Powering extractor fans

[Sigurd]

We are installing two extractor fans in a church hall which is used fro meetings, lectures, etc. Also occasionally for Lent lunches and coffee mornings. As you can guess, finance is an issue.

Is it safe and legal to power these from standard 13 amp sockets (which are fed from professionally installed RCD consumer units. Our intention is to plug the extractor fan into a count down type time which is in turn plugged into a 13 amp socket, so that at the end of a meeting or whatever, it can be switched on from the timer, and it will automatically switch off after a set time - usually 2 hours.

We haven't decided on a fan as yet but it needs a to be in the 9"/10"" size to fit the pane of glass.

Many thanks for any help offered.

 

[Pete999]

We are installing two extractor fans in a church hall which is used fro meetings, lectures, etc. Also occasionally for Lent lunches and coffee mornings. As you can guess, finance is an issue.

Is it safe and legal to power these from standard 13 amp sockets (which are fed from professionally installed RCD consumer units. Our intention is to plug the extractor fan into a count down type time which is in turn plugged into a 13 amp socket, so that at the end of a meeting or whatever, it can be switched on from the timer, and it will automatically switch off after a set time - usually 2 hours.

We haven't decided on a fan as yet but it needs a to be in the 9"/10"" size to fit the pane of glass.

Many thanks for any help offered.

Bit of an open ended question really Mate, from your description of the fans 10"- 9" fans, plugging them into a 13 Amp socket, would be theoretically OK, but not very practical, leaving trailing leads every where especially in a room populated as a meeting room, the type of fans I think you are describing usually have some sort of controller, adding further dangers of plugging them in.
Depending on the electrical size of the fans (Watts etc) you could probably wire them in a single circuit with a timer incorporated. you mention the finance issue. Your best bet would be to contact an Electrician to give you a quote for installing these fans.

 

[Gavin John Hyde]

theoretically what you are proposing is possible, but not all fans are equal, one of a smaller size can be more powerful and move more air than one much bigger. so check the airflow rates.
in terms of timer, you could set it up run for that long, but it would need a bit of planning, a timer switch could be used...
Also why 9 inches+?? cutting a circular hole in a pane of glass is not the hardest of things to do... if you arent confident get a local glass firm in to cut it. although the stuff (round glass cutter)to do it can be found in b and q ...

 

[HandySparks]

Sounds OK, although you'll probably end up with a neater job if the fan is properly wired in to a fixed countdown timer via a fused connection unit, leaving the socket available for other uses.

 

[Pete999]

Sounds OK, although you'll probably end up with a neater job if the fan is properly wired in to a fixed countdown timer via a fused connection unit, leaving the socket available for other uses.

Good idea HS never gave that a thought, svesome dosh that will.

 

[Marvo]

An occupancy is probably same price or cheaper than a programmable 7-day timer and far better suited to the application. As per Handysparks, installing an FCU off the socket circuit would probably be a better option than plugging them in.

You need to size the fans according to the airflow required. How many meters cubed is the place you need to ventilate? What kinds of activities take place in there (cooking etc?)? Is the area heated? How many people do you have in there?

 

[Pete999]

An occupancy is probably same price or cheaper than a programmable 7-day timer and far better suited to the application. A s per Handysparks, installing an FCU off the socket circuit would probably be a better option than plugging them in.

Surprising how a few ideas can change the outlook on a job.

 

[Gavin John Hyde]

I did a job a while back now for free, it was in a local village hall that had been trashed by vandals, got asked to give a hand and loads of trades helped out to do it for free. the hall paid for materials.
i used an earlier version of this for the heaters in the 2 side rooms. the same could be used for the fans if required.
https://www.NoLinkingToThis/p/green...ay-fused-digital-timer-spur-switch-230v/7643g

 

[HandySparks]

I was thinking of one of these, given the OP's stated requirements:
Electrisaver Immersion Heater Booster - https://www.tlc-direct.co.uk/Main_Index/Timers_Index/Immersion_Heater_Timers_2/index.html

 

[Sigurd]

Sounds OK, although you'll probably end up with a neater job if the fan is properly wired in to a fixed countdown timer via a fused connection unit, leaving the socket available for other uses.

I quite agree but the quote we got for that was £600 - a reasonable price for what was proposed by the electrician. To that I have to add £250 for the fans and the glazier to install them - total £850.

The problem is that we are restoring a Grade II Listed Building, have had to raise the cash by public donations and a couple of grants, so have to keep costs down as much as possible. Hence the original question - is my proposal safe and legal (Cost £275 for two timers plus fans versus a proper job at £850).

I had looked at required air movements and given planning restrictions, I have to stick with the best one I can find that will fit the space. Another compromise!

Thanks for the suggestions re timers. The one I was looking at is -
https://www.amazon.co.uk/Timeguard-...fkmr0&keywords=countdown+electrical+3KW+timer

Saves any re-wiring. All I have to do is maybe extend the cable that comes with the fan and add a plug. We have the spare could of sockets.

 

[Marvo]

I understand the budget constraints but you walk a thin line where if you cut too many corners or underspecify the fans for example, the system simply won't fulfil the requirements and you may as well have saved the money you spent.

Yes, the timer you've linked is capable of switching a fan, it's capable of switching two fans in fact. Problem is that the fans won't have any protection against locked rotor currents and if they're not designed as impedance protected then it could be a fire hazard.

Can you link to the fans you have in mind and state how big the volume of the area is?

 

[Gavin John Hyde]

being the building is listed have you liaised with building control as they may well have the final say over what fan can be installed and where and may also specify the flow rate etc... some councils are better than others.. as the building is listed they may decide that you have to have a specific type of ventilation and dictate where it can go....

 

[Marvo]

From the little info given, the unknown sized space is used for meetings of unknown numbers of people who may or may not be doing some light cooking and the fans are being specified according to the the size of the panes of glass in the window.....

To be honest a specification from building control wouldn't be a bad idea.

 

[HandySparks]

...Hence the original question - is my proposal safe and legal ...

Probably, but you need to check the fan manufacturer's instructions for fusing requirements and make sure that the wiring is safe from damage by the users of the hall, including children, if any.

 

[Sigurd]

The fan we were looking at, and the one we were given grudging Listed Building consent to install two Large 9" Axial Industrial/Commercial Extractor Fan & Wall Kit: Made at Vent Axia in two of the windows. Any larger capacity fan would require more fans or holes in the wall. According to planning officer, that was a no no! They were more concerned about spoiling the appearance of the windows or building than effectiveness of fans! So we haven't specified the fan size according to pane size.

The volume of the hall is around 200 c.m. which from the information I looked up and the sort of use would require a fan with a capacity of 1800 l/sec. With two fans we can achieve around 550. Given that at present, and for time immemorial, the church has managed with none without asphyxiating anyone, we are fairly relaxed about complying with the suggested air changes. One third of recommended level is better than none. And as I said above, we would not get permission for anything else. So while agreeing with Marvo's comments, we haven't really got anywhere with that consultation.

Marvo also pointed out the fire hazard, but according to sales blurb, the suggested fans have thermal protection. Rest of specs.
9" COMMERCIAL AXIAL FAN WITH STANDARD GRILLE Ideal for Offices, Clubs, Restaurants, Commercial Kitchens etc where the ventilation requirements are high. Manufactured by Vent Axia as a Branded Product for a Major Electrical Wholesaler. Wall Tube, External Wall Plate, External Grille. Impact Resistant High Gloss ABS for strength & durability. IP44 Rated. Suitable for Mounting in Walls up to 305mm thick, hole required 280mm. Suitable for Panel Mounting. Suitable for mounting in Windows with Glass up to 32mm thick, hole required 260mm. Demko approved to BS EN 603352-80. Conforms to LVD73/23/EEC. Conform to EMC 89/336/EEC. Tested to BS EN 55014-1/BS EN 55014-2 Extract Performance: Low: 680 cubic metres per hour/189 litres per second High: 1015 cubic metres per hour/282 litres per second Fan Speed: 1205 - 1915 rpm Noise Level: 52 dBA DIMENSIONS: Front Elevation/Grille: Approx 340mm square Wall Mounted: Fan will protude 50mm into room Window Mounted: Fan will protude 141mm into room External Grille protudes 31mm

I appreciate the warning about cutting corners, but this is not really about cutting corners on the performance of the fans - we are stuck with that because of the Listed Building consent. It's about reducing costs on the power supply. A fully professional permanent wiring job versus the simple fan - timer - socket approach. If that is safe and legal, then we need to consider that.

 

[Marvo]

Yeah, to achieve 1800 litres/sec you're in the realms of a boxed and ducted mixed flow fan. The 2 window fans you're looking might give 500 l/min in free air together which means you'll realistically get 300-400 l/min with normal real-life static pressure across them.

How do you intend to accomodate the entry of 'make-up' air into the hall where the fans are extracting? You're going to need to install some passive vents unless the building leaks air like a seive.

The fans you mentioned can be both started by a single timer or occupancy sensor and they don't need any additional protection other than the FCU.

 

[Sigurd]

Thanks Marvo
Entry of make up air is not an issue. The building is nearly 200 years old. Air entry is not a problem; well it is, but not from the point of view of lack of!
I realise we are well down on recommended air extraction rates, but the suggested fans will be adequate for our needs.
I am grateful that you have more or less confirmed that what I propose is safe and legal.

 

[Midwest]

Its not clear, well to me, what the intended use of the fans are for. Extraction obviously, for removal of damp or stale air, but IMO never works for temperature control, if that's the intended use?

 

[Sigurd]

After use the atmosphere in the hall is rather humid from 30 or so people breathing. Occasionally a bit smelly, for example once a month there is a "Men's breakfast". Spiritually healthy but physically not - too much fry up! I can't stop people breathing or eating fry ups, so the fans are intended to run for a couple of hours or so after the event. The hall does not have any opening windows as the Victorians who built it didn't seem to believe in them, and planning authorities are fussy about allowing changes to Listed buildings.

I know what we plan is not ideal. But I am up against planners and limited finance.

 

[Midwest]

Before you spend your money, it may worth consulting a professional ventilation 'expert', bearing in mind the size of the room, design & your intended use. Your plans may not achieve what you are seeking.