A question for the engineering types.

Currently on site I have 298 A/C units of which 295 are 20 years old, and in regular need of repairing.

I’m currently trying to show the owners that putting in place a rolling programme of replacing the more regulalry used ones, with more efficient A/C units will save them money in the long run.

Currently compressors outside are rated at 7kW inside blower is unknown as they don’t have the details on them, but lets call it 500W to be safe.

Of the 295 120ish are run at least 8 hours a day for the majority of the year. Another 50 run for around 12 hours a day.

The rest are intermittently used, and some only a couple of weeks of the year depending on groups.

I know that newer models are more efficient, but I am struggling to come up with the calculations to show this.

Our current units are overkill for the rooms most appear to be around 38-46,000 BTU, each room running two.

Where newer ones have been installed, they are still too powerful for the rooms, but are smaller.

Room sizes are 9mx6mx3.8m in general, double that for some rooms but the majority still have two in them, unless the room has been knocked together, then it is four.

Should I just be looking at the Wattage of the main compressor and the fan unit or is there something else to look at with AC units?

My newest one has that power rating 5 sticker on it as seen on many electrical appliances.

From a calculation I did many moons ago (I’m not an air conditioning engineer) you need to consider what equipment is running in the room and how many bodies it will hold. I allowed 500W per human adult and then checked what the wattage was on each PC and other constantly running kit was in the room.
Then its an application of what temp you want the room at in summer and winter allowing for the difference between external and internal temp.

I seem to remember it took me a bit of time getting the calculation right and I missed the losses/gains due to no insulation in the room construction which left me with a unit only just man enough for the job but 3 times more powerful than the one originally installed which didn’t meet spec for 20C in the room all year.

The info is available on-line, my experience was 20 years ago. Good luck.

I’d talk to some suppliers, I’m sure they do this all the time. Mention you want a planned upgrade over, say, 12 months. They may give a better deal if they can see something longterm, and will have all the info on power use.
Get a couple of quotes to convince your boss it makes sense, and don’t forget to add your time saving by not keeping the odd stuff running.

Cheers.

Difficulty I face here is the local suppliers want to fit the largest possible all the time, the concept of the correct sized unit mystifies them.

A 2×2 cupboard you say. 48,000BTU is needed, a 3×4 office, 58,000BTU is needed.

My site manager is a decent guy and has been listening to me when it has come to terminal AC unit failures and replacing them with something sensibly which has resulted in quotes for huge units of 800GBP ish dropping to 400 for a sensible option

THat has made it viable to replace rather than repair in some instances as well. Previously because it was so high due to the most expensive unit being pushed, it was seen as more economical to repair.

I came across some calculations on working out electrical units based on BTU and EER (some efficiency rating) and from some fag packet checks on our current units, were have an EER of around 5 where most modern units that we would fit start at least 12.

The company that fitted the AC 20+ years ago, is still in business, which is saying something for Thailand, and may get another shot if they are sensible.

According to some of the websites I read, that should mean the more efficient units pay for themselves within 3 years or so.

All I need now is the proof.

Are they due their TM 44? that’d give you some idea of how much you were losing comparedto a modern benchmark

This is not my area, but is there any benefit to getting A/C EPCs (the site sounds large enough?), i.e. if you got a before and after it would show the client the savings, I appreciate it may not be as bespoke as your own on site calcs, but should make the point?
Otherwise just show energy use improvement averaged out, also check distribution efficiencies and possible upgraded controls? but it sounds like they are near end of life anyway.

Without more information it’s difficult to be certain, but it does appear that your current units are of a larger capacity than needed.

Another thing that needs to be considered is the refrigerant that the old units are running on. Unless they’ve had a retro-fit, at that age it’ll probably be R22. This has been subject to a ‘phase out’ for over 10 years now. As from yesterday it’s illegal to buy & use for any service work- if it comes out of the unit it has to be disposed of correctly & a retro-fit gas used instead. You’re also not allowed to top any system with R22.
http://www.refcom.org.uk/downloads/rac8-phase-out.pdf

Re the efficiency of newer units, again this is quite a complex thing to go into, but in general they are more efficient, but combined with the ECA (Enhanced Capital Allowence) available for some equipment, if the money is availabe it’s a bit of a no-brainer to swap them out.
https://www.gov.uk/government/publications/enhanced-capital-allowance-scheme-for-energy-saving-technologies

You shouldn’t really have to do anything, any decent firm trying to sell you new equipment should propose any options put forward a case for you.

The costs you have posted for replacement units is very cheap, a decent unit on it’s own without fitting would normally cost more than that.

I’ve mailed you mate. I can give you a steer, too much info for a post.

Thanks will check the mail.