Indel refrigerator with Danfoss 50 compressor- How to figure out refrigerant pressure

[teneicm]

Hello- we've got an Indel refrigeration system that uses a Danfoss 50 compressor. The compressor only has one Schrader valve port to check pressure and/or add refrigerant. Anyone know if this one valve represents the high side or the low side of the compressor? Hooking up a manifold gauge shows very little pressure, both while the compressor is running and at rest, so not certain if there is another valve upstream that is preventing us from seeing the true pressure? Anyone familiar with this particular model? I haven't been able to do too much internet research because we're in the middle of nowhere in the Solomon Islands and web browsing doesn't work.

Cheers- Matt.


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[OldBawley]

From documentation it must be possible to know just how much Amps the compressor should be using while running. Measuring the running Amps and finding a lot less means no or to litlle gas.
Our danfoss 35 F is rated at 35 / 40watt and uses 4 to 4,2 Amp.
When the compressor uses only 3 or less Amps, not enough gas.

[GILow]

Not much help here, but using the smart logic of OldBawley, our Danfoss 50 draws 4.5 amps when running (battery bank at a nominal 12.3 volts) if that is any help. (Works astoundingly well too!)


I will watch this thread because I might need to know the answer one day too.

Sorry, ignore my idea, I just found an online manual that tells me the current for the BD50F is no good as an indicator as the motor speed is set by some kind of resistor in the control circuit. So the motor could be drawing anything between 2 amps and 6 amps depending on the configuration.

[ColdEH]

Why are you hooking up gauges ? Is the system not working ?
Hooking up gauges are the last thing you should do .
Regards

[pcmm]

Originally Posted by GILow

Not much help here, but using the smart logic of OldBawley, our Danfoss 50 draws 4.5 amps when running (battery bank at a nominal 12.3 volts) if that is any help. (Works astoundingly well too!)


I will watch this thread because I might need to know the answer one day too.

Sorry, ignore my idea, I just found an online manual that tells me the current for the BD50F is no good as an indicator as the motor speed is set by some kind of resistor in the control circuit. So the motor could be drawing anything between 2 amps and 6 amps depending on the configuration.

The DB50 can be defaulted to a non variable speed ( highest speed I belive) with a jumper wire between 2 of the posts. Set that, and then see how many amps are drawn to see if its running properly.

the DB50 also has a diagnostic led that you can connect up to see if there are any error codes.

[a64pilot]

It is to the Low pressure, suck side of the compressor.
Only real way I know to get refrigerant correct is if you know weight of the charge, let out all of the gas and refill with correct weight.
There are other ways, depending on your type of system, I believe most are overcharged when people start messing with them, overcharged won't cool well just like undercharged won't.

[a64pilot]

Originally Posted by pcmm

The DB50 can be defaulted to a non variable speed ( highest speed I belive) with a jumper wire between 2 of the posts. Set that, and then see how many amps are drawn to see if its running properly.

the DB50 also has a diagnostic led that you can connect up to see if there are any error codes.

Unless mistaken my BD-80 will go to the lowest speed with a jumper wire, to get to high speed it takes a resistor in line to the jumper wire, I assume a 50 may be similar

[ColdEH]

Originally Posted by a64pilot

Unless mistaken my BD-80 will go to the lowest speed with a jumper wire, to get to high speed it takes a resistor in line to the jumper wire, I assume a 50 may be similar

Yes , it takes a resistor in line with the thermostat wire to get higher speeds and no resistor for low or standard speed of 2000 rpm. Just like a BD35.

Again ,? why are you checking refrigerant with gauges ? You may be causing more trouble . Tell us your symptoms. !

And there will be no high side access or shrader valve for gauge hook up .

Regards

[Dance Aweigh]

That's the low pressure side. It should read about 3-5 mm Hg with compressor running. It takes very little gas to overcharge it, so add gas in small quantities, wait 15 minutes & look at gauge again. When you have about 3-5 mm Hg, you should be about right. Also, feel the return line near the compressor: it should be slightly cool. If it is icing, you are overcharged - then bleed off some gas & start over.

[newhaul]

Shoot sv third day an email or pm he's one of the refer gurus on here

[Dougtiff]

charge SLOWLY and wait for awhile for the unit to equalize, watch the return line and stop when frosting starts where the line exits the box, be careful to not inject any air into the system, it takes very little to screw up the whole thing, this is done by purging the charging hose while connecting to the port.

[Brewgyver]

Run current is NOT an accurate way to assess the state of charge in any refrigeration circuit. Neither is simply measuring the suction line pressure. There are too many variables. \

The correct way for a small, non-TXV circuit is to measure suction superheat. If you don't know what that is, you would be better off not touching it, and getting a qualified tech to check it out.

That being said, SOME problems can be simple fixes, which don't involve accessing the refrigerant circuit. As Typhoon said, what are the symptoms?

[Cadence]

Originally Posted by Dougtiff

charge SLOWLY and wait for awhile for the unit to equalize, watch the return line and stop when frosting starts where the line exits the box, be careful to not inject any air into the system, it takes very little to screw up the whole thing, this is done by purging the charging hose while connecting to the port.

[MCOS]

If there is only one fitting, it is for the low pressure/suction side of the system. It will also be evident by being a larger in diameter tube then the high side. If the gauge shows pressure while the system is running then you have too much gas in it. There should be a marked difference in temperature between the high side coming out of the compressor going to the condenser and the low side, coming out of the evaporator coil or cold plate and returning to the compressor. Check the tech manual for the exact specs for parameters of high side temp vs low side temp if you want to be exact but warm to hot on high side and cold on the low side is the main idea. If you are not getting a low pressure reading on the low side, then either the compressor is shot or the system has too much gas. If both the inlet and outlet temperature are about the same, the same is true. You can also purchase a schrader saddle pierce valve and install on the high side to check high pressure. If you find you have high side pressure equal or close to low side then the same is true. If you allow the pressure to equalize and then start the compressor the high side should slowly come up and the low side should likewise go down. Other possible problem could be a plugged up capillary tube, high side will go up, low side will go to vacuum, however this could be a bit low on gas also, a bit low on gas should still cool well. Plugged capillary tube should should not be a problem unless the system was opened/ depleted of refrigerant.


Caveat, if you don't feel like replacing the compressor - have a person with knowledge of refrigeration look at it. Over pressure and or "slugging" the compressor with liquid Freon have killed many an otherwise workable system.

[teneicm]

So the symptoms are basically that the system had started to run continuously without bringing down the temperature of the freezer box. There was still some cooling happening as the system was able to maintain about 25 degrees (by running continuously), but wasn't able to get down to the usual 16-18 degrees. With the system not running, after allowing 30 minutes for things to equalize, we hooked a gauge to the single Schrader port and found only 5 psi. Gave the system a couple of shots of 134a and didn't see the pressure go up, but stopped at that point because of concerns of overcharging. Turned the system back on and the compressor draws down the pressure to about 1 psi. The system is now running better, (as in it now cycles on and off, holding a temp around 20 degrees) but am still uncertain if it's over or undercharged at this point. Also wondering why we didn't see the pressure go up at all when we put some more gas in.

The Indel system has a 'smart' controller that varies the compressor (and water pump) speeds depending on battery voltage and temperature. The system is also a holding plate system, so hard to see how much of the plate is getting cooled. Would love to have a competent tech take a look, but we are on the SE end of Guadacanal where most folks barely have clothes, let alone HVAC training. So at this point I'm the most qualified person for miles around (scary thought!).

Any other info that would help?

Thanks for all the replies, Matt


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