# Forum Home Renovation Heating & Cooling  Air Transfer System for aircon

## m6sports

we installed a new air conditioner in our lounge room a couple of months ago. 
Its over kill for our small lounge room because we bought it from a family friend that bought it and never got around to installing it  
so now the problem we have is, it cools and heats the lounge room in less then 10mins but doesnt heat or cool the bedrooms that well 
our house is 90m2 and the air conditioner is a fujitsu 3.5Hp  
so to help with pushing some of the air from the lounge room im thinking of installing a Air Transfer System  Exhaust Inline fan Duct Ventilation Air Transfer System - eBay, Heaters, Lights, Fans, Bathroom, Home. (end time 28-Apr-10 19:00:33 AEST) 
any thoughts and ideas would be great the main thing im worried about is that the loss of the hot and cold air through the ducting as it will be run through the celling

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## m6sports

with a site full of knowledge someones got to have some input  :2thumbsup:

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## sundancewfs

You can get ducting rated to R1.5. If you were really concerned about loss you could also wrap batts around the ducting as well. There are a few companies that do air tranfer duct kits with an inline fan. (I think Bunnings has one) Obviously if you buy it in kit form you would be tied to the duct size and R value of the duct in the kit.
The ebay transfer kit looks like an "exhaust to outside" in-line exhaust fan.
All those components are avail from ducting/fan suppliers.
I think its a good idea.

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## commodorenut

I have bought something similar to install in our place, to get warm/cool air from the air-conned part of the house, into a section that needs it. 
I ended up going to Westaflex at Revesby (Milperra rd) and got my choice of grilles, duct & fan.  Listening to the advice Westaflex gave about my required duct length, I got an 8" fan (the one on the ebay link is only 6") and the best 8" duct they sell - I got a 3m section, and a 6m section, along with appropriate adapters for the powder-coated aluminium (not plastic!) grilles. 
In total, I paid a bit over $220, and in my opinion, I got far better value (and advice) than the eBay listing you've pointed to. 
The fan comes with a 3-pin plug, so just get a sparky to put a surface mount power point in the roof space near where you want the fan, and run a switch to a nearby wall - should only cost you $100 or so. 
I haven't installed the fan & duct yet, so I can't tell you how well it works!  
It's getting cooler, so it won't be long before I have to fit it all up (the icy stares aren't worth it!).

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## m6sports

I only showed the ebay one as an example  
i would prefer not to buy on ebay but to go into a store and pick one out suitable for the job 
Ive got one installed at work its an IXL brand but its used to remove steam above one of our machines in the lab 
it works well for that job but i dont think it will be powerful enough so i would be looking at getting somthing with a larger fan  
if i was to get the ebay one i would be looking at the 250mm or 300mm fan but would that be over kill, i would want to duct it from the lounge room into 3 bedrooms so i dont think the 150mm would cut it  
any other input or experience would be helpful

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## Moondog55

I have been thinking of something along the same lines, in our case the Coonara heater is too big for the room and the passive airflow isn't good enough, good ducting is well insulated and as has been stated you can always use a second wrap. 
Looking forward to reading more

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## Andy T

Interesting topic. I installed a heat transfer kit years ago. The room I have my wood heater has cathedral ceilings and the temp near the top was over 45 degrees and trapped. I ducted this from the high point of the ceiling through an internal wall down the hall. Given the length of the ducting, the heat and airflow drops a fair bit but does blow warm air out and in my situation works well. 
Some points to note, however. If you are removing air from the room, cool air will cause a draft when it comes in to replace the lost air. (and you need to ensure that this is allowed otherwise the output will be reduced) Windows, under doors etc - best to leave a door open but you also need to consider that the A/C may be more effective with the doors open and no ducting at all. 
The ducting must be insulated and generally this type of ducting is the concertina type which reduces airflow dramatically as opposed to the fixed ducting.  
You also get a hum from the motor and possible vibration. for best results the motor should be mounted in the middle of the ducting. I hung mine from the roof purlins to keep it off the ceiling and keep noise down. 
go for the biggest ducting you can get - nothing less than 250mm, and a decent fan unit. Mine has two blades either end of the motor.  
Whilst these sound good in principle, they are not the best way of supplementing cooling and heating and depending on the situation may even make it worse. Since hot air rises I expect that for hot air they would be better than for cold air. 
Personally I would avoid cheap Ebay import stuff and go to a specialist dealer for advice and to ensure the fan output. ducting etc are matched for the job.

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## Moondog55

I suppose another option would be to cut holes in the wall and install a fan in the hole. 
The problem with our room is the huge archway in the centre that acts as a warm air dam; trapping most of the heat in the one half of the room, we don't need to move much air to but a pedestal mounted fan is A: Noisy B: moves too much air even on slowest speedC: Our ceilings are too low to fit a ceiling fan

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## Smurf

I was wondering about using an air transfer fan in reverse? That is, suck the cold air out of the hallway and blow it into a heated room, thus causing warm air to be drawn back into the hallway. 
I'm thinking that this would overcome temperature loss in the ducting. Eg if it is 21 in the heated room and 1 degree is lost in the ducting then it can't possibly exceed 20 in the hallway. Reversing it would overcome that problem since 21 degree heated air would be directly drawn in with no loss. 
Can anyone spot any problems with this logic? Obviously I'd need to carefully locate the outlet vent to avoid creating a draft, but that would actually be pretty simple in my case.

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## Moondog55

The only problem I see at first glance is that hot air rises. I actually have no idea what the heat losses in the ducting are.
The heat losses are dependent on diameter of the duct, smoothness of the duct air speed and how much insulation is there; but I have never seen data to give heat losses in ducting. 
I would suggest that losses are minimal tho, and the best way to find out what works best may be to fit a bi-directional fan and switch

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## Smurf

I should add to the original post that this would be in conjunction with a new reverse cycle A/C placed opposite the door to the hall (ie in the heated room) blowing air toward the hallway. Hence my idea to effectively suck that air into the hall with the transfer ducting, returning the cold air to be reheated.  
I'm basically looking to (1) swap wood heater for reverse cycle A/C split system and (2) get some of the heat it produces into the hallway which is outright freezing at the moment. The A/C would be about 3m from the door to the hallway on the opposite wall. Size of the unit will be around 8kW output (heating). 
Other than wood, reverse cycle A/C is really the only cheap heating option here and it will be used quite a lot. Hence preferring not to use portable electric heaters in the bedrooms and hallway which cost $$$ to run.

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## Moondog55

Keep the wood heater ( just in case and for those really cold days when the A/C won't work well )  suck the warm air and return to add more heat is my gut feeling but only experimentation will tell.
We use both the wood heater and the heating function on the aircon and I think it is the lack of movement that makes cold air pockets that keep the house cold.
We won't know for sure tho until the insulation in walls floor and ceiling are finished

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## Smurf

Is anyone able to give some real world experience as to the performance of these systems? 
Right now it is 22 degrees in the heated room, 17 degrees in the bedrooms. Assuming that the heater can be turned up to provide the extra heat and maintain 22 where it is, what temperature would I expect in the bedrooms running one of these systems? 
I'm guessing that it won't be exactly 22, but how close would it get?  
I'm still trying to make my mind up on this one. But I'm not keen on freezing though next Winter as I have this year so I'm going to do something about it that's for sure...

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## Moondog55

I would guess it depends on more than how much air gets moved.
We have a reasonably sized reverse cycle unit, but we bought it to cool one big room with the heating function as a bonus.
Our big open living room is 5000 X 9000 wiith 2700 ceilings and the unit can warm it reasonably well and cool it during summer but it does not have the capacity to heat or cool the whole house.
Is your unit massively over-sized ?? If you are trying to heat the whole house I have a feeling the unit itself needs to be sized for the volume of the whole house, which is why we kept the wood heater. The Coonara is able to heat the big room but no spare capacity for the rest of the house, our intention was to use an air transfer system and run both the RC and the wood fire.
I have plans to increase the efficiency of the wood fire as a heat store but in Geelong this last week even running both the wood fire and the air-con without insulation it is a losing battle. My gut feeling is that tackling the passive losses first is the most efficient way to keep the house warm

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## Tarasa

> I was wondering about using an air transfer fan in reverse? That is, suck the cold air out of the hallway and blow it into a heated room, thus causing warm air to be drawn back into the hallway. 
> I'm thinking that this would overcome temperature loss in the ducting. Eg if it is 21 in the heated room and 1 degree is lost in the ducting then it can't possibly exceed 20 in the hallway. Reversing it would overcome that problem since 21 degree heated air would be directly drawn in with no loss. 
> Can anyone spot any problems with this logic? Obviously I'd need to carefully locate the outlet vent to avoid creating a draft, but that would actually be pretty simple in my case.

  One flaw will be that you are pressurising your room with the cold air and the hot air will flow out of every orifice it can find. Wall vents, gaps around windows and doors, will all allow heat to escape.  
Also, say for example you are trying to heat some bedrooms that are connected by a hallway then to the main room. By drawing air in from the bedrooms and blowing into the main room, any hot air will have to heat the hallway before it can heat the bedrooms where you want it. I think pulling the air form the hotter area, into the rooms, then into the hall is a better way. Once the rooms are heated then the hallway will start to heat up.  Hope this theory makes sense, it does in my head  :Smilie:

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## Moondog55

Tarasa that is a good and valid point, but making our buildings as air-tight as possible is a good thing so that is another attack point for saving energy, would the pressurization be that high though??

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## Tarasa

No, the pressurising wouldn't be high but it would still be there. Feel around your windows and wall vents (if you have them) on a windy night and you will feel quite a bit of airflow.

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## Smurf

> Also, say for example you are trying to heat some bedrooms that are connected by a hallway then to the main room. By drawing air in from the bedrooms and blowing into the main room, any hot air will have to heat the hallway before it can heat the bedrooms where you want it. I think pulling the air form the hotter area, into the rooms, then into the hall is a better way. Once the rooms are heated then the hallway will start to heat up. Hope this theory makes sense, it does in my head

  I've done some more thinking and plan is now as follows: 
Take hot air from existing heater room. Present heating is slow combustion, maybe change to reverse cycle A/C in the future. 
Duct the hot air directly to all 3 bedrooms. 
Maybe include an in-line electric heater in the system. I'm thinking that this will improve performance in very cold weather when heat losses etc might still leave the bedrooms a bit chilly.  
And of course it means I can heat the bedrooms without having to have the slow combustion heater running, a feature that might actually encourage me to keep the fire and forget the A/C. I can still have the fire for genuine cold weather, but use the ducted heater and the other electric heater I have in the lounge room (note that the slow combustion heater is in dining room, not lounge room) when it's not so cold. Less days using the fire, less messing about lighting it etc but still have the benefit of it in mid-Winter.  :Smilie:  
So what I should end up with is effectively a mini ducted heating system just in the bedrooms which also doubles as an air transfer system from the slow combustion heater when the in-line duct heater is turned off. 
So overall, I'll end up with electric heater in the lounge (existing), slow combustion heater in the dining room (existing) and a new ducted electric / heat transfer system in the bedrooms. Should be warm next winter.

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## Tarasa

Sounds like a plan  :2thumbsup:  
And if you put reverse cycle aircon in you can suck cold air and duct it into hot bedrooms during summer.

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## Bloss

> I've done some more thinking and plan is now as follows: 
> Maybe include an in-line electric heater in the system. I'm thinking that this will improve performance in very cold weather when heat losses etc might still leave the bedrooms a bit chilly.

  mmm - not something to be attempted without much thought about the possible problems/ dangers as a DIY and in any case likely to be not very effective. Fan forced systems need careful design to work properly. You might well find you use more energy (with an extra heat source) and yet get no comfort improvement - or at least no more than whacking a fan heater on the floor in the bedroom(s) - and maybe less. 
It's not always possible, but heating should be flowing from the floor up and cooling from the ceiling down.  :2thumbsup:

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