DR1 acquired and need refrigerant charge advice...

Hi Eugene, welcome to the forum! The little DR-1 machines are generally the most viable of the DR series. The DR machines were the first commercially successful Monitor Tops and a such had some design concerns which were improved on later models. As smallest model, the DR-1 seems to last the longest due to less stress on the motor and other moving parts. 

Several of us on the forum are HVAC technicians, or in other aspects of the trade. It is good to have you here, for sure. 

Your fridge may indeed have a low charge, or it could have some sort of restriction in the float valve system. The DR machines have a mechanism in the float valve which allows you to "force" the float open fully. This is accomplished by attaching the service valve and unscrewing the service port plug at least 5 turns. A pin will be allowed to rise up under spring pressure, lifting the float and opening the needle valve. This will help you confirm if the float metering valve is blocked; versus if the machine has lost its charge. 

Have you had a chance to download the manual on the DR series machines? Many good cutaway drawings and instructions. 

As for obtaining SO2; most of us move away from that refrigerant if the charge has to be removed. There are good alternatives to it these days.  In my workshop I have a DR1 which was given to me for dead. It was recharged with R152A several years ago and has served well ever since. 

Our member Coldspaces has obtained SO2 in the past, and if I remember he had to pay rent on a tank from a gas supplier and there was a minimum quantity which wasn't trivial. He may be able to chime in on this thread and offer assistance. 

I have formed an opinion that it is not worth the cost and hassle to go back with SO2 as opposed to a less noxious refrigerant. That is based on experience working on a wide variety of systems from the SO2 era, including Monitor Tops and other designs such as the belt-drive units of this era. I do understand the charm of keeping the SO2 as a form of originality but I didn't see it as worth the effort. Another concern is with rebuilt machines is material compatibility. Most modern materials aren't compatible with SO2 and degrade. Often we can't get exact replacement materials for gaskets and seals any longer, and have to use materials which are compatible with HFC refrigerants but not necessarily with SO2. 

Below are two videos where I troubleshoot and recharge my DR-1:

Sincerely,
David

https://youtu.be/2gXqcW7O25A



https://youtu.be/6D8Kpg4Z3-w

Hello David: You've given me hope about resurecting my DR-1! I watched the other 2 videos (after the first yesterday), and your troubleshooting (with experience, I'm sure) is spot on. I've got some events occuring within the next week or so, those will prevent any work on the frig, but it's going to happen soon now that I've seen how you work on these machines. I'll obtain the serial number and post it here, hoping someone can tell when this was made. Until a little later on, thanks big time! Your Grateful Retired DR-1 Novice Technician, Eugene.

Hi there, Eugene!

What an interesting case! It's very similar to that of mine. The little advice I could give you, me not being HVAC technician, is that if you have the ability to recover the refrigerant with one of those recovering machines you should do that and then thoroughly examine your system and exactly what needs to be done. Because then you will have a much better decision basis should you convert it or just stick with the SO2.

In my case I came to the conclusion to actually stay with sulfur dioxide, because like yours, my unit is in remarkably good condition. Though I'm not the owner of a GE machine, but that of a Frigidaire belt drive, from just the same time period! The evaporator and the float in it seems to work as intended, and the shaft seal is also appearing to shape up, after having it operating for some time now. Therefore it may not be needing any modifications (that in turn may prohibit the use of SO2). So as the saying goes; don't fix what's not broken! And yeah, this is one of the very few unrestored belt drive units still operational. Therefore I intend to, if possible, only perform regular maintenance, and pretend in some manner as a century didn't just pass by. In this way, you and I seem to also share the same mindset, not intending to perform full restoration. Like new paint and such (correct me if I'm wrong). The paint on mine isn't so bad, but it does show some signs of age and usage. I personally don't mind that. It only adds to authencity.

Here's a link to my own thread (with pictures), if you're interested: Frigidaire D-4 belt drive maintenance w/o losing SO2 charge?

With that said, if it was an already busted up unit I came across where it didn't matter opened I the evaporator header up, or tore the whole compressor down, maybe I would have considered converting it and doing the modifications required (with Davids assistance, of course).



Regards
Sasha

Those new ‘natural’ refrigerants are usually seen in the form of purified propane (R290) and isobutane (R600a). They have the advantages of being non-ozone depleting, non-toxic, no patents (unlike HFOs), no purchasing restrictions, low GWP, and excellent thermodynamic properties. However, they have one major drawback; extreme flammability. As such, they’re only used in very small charges in some newer systems, but can still be dangerous if you’re not careful. In fact, the Valencia apartment complex fire is believed to have been started by a refrigerator leaking one of these refrigerants. I can’t imagine the legislation impacting R152a too much. This latest round of legislature is specifically designed to target refrigerants with a high GWP. In the U.S, the new limit for GWP of refrigerants will be approx. 750. R152a has a GWP of 125, so it shouldn’t be affected. It also won’t ban the use of high GWP refrigerants that have already been imported or produced in the U.S, much like how it’s still perfectly legal to use R12 that was brought here before 1995. I’m with you on other options not being explored. Frankly, I think that the only reason the law was written was to give DuPont a monopoly on the market with their new product, HFO’s, and to try and force people to buy new stuff that they don’t need.
Hope this helps,
Monitorhead.

That is frightening about the air conditioner having a failure wherein the overload breakers on both the fan and compressor failed to shut it down before that level of burning happened! 

There is a lot of hype, puffery and ballyhoo around global warming potential of products. As monitorhead mentioned, it is not a high GWP chemical and is not a phase-out material in the States. There are other areas of the world where they are going further off the deep end with this sort of thing and may continue to claim that it is bad. But when you compare it to other refrigerants and products, it is well on the least harmful end; if you buy into this theory at all. 

Yeah! This experience was, to say the least, pretty unpleasant. I start to wonder if there even were any protection circuits installed.

And the GWP stuff. No, I never bought in to that. I totally understand you and I also try to avoid those topics generally.


Regards
Sasha