Digital gauge manifold

[mark beiser]

In case anyone hasn't figured it out, I'm a true believer in digital refrigerant gauges. Other than the compound gauge sitting on top of my vacuum tree, and an old set of class 1 brass gauges in a junk drawer in my garage, I haven't owned or used analogue gauges in more than 7 years.

Even my burnout/recovery set is digital.

[jbeckham]

They are 1% accuracy when they are brand new, so the 800 psi high pressure gauge could be off by 8psi, and still be in spec.
Once they have been used for a while, or get dropped once, they are no longer 1% accuracy.
Additional measurement errors get added on top of that due to the parallax error inherent when viewing a gauge needle over a gauge face through a protective lens.
On top of the inherent instrument error, and the parallax error, you get an additional error factor introduced when you interpolate between the points of a PT chart.
If you are not using a PT chart, but trying to read the temperature scale printed on the gauge face, the error can be even more severe than PT chart interpolation errors.

When I hook up my digital gauges, depending on which ones I'm using, the pressure reading has an accuracy rating of anywhere from 0.5% of the reading on the most accurate of the instrument, to 0.75% full scale, of a 575psig scale.
On top of the greatly reduced instrument error, there is no possibility of parallax errors, as the reading is digitally displayed. The reading is the same, no matter who is looking at it, or from what angle.
Since the exact saturated temperature is also displayed, there is no possibility of interpolation error from converting the pressure to a saturated temperature.

There have been numerous studies done on the state of the charge in systems in the field in recent years.
Depending on the study, anywhere from 52 to 74% of the systems tested were incorrectly charged by 10% or more.
Much of that is due to poor training, or "techs" that don't give a crap, but I believe much of it is also due to the use of inadequate instruments, like analogue gauges.

Analogue gauges were a necessary evil for many decades, because they were the only thing we had, but with the ready availability of highly accurate digital instruments we have today, there is no place for analogue gauges when servicing modern high efficiency air conditioning and refrigeration equipment.

I can get on board with the inherent 0.5% accuracy, and the 0.75% scale accuracy... but, parallax error from the lens...c'mon man... the face of the gauge is maybe 8mm below the lens...and it just a 1x protective lens. Just take off the lens if it bothers you that much...

At what point do you rule out that a digital instrument won't be incorrect either, just because it's a solid state device doesn't mean it can't be wrong.

At least with analog gauges I can carry around 3 or 4 sets and compare measurements between them if I suspect something is wrong, and I'll still be under the cost of one set of digital gauges...

Also, no one is stopping you from putting your analog gauge manifolds in a foam padded pelican case when they aren't being used...

Furthermore, lets drop an analog manifold and a digital manifold from the top of a 20' extension ladder and see which one is more accurate afterwards... I'm gonna contend that both sets of gauges will be junk...

[ryan1088]

I can get on board with the inherent 0.5% accuracy, and the 0.75% scale accuracy... but, parallax error from the lens...c'mon man... the face of the gauge is maybe 8mm below the lens...and it just a 1x protective lens. Just take off the lens if it bothers you that much...

At what point do you rule out that a digital instrument won't be incorrect either, just because it's a solid state device doesn't mean it can't be wrong.

At least with analog gauges I can carry around 3 or 4 sets and compare measurements between them if I suspect something is wrong, and I'll still be under the cost of one set of digital gauges...

Also, no one is stopping you from putting your analog gauge manifolds in a foam padded pelican case when they aren't being used...

Furthermore, lets drop an analog manifold and a digital manifold from the top of a 20' extension ladder and see which one is more accurate afterwards... I'm gonna contend that both sets of gauges will be junk...

I got 50 on my digicools working better than your analogs in this scenario.

[jbeckham]

And to comment on your observation concerning detecting leaks with an analog gauge set, yes, that is an exercise in futility... Providing you're always attempting to do so with a manifold gauge set that wasn't assembled to perform that task...

[mason]

We putting paychecks on this challenge : )?

I've got 50 says my DC's are more accurate this second, forget dropping them 20' it's over already.

[jbeckham]

I got 50 on my digicools working better than your analogs in this scenario.

Ha, this is hilarious...

Lets parlay and add full retail market price for each others gauge set...

I'm gonna be laughing about the gig all the way through, but unless you just turned over a fire engine red quarter... You, probably not so much...

[Joehvac25]

Il put another 50, we can drop my digi's and save the analogs by not dropping them.

[jbeckham]

We putting paychecks on this challenge : )?

I've got 50 says my DC's are more accurate this second, forget dropping them 20' it's over already.

I don't have anything against the digital gauges... Other than my frugal nature.

Now, just present me with the parameters for how we're going to compare and measure said accuracy on said system...

[jtrammel]

Put a drum of 22 in an ice chest, get her down to 32*, hook up and see what the pressure is. No messing with the calibration screw on the analogues once its hooked up.

[kamersoutdoor]

Ha, this is hilarious...

Lets parlay and add full retail market price for each others gauge set...

I'm gonna be laughing about the gig all the way through, but unless you just turned over a fire engine red quarter... You, probably not so much...

I can barely look at my analogs without the guages breaking!
I'm sure it is partially due to the abuse my ak's take daily, I forget to baby the dinosaurs!

sent from my Samsung Galaxy Note

[jbeckham]

Put a drum of 22 in an ice chest, get her down to 32*, hook up and see what the pressure is. No messing with the calibration screw on the analogues once its hooked up.

Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...

[mason]

It appears the digi-queen nest has been stirred again LOL!

[jbeckham]

By the way, if we aren't working on cryogenic processes with these gauge manifolds...we're really taking this discussion to far...and if we are, we're probably not going to be using them...

So again, I will state my case that they are just more than the trade requires...unless your doing cryogenic lab grade work...in which case you won't be using a manifold gage set you purchased over the counter at the local parts house...

[jbeckham]

I just wanted to get a point across to the OP that the trade doesn't require that much of an initial investment on a gauge manifold to be a successful tech.

[mason]

Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...

On analogs you would be better off leaving a drum in your house at about 74*/130psi, confirming bottle temp with a calibrated temp sensor, and setting your needle to 130psi on high side, with a different bottle at 32*/57.5psi to set low side needle. You might be surprised where those needles land with 0psi after that calibration.

Or buy some digi-cools : P.

I've been using some analogs for the past couple weeks with my separate temp sensors and wow do I hate it now. The parallax thing is real, hook your analogs up to a bottle in your shop, then have one person at a time go in alone without sharing any information and ask ever tech to write down the psi and the face saturation temp on a piece of paper. You will not get the same numbers.

[jbeckham]

On analogs you would be better off leaving a drum in your house at about 74*/130psi, confirming bottle temp with a calibrated temp sensor, and setting your needle to 130psi on high side, with a different bottle at 32*/57.5psi to set low side needle. You might be surprised where those needles land with 0psi after that calibration.

Or buy some digi-cools : P.

I've been using some analogs for the past couple weeks with my separate temp sensors and wow do I hate it now. The parallax thing is real, hook your analogs up to a bottle in your shop, then have one person at a time go in alone without sharing any information and ask ever tech to write down the psi and the face saturation temp on a piece of paper. You will not get the same numbers.

i will argue that what you are calling parallax is just the difference in opinion on where that needle is on the dial... unless you have a gauge graduated in 1 psi increments, there will most likely be some discrepancy in interpretation every time...

and as far as where the needle comes back to, if it's not within 1% of the test sample for our respective gauge ranges... i guess it's time to swap it out...

for what it's worth, managing and understanding error is just part of understanding physics... there is a time and place where it matters, and there is a time and place where it really, really matters... looking at that hodgepodge split system that was originally installed 8 years ago by some other jack-leg that never even looked at the duct work... is not one of those times.

its all relative, and what your are doing with your gear will dictate your kit...

[mark beiser]

I can get on board with the inherent 0.5% accuracy, and the 0.75% scale accuracy... but, parallax error from the lens...c'mon man... the face of the gauge is maybe 8mm below the lens...and it just a 1x protective lens. Just take off the lens if it bothers you that much...

The reading still changes with the angle it is viewed at, or which eye you are squinting at it with.
Then there is the PT chart interpolation error.

With digitals, you don't even have to look at pressure, you get a direct saturated temperature reading, which is what you really need.

At what point do you rule out that a digital instrument won't be incorrect either, just because it's a solid state device doesn't mean it can't be wrong.

At least with analog gauges I can carry around 3 or 4 sets and compare measurements between them if I suspect something is wrong

There is a 9 year span in instrument ages in this picture. They are from 3 different manufacturers, use 4 different types of pressure transducers, and 4 different types of 3 different technologies of temperature sensors.
There is only about a 1.5 psi difference between the lowest and highest pressure reading, and 1.1º difference in the temperature probe readings among the 4 instruments that have temperature probes. The BTD-1000(top left) has no temperature probes.

Furthermore, lets drop an analog manifold and a digital manifold from the top of a 20' extension ladder and see which one is more accurate afterwards... I'm gonna contend that both sets of gauges will be junk...

I'd put some money on the table that says my Digi-Cool DRSA-1250 would still work fine. The manifold it is mounted on may need to be replaced though.
My BTD-1000 has survived such a drop, onto concrete.

[XcelTech]

I completely disagree with Jbeckham; however, I strongly suggest against buying digital gauges until you have been in the business for 2 to 3 years.

1.) some people get into the trade and find it is not what they are looking for so an expensive initial investment goes down the drain.

2.) You need to spend time getting not just accumulated with analog gauges but proficient with using superheat sub-cooling. I don't mean learn the math, I mean you understand what it truly is, how it helps you, and the physics of what you can't see.
Although digital gauges do not prevent you from learning this stuff, knowing how to use the rudimentary tools precisely comes with a very strong understanding that will make you a confident self-aware technician.

3.) New guys break stuff left and right. Its a growing pain trust me it will happen.

4.) You will most likely spend your first 6 months to a year in someone elses van. Do you really want to let other people use your crazy expensive tools day in and day out? Do you really want to move those tools from van to van and lug them out every night.

5.) By the time you are really ready to use these tools and have your own van something better will have replaced them on the market.

6.) Make sure any digital gauges you purchase have a respectable micron gauge. A bad micron gauge setup will turn your would upside down on large equipment like chillers.

[mark beiser]

Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...

And what does altitude have to do with what is going on inside a hermetically sealed system?

Altitude does not change the PT relationships inside a sealed system, the saturated pressure at a given temperature will be the same at sea level as it would be at 20,000 feet.

Gauges need to be calibrated in the pressure range they are intended to operate in.
Zeroing the gauge actually introduces more inaccuracy into the gauge, especially at higher elevations where the atmospheric pressure is lower.

[mark beiser]

2.) You need to spend time getting not just accumulated with analog gauges but proficient with using superheat sub-cooling. I don't mean learn the math, I mean you understand what it truly is, how it helps you, and the physics of what you can't see.
Although digital gauges do not prevent you from learning this stuff, knowing how to use the rudimentary tools precisely comes with a very strong understanding that will make you a confident self-aware technician.

I disagree completely with this.
Using digital gauges, that give a direct saturated temperature conversion, will help new technicians to think in terms of saturated temperature, instead of pressure.
Thinking in terms of saturated temperature makes understanding superheat, subcooling, and other things going on inside the system much more intuitive.

When you think in terms of saturated temperatures, it doesn't really matter what refrigerant you are working with, as the saturated temperatures will usually be close to the same for a given application, regardless of the refrigerant used.

The only reason we even look at pressure is to convert it to a saturated temperature.
Having to read pressures, and do PT conversions, is a distracting, diagnostically useless step, that doesn't do anything to enhance the understanding of the refrigerant cycle.

5.) By the time you are really ready to use these tools and have your own van something better will have replaced them on the market.

As with all things technological, if your reason for waiting to make a purchase is because something better will be coming along in 6 months, you will be stuck with not experiencing the benefits of the technology for that period, and in 6 months you will again be faced with the dilemma of knowing that something better will be coming out in 6 months.

6.) Make sure any digital gauges you purchase have a respectable micron gauge. A bad micron gauge setup will turn your would upside down on large equipment like chillers.

A micron gauge in the manifold is a fluff feature that I find pointless and annoying that I have to pay for.
The fastest evacuations are had with no refrigerant manifold or hoses involved, and it is best to have the micron gauge connected to the system, as far from the pump as possible.
This is doubly true on "large equipment like chillers."

Having said that, if a new guy is mainly doing start-up of new residential systems, etc., pulling a vacuum with a service manifold and hoses doesn't take that long.
If having a micron gauge built into the gauge set gets some people actually paying attention to micron readings, and proper evacuation, that otherwise have not ever done so, it is a good thing.