R404a to R407a conversion

[Silhouette]

Hi All,
Has anyone had any experience of the gas change R404a to R407a?
Waitrose are changing their HT packs over and I've heard they are having a few problems afterwards with flood-back etc.:eek:

Any comments appreciated as I'll probably get dragged into doing a few!

Thanks,
Mel.

[coolhibby1875]

i hope not as 407a costs a absolute fortune and its made up of tiny small molocules it leaks like hell even through the smallest of leaks!

[Silhouette]

Another thing, I heard they removed 120Kgs R404a from a fully charged system and had to recharge with 220Kg R407a to get the system back to the same level!!!!!

[motleyshue]

R407a does have a higher density than R404a but not sure it is that much different! Although every system I have changed required more gas than was taken out.

Not had any problems with leaks although i dont know what the long term issues of drying out valve seals will be. what ever happens it cant be as bad as the isceon range!

Not had too many issues with it just flood back with mechanical valves (akv's are ok).

[esulx]

We're finding with the Morrison Gas Changes (R22 to R422d, FX10 to R422a) that we have to put more gas in than we took out to achieve the same operation of the system.

[SCFC]

Hi Silhoutte

I have carried a number of retrofits with these Refrigerants and found it to be unpridictable when trying to set up the Superheats across the coils. I found the best soulution to reduce the flood back was to fit R22 Expansion valves or R407c valves.

[Silhouette]

Thanks for the comments guy's!
I bear it all in mind when I get involved!!

Silhouette.

[elliswyatt]

Make sure you're using a pressure gauge and temperature probe to set superheats. A temp probe on the inlet and the outlet of the coil will fool you. R407A has a high glide; use the dew point numbers for superheat calcs. Set it up this way and your floodback issues should go away.

[eskimotoe]

Probably because its leaking out as quick as it goes in, Terrible Idea 422d and 422a, well done Morrisons for showing how not to do things LOL

[chillled]

The idea of the morrisons gas conversions was to replace all components that would potentially leak, so as long as job's managed correctly no problems, items such as old ball valves, flexible lines, etc etc. Done 3 now with no real problems, does need a better reciever level though, about 50% seems best.
Does anyone know what Sainsburys are doing with their R22/R408 plant of which they have loads in the immediate future? i know co2 is planned but not for Jan 1 2010!!

[Latte]

REALLY stupid question here but.....

Why change packs from 404 to 407 ?

[Silhouette]

Chillled - Refits to CO2 start in February.

Latte - R407a is more efficient (GWP)and less ODP than R404a.

[smc200276]

R407a has the same ODP as R404a - Zero

[ICE/RUNNER]

You can't use R408a as it has been baned since the start of 2010. We are haveing the same trouble we have to use R422D or A, need to calc the difference in proformace frist.

[oldesky]

I wonder if anybody has calculated the tons of carbon used to build a plant to produce R407 to transport and then to retrofit a gas that was already in the system. A refrigerant that will probably have a limited life span and will be replaced by something else. If the Kiwi researchers come up with a way to reduce methane emissions from cattle, they will have done more to affect the global carbon levels than all the european directives on refrigerant put together. This doesnt mean we should do nothing but I wish Governments would get the solution right first before making changes. How many "transition" refrigerants were there to replace R12 and R502.

[smc200276]

You can't use R404a as it has been baned since the start of 2010. We are haveing the same trouble we have to use R422D or A, need to calc the difference in proformace frist.

R404a has not been banned.

I suspect you are thinking of R22. As of 1st Jan 2010, you can no longer use virgin R22 in a system. However you can still use reclaimed / recycled R22 until 31st December 2014 when you will no longer be able to use it.

[Tayters]

What would happen after a major loss of refrigerant then?
With R404a I've seen you can get away with topping up the system as the glide is quite narrow.
R407c on the other hand has a glide wider than a Darren Southgate penalty kick. :cool: This would mean the entire system would need reclaiming and filling from scratch.

http://www.axlr8demo.co.uk/thermagroup/documents/TheTroublewithR407c.pdf - Not directly related to this thread but may be of some insterest to some of ya. Time for some more 407c bashing!

[esulx]

Does anyone know the Allowable Pressures (HP & LP) for R407a as I want to ensure that we've selected the right PRVs and set the HP switch correctly.
Can't seem to find it on the internet for some reason.

[displaced paddy]

Set the high pressure switch 25 to 50 psi lower than the receiver safety (pop off) or the reciever max working press. It'll be stamped on both. What's a PRV? Pressure Reducing Valve maybe?

[tim smedley]

pressure relief valve, standard fit on high and low side!

[bijumonss]

how much can be a normal suction pressure in a ground freezer which is having f 404a

[bijumonss]

i mean in psig?

[bijumonss]

any body have an idea about?pls

[wilks]

thought waitrose had moved to hydrocarbons ? all water cooled from a hydrocarbon chiller ?

[smc200276]

@wilks

Waitrose have moved to an all natural solution for new builds and major refits. However, they still have a large estate of DX systems and are using R407a in MT systems to reduce the impact of any leakage due to R407a's lower GWP.

[Blueboy]

Hi All,
Has anyone had any experience of the gas change R404a to R407a?
Waitrose are changing their HT packs over and I've heard they are having a few problems afterwards with flood-back etc.:eek:

Any comments appreciated as I'll probably get dragged into doing a few!

Thanks,
Mel.

I have been doing some-work with R407a Post conversion - The following information may be useful to anyone converting from R404a to R407A

R407a is not the same gas as R407c- they operate at different pressures although they have the same constituent gases.

R407c Thermostatic expansion valves DO NOT WORK with R407a- They cause the front of the coils to freeze up they cause liquid flood back and and the case will struggle to maintain temperature. EEV's are fine. If you have TEV's Change them to R22 they work just fine and eliminate flood back to the most part

R407a operates at different pressures to R404a. If you are running an HT/IT pack on R404a and you change to R407a. You must change to suction control pressure. I have found that dropping it from 3.2 BAR (-11C) on R404a to 2.5BAR(-10C) on R407a works form me.

If you have meat serve overs that employ an EPRV and a TEV on R404a- Change the TEV to a R22 ex eq. I used a no3 orifice. I set the super heat to 4C to keep the coil wet and set the EPRV to 3.1 bar. The case works perfectly with 6 defrost per day ( SAT GAS DEFROST ON THIS CASE) before I carried out this work the case always went high temp on the left hand side as you are standing behind it. This problem no longer occurs.


I hope this is useful