Aircon Pipes Already Installed

[JimmyGreaves]

Hi about 3 months ago during the construction of the my house I got a aircon company to install the piping so that it would not be easily seen (rendered behind walls etc).

I did not pay too much attention to the BTU sizes that they quoted as thought I would sort that out later. For the master bedroom I wanted an inverter and Daikin as I heard they were a good brand. The bedroom is 7 x 4 Metres. Ok they specified a 24,000 BTU unit FTKD24GV2S which is priced at 46,500 baht with the new tax reductions. I have 20cm Qcon blocks and the house is very cool and I also learnt that an 18,000 BTU unit would be fine at this is priced at 33,600 baht a massive saving.

Now the crunch. I have checked the pipes and the brochure of the pipe specs are as so:

18,000 BTU

Liquid 6.4mm (1/4 inch)

Gas 15.9mm (5/8 inch)

Drain 18mm (3/4 inch)

24,000 BTU

Liquid 9.5mm (3/8 inch)

Gas 15.9mm (5/8 inch)

Drain 18mm (3/4 inch)

The Liquid pipe sizes are different. Does it look like I'm now locked in to the 24,000 BTU unit?

Edited September 28, 2009 by jflundy

[elkangorito]

Unless you've got one wall that is all glass, kilowatts of electrical equipment/lighting & many people in the room, a 3 to 4kW unit should do the job (10k to 15k BTU).

If you don't change the pipework, you're stuck with a 24 000 BTU init (7kW).

[JimmyGreaves]

ok big balls up by me then as i dont want to start chipping the pipe out of the new rendering etc

Looking at the brochure it says btu (20,500) 9,900 - 25,600 - KW 6 (2.9 -7.5)

Will it still run efficiently based on the low numbers or have they stitched me up like a real kipper?

Edited September 28, 2009 by jflundy

[elkangorito]

From the webpage [http://www.daikin.co.th/Eng/product/room_air/inverter.htm], it will be working at a minimum. Looking at this site, I'd say an "Indoor unit - FTKD12GV2S" & an "Outdoor unit - RKD12GV2S" may be more suitable.

I'm not an A/C expert...I'm electrical. Maybe if you go into more detail about the room where this unit will be installed, more definitive answers may follow.

My "rough" calculations are based on the below attachment:

air_con_calc.txt

I've found this calc to be ok as a rough guide providing that the room errs on the side of "good insulation"...as opposed to poor insulation (i.e. wooden walls etc).

Compare the money savings of a smaller A/C unit with that of ripping out the pipework & replacing it with the correct pipework.

Which would you like to do? Leave the existing pipework & pay for the unit that suits the pipework...& pay the extra running costs?

Or rip out the existing pipework & use a smaller (cheaper) A/C, which will also have cheaper ongoing costs?

Remember - purchasing/installation costs only occur once. Running/maintenance costs will remain for the life of the equipment installed.

Edited September 28, 2009 by elkangorito

[JimmyGreaves]

I'm shagged as a long length of pipework is behind bathroom tiles and would mean a whole redo of the bathroom as the tiles are no longer available arghhhhhhhhhhh

[elkangorito]

Look on the bright side...you only have to rip out the tiles once. Maybe then, you can find tiles that are more easily available.

[harrry]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

[elkangorito]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

Not quite Harrry. It's all about temperatures & pressures.

[jombom]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

The air con calcs shown are an interesting mixture of metric and imperial systems. Ceiling height appears to be assumed at 2.5m, and I am guessing that the design temperature reduction is 10 degrees C, but I am no aircon expert.

On a slightly separate issue, I notice that the aircon units commonly installed in Thailand are actually air coolers and not conditioners, as their name suggests.

[elkangorito]

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

The air con calcs shown are an interesting mixture of metric and imperial systems. Ceiling height appears to be assumed at 2.5m, and I am guessing that the design temperature reduction is 10 degrees C, but I am no aircon expert.

If you are not an A/C expert (like myself), please explain your idea about the reducers (for the benefit of all).

My previous job in Australia was with an A/C company. I was a Facilities Manager for them (they were also an FM company). From what the A/C techs told me (repeatedly), the size of pipework is very important with regard to proper operation & efficiency of the A/C unit connected to the pipework. This makes perfect sense to me with regard to temperatures & pressures (PV=NKT). Of course, one size of pipework can cover a small range of A/C units, depending upon their operating parameters. But if a large A/C size change should occur, the pipework would need to be cganged in order to provide correct operating parameters for the A/C unit.

[jombom]

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

The air con calcs shown are an interesting mixture of metric and imperial systems. Ceiling height appears to be assumed at 2.5m, and I am guessing that the design temperature reduction is 10 degrees C, but I am no aircon expert.

If you are not an A/C expert (like myself), please explain your idea about the reducers (for the benefit of all).

My previous job in Australia was with an A/C company. I was a Facilities Manager for them (they were also an FM company). From what the A/C techs told me (repeatedly), the size of pipework is very important with regard to proper operation & efficiency of the A/C unit connected to the pipework. This makes perfect sense to me with regard to temperatures & pressures (PV=NKT). Of course, one size of pipework can cover a small range of A/C units, depending upon their operating parameters. But if a large A/C size change should occur, the pipework would need to be cganged in order to provide correct operating parameters for the A/C unit.

Agree with all that. However, breaking the problem into its components, I don't see how an oversized pipe should cause a problem, if it is reduced to the correct size at each end, which is 1/4 inch in each case.

From the manufacturers data sheet, the pipeline size will have been chosen to minimise pressure losses, therefore a larger pipe size should not pose a problem, except from a volume aspect. Liquids are generally regarded as incompressible, therefore the pressure is essentially constant along a properly designed pipe run, and is defined by the pump pressure (or compressor). The flowrate will reduce in the larger pipe, but the pressure will remain the same, and the flowrate will increase again after the reducer.

If the pipes are properly insulated, the temperature should not be a problem.

Just my tuppence worth. But I would accept the pressure and temperature are extremely important for the gaseous part of the circuit, which seems to be the same for each system (ref OP data supplied)

[elkangorito]

This would all be well & good if we were talking about water, which we are not. The medium here is refrigerant.

It all goes back to PV=NKT (the Universal Gas Equation). Energy lost in a system needs to be regained somewhere.

[JimmyGreaves]

If it is a risk or unknown how reducing the liquid pipe down to 1/4 inch each end will effect the performance of the unit I don't think I'll do it. Just really want to know now if it will be still efficient running at minimum thrust. Ceilings are high 2.5+. Big patio window facing NE 2.2M * 3.2M (No Sun as deep balcony outside) 3 Meter * 1 Meter window facing NW

[elkangorito]

Jflundy, I think you need to "bite the bullet" & realise that your installation is quite probably incorrect for what you anticipated.

It's now time to do a real cost analysis of how you can rectify your situation, since the "ongoing" costs will outweigh the installation costs after a period of time. Of course, if you are happy with paying the extra & permanent ongoing costs, all is well.

With regard to your above post, I really think you need a qualified farang refrigeration mechanic to supply your answers.

This is much the same as the "electrical world" in Thailand. Can you trust TIT?

[JimmyGreaves]

What I don't understand if something has the capacity to burn heaps of fuel but never reaches that capacitiy because it don't need to, how can my ongoing costs be more than a machine that maybe uses full capacity to do the same job, surely ongoing costs would be the same?

[elkangorito]

If the machine is bigger, ongoing costs are more than likely to be bigger. E.g bigger TX valves. Bigger electrical protection equipment. Larger quantity of gas. More energy usage.

Also bear in mind that the amazing Thai refrigeration mechanics (that I have witnessed), do not do good soldering work. Also, their pipework has kinks in it (not all the time), which creates noise & gas flow problems.

So, after a couple of years of service, your A/C unit develops a leak. Because it was installed by the TIT method, vibration wasn't accounted for, thus the leak. A bigger unit requires more refrigerant amongst other things & once a unit has had TIT attention, it may never be the same again. I'm not sorry for being negative. On the other hand, this is being "pro-active" in this country. I also understand that not all Thai refrigeration mechanics are useless.

Just because it uses inverter technology doesn't mean that it will be amazingly efficient. Quite simply, any electrically powered machine that is not loaded to at least 80%, will be inefficient. Basically, it's like buying Mack truck to haul a 10 tonne load when the truck has been designed to haul a 40 tonne load.

I think many people have some strange ideas about inverter technology. It is not magic...it can only truly perform efficiently when it's within the required design criteria.

It's up to you. If you want to buy an A/C unit that is too big for its purpose, you will pay for it one way or another.

[JimmyGreaves]

Quote 'ongoing costs are more than likely to be bigger' well at least you didn't use the word 'will' which gives an uncertain tone

Well my only hope is that the btu estimate of a 7 * 4 room with high ceiling, large patio and windows etc is closer to the 24 btu - (Range 9,900 - 25,600 Btu) than the 18,000 btu that Index recommend. 24,000 btu that Homepro recommend, 24,000 that this large private company of engineers in Hua Hin recommended or the 28,000 btu that a new company here also recommended. Trying to calculate the correct btu range through different calculators on the internet is a mine field with many differing variables! arghhhhhhh again

Edited September 28, 2009 by jflundy

[elkangorito]

Remember that you will not be cooling the air at the top of your ceiling. The fan coil unit (the indoor unit) should not be any higher than 2.5 metres.

IF your inverter unit is too big for your room, it will behave in exactly the same way an ordinary A/C unit would behave. That is, the compressor will switch off when the setpoint is reached & it will switch on when the setpoint is exceeded. Because it is too big, the inverter part of the unit may never actually function as such.

I don't have much faith in the engineers (said "money grabbing people") at any of these hardware stores.

I'm sure there must be at least one qualified refrigeration mechanic on this forum who can give some definitive advice. Then again, there aren't many qualified electrical people on this forum

Good luck.

[JimmyGreaves]

I don't have much faith in the engineers (said "money grabbing people") at any of these hardware stores.

Totally agree. Also about the inverter not being useful.I'm gonna look at the non invert 24000 to see if the pipe sizes are the same and which will reduce my initial costs. Can't find the specs on the net so will visit a shop tomorrow

http://www.thaivisa.com/forum/Air-Consitio...rt-t185082.html

[elkangorito]

Also about the inverter not being useful.I'm gonna look at the non invert 24000 to see if the pipe sizes are the same and which will reduce my initial costs. Can't find the specs on the net so will visit a shop tomorrow

http://www.thaivisa.com/forum/Air-Consitio...rt-t185082.html

The figures in the above link are "rougher" than the figures I come up with using the A/C calc I got from the internet. Use the "rough" calc info I gave you & see what you come up with.

[Naam]

Unless you've got one wall that is all glass, kilowatts of electrical equipment/lighting & many people in the room, a 3 to 4kW unit should do the job (10k to 15k BTU).

If you don't change the pipework, you're stuck with a 24 000 BTU init (7kW).

i [not so] humbly beg to differ Señor Kangorito. if it was the other way round there'd be a problem. suction and pressure pipe for a 24k unit will work on an 18k or even lower capacity unit as well. in fact in my house i run a number of 13k units on pipes normally used for 18 and 24k because of the distance between inside and outside unit.

perhaps you remember... for aesthetic reasons my outside are lined up left and right of the house, that means some of the units have a pipe distance of 16-20 meters.

[Naam]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

what crime did i commit that you two are torturing me?

[Gary A]

Before you go to a lot of changes and expense, I'd suggest that you listen to Naam. Too small would be a problem, too big is not a problem. It will simply take more refrigerant.

Edited September 28, 2009 by Gary A

[JimmyGreaves]

My "rough" calculations are based on the below attachment:

air_con_calc.txt

I've found this calc to be ok as a rough guide providing that the room errs on the side of "good insulation"...as opposed to poor insulation (i.e. wooden walls etc).

Based on the attached calc formula

I get this approx:

7000 Room

6125 Patio Door

2610 Windows

1200 People

500 Lights

500 TV

about 18000 = 5.275 KW = 18,000 btu machine.

[JimmyGreaves]

Unless you've got one wall that is all glass, kilowatts of electrical equipment/lighting & many people in the room, a 3 to 4kW unit should do the job (10k to 15k BTU).

If you don't change the pipework, you're stuck with a 24 000 BTU init (7kW).

i [not so] humbly beg to differ Señor Kangorito. if it was the other way round there'd be a problem. suction and pressure pipe for a 24k unit will work on an 18k or even lower capacity unit as well. in fact in my house i run a number of 13k units on pipes normally used for 18 and 24k because of the distance between inside and outside unit.

perhaps you remember... for aesthetic reasons my outside are lined up left and right of the house, that means some of the units have a pipe distance of 16-20 meters.

Does this mean that I can just install the 18,000 btu unit with the larger piping or do they need the reducers?

[harrry]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

what crime did i commit that you two are torturing me?

I cannot speak for jomborn but I thought I would just give you a chance to pontificate Naam.

Edited September 28, 2009 by harrry

[jombom]

If it is a risk or unknown how reducing the liquid pipe down to 1/4 inch each end will effect the performance of the unit I don't think I'll do it. Just really want to know now if it will be still efficient running at minimum thrust. Ceilings are high 2.5+. Big patio window facing NE 2.2M * 3.2M (No Sun as deep balcony outside) 3 Meter * 1 Meter window facing NW

The max pipe length is listed as 25M for the 1/4 inch pipe. This figure will reduce to 11.1M for the 3/8 inch pipe. However, I doubt if all of the pipe run is behind tiles, so you may be able to change part of it fairly easily.

If in doubt, you could contact manufacturer's technical support office. If it is not available in Thailand, there is normally a base in Singapore.

[jombom]

As the pipes are bigger than needed I would have thought an adaptor was all that is required.

Yes, I would try 2 x 3/8 to 1/4 reducers, installing 1 at either end of the liquid pipe run. You will need to check the max length of pipe run allowed, as you are effectively reducing this by 50% -- by increasing the volume of liquid in the pipe.

what crime did i commit that you two are torturing me?

Sorry Naam, if my comments caused you some pain. Please accept, that they were never intended to cause you any distress.

My suggested solution was an effort to spare the OP from ripping off his wall tiles, and also allow him use the smaller AC unit, if he wished. Other posters have made various comments, but nobody has given a reasonable technical argument, as to why, it will not work.

[JimmyGreaves]

Interesting post about the length of the pipe Jombom. It about 6 meters from the compessor and maybe 2.5 meters is behind the tiles they could easily reduce 3 meters that is exposed in the roof space. Not sure I understand it all fully though. Does it mean that if I only had a meter between compressor and units then I could use 2 inch pipes which equates to 8 meters on using a 1/4 inch pipe?

[jombom]

Interesting post about the length of the pipe Jombom. It about 6 meters from the compessor and maybe 2.5 meters is behind the tiles they could easily reduce 3 meters that is exposed in the roof space. Not sure I understand it all fully though. Does it mean that if I only had a meter between compressor and units then I could use 2 inch pipes which equates to 8 meters on using a 1/4 inch pipe?

Sorry, but no!

Perhaps I should have explained in more detail. The max length of pipe on the data sheet is 25 M for a 1/4 inch pipe. I suspect this is worked out, based on calculated pressure losses along the pipe run ( due to friction) and probably contains a safety factor of 1.5, but would be 1.3 as a minimum. However, I have no way of knowing the design calculations used.

Engineers generally use the square of the diameter when comparing pipe sizes. The value for Pi can be ignored as it occurs on both sides of the equation and can therefore be cancelled. As the Pi symbol and squared symbol are not obvious on this forum, it is difficult to show the maths.

Anyway, suffice to say the 1/4 inch pipe, is also 2/8, and the square is 4/64.

The 3/8 inch pipe has a square of 9/64.

The relationship between the cross sectional areas of the pipes is therefore 4:9.

So, 25 M of 1/4 inch pipe equates to 25M x 4/9 of 3/8 inch pipe = 11.1M.

However, there are 2 other minor issues, which would be worth ''putting to bed'', before proceeding, as follows;

1) The data sheet does not say the liquid and gas pipes should be the same length. It is often the case in engineering of closed systems, that a ''balance'' is required, to avoid unequal pressure drops. You should check this.

2) A plan B does not readily present itself. Normally ''service exchange'' units are available in the trade, and I would check for availability, if in your situation.

As an engineer, I never liked to go to a place (engineering solution) from which there was no return.

I conclusion, you appear to like Guinness, and are probably aware the brand is 250 years young this year, having been first brewed in 1759. Guinness are promoting events all over the world to celebrate.