Charging a system

[shark26]

Hello everyone. Need a little help with this one as i am not very good at putting practice into words and dont want to get it wrong and confuse people.

I need to provide a simple step by step chart on how to charge our equipment when out on site without scales. (for our junior/apprentice staff)

The equipment is Koxka M-19 Multidecks.
Capilary tubed and running on 134a and some on 404a.

Many thanks.

[slingblade]

The difficulty in this case is the fact that many different things can affect the way a system is percieved to contain a full charge by an individual. some may look at a set of gauge readings and see undercharge or overcharge where there is none. fans held off for instance , a blocked condensor or low or high ambient temp., amongst many others are possible reasons. the only true way of assesing a system charge is ultimately by experience and knowledge of all the factors involved. this will prove difficult for the junior engineer as his/her experience is limited. i cant really think of a chart that would have helped me as i was starting out or one that would help me in any way these days where charging a multideck is the job at hand. good luck in your search anyway.

[chillin out]

I need to provide a simple step by step chart on how to charge our equipment when out on site without scales.

Do you not have portable scales?

Only other way is to stop the evap fans and charge untill the whole coil is frosted but no more.

Why teach this method if you do have scales?

Surely if it is SOG, then find leak - reclaim rest of gas -repair - Vac and recharge to weight. This way you get it right every time.


Chillin

[shark26]

Thanks Marc. Will give that link a look.

Chillin. Thanks. We have a few systems that have some very useless line taps fitted. Some leak and some are ok.
The taps are on the process tube and so can be pinched off, removed and a new tap fitted. The system then needs to be topped up. Thanks

[shark26]

Hello. Obviously we need to charge the system while checking the superheat. Anyone have a clear guide for this method. + what should the superheat values be?

[chillin out]

Some leak and some are ok.
The taps are on the process tube and so can be pinched off, removed and a new tap fitted.

Use shrieder valves with tails , remove old LTV and braize on new valve.

Much more secure than LTV`s.

Chillin

[shark26]

hi chillin. thanks. thats what we are doing

[slingblade]

Shark, don't listen to that crap.

Get the Tech Method Lesson Series
https://www.merchantamerica.com/tmethod/

Call it crap if you like but the fact remains the same, experience cannot be learnt from a book regardless of the level of technical content.

[Peter_1]

Shark 26, you needed a method for your apprentices?

If you give them a chart or a step by step method without any theoretical knowledge, then you're completely wrong.

As Slingblade said: what if the evaporator is frosted and they follow the step by step method?

With that litlle knowledge, is it anyway allowed legally that they charge systems?
Sorry I have to say, but I don't believe it's for you apprentices.

And sorry but some know what I think about the TECH method. It's not bad but for me it's not the right approach to start in refrigeration.

[shark26]

Hi guys. Yes i agree but these guys have been working in ref for over a year and have a little experience.They know the workings of refrig and various probs. I ust need to give them guidlines on charging via superheat

[phil68]

Hi guys. Yes i agree but these guys have been working in ref for over a year and have a little experience.They know the workings of refrig and various probs. I ust need to give them guidlines on charging via superheat

Making sure that the condenser coil is clean & the evap. is clear of ice & that all fans are operational I'd aim for 18 psig suction for R134A on a chiller & the same for R404A on a freezer with capillary expansion devices. Check for sweating back of the suction line & temperature of the liquid line but to be honest it's quite a bit more involved than that, ideally an experienced fridgie should do it. Would still be much better to weigh it in if the refrigerant weight is known though, would be a lot quicker (& idiot-proof, no offence intended toward your apprentices ) & at least then you'd know it's correctly charged.
Agree with slingblade, when I was a green 18 year old I managed to blow a pressure blow-off valve while trying to clear a bubbling sight-glass, charging with R502 when the system had a blocked drier

[shark26]

Hi phil
What about superheat values ?

[phil68]

Hi phil
What about superheat values ?

I'll be honest with you I've never measured superheat on a capillary system, only on systems with a TEV. Usually a capillary system has a refrigerant weight on it. If not I'll charge to 18 psig suction & take it from there.

[oogene]

hey,Marc; I am a newly registered member. I have heard of you a few times and from what I've read, You are one smart refrig dude as well as very sharp on computers; I happen to have that tech method book and it is very informative, I've also been downloading some info from various sources but haven't read most of it yet, I live in the midwest USA. I worked on Carrier tranportation refrig products for about 15 months,then got hired as a commercial HVACR tech apprentice doing heat, refrig, A/C,food service and...they seem intent on throwing me to the wolves the comm stuff is different to me from trans stuff. What other books would you recommend I read to help me get up to speed. (I am married with 2 young kids even though I'm in my 40's)

[chillin out]

hey,Marc; I am a newly registered member. I have heard of you a few times and from what I've read, You are one smart refrig dude as well as very sharp on computers

LOL LOL HE HEE

You don`t know him then...


Welcome anyway, just don`t let him fool you.


Chillin

[oogene]

chillin; how do you get anything done with the hotties dancin in your head ???

[oogene]

I pretty much understand the TECH method, just need more application, when I worked in transport, most units had the same parts and operation and you learn about probable causes sometimes without having the theory down pat. there are more complex systems but we never really see them that much, although I think I also understand most of the HVACR theory as well. The big thing I see is the variety of stuff(valves,mechanical hardware, etc.) and applications. I also haven't seen any really big stuff,chillers, absorption, screws, etc. yet.I've only been on the job as a comm HVACR tech apprentice for two full months, then laid off due to lack of business subject to rehire. I appreciate your help immensely even if your head may be swelling a little...

[dogma]

Surely if it is SOG, then find leak - reclaim rest of gas -repair - Vac and recharge to weight. This way you get it right every time.


Chillin

[shark26]

OK OK OK OK..........
So explain how you would top up a multideck (after repairing leak) I do and have shown them how to weigh refrigerant in. But would be good to have clear tech knowledge on topping up CORRECTLY for a cap system. Is superheat method correct - please explain. The way i have done it in the past is to fill untill cabinet runs correctly. These cabinets only hold 1 - 2 kg model dependant. (dont want to do it hit or miss way. + increase everyones knowledge)
Really just want the correct method.........
PLEASE

[Temprite]

I will probably get reamed for saying this but....

What is wrong by charging to frostline on a capillary system (assuming you dont have a nameplate charge) and sightglass on a TX,when the systems are at temperature

Sure you can overcharge if you try and clear the glass (blends) but if both gauges are on and you know what you are doing all should be fine.

I purchased the tech method books and found the information in them most useful and would have to say I learnt a few things.

The problem is that a majority of the ****e I work on is mismatched and the recommended subcool and superheat values dont work for these systems.

When you are looking at a long list of jobs that is going to take you well into the evening, you kind of lose interest in strapping sensors and guages to every system you come across even ones that appear to have correct charge.(If it ain't broke dont fix it!)

Sure if you are charging a system you can strap a sensor to the suction line to be sure that you are not flooding back.I certainly think that is a good idea or when commisioning a new install.

I think the main benifit of Gary's books is it highlights the importance of checking superheat and subcool for troubleshooting purposes and for this I would recommend them to anyone.

Just my opinion.

Regards

[crustyx]

Hi everyone.

I have been working in refrigeratio for a short while. I have no money hence cant afford the book you write about (marc). I currently charge using scales and everything is fine, but woul like to be able to top up. Can you please explain about the superheat and subcooling. ( be kind on me ) I too work on all cap systems. I work alongside an engineer but need to expand my knowledge - he is too busy to explain things in detail. If i could learn a bit of theory i could help more. I am young and Keen. Please dont make me have to look for job change - i like refrigeration.

[shark26]

This is the type of person i am looking at info for.

[Peter_1]

... I am somewhat familiar with it because I had to read through it when I changed all the numbers from F to C for the UK market.

Now I understand why you promote it

[Peter_1]

I know how but I'm not the best they told me to explain it.
So....let the smarts ones explain it then.

[chillin out]

OK,

Find leak, repair leak, (how you can do this without removing all the gas is puzzling, there is no LR on capilary) ,

Stop evaporator fans, run comp, add gas untill your licked finger sticks to all of the evap.

Take it slowly don`t overcharge it.

Reconnect fans and there you go.

Chillin

[slingblade]

Brilliant. then restart fans, increase load on evap. hey presto SOG.

[chillin out]

Brilliant. then restart fans, increase load on evap. hey presto SOG.

No it wont... This method is fail safe. It will work every time....try it.

The only time it didn`t work was when there was a blockage in the system.

Chillin

[slingblade]

ill take your word for it. it just strikes me that charging a forced air evap with no air will over-simulate low load conditions. to then charge to a frost line will potentially leave the unit sog. think about a cooler with a full charge where the fans have stopped (or its frozen) you may get liquid back. this would look like overcharge to an apprentice.

[bernard]

Hi If for what ever reason my scales are not working then I subtract 12 c from the cabinet temperature I want to acheive convert to psig and slowly add gas until I acheive this while watching the suction at the compressor for frosting.For blends I will subtract 15 c.

If I ever open the system I always replace the drier,after recovering gas I will haxsaw through the drier before de-brazing it then replace it with a 1/4 flared dier.

Always wash the condenser with hot water with some hydr-coil mixed in.Clean the trailing ends of the evap fan blades.

Regards Bernard

[shark26]

Thanks guys. I will try these methods.
Another quick (!) question. The ambient temp in our warehouse is about 4 C How will this effect these charging processes. The cabinets are designed to run at about 2 C.
(or how would you charge in these conditions - apart from in i warm coat and hat)

[slingblade]

Youre just being silly now aren't you. stick a piece of cardboard over the condenser to lift the head pressure.

[dogma]

Hi mate. I've charged without scales and the quikist method, and most reasonably accurate I've found when it is time consuming to or difficult to obtain superheat readings is as follows.
Connect to high and low sides and dump around quarter chrge in. Now start the compressor and slowly allow "liquid" refrigerant in by throttling your manifold and holding the needle at just below desired SST. once the needle begins to rise stop. Now allow one cycle and observe high pressures. You want to make sure you have your condensing just right also.

If it needs a bit more, just repeat above steps.

I have tried this on commercial cabinets only and have used scales as a back up plan. Seems to be within 15g in a 1kg and lower system.

Oh yeah, has any one had experience with an atomiser for liquid charging?

[shark26]

Thank you everyone