by adjusting the valve or fitting a larger valve or orifice. You may also have to do some tweaking of the system.

Hi Glen and thanks for your reply.
The system is using a Danfoss TEX20, the orifice size unknown. I've opened the valve adjustment to the max so a larger orifice is looking like the next option. Fortunately the oil return, which is mineral, hasn't been a problem but the plant has only been running for 1 week so monitoring closely for now.
When you mention some systems loosing up to 20% capacity after retrofit are these also systems with EEV's?
This might have to be an option changing to EEV if the Thermostatic doesn't work correctly.

Most Pirie units used EEV's and some of them needed a larger orifice . It all depends how tight the original orifice had been sized. The valve fitted must be the TEX 20-30 as there was only one size of TE 20 orifices,but the new range of TE valves there are 3 sizes of orifice that fit the T20 . I would try the T 20 No9 orifice code 067B2773 .
this will give you more capacity, but the superheat control may be a little erratic due to the valve not being designed for R442D
If you change to an EEV the controller has this refrigerant in its set up list and it will operate with a low s/heat and give you better efficiency Kr Glenn

Never got a chance to get to the site today but i do have some pics of the valveAttachment 11811Attachment 11812Will that be enough information for ordering an EEV Glen? Is it correct to say you are the Danfoss guy that writes in the fridge mags about expansion valves etc? If so then would like to say thanks for great bedtime reading ;)

Hi
Yes thats me glad you enjoyed them. Still writing articles and tech stuff but I recently retired from Danfoss so have to get one of the lads to get them published for me now .Hopefully the Service side of the IOR will publish them. A lot are on the Danfoss.com website. Just doing site trouble shooting stuff for old customers, still get a kick out of this industry. Maybe write a book

To sort your store, going to EEV's I would fit the following

1) EKD 316 Controller Code no 084B8040
2) EKA 164A Setting Display code no 084B8563
3) ETS 50 Expansion Valve Code no 034G1705
4) ETS Cable Code no 034G2200
5) AKS 32R Transmitter Code No 060G1036
6) AKS32R Cable code no 060G1034
7) AKS 21A Sensor 084N2007

Set EKD Controller parameter o30 to 33 which sets the controller refrigerant setting for R422D

If you speak to the tech guys in the Glasgow branch they will give you my mob no if you need help

Kind regards Glenn