master bilt freezer charge

[joebear]

working on master-bilt blg-48hd model reach-in freezer,r404a,tx valve,several months old. data plate charge states 55 oz.,when 55 oz. is weighted in and box pulls down to -8deg.,there is no subcooling at liquid line. i believe data plate is wrong,to get 15 deg. subcool i need to add about 20 oz. extra.anybody been in this situation?

[icemeister]

Just weigh it in per the dataplate, collect your money and go.

It's unlikely you'll ever see 15ºF subcooling on one of these unless you're grossly overcharged. I would be more concerned about suction superheat than liquid subcooling, anyway.

[r404a]

Joe Bear,
I wanted to add a comment or two about this subject. The above posts are good advice. While I have not worked on the exact machine you listed, I have had an issue like you mentioned and it was on a coffin case. As stated above: Weigh the charge in. While it is possible it is HIGHLY unlikey that the charge stamped on the box is incorrect and it is very simple to find out. Call the factory and check another box (if one is onsite or at another location) and see if it is the same. I had a case that had a louvered panel on it and I remember that a tech was out there charging the thing and he had to add a bit more gas to get any subcooling. He put the cover on it and the thing wouldn't hold temp. Turns out, that charge that was added to get subcooling was causing the head to skyrocket with the panel inplace. Use your name plate and go from there. Good luck.

r404a

[eng2sales4mny]

Joebear listen to R-404a. Many people do not realize that certain design features of the equipment are not optional and can play a huge role in there performance. As for the manufacturer making a mistake, this happens more than anyone ever realizes. if you are not seeing the sub cooling as you expected this could be caused by a number of things, make sure the condenser is not dirty and that the ambient temp in the store is not above 85 F.Following the nameplate is best. The criteria on the nameplate is a function of UL and they stipulate the requirements, often they are related to the tests they perform.

thanks

[r404a]

Eng,

Good advice. Also, relative humidity is a performance factor. Joebear, if you have a lot of boxes like this, time a couple of them for pulldown and that will set a trend for you to gauge how they should work. Take care.


r404a