Auditorium fans (not FX fans)

[howartp]

Hi.

 

Our school theatre, which doubles as assembly hall and drama classroom, is generally ok heat-wise during the school day - in fact it's pleasantly cool.

 

The problem comes when we put on productions or parents evenings etc where we're using the stage lights - the combination of lights and 350 people makes for an unpleasant experience.

 

We're therefore looking at putting some fans in to at least get some air-flow going for these events.

 

Getting power and wiring to wherever they go in the room is going to be interesting, so I wondered about using some of our spare dimmer channels and sockets - there's two on the side bars in front of the curtains which are never used for lights, so they'd be ideal.

 

Does anyone have, or know of, any dimmable-fans where dimming the power safely controls the speed of the fan? Or, any DMX-controllable fans that would be suitable for auditorium fans, rather than FX purposes?

 

Peter

[Dave m]

IMHO the fans won't do much as they need to extract the hot air to do anything.You basically need a hole in the roof to let the heat out, possibly assisted by fans.

 

Some dimmers can be switched to be basically on or off. I wouldn't run a fan off a dimmed circuit.

[howartp]

We already have monodraught vents in the roof, and my premises team have spent 3 years trying to get the builders to get the whole BMS working correctly. They cool the room down nicely in winter (ahem!) but unless there's wind outside in summer, they don't do anything.

 

The building is only 3 years old, so most lights are LED already; tonight I purposely only used LEDs to avoid the heat output from the incandescents, but it didn't do much to help.

 

We have patchable dimmers with 1x Live and 2x Dim sockets per channel, so I would patch the fan circuits to Live only if dimming is a bad idea.

 

I can't do anything that touches the fabric of the building or the existing systems - that's the realm of the premises team and the builders, but is going absolutely nowhere and I doubt will ever be sorted. I therefore need a solution I can run under my remit as technical manager - fans I can plug into my sockets would therefore be ideal, even if I have to chop the plug off and put a 15a one on.

 

 

 

[vinntec]

This will make you mad, but after almost killing some of our audience last year in the heat (we have very thick walls as the theatre is a former medieval church so if it gets hot it stays hot), not to mention cast in costume, even multiple intervals and free water bottles was not enough. I don't know how they did it but our committee got a grant to put air conditioning in and our small size for once was an asset as a couple of decent units can now freeze the auditorium on demand (I exaggerate slightly) and even act as backup heaters in the winter. If you consider we are Grade 2 listed and all the restrictions on making holes this brings, it is a miracle that it is there at all. And it was in and working just in time for our mid-summer ballet!

 

Before this we did try big horizontal fans (which are still there) over the audience and these worked pretty well when it was just warm to quite hot as we could speed them up before the show and during the interval, but once you reached hot, like we have now, they just circulated the hot air around the place. So we had to put in extra intervals and open the outside doors while extra water was consumed.

[IRW]

Now I'm always one to try and find a solution to a problem, but just to put it out there, from my own experience if you put in a 'temporary fix' to this problem, in a school theatre situation, you may find the permanent one never comes along!

[Jivemaster]

Air con actually means moving lots of heat by a refrigeration plant, of moving lots of air via some big fans and ducts, then it's hard to keep the noise right down.

 

Refrigeration plant means that you need to clear any condensation that will form, Vents mean that you need to move cold air in to replace warm air.

 

Vents will be cheaper but are limited by the outside temperature, refrigeration ma help more in the summer (ambient air was 32c near me today which will not cool a room much.

 

My firm hires through window aircon units for the summer, -each window has a special filler made with holes for the fridge pipes (just a bit of 2x1 with holes) These could run from a power point, but hard power not even connected to a dimmer.

 

Start guessing that a standing person gives off 100w so 300 people give off 30KW and that's what you have to remove across whatever temperature difference there is between inside and out - you could need a big fridge plant.

[Dave m]

Natural ventilation only works if you have a pressure differential.

So you need windows or a door open on one side to allow the roof vents to circulate the air.

I was once in a turn of the century ( last one) Hall and it was built for natural ventilation but nobody understood it.It had a series of vents to enable hot air to rise and filter out through louvres

Over the years bits were "insulated " to stop draughts but there was a winter/summer mode that looked like nobody had touched since about 1920.It was simple, but a baffle made it less efficient for winter use and remained in use for knocking on 100 years because nobody really understood it.

Your system is either rubbish or nobody read the book (assuming that the specification was clear to the installers)Allow cooler air in to get the hot air out.

[Andrew C]

Allow cooler air in to get the hot air out.

Heard that one before (twice) "You don't need A/C, you just need air handling". While it is a nice idea, unless the temperature drops rapidly in the evening, the air you bring in will be only a little cooler that the air you want to remove. It helps, but not a lot.

 

I've won the battle in one venue, and had chilling retrofitted. It was designed in as an option. Still trying at the other. Lovely it is mid-day this week.

[Brian]

...Allow cooler air in to get the hot air out.

 

The conventional wisdom is that you extract hot air; I think this is wrong.

 

A few years ago I installed a hot air extraction system here at home. Vents in all the upstairs room's ceilings, ductwork in the loft and a large duct fan to extract hot air and push it outside. Even when properly balanced and with cool air allowed in in it never really worked.

 

Then, one evening as I stood outside after a hot day thinking to myself "It's nice and cool out here.", it came to me. Don't suck hot air out, suck cold air in.

 

An hours work the next day to swap around the fan and swap out the backdraft shutters for an inlet grille with fly-screen and I had a working system.

 

Now, after a hot day, I simply turn on the air-intake system and lovely cool(er) air is dumped into the centre of each room where it sinks to the floor.

[adam2]

Fans that simply circulate the air within the space wont actually reduce the temperature, but can considerably improve comfort. Moving air at say 30 degrees is far more comfortable than static or almost static air at the same temperature. Note for example how popular desk fans are in hot conditions.

 

Ceiling fans help to an extent and can be installed in most venues, you may be able to fix these to whatever supports your lanterns, rather than to the building fabric. Do of course take great care re the fixings/supports. The power requirements are modest and numerous such fans may be connected via suitable extension leads to a 13 amp socket, preferably in the control area. If the use of `15 amp extension leads is allowed for lanterns then similar ones for the fans should be fine.

 

This has the merit of being portable equipment like lanterns or practicals on stage and not a permanent installation.

 

Ventilation whereby hot air is replaced with fresh and hopefully cooler air from outside is better but not always practical on a sufficient scale without building alterations.

 

Proper refrigerated air conditioning is better still but expensive in both capital and running costs. Large portable air conditioners can be hired from the usual suspects but need access to the outside air to dump the heat. Some units are located outside the space to be cooled and blow chilled air in via flexible ducting. Others are located in the space to be cooled and blow hot air to the outside via flexible ducting. The larger units are only just portable and although they are stated to work from a standard 13 amp socket, they use a generous 13 amps. Certainly no more than 2 units per 32 amp ring or radial circuit.

 

 

 

[Junior8]

Many years ago I had a similar problem in that the performance space had one complete glass wall facing due south. (Yes it was a devil to black out) Fortunately there was plenty of height but it could be unpleasant at this time of year. In that space the maximum load available to me was 12Kw so little of the heat problem was to do with the rig - it was all to do with the building which had ventilation only in the sense that you could open some of the windows. What I did do was keep every door and window open until the last possible minute and open all the exits to the outside at the interval. Greenhouse shading also made a difference. However we were helped by the fact that the place was a Gerry built 1950s concrete building, with a single skin flat roof, offering no insulation properties at all so at least once it cooled down outside after about eight o'clock what heat had built up inside went straight out through the walls and the many gaps in the joinery! With today's insulation we wouldn't be so lucky...

[adam2]

Andres air conditioningThis is the sort of large portable air conditioner that might help if you have enough money, enough power, and enough space !

 

They are marginal on a 13 amp plug though, have spare fuses to hand ! and watch what else is on the same circuit.

 

 

 

 

 

[the kid]

We used a few of those aircon units for some shows, kinda noisey but dropping the room temp to start with was the key.

 

You will find no one has them though.

[howartp]

Natural ventilation only works if you have a pressure differential.

So you need windows or a door open on one side to allow the roof vents to circulate the air.

 

 

Your system is either rubbish or nobody read the book (assuming that the specification was clear to the installers)Allow cooler air in to get the hot air out.

That actually makes 100% sense to me, and explains why nothing is working.

 

There are two low-level vents in the room.

 

One is backstage, behind the 80% high false-wall which forms the rear of the stage, and provides an excellent source of puddles. And the second one is behind the audience seating with two Moving Head flight-cases and a drumkit in front of it. The theory being nobody will be anywhere near that vent so it's not got any functional purpose being there.

 

Now I can, and most certainly will, move the flight cases and drumkit, but there's no 'path' between the low-level vents and the ceiling vents without going through the floor of the audience seating. The builders have obviously designed the pressure-flow based on an empty room, before the theatre designers came and put the back-stage wall and the audience seating in place.

 

Thanks for this and everyone else's replies - particularly Adam2 about moving air increasing comfort - that's what I'm aiming for if I don't actually achieve 'cooling'. Our local Playhouse has three fans - two regular ceiling fans that are on all through the show, and one smaller but horrendously noisy that waves its magic wand during the interval. The fans help the comfort-flow so much compared to when they're not on.

 

Peter

 

 

[Junior8]

 

The builders have obviously designed the pressure-flow based on an empty room, before the theatre designers came and put the back-stage wall and the audience seating in place.

Peter

 

The old story....