Hi, Can anyone suggest what type of fan i will need for the following, grill or fan on ceiling, then fed to flat chanel down the wall, approx 2.5m then 4.5m solid round duct to external vent. (plenty of fall on the round duct)
Cheers
Cheers
Fan Install
- Thread starter soulman
- Start date
Help Support Talk Electrician Forum:
what is it for?
how big is the room?
what are building requirements?
how big is the room?
what are building requirements?
- Joined
- Feb 5, 2009
- Messages
- 5,612
- Reaction score
- 0
Gonna be a powerful one. A centrifugal ?
might be 900mm :C
its kinda hard this psychic calculation stuff
its kinda hard this psychic calculation stuff
how small?
how many air changes do you require?
thats a good starting point,
then we can get on to how much power you will need to actually shift the air through all that pipework of yours
Given the length of duct that you are using, as a minimum I fit a Manrose CFD200T but I might even up that to a mixed flow type
Like I said, I would consider that fan the absolute minimum and TBH would probably go for a mixed flow one due to the length of the duct.
Air changes per hour is usually specified in the building regs. It's the number of times each our the fan is replacing the volume of air in the room.
I'd be careful with a very small bathroom, often the recommendation for bathrooms might be 20 changes per hour for example but with a very small ensuite you'd be better trying to achieve 30-40 changes.
If your bathroom is 2 x 1.5 x 2.5 then the volume is 7.5 cubes. If you work on 30 changes per hour you need to move 225 cubes/hour of air. Next you need to work out an approximate static pressure for your ducting at that volume/hr. This can be tricky if you don't have a program or charts to assist so speak to the duct suppliers for this info.
Once you have a required volume and a system static pressure you can spec a fan using the graphs that all fan manufacturers supply. You need to find a fan that's around the middle of its curve at those figures. If the fan is right at one end of its performance curve you'll have issues such as under-performance or noise (breakout and in-duct).
From what little I understand of your installation it sounds like you have close to 10 meters of ducting so I suspect you'll need a fair sized centrifugal rather than an axial.
Here's a few questions that might help you get a more specific answer; What are the dimensions of the flat ducting and the solid round ducting? Where and how do you intend to install the fan unit? Will there be an overrun timer/humidity/occupancy sensor?
Also remember that your client has to heat the air in the room the same number of times as the air is changed, this can turn out to be expensive!
- Joined
- Nov 28, 2009
- Messages
- 14,686
- Reaction score
- 838
I that's an issue, Vent Axia do a heat recovery individual fan.
That reminds me, you'll need to make provision for air to enter the bathroom otherwise the fan will be sucking against a dead end. You'll need to install a decent sized louvre in the bathroom doors assuming the bathroom windows are likely to be closed in colder weather. The fan will be pulling air from the adjoining bedroom so if you need the bathroom to keep warm you'll need to heat the bedroom in order to achieve this.
Quite, make up air is very important.
7.5 cubes is about right, the ducting i was going to use was 100mm and flat chanel 110 x 54. The fan will have a timer to overun. This room was a lounge, but has now been changed into a bedroom with ensuite. Do the same rules apply with an existing property the same as a new build.
I didn't realise there was so much to learn about fans & ventilation for a domestic property. Thanks for the help, much appreciated.
I didn't realise there was so much to learn about fans & ventilation for a domestic property. Thanks for the help, much appreciated.
well, Ive just done my very small bathroom,1.7 x 2 x 2.4 and I have installed a vent axia 100m VA100SVXHT SELV [cos I had it lying in my shed :B- )direct ducted via <300mm of solid 105mm round direct to outside,that I would regard as the minimum fan I would even consider installing, for a run of your length you will need something way more powerful.
Last edited by a moderator:
- Joined
- Nov 28, 2009
- Messages
- 14,686
- Reaction score
- 838
Building regulations apply equally to a new build an an alteration.
Since you are installing a new bathroom, which will have new drains etc, I would expect you need a building warrant (or whatever they call it down south, building notice or something like that)
you have checked with building control to see if it needs building regs approval haven't you?
It is easy to do, just do the calculations for the required air changes for the requirements, allow the appropriate mixing factor and you will have the fan flow required.
No different to an other design work, you just need to be competent.
No different to an other design work, you just need to be competent.
Yes building control are coming out tommorrow, they were telephone in advance for advice, the requirements for ventilation was that the only litres per second of the fan exceeded 20L p/s which the majority of fans do. Yes sidewinder i have a lot learn (time for a bit homework i think)
Cheers
Cheers
Similar threads
