Theatre air-con

[paulears]

Just a small amusing aside - my venue have 6ft ducting in the roofspace, and two almost aeroplane size 3 phase fans to remove foul hot air in the summer. In true Norfolk fashion, when the external wooden grills rotted away, they simply boarded up the opening and removed the fuses! In the height of the summer, we've been known to run a show with the fire exits all open! In the winter, the audience are advised to bring warm clothing. Air con has a different meaning here.

[adam2]

In our smaller venue, which is a max capacity of 250 standing, we had a tempered air ventilation system installed last year.

 

It doesn't chill the air - so in the summer months it just pulls fresh air in from outside (via filters). In the colder months, the air is tempered by passing through a radiator which is connected to our central heating system.

 

I was sceptical last summer that it would work, but this summer is turning into a scorcher and it is performing very well - It always feels "fresh".

 

The system feeds the air into the room via standard ventilation ducting and because the fan/motor is back close to the inlet, all you hear in the room is the rustle of fresh air!

 

This system cost about £15k installed.

 

A system of this type cant cool the space below the outside air temperature, but is certainly better than nothing.

 

I would however urge that anyone installing such a system should ensure that cooling can be retrofitted later if required. As noted above, the air is filtered, and if required heated, before being blown into the space.

The equipment should include room to add a cooling coil later if desired, this adds little to the cost and simplifies the future addition of cooling.

Some designs use a coil through which chilled water at about 6/10 degrees is passed, and other designs use a coil through which cold refrigerant gas is passed.

Any new air handling unit should include space to fit either type of coil later if required.

[rooftop]

I believe there is space to do this on ours, should funds permit. However, the local authority is shying away from installing large AC units wherever possible due to the running costs.

[andy_s]

re: adam's post - this is exactly what we did - installed AHUs which drew in air from outside into our two auditoria. but omitted any chilling factor (as a value engineering factor).We "survived" many many heart-felt complaints from staff and punters about the heat in the first summer and decided to retro-fit the chilling system. The cheapest quote was well over £200k, more than three times what we had "saved" by omitting the chiller from the original heating and ventilation contract, so I'd be sceptical about the "adds little cost" bit of the previous post. Making a retro-fit possible may not cost much, but actually doing it costs the proverbial arm and another limb. However, to be fair, the spec for the system had changed, as we had found that some rooms where cooling had not been thought to be necessary were unusable without it. Temperatures of 50 degrees plus were measured in the green room (glass walls and roof, south facing), the rehearsal room and the education workshop were also registering well into the 40s.(also lots of glazing in direct sunlight for much of the day), so this added to the cost.

 

Also, the work, despite the best efforts of the contractors, was disruptive, and took longer than expected as they had to work around a more or less fully functioning building, and of course the pipework that had been previously installed to make retro-fitting a feasible option was by no means extensive enough, but now the cooling is there, the spaces which had it fitted are now useable We couldn't afford to extend the cooling into the offices, so they are currently rather uncomfortable places, but we can at least go to the green room to cool down a bit, and the theatres and rehearsal spaces are OK.

 

My advice for a new build would be to definitely include a chilling system, the money we saved in the original cost plan was nowhere near what it eventually cost us, and also make sure it's appropriately specced for all rooms. For older buildings, obviously it's a much more complicated equation. I would say that we have some wall-mounted cassette-type FCUs in some of the spaces, and they are not what I'd call quiet, so my advice here would be to find examples of similar installations and go and listen to them so you have some basis for discussion. (we did this when we were speccing our CW flying system, and had a lovely day trogging around theatres listening to bars being flown in and out....sounds silly, but was really useful as we had something definite to relate things to in discussions with the consultants.)

[adam2]

My remark about designing an AHU so as to allow for the future addition of a cooling coil, was intended to mean that so doing would add little cost to the original AHU installation.

It is usually a short piece of plain ducting, that can later be removed and replaced with a cooling coil, the cost of this is minimal, but the subsequent cost if space was not allowed can be substantial.

 

The cost of the chiller is of course substantial, whether installed initialy or added later.

 

Large installations normally use one or more water chillers that cool water to about 6 or 10 degrees, this is passed through a coil in the air duct thus cooling the supply air.

Very precise temperature controll is achieved by a power operated valve in the chilled water system.

A central chiller plant can supply a number of AHUs and also fan coil units to cool smaller areas.

 

A small installation of a single relativly small AHU may be cooled directly by a refrigerating unit.

The coil containing cold refrigerant is placed in the air duct, this system is cheaper and simpler since there are no water pumps to break and no water to leak or freeze in the winter.

Such a system does not give precise temperature controll since the refrigerating unit is simply "on" or "off" and not normally variable. It may of course be controlled by a thermostat, but the air temperature will vary a lot.

 

A budget system can consist of a relativly small direct refrigeration unit, sized so as to cool the supply air by perhaps 8 degrees.

In normal UK summer conditions, with outside air at 28 degrees, this will supply air at 20 degrees, and result in a space temperature of perhaps 22/24 degrees.

In extreme heat wave conditions with outside air at say 38 degrees, the supply air will be at about 30 degrees, and the space temperature at about 32/34 degrees. This will be somwhat uncomfortable but still an improvement over supply air at 38 degrees and a space temperature of at least 40 degrees that would otherwise result.

[Tomo]

At risk of going off-topic, I've heard of "Groundwater" or "buried" cooling systems that pump water a few metres down into buried radiators and then bring it back up cooled to around 10-15 degC, without use of a compressor.

 

Those sound considerably cheaper to run than a classic refrigerant system - does anybody have any experience of them?

[boswell]

In our smaller venue, which is a max capacity of 250 standing, we had a tempered air ventilation system installed last year.

 

It doesn't chill the air - so in the summer months it just pulls fresh air in from outside (via filters). In the colder months, the air is tempered by passing through a radiator which is connected to our central heating system.

 

I was sceptical last summer that it would work, but this summer is turning into a scorcher and it is performing very well - It always feels "fresh".

 

The system feeds the air into the room via standard ventilation ducting and because the fan/motor is back close to the inlet, all you hear in the room is the rustle of fresh air!

 

This system cost about £15k installed.

Our theatre is 410 seated and we have the above system, large volume, low velocity, we change the air at the rate recommended in the 'Yellow book' (8L/s/p) and it works well.

When you consider that the performances are in the evening (cooler air) and the number of hot days we have in the UK, the number of times that a cooling system is required is minimal and does not justify the cost. Last night at 8pm with a full house we had outside air temp of 25C and indoor was 28C.

If you push sufficient air in then the temperature rise is small.

Keep it simple, and cheap to run!

[smalljoshua]

Nowhere as big as a theatre but I live in a house with exactly this (buried cooling) being used at the moment.

 

We've got a couple of radiators buried about 2m under the patio. Water is pumped through this and instead of going to a ducted air system, it is fed into the radiator piping saving even more cost.

 

The pump is small and only costs a few pounds to run a year and by using the existing piping for the heating, all that is needed is a switchover valve to select between the Boiler and the Cooler.

 

Josh

[rooftop]

Our theatre is 410 seated and we have the above system, large volume, low velocity, we change the air at the rate recommended in the 'Yellow book' (8L/s/p) and it works well.

When you consider that the performances are in the evening (cooler air) and the number of hot days we have in the UK, the number of times that a cooling system is required is minimal and does not justify the cost. Last night at 8pm with a full house we had outside air temp of 25C and indoor was 28C.

If you push sufficient air in then the temperature rise is small.

Keep it simple, and cheap to run!

 

My thoughts entirely - summer is quieter for us; most performances are evening time; Giving people the recommended fresh air requirement (isn't it something like 10 litres per second per person for a new build?) then they stay fresh, even if they are warm. Sell more ice cream as well.