Air Con Sizing

Danny30

Hi, I was after some advice as am looking to get air con installed in my home and have had 2 different installers providing very different opinions on the size of the air con BTU required.

I wanted to air con for the downstairs which consists of:

A living room and dining room area which is 31.5 m2

An entrance hall and small kitchen are connected to the above area with two open doors at around 22.5 m2

My original and preferred plan was to get one 24.000 btu to cover the whole downstairs but apparently air con will not travel well through 2 open doors so was recommended 2 units.

First guy recommended an 18,000 btu for the living room and dining room area and a 10 - 12,000 unit for the kitchen / hallway.

Second guy who has only seen the floorplans so far has recommended a 21,000 btu for the living room and dining room area and a 18,000 unit for the kitchen / hallway area.

The back of the house is west facing and has glass doors and windows which adds more solar heating to the equation, but I still think the second recommendation seems a bit overkill. I want to make sure that I get a strong enough installation which means the air con doesn't struggle to cool the room, but am a bit concerned about running 2 air con units just for the downstairs, particularly two powerful units.

Any suggestions on what you think may be suitable would be much appreciated. Floor plans attached as well for clarity.

Danny30

Hi, I was after some advice as am looking to get air con installed in my home and have had 2 different installers providing very different opinions on the size of the air con BTU required.

I wanted to air con for the downstairs which consists of:

A living room and dining room area which is 31.5 m2

An entrance hall and small kitchen are connected to the above area with two open doors at around 22.5 m2

My original and preferred plan was to get one 24.000 btu to cover the whole downstairs but apparently air con will not travel well through 2 open doors so was recommended 2 units.

First guy recommended an 18,000 btu for the living room and dining room area and a 10 - 12,000 unit for the kitchen / hallway.

Second guy who has only seen the floorplans so far has recommended a 21,000 btu for the living room and dining room area and a 18,000 unit for the kitchen / hallway area.

The back of the house is west facing and has glass doors and windows which adds more solar heating to the equation, but I still think the second recommendation seems a bit overkill. I want to make sure that I get a strong enough installation which means the air con doesn't struggle to cool the room, but am a bit concerned about running 2 air con units just for the downstairs, particularly two powerful units.

Any suggestions on what you think may be suitable would be much appreciated. Floor plans attached as well for clarity.

Danny30

Hi, I was after some advice as am looking to get air con installed in my home and have had 2 different installers providing very different opinions on the size of the air con BTU required.

I wanted to air con for the downstairs which consists of:

A living room and dining room area which is 31.5 m2

An entrance hall and small kitchen are connected to the above area with two open doors at around 22.5 m2

My original and preferred plan was to get one 24.000 btu to cover the whole downstairs but apparently air con will not travel well through 2 open doors so was recommended 2 units.

First guy recommended an 18,000 btu for the living room and dining room area and a 10 - 12,000 unit for the kitchen / hallway.

Second guy who has only seen the floorplans so far has recommended a 21,000 btu for the living room and dining room area and a 18,000 unit for the kitchen / hallway area.

The back of the house is west facing and has glass doors and windows which adds more solar heating to the equation, but I still think the second recommendation seems a bit overkill. I want to make sure that I get a strong enough installation which means the air con doesn't struggle to cool the room, but am a bit concerned about running 2 air con units just for the downstairs, particularly two powerful units.

Any suggestions on what you think may be suitable would be much appreciated. Floor plans attached as well for clarity.

QrizB

I'm no expert but I'd have thought 2x12k would be plenty. 2x9k might even suffice.

I know they folk on this forum have had good results in this latest heatwave with 12k downstairs and 12k upstairs, in larger houses than yours.

See the recent air-to-air threads on the Heat Pumps sub-forum:

https://forums.moneysavingexpert.com/categories/heat-pumps

Reed_Richards

Do you still need planning permission for multiple aircon units?

ritz55

We've has AC fitted a few years back now in 8 rooms around the house.

For the Kitchen which you mention, we have a bedrooms of similar size which all have a 2kw unit and it's more than enough.

For the larger open plan area we have one unit which in our case would be similar size to your whole of the downstairs we have a 5kw unit and it most cases is sufficient, however last week when we have around 30 people and temperature outside was 30 degress, it was struggling to keep the room cool enough.

As a FYI We have the Mitsubishi industry split system installed

MattMattMattUK

The best would probably be one multi-split external condenser unit feeding two internal, but I have to ask, why not bedrooms as well? You would probably not need to spec the unit much larger as you will not need to run upstairs and downstairs at the same time, so just the cost of some ducting and head units which will be minimal compared to the overall installation.

Some quick calculations come back at a combined total of 49,000-54,000 total.

Based on dimensions:

Kitchen - 5,100 BTU

Dining Room - 12,200

Reception room - 12,800

Hallway and WC - 9,400

You then have 4,000 BTU for the kitchen (cooking, as well as background heat from fridges, dishwasher and washing machine usage etc.), West facing with large glass doors 4,000 BTU. Bay window 1,200 BTU. If in the South add 10-20% compared to Midlands, North, or take 10-20% off for Scotland.

Danny30

Thanks @MattMattMattUK . The living room and dining area is one open plan area and the kitchen / hallway entrance is also one open plan area and both areas are divided by 2 open door areas.

With that in mind, I wouldn't be installing 4 separate aircon units as I only need 1 for the open plan living room and dining area and 1 to cover the kitchen and hallway. Originally, I intended to have one strong unit to cover both but am not sure it will works due to both areas being separated by two doors.

I was also looking for upstairs and was considering either 1 9000 btu unit for bedroom 2, or a 24,000 unit in the hallway that hopefully cool all the rooms upstairs if the doors are left open. Upstairs floor plan attached.

FreeBear

https://forums.moneysavingexpert.com/discussion/comment/82054133#Comment_82054133

Multiple units outside, yes. But with a single unit outside serving two or units inside, pretty sure you don't.

Ayr_Rage

Don't put a unit in the hallway, use your noggin, cold air will just descend and have minimal effect in the bedrooms.

Yorkie1

I was at a friend's house last week in the heat wave. She has an open plan living / dining room like yours. She has AC in that main room, and then one in the master bedroom. It does the trick for her. With the door between the hallway and living room area closed, the living area stays cool.

I don't know what size AC she has though, sorry.