dial-a-charge

[absoair]

We have a R134a dial-a-charge. We weigh the R404a in. I started looking for a R404a dial-a-charge and was told it does not exist. No one can tell me, why not?

[SouthTex]

most people use electronic scales, which makes more sense with all the different refrigerants out there. Anyone building a dial a charge for one refrigerant would have a very limited market place

[icemeister]

Just use the ratio of the refrigerant liquid densities to adjust your Dial-A-Charge setting. Here's an old thread discussing how to do it:
http://hvac-talk.com/vbb/showthread.php?t=55731

(R134A Density)/(R404A Density) x (Required Weight)

R134A Density = 74.9 lbs/cu ft
R404A Density = 64.7 lbs/cu ft

EXAMPLE: If you need 2 lbs of R404A:

2 lbs R404A = (74.9 / 64.7) x 2 = 2.32 lbs on the R134A scale

(This is why a "30 lb" drum of R404A only contains 24 lbs.)

Here's a Genetron info page which includes refrigerant densities:
http://www51.honeywell.com/sm/genetr...ture-Chart.pdf

You'll note that this page also includes a similar formula involving density ratios. Don't get these two methods confused as the ratio is reversed.

My formula applies only for a Dial-A-Charge where you're calculating what volume of the new refrigerant you need to arrive at a specific weight according to the old refrigerant scale on the Dial-A-Charge .

The Gentron formula is used when you're calculating how much weight of new refrigerant is needed to fill the same volume in a system as the old refrigerant did.

[absoair]

Got it. Makes sense now.

[wannafreeze]

Just use the ratio of the refrigerant liquid densities to adjust your Dial-A-Charge setting. Here's an old thread discussing how to do it:
http://hvac-talk.com/vbb/showthread.php?t=55731

(R134A Density)/(R404A Density) x (Required Weight)

R134A Density = 74.9 lbs/cu ft
R404A Density = 64.7 lbs/cu ft

EXAMPLE: If you need 2 lbs of R404A:

2 lbs R404A = (74.9 / 64.7) x 2 = 2.32 lbs on the R134A scale

(This is why a "30 lb" drum of R404A only contains 24 lbs.)

Here's a Genetron info page which includes refrigerant densities:
http://www51.honeywell.com/sm/genetr...ture-Chart.pdf

You'll note that this page also includes a similar formula involving density ratios. Don't get these two methods confused as the ratio is reversed.

My formula applies only for a Dial-A-Charge where you're calculating what volume of the new refrigerant you need to arrive at a specific weight according to the old refrigerant scale on the Dial-A-Charge .

The Gentron formula is used when you're calculating how much weight of new refrigerant is needed to fill the same volume in a system as the old refrigerant did.

Ice,
I have been looking into this again, recently .
What I am trying to understand today is,since the charging cylinder works with volume instead of weight,could I use the same marking for a replacement refrigerant on the dial?
Say an ice maker label says 20 oz of 502a and I wanna replace it with 408.
If I used the 502 scale up to the 20 oz marking for 404 that would be the same volume eventhough that much 404 would weigh only 17 oz.
According to the 80% rule (I don't know whose..) it would be about that much 404 anyway.
If I needed 17 oz 404 (or 408) according to the volume formula I would fill the cylinder up to the 20 oz marking for 502 also.
I used to work for a manit csr when I was a novice,he always used a dial-a-charge without the pressure adjustment lines.(just horizental lines).If I remember correctly we weren't doing any correction.I would think something would go wrong to let him know if this wasn't correct..
Could you clear the air for me?I am going back to dial-a-charge and a handheld anolog scale after my second tif 9010 in 6 years.

[Joe Harper]

It was my understanding that you should not be using blended refrigerants with a charging cylinder.

I dont want to sound ignorant or inexperienced here. But in my 16 years I have never heard of dial-a-charge. What is that??

[icemeister]

Ice,
I have been looking into this again, recently .
What I am trying to understand today is,since the charging cylinder works with volume instead of weight,could I use the same marking for a replacement refrigerant on the dial?
Say an ice maker label says 20 oz of 502a and I wanna replace it with 408.
If I used the 502 scale up to the 20 oz marking for 404 that would be the same volume eventhough that much 404 would weigh only 17 oz.
According to the 80% rule (I don't know whose..) it would be about that much 404 anyway.
If I needed 17 oz 404 (or 408) according to the volume formula I would fill the cylinder up to the 20 oz marking for 502 also.
I used to work for a manit csr when I was a novice,he always used a dial-a-charge without the pressure adjustment lines.(just horizental lines).If I remember correctly we weren't doing any correction.I would think something would go wrong to let him know if this wasn't correct..
Could you clear the air for me?I am going back to dial-a-charge and a handheld anolog scale after my second tif 9010 in 6 years.

Yes, since your goal is to measure out R408A in a volume equal to that of R502 then just use the R502 scale on your Dial-A-Charge and fill to the nameplate weight of R502 listed.

The density ratio method is used when a refrigerant isn't included on the Dial-A-Charge's scales.

[wannafreeze]

Yes, since your goal is to measure out R408A in a volume equal to that of R502 then just use the R502 scale on your Dial-A-Charge and fill to the nameplate weight of R502 listed.

The density ratio method is used when a refrigerant isn't included on the Dial-A-Charge's scales.

Thanks.

[jhd1234]

It was my understanding that you should not be using blended refrigerants with a charging cylinder.

I dont want to sound ignorant or inexperienced here. But in my 16 years I have never heard of dial-a-charge. What is that??

http://www.thermalengineeringcompany...p=12&cat_id=10

http://www.testersandtools.com/Charging-Cylinder.php

[Joe Harper]

Ohhh, its a charging cylinder with a fancy rotating thing... I dont feel so bad, I have seen that.

So if you are using these cylinders, you are charging by volume and not weight?

[wannafreeze]

Yes, since your goal is to measure out R408A in a volume equal to that of R502 then just use the R502 scale on your Dial-A-Charge and fill to the nameplate weight of R502 listed.

The density ratio method is used when a refrigerant isn't included on the Dial-A-Charge's scales.

Hey Ice,
I just got my 2.5 LBS Robinair dial-a-charge with heater.I used it on an ice cream dip box that a friend of mine has.He just had the compressor rewound for $220 and he placed it back.I went there to give him oil and refrigerant.
It called for 59 OZ 404a.I used 408a with AB oil.Anyway I let him know that I haven't used a cylinder for five years so we enjoyed filling it in my truck.I made a mistake instead of multipliying 59 by 1.16 I devided it and I put the 408a up to the 51 OZ marking on the 502 scale.I was way low on charge I pulled out the CPR valve so he would get one on monday.So I came home to read this thread and specifically my recent response that you confirmed me on.
Stupid me,or I guess my stomach was bothering me so much that I wasn't thinking clearly.I was supposed to fill it up to 68.4 OZ marking on the 502 scale.I called him right away and told him about it so tomorrow I will correct the issue.
But aside from all the screw ups,the cylinder worked like a charm.I was able to put all the charge from the high side valve.When it wasn't coming out anymore I plugged the heater and with an amaizing speed the freon left the cylinder into the high side.I think in the winter I won't worry about the cans being cold anymore either.Also won't drag the 30# tanks to every job site anymore.Also I am keeping 3 feet hoses with low loss fittings on both ends for each refrigerant for using from can to cylinder..I don't have to purge hoses..
I love it.

[wannafreeze]

Today into another upright Bev.Air freezer I had to put refrigerant.It called for 13 OZ 502.I filled my 2.5 lbs cylinder up to the 13 oz marking of 502 scale with 408a (which would weigh less than 13 oz).Didn't have to bring the tank to the store then up to the freezer with the electronic scale.There is no comparison..The charging cylinder is so much easier to use.

[icemeister]

I found this handy conversion chart for charging various refrigerants with a charging cylinder:

http://www.thermalengineeringcompany...on%20Chart.pdf

[Airmechanical]

What I am trying to understand today is,since the charging cylinder works with volume instead of weight

i used to only use the charging cylinder

what a confusing concept

i critically charged a little vending machine a few days ago with 3 oz's of 134A using my digital scale

i start thinking about the 3 oz's in a charging cylinder

an ounce on a digital scale or an ounce in the charging scale, is it the same for all refrigerants

confusing concept!



.

[deux]

Umm... dial a charge is so 1970's. Not to mention wastefull with venting. And you have to have a KNOWN temp of the freon. Without the known temp your going to be wrong.
How long does it take for the truck temp freon to match up on the dial a charge?

You know, to be honest, I never had any luck with dial a charge in 1980. Suction line frost back worked way better. I sooooo bought the first digital scale I seen!

[absoair]

Umm... dial a charge is so 1970's. Not to mention wastefull with venting. And you have to have a KNOWN temp of the freon. Without the known temp your going to be wrong.
How long does it take for the truck temp freon to match up on the dial a charge?

You know, to be honest, I never had any luck with dial a charge in 1980. Suction line frost back worked way better. I sooooo bought the first digital scale I seen!

The one in the maint. shop stays in the maint. shop pretty close to the refrigerant. It comes in handy in that aspect. Don't ever remember using one in the field.

[wannafreeze]

I have been using it on small systems.It's pretty handy.(Actually I have a 5#er using it with 134a and 2.5# er using it with 404a.)
I verified it with an electronic scale,that when I use it for R12 replacements using 1.10 of the cylinder scale,and for 502 replacements using 1.16 of the cylinder scale,the amount weighs correct.
And if it happens to be an R12 or 502 unit the multiplier is only '1'.Basicaly going by the same volume.
Since I use them with only 134 and 404a there is no major venting going on.Also in the winter it will be easier to get it out of the tank,since I will use pressure differential for filling the cylinder.
It's so much easier to take a 3 lbs cylinder on top of a traulsen in a tight kitchen and to and fro truck,than a 36 lbs tank.
As for the refrigerant temperature issue someone brought up...there is a high side gauge on the cylinder and you can do adjustments accordingly.
If anyone would consider using it I would recommend Robinair with heating element (you can actually charge it only from the high side if you want.)
I tried thermal eng. had to return it..

[chilliwilly]

Yes I too have purchased a dialacharge about a year ago, but it's calibrated for CFCs and I only tend to use 134a, isceon 49, and 404.

Its still in the plastic case and I bought it thinking that could buy a new calibrated sleeve from Robinair. But when I rung them they spoke to me like a parent speaks to a child that wants to help with fixing the car or unblocking the sink.

I was thinking of weighing out amounts of 134a and adding to the diala charge and checking the pressures then engraving the quantity on the sleeve where the liquid level is, but I can't be arsed.

I though it would come in handy when you are trying to gas up off steps or ladders, or where theres no level surface for the scales, and your hoses won't reach.

[wannafreeze]

Yes I too have purchased a dialacharge about a year ago, but it's calibrated for CFCs and I only tend to use 134a, isceon 49, and 404.

Its still in the plastic case and I bought it thinking that could buy a new calibrated sleeve from Robinair. But when I rung them they spoke to me like a parent speaks to a child that wants to help with fixing the car or unblocking the sink.

I was thinking of weighing out amounts of 134a and adding to the diala charge and checking the pressures then engraving the quantity on the sleeve where the liquid level is, but I can't be arsed.

I though it would come in handy when you are trying to gas up off steps or ladders, or where theres no level surface for the scales, and your hoses won't reach.

Check what I said.It's very easy to adjust for new refrigerants.Use multipliers 1.10 and 1.16.I confirmed it with the electronic scale.And when the amount is stated for the old refrigerants just fill the charger up to that amount with the new refrigerant.It's the same volume and there doesn't seem to be any problem with that either.

[thrashme]

It has been out of touch for quite some time. I used to enjoy using a charging cylinder...in the 80's. Since I have been using digital scales I couldn't imagine going back to a charging cylinder, Much less converting from the existing scale to use it for a different refrigerant. call me lazy or maybe simple minded, but doesn't that method make for more work? I can appreciate the tight spaces we have to work in, particularly above a reach-in with a low ceiling, but I carry long hoses for those difficult places.

I do enjoy nostalgic tools. I recently purchased a Simpson 260 Analog Meter.