Air handling systems do not have to be a permaent fixture says Mark White, UK sales director (temperature control) Carrier Rental Systems. They can be hired.
AIR handling systems do not have to be such a permanent, plant-room-based fixture as most people probably believe – they can be rented.

They can be hired on either a stand-alone basis, plumbed into the on-site plant, or can come with a hired chiller too. From Farnborough Air Show’s corporate hospitality village to the printing works that handles our telephone bills, there are circumstances where most contractors sooner or later will get called on to provide temporary site cooling, or indeed, heating services.

The commonest reason for a call to our dedicated specification team is that planned maintenance work is putting the fixed ac system out of action either on a single floor or an entire building. If this is just the fan coil units in the floor or the ductwork and hence the air handling system then following a rapid site visit our specification team will suggest temporary air handlers which can take a chilled water feed from the existing chiller plant and or hot water from a boiler system. We can ‘hot tap’ into a customer’s pipe work without the need to drain down the system or stop production.

If additional pipe work is necessary we are used to running pipe work up the side of a building without the need for unsightly scaffolding. Our special catinary wiring method is the safest way with the pipe work or power cables being secured every meter and it also looks unobtrusive.

Typically, this sort of hire may last from two to twelve weeks. We can easily and seamlessly act as part of your team and can install, commission and de-install the equipment as necessary with a minimum of fuss. If additional power generation and fuel management are required we can supply this too.

Large range

Carrier Rental Systems has a big range of individual ahus from 15kW to 450kW cooling capacities. These can be made up into a system to match chiller capacities up to the 1.2MW chiller that we offer – the largest available on hire in the UK. Our technical specialists can design an appropriately balanced system.

A particular advantage of our specialist involvement and our insistence on not just hiring boxes is illustrated by the fact that if it is at all possible we will recommend an air handling system that uses 100% re circulated air. In other words a heat recovery system that will halve the chiller or heat pump capacity required saving money, energy, fuel and hire.

Units come either with plenums or without. Our most popular unit the CRS 50 ahu has a removable plenum box on top to give air distribution from three sides of the unit, this is at the top of the unit for maximum cooling effect, any of these grilles can be angled towards an area or closed to give more air flow from the other two grilles. Another option for this unit is to remove the top plenum box, to be able to connect 600mm flexible ducting to the unit – this can be used for either more directed chilled air flow for a customer’s processes or for our downflow system.

The downflow system is used in data centres or computer rooms. Most of these rooms have existing downflow units which means that the cooled air is pumped into the floor space. This floor space then acts as a giant plenum. The chilled air flows up through the designed holes in the floor under the computer/data racks and passes cool air through the computers and out at the top – the warmer air that comes out of the top is then returned to the ahu to start the process again – transferring the heat from the air, into the chilled water and then rejecting it to the outside via the chiller. (If this was done by using a normal ahu and free blowing the air into the room it would not put cool air into the racks and therefore not force the warm air through for it to be rejected).

Our 100,150, and 450kW units are all 2.5m square boxes and are stackable for further installation flexibility. The 450 ahu has an inverter driven motor so it can provide anything from 0 to 60,000m2/h – we can add separate variable controls to other units at additional cost.

Recently, we hired out eighteen CRS 50 ahus to a mobile phone billing datacentre that needed to do power modifications to three server rooms. Of course, with the power down the in-house ac system couldn’t operate no matter how many standby systems they had. Carrier Rental Systems supplied stand-alone systems with their own chillers and generators.

We supplied 18 internal units to ensure that we could direct the airflow under the floor to duplicate the existing down flow system and that there was enough capacity for effective heat rejection.

As this was a critical site we had to ensure that we built in maximum contingency. This was done by providing two chillers – each chiller with four compressors and two circuits for maximum efficiency and contingency. Each chiller had its own generator rather than one main generator; this meant that if one failed we would still able to run 50% of the system. The same principle applied to the pumps. The system was designed so that we fed the main buffer tank with two chillers and then took feeds from the buffer tank to each water circuit for the ahus.

Carrier Rental Systems 0808 168 2013