View Full Version : AC/DC Norcold - I could use some help getting this unit running

25-11-2013, 06:28 PM
I have a Norcold SCQT 4407 that is designed to convert a boat's icebox to a refrigerator. It has never been used, but the lines were damaged while being installed. Also a piece is missing as noted later.

If not familiar with this unit, it is a similar design as a mini fridge (the evaporator plate is the freezer). Similar except this unit is for "marine" use, which means it runs on either AC or DC and costs $850+ (ouch). Point being, it is harder to simply say "replace it" as I would a mini fridge, so I'd really like to get it working. Norcold's support is TERRIBLE - they say the units are not serviceable if they have lost their charge (Oh, get real!!)

Anyhow, I have soldered a valve to the pinched stem so that the system can be recharged with R134a, but a few other things have me stumped.

The suction line is 1/4" from compressor to evaporator, but the delivery line is a very small diameter (have yet to measure it) that is actually inside the suction line for much of the 8' run. At some point the small delivery line breaks out of the suction line and attaches to the compressor using 1/4" similarly to the suction line. Unfortunately, the piece that has the break out is missing.

Here is where I could use some help:
1) How does someone splice/repair the small diameter, delivery line? Do they make couplers that small?

2) Am I correct in assuming I can break a new delivery line out of a new suction line (1/4") by drilling a hole in the 1/4" tube, then soldering this area to make the piece hold pressure again?

3) How critical is it to have the delivery line inside the 1/4" suction line? I noticed that both the suction and delivery lines are 1/4" at the compressor end, which got me wondering if instead could I just run a second 1/4" piece from the compressor's delivery port to the evaporator and then splice it to the small diameter nub at that point before it goes into the evaporator (this is the point where it broke off when incorrectly installed the first time)?

In case it is relevant, it looks like the evaporator plate has a built in capillary tube (hopefully I am using the terms correctly) much like what is seen in the evaporator plates in a mini fridge.

Thank you in advance.

25-11-2013, 08:24 PM
Oh, oh. I may have stumbled onto an answer to my #3 question. It looks like I was incorrectly thinking the cap tube was a small section in the evaporator. Instead it seems that the entire piece of small diameter line (from where it goes into the larger diameter line to where they both go into the evaporator) IS the capillary tube. This reference also noted that the length of this line is critical for the correct operation of the unit.

Any thoughts on how I figure out what to use since I do not have the old piece to use as a gauge for the length?

I have a piece to determine the diameter, but how critical is the length?

The MG Pony
22-03-2014, 04:19 PM
Being I just noticed this is a prehistoric post I'll leave the answer up for others edification!

Q2 yes you can

Q3 this is for sub cooling, it improves performance a little bit

As for the length of cap tube, longer will make it colder, but it will take longer and it won't hold it well (It will run lots)

Shorter it will remove more heat (Within limmits of the compressor) but at a warmer temp, I'd pop shot at it of being 9 to 10 feet is the average but this depends on size of cap tube as well. there is a sizing programe out there from danfoss.

Q1 you take a small pice of pipe and squish it down over the cap tub if one must.

for the cap tube if tuning is needed use harris stay silve #8 as it will make for easier low temp removal should you need to shorten it.

a trick for eye ball charging is charge it with enough gas to run, once the box is to a temp you like 0c is where I like to do mine, slowely add gass till frost just apears out side the box on the suction line. Insulate it all up good and you'll have a system that aut to work fairly well.