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View Full Version : Low, Medium or High Fan Speed for indoor units in heating?



back2space
13-12-2012, 07:15 PM
Running my wall mounts at low fan speed produces a higher more comfortable air off temperature with less draught. Seems to produce less defrosts on the outdoor unit as well?

Been -4C here all day and only just got the house upto 22C by turning the upstairs units off during the day time(multi split system). They came back on at 5 and since then the system is working hard to try to maintain the set point of 23C. Room temps are hovering between 22 & 22.5, system then goes into defrost and it then drops to about 21.9C.

Ive spent £2.40 today to get the house upto comfortable temperature from 18C is it worth me setting them back to perhaps 20C overnight as it will then tick away during the night then doesnt have to work as hard tmrw?

Also what is the best fan speed to choose? I prefer low as its less noisy and at sitting level its a higher temp that is reaching you. If in higher speeds its more draughty and the air feels cooler.

The units are LG wall mount Libero range with multi outdoor condenser, usually in heating all 4 indoors running set points are reached and maintained no problem but today with sub zero temps and freezing fog all day long its struggled and I had to knock the upstairs units off as couldnt get temps about 20.5C. Outdoor unit is over capacity when all 4 indoors are running but only noticeable as an issue on days like today.

Even had to bump the set points to 23C as when the system goes off on thermo off the cool draught coming under the windows makes it feel cold.

Was thinking of using the gas fire for a bit to help it when its really cold. Seems to be ok now with upstairs units running as well as they are only kept at 20C set points and at floor level it maintaints 19c which is fine for the bedroom. Initially turned all 4 indoors on together as usual but increased upstairs set points to 21C so they never cycled off it struggles to get upto this temp when its this cold outside but 20C is fine.

Upstairs units are smaller 2 x 7000btu and I run them on medium fan speed as its weak on low speed. Downstairs are 2 x 12000btu and sufficient air flow on low speed and technically oversized.

Your thoughts please.

Kind Regards

frank
13-12-2012, 09:21 PM
First thing to ask is...what are the heat loss levels in the rooms, and what are the heat input levels to the rooms?
Second thing to ask is....what are your design temps?

Brian_UK
13-12-2012, 11:54 PM
Third thing to ask surely, if you have a gas fire and the AC isn't keeping you warm then turn it on.

install monkey
14-12-2012, 12:14 AM
you shouldn't have a gas fire working with ac as its against gas regs

Brian_UK
14-12-2012, 12:20 AM
you shouldn't have a gas fire working with ac as its against gas regs

Surely not, it's only recirculating air not a positive pressure fan, or have I got to read up some more ??

install monkey
14-12-2012, 12:23 AM
im sure its to do with if the gas fire emits co2 then its going to recirculate it in the room-ac in a commercial kitchen has a gas interlock wired to stop gas if extract fan stops
Surely not, it's only recirculating air not a positive pressure fan, or have I got to read up some more ??

Tesla
14-12-2012, 11:10 AM
Another thing to check if they are mounted high ensure the vents point down, as with lower air flow = higher heat transfer = possible stagnation layers of heat layers. With the louvers down it will use natural convection currents for better heating at lower levels.

back2space
14-12-2012, 11:35 AM
Another thing to check if they are mounted high ensure the vents point down, as with lower air flow = higher heat transfer = possible stagnation layers of heat layers. With the louvers down it will use natural convection currents for better heating at lower levels.

Louvres are pointing down so all good there. Design temps are 22c and we were achieving 23c last night think if it goes really cold again I know night set back to be 20c rather than off complelty when it drops to 17/18c.