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Changing an open air exhaust fan to a ducted exhaust fan

CSParnell
Amassing an Audience

Changing an open air exhaust fan to a ducted exhaust fan

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Last week I decided to add another downlight into the hallway connected into my Grid Connect Automation system which was just outside the main bathroom and when I poked my head up in the ceiling space I was surprised to see mould spores all over the insulation  bags. Now this was all in the region  of the main bathroom and no sign of direct leaks so I can only put it down to the open air exhaust fan combined with the wet weather we have been having. Well I can't have that so into work and I had my eye on some discontinued line of ducted exhaust fans and thought beauty this will do me at bargin prices so here is number 1 mistake the rookie Sparkie if 20 years made (yes I'm not perfect forgive me)

 

I assumed just because it was a 250mm that all hole sizes were equal. Wrong after running the ducting and making the hole in the eves and getting to the final step of installing the fan did I realise that it did not cover the hole all the way around...

 

Ok so let's start this lesson.

 

You need to measure your existing cut out hole and the cover plate diameter (one side to the other) write that down as you will need that.

To do that you will need to remove the existing exhaust fan so you will need the following.

 

A step ladder 

A Phillips Head screw driver or battery drill #2 bit

A dust mask if allergic to dust there will be plenty.

A tape measure

A note pad and pen or your mobile device to record the measurements.

 

So you will need to climb up the ladder, the cover plate will either clip off, screw off or come off 2 spring clips but before you remove don't forget to measure it and record it.

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After the cover you will have 3 or 4 screws that will be holding tabs that either spin to hold or lift up then slot inwards that you may have to slide in with your finger as per below.

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After undoing all of these the exhaust fan will drop from the ceiling so hold onto it, then gently pulling on the power cord the plug base should fall from the ceiling too. Unplug the lead and then place the fan on the floor allowing you to then measure the cut out properly. 

 

The next thing to measure is the distance from the middle of the cut out to the middle of the eves in a straight line and right this down.

 

With your measurements you are ready to hit your local Bunnings store or do some research first on the Bunnings Product App for your platform.

You are going to want to look for the closest in cutout size and overall size, the overall must be bigger than your cutout otherwise you will not cover the existing hole. If you have a good match on cut out you can look at square if you existing is round but if like me there is very little forgiveness the  chances it may not cover.

 

So you have found the suitable ducted exhaust fan based on your existing cutout and also room size (found on boxes), the next thing is check the distance of the included ducting you may need to purchase a longer duct for the rated size or a joiner and a extended duct. I also decided to grab a different vent as the ones that came with it were for vertical wall not horizontal eves as per below.

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Whilst you are at Bunnings make sure you have the following tools.

 

A small blade screw driver

A small head hammer or pair or pliers

Some bricky line or string line

Gyprock saw (if you need to cut any out of ceiling)

Pencil

Duct tape 

A torch of some kind

A wire coat hanger

A length of conduit 20mm or what ever length from exhaust to eves  

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So we are back with the exhaust fan, the ducting and all the tools required let's get started.

 

First off in the bathroom open the window if possible so we have line of sight to the hole.

Next look at the outside vent grab hold of that and head outside with your set of steps, pencil, flat head screw driver, small hammer or pliers, tape measure and coat hanger. We are going to find the center of the timbers which can be identified by looking for the clouts running from the wall to the gutters, you can also push on the eves with your palm and check for movement, good movement and no sign of clouts your pretty safe.

 

Next we are going to measure centre between wall and gutter and mark. Next with the small flat head and small hammer bang a hole in the eves.

Next with the coat hanger we are going to measure it against the duct grill to half way and bend a right angle, then we will poke the coat hanger up into the hole and spin it around and push it up feeling for any obstructions. If all clear we are good to mark out the circle, if we have an obstruction one side we just need to shift over.

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So next place to grill with the circle over the hole and mark with a pencil

After this the fun part and trust me I've tried all the methods and they dont work so its down to burning arms. You work your way around the circle taping out the hole with your screw driver keeping the spacings tight once complete hit the centre and it will pop up.

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Next we will head back inside, you want to poke a hole in the start and end of the ducting one end cut a short bit of brickie line enough to tie off to something new the inside cut out.

With the rest of brickie line tape it to the end of the conduit but leave it on the roll.

Next head up on the ceiling unless you can squeeze up enough in the exhaust fan hole we are going to push the conduit and brickie line to the hole in the eves.

Once there head to the eves and grab the conduit and the line and tie it off to something.

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Next we want to take the duct up and tie one end off to stay at the inside hole and the other end we are going ro cut the brickie line off the roll and tie it to the other end of the duct.

Then head back outside and pull the line pulling the duct to the hole, take it slowly once near the hole put your hand up and grab it and pull it through.

I have just saved you squeezing into the corners of the roof cavity. The other option is to kick tiles but if like me you have solar panels it's not an option.

 

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Next I trimmed off the duct and put the eve grill on and fixed on with cable ties then fixed up with button screws.

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It's time to head inside and finish this off, now it's a matter of cutting brickie line off the duct trimming up and then grabbing the new ducted exhaust fan. Slot the duct over the outlet of the fan and fix with the provided cable ties or clamps and finish off with some duct tape for extra seal.

Plug the plug and lead into the socket outlet ask for help to test the fan to make sure it works and then feed the fan up into the ceiling. Then just push the fixing tabs across and screw down or just screw down.

 

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Finally install the cover, wipe clean then head to the bar fridge for a beer, wine or spirits.

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Carl

EricL
Bunnings Team Member
Bunnings Team Member

Re: Changing an open air exhaust fan to a ducted exhaust fan

Hi @CSParnell

 

Thank you so much for sharing that very detailed guide on how to install a ducted exhaust fan. Using a PVC pipe as a rope feeder is a clever way to get the rope across your ceiling. It certainly beats crawling on all fours in your roof space.

 

Eric 

 

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CSParnell
Amassing an Audience

Re: Changing an open air exhaust fan to a ducted exhaust fan

I have far to much Titanium in my back @EricL to be crawling through tight roof spaces these days.

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