Hi Guys,
Just found my PDA on the floor smashed and i had my calculations saved on it.
Can someone remind me the calculations for A/C
Got a room approx 40ft x 30 ft x 8ft
What KW Colling would it need (Normal Conditions)
Cheers
fatboy
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Hi Guys,
Just found my PDA on the floor smashed and i had my calculations saved on it.
Can someone remind me the calculations for A/C
Got a room approx 40ft x 30 ft x 8ft
What KW Colling would it need (Normal Conditions)
Cheers
fatboy
Sorry to hear about the PDA, may it rest in pieces.
(My translator met the same fate once, poor little thing served me well)
Hi Raymond
Are you talking about CIBSE Rule of Thumb calc's for cooling? - if so, for normal occupation, i.e. offices etc. it is 125w/m2.
This will give a high estimation result but full heat gain calcs should be used before selecting any equipment.
To list out all the calcs for solar, building fabric, infiltration, ventilation, occupancy, equipment etc would be a nightmare - something like re-writing the CIBSE guide (ASHRAE guide) :D
Thanks Frank,
Casn you just check me on this then
Room 13m x 10mx 3m
Should work out ABOUT 35KW ?
Regards
Fatboy
No Ray - much to much. You only apply the AREA not the VOLUME.
Based on CIBSE Rule of Thumb 1
13m x 10m = 130m2
130m2 x 125w/m2 = 16.25kw :)
Having a nosey round on the net I downloaded these 2 bits of information which may be of use. :)
I used to work on 150wat/sqm2
now I use
I use 125 watt/m2 as a general rule of thumb
and look out for extenuating issues like:
Large glazing, south facing
High roofs
Occupancies
Work loads
etc
Anything which raises an eyebrow
Thanks Guys,
All it was is that my wife works ( I think she calls it that):D at the local pre-school. Their main hall get stuffy, not majorly (Is that a word) hot and wanted to know roughly how much a/c would be
Any suggestions for a 15-20 KW Wall mount
Preferably wall mount
Regards
Fatboy
Large Halls are a different kettle of fish. tread carefully in your calculations.
Frank would be in a better position to advise.
I find floor mounted systems very appropriate for this kind of duty.
LG do a good 13.5 Kw model for around £1500.00 which will prob suffice, but check calcs again.
Im not sure if Daikin , etc do the floor mount.
I fitted one the other day.
Heres a picture of it
For some reason did not upload on my earlier post
Daikin dose not have this tipe of units, and if u whant a Daikin i whould recomand a Cassette type because thouse are powerful up to 14Kw , and have a good fan speed, but there are cheep AC floor colloms like Abe shows and at a very low low price for that capacity from other makers (at list here in Romania u can gat a R22 less than 1000USD but i know only here is r22 allowd :P ), and a wall mounted it whould be a'n elephant, daikin bigheste wall mounted is 10Kw
I Suppose they had to make one good one :D ;)Quote:
Originally Posted by Abe
Regards
Fatboy
Fat
The floor is about the only one I will touch......:D :D
But it performs well.........blasts the air right out of the vent to the far end.
Couple of years ago I installed 2 X 20KW versions in a large hall where the place was packed.............and I mean packed...........like sardines..........approx 450 people.
Ok, it was a mosque...........and them praying was akin to everyone doing meduim work.
well..............Those LG's cooled the place down a treat........
so youre right.........They had to make something good!!
Geez Abe - how come you are advising one of our own to buy LG :confused: :eek: :eek: :)
A 20kw wall mount - now that would be something to see :D (and to lift) :p
Fatboy - give me a PM if you want help
FrankQuote:
Originally Posted by frank
If its any consolation the one I put in two weeks ago had leaking valves, which entailed a lot of extra work weighing in a fresh charge.
But.........Daikin or Mitshubishi, or any other dont do Floor Mounts?
Or do they??
toshiba definatly do! i would speak to hrp about them.Quote:
Originally Posted by Abe
i used to fit them in orange mobile phone masts, and would recommend them. very easy to work on.
With a room size of 40ft x 30 ft x 8ft, I’d say you need something in the middle of the room, rather than a wall mounted thing.
A large cassette would be happier with a slightly higher ceiling. 3m would be great but an 8ft high ceiling is just a bit on the edge, though that won't stop most people.
If there is some room in the ceiling void (if there is a ceiling void, even) maybe a ducted unit would do a nice job of things, connected to 4 grilles around the room.
Failing that, if you go back to wall mounts, you should maybe think in terms of two Room Units – one on each side of the room.
What about a pair of 7kW tall floor unit (positioned suitably for good air patterns) connected to a small 14kW VRF 2-pipe outdoor - maybe more expensive. But running costs could be less and if appropriate manuafcturer selected there is the ECA tax break to consider.
Why would you need to go to the expense of VRF for 14kw? A twin split would do.
I couldn't think of anyone that does tall floor units at 7kW suitable for a pair of single splits or a twin split option.
However there are a few tall floor (sod it wardrobe!)indoors for VRF and some of the newer "MINI-VRF" outdoor units (4HP, 5HP, 6HP sort of sizes) look like single split outdoor units.
Accepted this isn't the cheapest way to go but maybe the only option IF wardrobes are insisted on.
And anyway this forum is open for suggestions (how ever daft some may seem - mine especially!!)
Have a good bank holiday weekend all you Brits.
Cheers
Loops
I like the unit Abe.
I never like rule of thumb but i do use it all the time, Just very carfull to take into acount any thing unusual, like high ocupancy, pcs, skylights are a fav,
I follow Abe's tendancy to use rule of thumb and then start looking for extra considerations for correct heat load calcs.
Ps NRS now Control Center used to sell a heat load calc (accalc) program for 25 quid, If they still do it i would buy it, I use it all the time and its the best ive come across.
Hi FatboyQuote:
Originally Posted by rdocwra
Rule of thumb for service engineers load testing. I've allways used this formula. Its been tested by design guys & it's been found to be accurate to 10% over. The Formula is
CUBIC CAPACITY of the ROOM/SPACE to be conditioned X 5 in FEET
PLUS the HEAT OUTPUTS of any equipment in BTU's
PLUS 2,000 BTU,s/PERSON
Your answer is in BTU,s 12,000 BTU,s = 1Ton Refrigeration & 1TR = roughly 3.5 KW
CHEERS
Frostycold:) :cool:
Quote:
Originally Posted by Frostycold
Cubic capacity alone is 48 000 Btu ( not 12 000 )
Something amiss here
will any body give the calculation of chiller
Q = m x c x dtQuote:
Originally Posted by Soumo_roy
Maybe if the word " please" was added Frank might say what the m in the formula means!!!Quote:
Originally Posted by Soumo_roy
:D :D
It should be a small m with a dot above it Abe meaning Mass Flow but I don't know how you can write the small dot on here :)Quote:
Originally Posted by Abe
Rule of Thumb is a good load check figure after the fact, especially for cooling.
BUT, I guess it is not all that humid in the UK so you do not have to worry about over sizing and then having humidity control problems.
If the ambient dewpoint was say 15C as a worst case maximum, then not in much danger from high humidity by over sizing as long as there was not a big latent load generated inside of the space.