BD35 compressor not making frost on plate .

[a64pilot]

Originally Posted by typhoon

I have about 12 inches of frost running down the pipes from the evaporator , but the entire plate is not frosted , still running at 7.5 psi .

Regards

There is frost from the output line from the condenser?
The cold shouldn't begin until just after the restricted orifice, which is at the beginning of the plate?

[a64pilot]

If i understand what your saying your charge is low, add slightly until ideally the entire plate is frosted, if the return line from the plate frosts up, then you have a tiny bit too much.
I've never done this hit and miss method, but understand it, patience will be your friend as it takes quite a while after you add refrigerant until it hits equilibrium, and you can't tell anything until equilibrium is reached.

Or, I misunderstand the process

[ColdEH]

Originally Posted by a64pilot

It will frost up in open air, unless of course open air is not a 100 deg day and a 20 MPH wind or something, but in a shop, yes.

I have about 50 percent frost from the end where the pipes enter the plate , from left to right , and a foot of frost on the pipes , been running for about an hour now . The temperature in the shop is 70 degrees.

Regards

[ColdEH]

Originally Posted by a64pilot

If i understand what your saying your charge is low, add slightly until ideally the entire plate is frosted, if the return line from the plate frosts up, then you have a tiny bit too much.
I've never done this hit and miss method, but understand it, patience will be your friend as it takes quite a while after you add refrigerant until it hits equilibrium, and you can't tell anything until equilibrium is reached.

Or, I misunderstand the


process

If I add refrigerant the pressure climbs accordingly shouldn't I keep it in the 6 to 8 psi range ?

Regards

[Cadence]

Originally Posted by typhoon

I have about 12 inches of frost running down the pipes from the evaporator , but the entire plate is not frosted , still running at 7.5 psi .

Regards

I was speaking frosting at ambient temp. outside the box. Not inside the box? I am by no means an expert on refrigeration. It couldn't cost that much to put a little more refrigerant in. Just be prudent and not blow seals.

[ColdEH]

Just added a 3 second shot of refrigerant . Been about 5 minutes no difference in frosting of the plate , running at 14 psi ,

Regards

[ColdEH]

Originally Posted by a64pilot

There is frost from the output line from the condenser?
The cold shouldn't begin until just after the restricted orifice, which is at the beginning of the plate?

No , frost is just on the orifice. And about 8 inches on the plate where it connects .

[Cadence]

Button it up and let it run for awhile. You maybe over reacting. If you have frost on the lines something is cooling. It isn't an immediate thing.

[a64pilot]

Originally Posted by Cadence

Button it up and let it run for awhile. You maybe over reacting. If you have frost on the lines something is cooling. It isn't an immediate thing.

Hopefully Rich will chime in, but I think it may take an hour or more for everything to equalize, if I understand this process, its an add for 3 sec, go out to eat, add 3 sec, go to sleep and check in the morning kind of thing, could take a day or two?

[Richard Kollmann]

If the gurgling sound never stops during an extended run and suction pressure stays near 7.5 psi indicates refrigerant contaminated or refrigerant is some what restricted. Lowering static pressure to less than 300 micron for a duration of four hours while keeping system warmed to near 100 degrees F is necessary on systems lubricated with POE oils. This process will remove all vapor gas and dehydrate moisture from system.

Whenever an evaporator is replaced it must be vacuumed clear of test gases Many evaporators are shipped with nitrogen inside as it is not legal to ship them with refrigerant inside. Your system report matches a $2000 experience one other boater had with what was believed to be nitrogen mixed with refrigerant after installing new evaporator.

If this system's oil was contaminated with other additives or unapproved oils you may as well replace complete system.

[RaymondR]

If your condenser is hardly warming up with the compressor running continuously it sounds like it may not have enough gas in it.


The pressures you are quoting seem a little low for a warm plate, the pressure depends upon the temperature of the gas and should decrease from a high to a low value as the plate freezes down.


Gurgling indicates liquid flow so there is some gas in the system.


If you have the equipment I would vacuum it down and refill, these little BD 35 systems usually take around 100 grams of refrigerant.

[ColdEH]

Excellent advice !

I do have the equipment to refill this unit, and also have a spray booth / oven for cars so I can get the entire unit up to any temperature needed.

So this is the plan , install a high pressure connection , a filter drier with a sight glass , evac the system , add new refrigerant. Cross fingers .

Any suggestions on a filter drier/sight glass . A all in one unit would be best , Less to solder . Or any other ideas to make the system more reliable .

Maybe a constant pressure expansion valve instead the fixed orifice?

Regards

[a64pilot]

I'd install an automotive type drier, one with the sight glass in the top, I'd look for one with a big glass, and glass if possible, not a tiny piece of plastic.
I believe the temp isn't that important to be precise, idea being to get it very warm so along with the vacuum (a deep vacuum, held for a significant period, you can't vacuum too much) to remove as much of any moisture there is.
I would not change the expansion valve, at some point your re-engineering the system, at some point just build your own from scratch starting with a new compressor?

[ColdEH]

Originally Posted by a64pilot

I'd install an automotive type drier, one with the sight glass in the top, I'd look for one with a big glass, and glass if possible, not a tiny piece of plastic.
I believe the temp isn't that important to be precise, idea being to get it very warm so along with the vacuum (a deep vacuum, held for a significant period, you can't vacuum too much) to remove as much of any moisture there is.
I would not change the expansion valve, at some point your re-engineering the system, at some point just build your own from scratch starting with a new compressor?

Thanks, that's a good idea , never thought of using one for a car , I guess there is no "to big" when it comes to filter driers .
Build my own from scratch , that sounds like fun , I still have to do the freezer 🤔
Regards

[Richard Kollmann]

You would not want to alter refrigerant capacity with a receiver filter dryer and sight glass on a capillary tube refrigerant flow control system.