AHU capacity

Hire an air conditioning Consultant or sit down with one to help you out. It's engineering and not rule of the thumb.

dear ducon

Definitely i'll discuss with them, I only need some information with you all before i go further with them.i have to source it in many ways not only depend on the consultant? am i right?how you going to discuss with other people which have better knowledge than you.

syachah

I totally agree with you but take it like this - a person going for a complex surgery requirement. Now how much knowledge does he need to talk with a Surgeon. Obvious with all his test reports(data) he trys 2-3 Surgeons and finds out about reputation from friends/ friend's friends before he decides.

Yours too, is a complex system involving engineering, so you have to go with your data of room size, amb. temperature, required temp. etc. to an HVAC Consultant to first advice you what other data more is required. You then take the missing data and he/others discusses with you on your system highlighting requirement of chiller/AHUs/ ducting etc. etc. etc.

You then try the next one & the next. Makeing your decision since now you are aware.

Now if you think you can design it - best of luck or, hire the HVAC Consultant think best. No hard feelings about this.

THanks Ducon and everybody..your comments are highly appreciated...i never hard feeling about this :)...

Mr. ducon,

You are great,

the last line in your reply which reads as " Now if you think you can design it - best of luck or, hire the HVAC Consultant think best. No hard feelings about this."

DHAYANANDHAN.S

hi the capacity of the AHU ( air handling unit) unit is worked out in cubic feet of cubic meter.

e.g. if lenth of room is 20feet. width is 20 feet and is 12 feet high. then the

cubic capacity =20x20x12=4800 cft.

as u need AHU for packaging area. consider 1 ton capacity for 1000 cft

so the tonnage required is 5ton

Hi there!

May I ask if when can I apply the computation that you gave? Does it apply in genereal estimation of AHU?.

Thank you very much!

egan jade

yes ,general estimation to determine the AHU cooling capacity..we need to know the room volume in order to determine the required AHU air flow design and room air change as well.

thanks,.

Hi Ducon and syachah,

You guys both have valid points, we're all members must help each other. maybe we just misinterpret each other. be patient. I do beleived that this is not a group of forum to criticize each other, I agree with Ducon better to hire the consultant, however syachah also want to know before dealing with the contractor or consultant to give him little idea and guide how the contractor come up with the proposal, "if you don't know you ask" not to pretend you know everything and then later found you're stupid in doing wrong things by your own. on your side syachah, you better have tell that in the beginning so we know how we supposed to help, keep calm guys

my contribution base on my knowledge.

W x L x H multiply by 50 or 60 then that the total Btu you can fit.

10' x 20' x 9' x 50 = 90,000 Btu capacity you can fit. or

10' x 20' x 9' x 60 = 108,00 Btu capacity or nearest Btu capacity available you can fit. this are the calculation I apply if i want to put air-con in the room.

reason why the multiplier is not fixed in simple reason that depending on the place of application, like packaging room need not to be same maintaining room temperature with the Hospital ICCU. consider also the room location if it is in the middle of the dessert or in the middle of building structure where heat load is not too excessive. Hope will help you to have small idea on my small knowledge in air-conditioning calculation.

Kind regards

Roman

Thanks & i agree. syachah, I' m sorry.

Thanks for teaching me too 'cause i'm a heating guy.

OK now here we get A/C Split Unit 1.5 T = 18000 Btu. & 1 T = 12000 Btu

So

90000 Btu/18000 Btu = 5 T = 3 nos A/c split units of 1.5 T+ 1 no 1 T ?

108000 Btu/18000 Btu = 6 T = 4 nos A/c split units of 1.5 T?

Is this correct ?

Hi ducon, great!!! on my calculation you are 100% right, now syachah at least have an idea and deal with the contractor on the capacity required. now duco how nice you feel we both help syachah on his question. keep it up being patient and keep helping others someday somehow me too i need your input, if you can have a look on yesterday forum I posted tha "wind turbine generator" at least a lot of our member contributed and I gained from that info. well done!!!

kind regards

Roman

Thanks buddy you brightened my day

dear ducon/roman/bawa/jcchiefeng

i just went back from my leave.Thanks for the good information, its very useful for me.ducon , sorry for that, i dont have any hard feeling on that.

ducon/roman

why you use the WXLXH (m3) to get the capacity .I have told by my consultant to use only m2 ( wxL) to get the capacity .which one is correct?. Is it correct from the room volume we can determine the required air flowrate and air change for the AHU?.

I have checked the internal heat load of the room ( lighting/human/general power/

machine heat load).for the lighting load and general power- how to determine their heat load?.is it power in KW for each equipment multiply with 860 kcal/hr.please confirm.

thanks

Hi Syachah,

He was also right due to different aprroach in calculation base on the below;

Heat Load - the amount of heat generated is know as the heat load. Heat is measured in either British Thermal Units (BTU) or Killowatts (kW). 1 kW is equivalent to 3412BTUs.

The heat load depends on a number of factors, by taking into account those that apply in your circumtances and adding them together a reasonably accurate measure of of the total heat can be calculated.

Factors include:

The floor area of the room

The size and position of the window

The number of room occupants (if any)

The heat generated by equipment

The heat generated by lighting

Floor area

The amount of cooling required depends on the area of the room. to calculate the are in square meter

To get Room Area BTU = Length (m) x Width (m) x 337

Window Size and Position

If your room has no window then you can ignore this part of calculation, how ever as rule of thumb there are window you need to take and orientation into account.

South window BTU = south facing window Lenght (m) x Width (m) x 870

North window BTU= North facing window Lenght (m) x Width x 165

If there no blinds on the window multiply the results by 1.5

Add together all the BTUs for the window

Window(s) BTU = South window(s) BTU + North window (s) BTU

Occupants

You will have to take into account people who normally working in the space. the heat output is around 400 BTU per person.

Total Occupants BTU = Niumber of Accupants x 400

Equipment

Clearly most heat in the roo is generated by the equipment. this is trickier to calculate that you might think. the wattage on equipment is the maximum power consumption rating, the actual power consumed may be less. However it is probably safer to overestimate the wattage than underestimate it.

Equipment BTU = total wattage for all equipment x 3.5

Lighting

Take the total wattage of the lighting and multiply by 4.25

Lighting BTU = Total wattage for all lighting x 4.25

Syachah, hope that the above information will help you on your project.

Take note:

If your monthly energy bills cost you more than $75,000 a month should need my services in making it 15% to 30% lower with zero investment from your side send me your email add and will send you proposal I am starting a new business of Energy Management services. Remember ZERO investment from your company just let me manage your energy without adversely affecting your production or operation.

Kind regards

Roman

Dear Roman

Very good information! thanks a alot.Now , i have confident to further my discussion with my consultant.anyway what is ur email add? i could't find it in this page.

thanks & regards

syachah

Hi syachah,

you can email me here: ceo@megaenercon.com

u r right bro, plz think a little , u want to cool ur room , that means the air in that room have to be cooled and the air is in cubic meter of cubic feet ,,u consider length and width of the room ...

what about hight of the room ,,,,consider two rooms both have same width and length 20 ft by 20 ft. now if one room is 14 feet high and other is 10 feet. than according to ur consultant the capacity of air handing unit will be same . but according to the law one room have capacity=20x20x15= 6000cft. that means 6 ton and the other will have 20x20x10=4000 means 4 ton

consider it

Please read below. This is how complicated the engineering of a system becomes when the need to conform to local, district or national codes. I prefer to design according to ASHRAE requirements and then "tweak" as per local building requirements or owner specification. Research the books or documents for content. This is NOT an advertisement to buy these products!

Please forgive the long text, but it seems this thread needed to cover all bases for the original request.

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• Advanced Energy Design Guide for Small Office Buildings

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