Help with additional fridge charging

[Stretch79]

Hi all,

Trying to calculate what additional fridge I need for a Mitsu PURY-P200YJM-A

Looking at their website it is confusing me (not difficult).

I have the diameter of the pipe and length, but their calculation is throwing me.

Any help appreciated.

FCU 1 3/8, 5/8 is 12.5m liquid and gas
FCU 2 3/8, 5/8 is 6.7m liquid and gas
FCU 3 3/8, 5/8 is 5m liquid and gas
FCU 4 3/8, 5/8 is 1.5m liquid and gas

https://library.mitsubishielectric.co.uk/pdf/book/pury-p200-900y_s_jm-a_1__service_manual__hwe10050#page-170-171

Don't see how they get the 0.36 etc

Any pointers is appreciated, thanks.

[Stretch79]

Think I have it.

So it's 0.06 for a 3/8 liquid line X the length in meters?

25.7m in total of liquid line rounding up to 26m x 0.06= 1.56kg additional?

[Tayters]

That sounds right. You then need to add the correct amount for the BC box and the amount for the duty of the indoor units.
Not sure if the Mitsi app has a charging calculation on it, might have...

Cheers,
Andy.

[Stretch79]

That sounds right. You then need to add the correct amount for the BC box and the amount for the duty of the indoor units.
Not sure if the Mitsi app has a charging calculation on it, might have...

Cheers,
Andy.

Hi Andy

Thanks for the help.

Only thing I haven’t done is go by size of the unit, only went by the liquid line size. Wasn’t sure what I should add for a different size fcu.

I did the base charge of 9.5kg for outdoor unit to BS box. Then my cal from that to each fcu on the liquid line only

Also my system only has 4 fcu’s direct from the BS box, no branch kits.

[Tayters]

Ah I see, two things then:

Base charge doesn't include any pipe run so that needs to be calculated.



For the fan coils you need to tally up the duty then add the amount suggested from the table bottom right of page 160. That's the actual page, not what's in the box up top. The two don't match up!


I had a good look at the example and it took a bit of studying to get my head round but from what I can see the example is only using liquid size even though there is a value listed for high pressure pipe. It's not normally used is it so unsure why it's mentioned in the manual.

So as I see it...

get all liquid pipe lengths and calculate - you just need outdoor to BC box.



Next add box 1 (page 160) value for BC box



Then add box 2 value for next BC box (I guess an HA1 type, check your model number but I think HA1 is a 16 port box connected to a much larger outdoor)



Then add box 3 value for next (sub) BC box (another HA1 type). You probably only have 1 BC box so I imagine just box 1 calculation required.



Next up add together the total indoor unit duty then figure the amount to add from box 4 (i.e. let's say you have 4 cassettes PLFY-P80. 4x80=320. This falls in the range 161-330 so add 3kg)


I've checked the app and charge calculation is there so try giving that a shot.
Otherwise go the paper route but I'd give Mitsi a call and confirm your value.

I seem to recall they did have an issue with extra charge calculations a few years back. Something about a spreadsheet they used wasn't set up right but would think they are on the ball now.

I need a lie down now, that manual is a bit crazy!

Cheers,
Andy.

Edit: I just tried the app, made no sense! Included high pressure pipe size, didn't add any for BC box... Mitsi number 0161 866 6089 :-)

[Stretch79]

Hello Andy,

Thanks for coming back to me.

Looking at what you have noted, it would appear I have left out the charge needed for the FCU's themselves.

In the manual Mitsu noted that base charge is 9.5Kg, I assumed (maybe incorrectly) that this would be sufficient up to say 10m, would need to recheck the manual though.

I'll work through what you have written, and see how short I am, can see it being a minimum of 5Kg.

The app is pony, unless it's me not understanding it, but it doesn't give me anything useful.

Many thanks for the help btw

[Tayters]

No problem and yes, the app could do with a bit of work.