Newbie. Charging Refrigerant. Mitsubishi SRK 40HG.

[smoking_muzzle]

Hi Guys.

Further to my recent post where my unit had a fault code saying overheat of compressor. With your advice I have checked and re-torqued all flare nuts as there was a very slight leak on the indoor gas side flare nut.

I have vacuum pumped the system and I am getting a reading of -30InHg on my manifold gauge. This is the same reading I get if I connect my vac pump the the gauges directly so I guess I am acheiving maximun vacuum pressure. After 30mins I closed the low pressure valve and turned off pump leaving the system in vacuum. Over the next 2 hours the gauge did not move so I guess I am heading in the right direction.

On other posts I have read that my next move should be a strength / pressure test. What is the correct procedure for this job?

I have ordered a R410a refrigerant bottle from SRW which will arrive shortly. They can only supply an 11Kg bottle which may make things tricky at charging stage. I plan to recharge as per below. Any advise or much appreciated. My outdoor unit says recharge 1.15Kg.

1) Connect up low pressure blue hose to service port. Conect yellow hose to vac pump. High pressure gauge closed and low pressure gauge open. Open both valves on outdoor unit and vac for 30 minutes minimum.
2) Close low pressure valve and disconnect yellow hose from pump and connect to refrigerant cylinder. I don't know if cylinder will have liquid only or both gas and liquid valves. In either case do I always invert bottle?
3) Place bottle on digital scales and open low pressure valve until reading on scales reduces by 1.15kg. Should I use the opening and closing 'throttle technique when adding gas? What frequencies should I be opening and closing the valve or is it a continuous procedure?
4) After correct weight is added disconnect all hoses and run unit in cool mode for 20 mins or so and recheck for any leaks.

My outdoor unit is high on the wall and to make the job safer where could I purchase a long hose approx 5metres to go from the service port on outdoor unit to the low pressure gauge. This way the manifold and refrigerant bottle are at ground level and ladder work is kept to a minimum.

How much extra refrigerant should I allow for on the scales if I were to use a 5 metre hose up to the outdoor unit. My indoor and outdoor units are back to back with less than 1 metre of pipe connecting to two.

Any help or advise much appreciated.

[Abe]

Smoking muzzle

From your post it is apparent that you are relatively inexperienced in this area.

It may help from an advice point of view if you confirm exactly how experienced you are on the installation of ac's

Is this your first install for instance?

If we can evaluate your skill , then the advice we give will be suited to your ability.

[robin r33 gtr]

smoking muzzle

I see your in the uk so why dont you tell people what town your in and see if anyone local can help? Im sure paying someone will be a lot cheaper than buying a cylinder of r410a.

[The Viking]

1. Your manifold gauges are nowhere near good enough to check for a good vacuum, especially so when you talking about modern refrigerants/oils!

Sorry, just read the rest of your post.
Please get hands on advice from a qualified A/C or Fridge Engineer, there are too many questions about a simple task for us to safely be able to advice you over the net...

Sorry

[monkey spanners]

1 meter is a VERY short pipe run. most units have a minimum pipe run of around 5 meters. You will need to find the minimum length for the unit, the aditional charge per meter for if the system had a long pipe run above the factory precharge lenght e.g. 20grams a meter and reduce the amount you charge by the difference between the minimum pipe length and what you have.
e.g. factory minimum length 5m
you have 1m!!!
added charge per m 20g
factory charge 1.15kg
you charge 1.15kg - 20gx4m=80g= 1.07kg
This is just an example, you need to get the correct figures from mitsubishi.
The 5meter hose sounds a bit iffy to me. Hire a scaffold or a cherry picker, this is what people get when they want things put 5 meters up in the air.
Don't forget you need to be testing this with OFN before charging with refrigerant to remain legal.

[Brian_UK]

Smoking Muzzle, you are approaching the mechanics of this job all the wrong way round.

Your logic is flawed and your misunderstanding of the correct methods is not going to help your project.

Your manifold guage is absolutely useless for testing a vacuum. The amount of movement that may be seen at the lower ends of the vacuum is less that half the width of the needle on your gauge.

If you don't have a proper Torr gauge or a digital vacuum gauge then you are unable to perform a proper vacuum test.

Doing a vacuum test before a strength/pressure test serves no purpose whatsoever.

A simple thought, a strength test could be at 560psig whilst your vacuum test is at a maximum of 14.7psig.

Another thing to bear in mind, a bit like the dreaded Part P electrical ticket, if when you come to sell on your property can you produce documentation to show that this aircon kit has been installed legally?

[expat]

Smoking Muzzle, you are approaching the mechanics of this job all the wrong way round.

Your logic is flawed and your misunderstanding of the correct methods is not going to help your project.



HERE HERE

I'm sorry mate, but I don't think you're up to this.
Get some help this time and you will learn enough about what you don't know to scare you into getting some propper training or a bit more experience.

No offense intended but this industry is...I was going to say complicated but even that doesn't sound right.

[The MG Pony]

This sounds very wrong, I have doubts that you are ready for this as well, do you under stand super heat & sub cooling are? Do you under stand gas mixes and how they work? by the sounds of it you don't and this is very important facet of the job.

[smoking_muzzle]

Many thanks for the replies. If it is ok with you guys I will reply to some of the points you have raised.This is my first a/c installation and it would be correct in saying I am inexperianced but learning all the time. I am by trade an electrical contractor (don't hate me!) and have been doing this for 19 years straight. This may not be relevant but I have City & Guilds Part 1 and 2 in electrical installations, City & Guilds for 16th edition, pat testing and inspection and testing. I am also Part P qualified and an NIC/EIC qualified supervisor. I also have reasonable skill with motorcycle maintenance and mechanics. I mention this as I have quality torque wrenches and tools to undertake most jobs. Not many people would strip and service the brakes on a superbike and then test them at speed on a track with no problems. Most jobs are relatively simple done in the correct manner and that is why I have asked you guys for your opinions. In live in Sleaford, Lincolnshire. I would be happy if anyone on the forum was local to me and able to give further help or advise.

The reason I mention a longer charge hose is that I have seen 72 inch hoses for sale and wondered if that was the maximum length available. I always prefer to work at ground level than at heights. The health and safety advise saying working above 6inches is working at height is a bit over the top though! I appreciate cherry pickers or scaffold are safer than ladders but not as safe as working at ground level.

I understand that my vaccum gauges are pretty inaccurate for the job. I should have mentioned in the first post that I will have a more accurate Torr gauge later in the week hopefully and I will be able to give you more detailed information when I carry out another vacuum test. Sorry if it sounded like I was using the gauge on my manifold as an accurate reading. I understand it is to be used only as a guide if at all.

I respect other trades and opinions, but would it be possible to ask as to why my logic is flawed. Am I to assume that my propsed method for recharging refrigerant in my post is completely wrong and no where near correct. If so could I ask what would the correct method be.

In the future I would like to introduce domestic split ac units in to our contracting work. What training and qualifications are the national standards in your industry and are there any training centres in Lincolnshire.

I look forward to your replies.

[sean241]

when using refrigerant's you are accountable for the all gas lost so using longer lines means more gases released into the ozone, so unless your using hc there is the odp
and the gwp to thinkabout

[Brian_UK]

SM, thanks for the information which shows that you are a capable and learned person.

We tend to get a bit paranoid on here at times as I'm sure you do when "DIYers" start playing with electricity.

Firstly if you are proposing to enter the field of supply and fit for air conditioning then you will need to have a Refrigerant Safe Handling Cerificate and be aware of the requirements for installation and commissioning of equipment. There are some short courses which may be useful but a full City and Guilds course is to be recommended.

Your propsed methods are back to front in effect.

After installation of the pipework the first thing to be performed is a strength test of the pipework and system.

This is followed by a pressure test which will establish if you have a leak free system.

You would then release the pressure and evacuate the system to remove all moisture and contaminents.

A vacuum test can then be performed.

Only after satisfactory results would you introduce the refrigerant into the lines.

+
As far as using 'long' hoses to reach up the wall a better way would be to make a charging line using copper tubing with suitable adaptors fitted at each end.

Also remember that you should really use hoses etc with isolating valves so that to do not release refrigerant when you disconnect.

[The Viking]

I'm speechless....

So, if I as a fully qualified A/C Engineer with 20 odd years experience ask you on an on-line forum how to proceed with my main distribution board installation after I replaced the tails from the meeter to slightly more flexible cable, you would be happy to advice me??

[TetraFluor]

hey all, to smoking_muzzle , your method for recharging is not totally wrong. what's wrong is that you do a vacuum test before pressure test, you need to pressure test with nitrogen first, when you sure it's leak proof, you can then vacuum and do a test like you already did to see for leaks again (i think that after a nitrogen pressure test that step is not necessary). then you can charge. close the low pressure side on your manifold. unplug hose from vacuum pump and connect to refrigerant bottle. charge only liquid (use liquid valve on bottle, if no liquid valve turn bottle upside down). remember to purge the air from the hose you connect to the bottle before charging! i didn't understand from your first post if you have 1m or 5m of pipes between units, if it's 1m you have to check if there is a minimum pipe length on your ac. if yes you'll have to charge less. when charging is done, close the low pressure valve on manifold, and you can start your ac. test drive your ac to see if all is fine and then you'll have to remove the manifold. when running on warm the pressure will probably rise up to 30 bars or more so you must run you ac in maximum cool to get the lowest pressure possible on the manifold so you can safely (for you and the atmosphere) remove the manifold. you're done.

[expat]

Your reply was humble and honest, so I now feel adequetly embarassed. But Viking's point, albeit unsubtely put, was correct.

The French have a saying "chaqu'un son metier" which roughly translates to -each to his own expertise- so if you now want to work in a/c: you have to make it your expertise, and for that you must have guidance or tutoring.

Given your current level of competance in electricity, guidance would seem a good option if you are a quick learner:)

[Abe]

Smokin

The only advice is I can give is,

Stick to what youre best at, youre an intelligent and skilled guy. Its tempting to want to add more strings to your bow, I understand.

But, most proffessional AC engineers have been in this game for donkey years and , even though an install appears straightforward, there are underlying principles of operation which only an engineer comprehends.

The most important area is containment of refrigerant. For a novice its all too easy to make a slip and allow escape. This is not a joking matter any longer.

The best advice I can give to you is, I respect you and your willingness to learn and your expertise in other areas, but get hold of a decent bloke around where you live. Let him handle it for you. It wont break the bank either!

Good luck

Abes