Air Conditioners FAQs

Air Conditioners FAQS

At CAS-Hire we focus on educating customers about our range of portable air conditioning units helping them find the correct model to meet their cooling requirements. Our range of portable air conditioners is ideal for hospitals, schools and universities, computer rooms, server rooms and offices. We also supply cooling/air conditioning for other larger areas such as galleries, factories, production lines, processes, television production sets and studios. We can provide you with our knowledge and information based on over 30 years of experience in dealing primarily with air conditioning and specifically hire of portable air conditioning units.

How to choose the correct portable air conditioning unit?

In order to choose the correct air conditioning unit, you need answers to the following points. In each individual case, a heat load calculation will be required to assist determine the most suitable sized unit selection. e.g. no. of people, windows and which direction they face, lights, PC’s, servers, printers, vending machines, amplifiers, ovens etc.

    • What are the ventilation exhaust routes available? E.g. how many windows open, ceiling voids with ventilation, doorways etc.
    • Do you require moving the portable air conditioner from room to room?
      If you are moving a portable air conditioner often, you should consider the cooling needs of the different rooms that you will be using it in and try to get a model that covers all aspects of your requirements best. A portable air conditioner that catches or drains all condensation into a container will need to be emptied more often, but it will exhaust warm, dry air. A unit that exhausts moisture will rarely require to be emptied, but the air it exhausts will be moist, and should not be vented somewhere that this moisture would create a problem (such as a dropped ceiling).
    • How many electrical power outlets do you have and have you checked you have suitable capacity available on your ring mains electrical power supply (e.g. fuse box) to accommodate more than one air conditioning unit?
    • How much space is there available in each room to accommodate portable air conditioning units?
      If you select a unit that doesn’t have enough capacity to properly cool your room? It will probably run all the time as a spot cooler only and not lower the temperature as much as you would like.

What should you know if you select an air conditioning unit that is substantially oversized for your room?

The air conditioning unit will run for too short a cycle, this reduces the room temperature quickly and the compressor will shut off. When the compressor cycle does not operate for a long enough period to properly dehumidify your room the room will reduce temperature, but you may have a larger humidity level than you may desire. Also, please note, that the room sizes that each machine is rated for are approximations and high levels of sun, high ceilings, or the number of people, computers, and machinery will increase the cooling burden in the room. Also, most portable air conditioners have different fan settings to help alleviate the problem of too much cooling power.

What is a portable air conditioner?

A portable air conditioner is an air conditioner that is mobile. Unlike ceiling suspended, wall fixed, or central air conditioning units, portable air conditioners do not require permanent installation. Commonly, these units have caster wheels for easy manoeuvrability and are generally 75cm to 125cm tall.

How does a portable ducted air conditioner or monobloc air conditioner work?

Portable Ducted Air conditioners work similarly to traditional fixed split type air conditioners in that they produce a cooling effect utilising the refrigeration cycle and a refrigerant gas such as Freon. The equipment incorporates the cold and hot sides of the traditional air conditioning in one case, and an exhaust hose expels the hot air out of a window or suitable alternative location away from the unit itself. Once a portable ducted air conditioner cools the air, water is extracted from the air, and most of the water is then used to cool the actual unit.

The remaining water is then removed by one of three methods:

  • A bucket or tray located within the unit collects the condensate, and this needs to be emptied periodically
  • The second method actually involves evaporating the water and exhausting it through a main venting duct and through a window or drop ceiling.
  • The final method is by using a condensate pump located in the water tank that allows the water to be pumped up to 3-5m to a suitable drainage point.

Portable air conditioning units do not require permanent installation. However, they still require flexible exhaust ducting to be vented outside or into an extract system.

What is a portable split air conditioner?

A Portable Split air conditioning system (PSA unit) has an indoor unit on wheels connected to a lightweight outdoor unit by interconnecting refrigerant or water-filled flexible pipes. The interconnecting pipework generally ranges between 5 meters for refrigerant only versions up to 30 meters of interconnecting pipe for the water-cooled split type systems. The PWCSA23 and PWCSA50 chilled water air conditioners can provide a large cooling capacity with the advantages of being mobile and readily operational and require minimal installation work.

Do portable ducted air conditioners or monobloc units require venting?

Yes, all refrigerant-based portable air conditioning units need to expel hot air that they remove from the room. This range of units generally is supplied with flexi ducts to vent the hot air exhaust to a suitable outdoors or well-vented area. For example, through a wall or into a false suspended ceiling void.

Can portable air conditioning units operate properly without an exhaust duct to vent?

Portable air conditioning units are designed to operate with a flexi duct attachment. If you do not direct the hot air that is being generated by the machine outside or suitably vented area (other than the same room that you are trying to cool), the portable air conditioner will not regulate and cool very effectively at all.

What is the standard length of exhaust pipe / flexi duct hose that the portable air conditioning unit is provided with?

Exhaust duct lengths vary by model, but generally, they are 4-7 feet in length. They are mainly made of temperature-resistant plastic reinforced with metal.

Why if using a heat pump portable system to heat do I require attaching and using a drain hose and bucket?

If using the heat pump function on one of our VC9PT or VC12PT models the units are designed to draw air through the flexi-duct into the air conditioner and strip moisture out of the air before producing warm dry air out of the front of the air conditioner. If you are using the cooling function the unit removes moisture out of the air intake then exhausts warm moist air outside minimising the level of water stored internally in the unit.

However, when using the heat pump function the flexi duct is drawing air back into the system, basically reversing the cycle. The moisture removed from the air is then designed to be continuously drained. If the water fills the internal water tank, the unit will automatically shut off until the water is drained from the sump drain located at the very bottom of the unit. Heat pumps are an energy-efficient method of heating compared to most other portable air conditioners. Usually, standard air conditioners only offer an electric heater function which produces less economical running costs.

Can we extend the exhaust duct/hose or our portable ducted system?

We can provide extension ducts on request. The duct must be the same diameter as the exhaust hose supplied with the unit. However, we would advise that the longer the exhaust duct gets, the less efficiently the portable air conditioning unit will perform. We advise that you should avoid making the exhaust duct for one of our office style smaller air conditioners longer than 9-10 feet unless you hire an inline fan to attach the exhaust duct to ensure the hot air can be suitably cleared from the duct.

Note any 90° bends or greater turns in the exhaust duct will substantially reduce the effective length of the exhaust hose. Industrial portable ducted air conditioners like the SF15 or the HSC2500, HSC3500 or the B24 require a larger diameter exhaust flexi duct however they can be extended from 3 meters up to 12 meters in length.

Can I use a portable air conditioner to cool my server room?

Portable air conditioners are an excellent way to regulate and assist computer server room temperatures. Even with fixed installed air conditioning systems, computer server rooms have more specific area cooling requirements than general office comfort cooling and portable units can be used to direct airflow into more specific areas.

Why do portable air conditioning units collect water?

When portable air conditioners cool the air, they also dry it. The water they extract out of the air by a form of condensation is collected into an inbuilt water tank or exhausted out the exhaust hose.

If I use the external drain option, how far can the water be pumped?

Only our SKU155 model come with drain pumps – the other portable ducted models all come with gravity drains. This allows the water to only drain lower than the unit and as far away from the machine as gravity will take it. Most commonly, the drain line is run to a large bucket or water container that is then emptied regularly. If you hire our SKU155 model you can drain the water up to 16ft away or above the height of the unit itself. Portable split systems for example the PWCSA23 and PWCSA50 models can condensate water up to 30 meters away from the indoor unit.

What type of electrical power supply do portable air conditioners require?

Most of the portable air conditioners that we can provide operate on 230 Volt/ 50Hz 13amp power supplies as this is standard household voltage. Larger systems for example the 15kw output PWCSA50 heavy duty water-cooled portable split air conditioner requires a single phase 230v 32amp power supply. Our B24 and HSC3500 can use a 13amp 230v supply however we recommend using a 16amp 230volt as they draw 12amps. The 9.3kw TC32 Industrial Portable ducted system requires a 20 amp 230volt power supply.

Is a portable air cooler / evaporative cooler the same thing as a portable air conditioner?

No. An air cooler / evaporative cooler uses water as its cooling agent as opposed to refrigerant gas used in an air conditioning unit. Air coolers do not have a hot air duct that requires to be vented however they do require cold water to be topped up regularly to maximum efficiency. We do recommend that they are used in well-vented areas to reduce excessive humidity build-up.

Can you provide a basic size guide for selecting an air conditioner?

Small rooms (up to 18sq/m or 6m x 3m): we recommend units that can offer a cooling capacity of 8500btu or 2.5kw.
Medium-sized rooms (up to 24sq/m or 6m x 4m): we recommend units that can offer a capacity of 12000btu or 3.5kw.
Larger sized rooms (up to 36sq/m or 6m x 6m): we recommend units that can offer a capacity of 14000btu or 4.1kw or greater.

What are fixed split air conditioners?

CAS Hire offers a comprehensive range of fixed split air conditioning units from leading manufacturers. We recommend to our customers when possible to consider this range as an option as a long term solution to overcome your air conditioning requirements. We can provide high wall mounted split systems, floor and ceiling mounted split systems, ceiling cassette split systems, floor standing split systems, ducted ceiling void mounted split systems and multi-split air conditioning systems. Each of the listed styles of fixed units is installed by fixing the internal unit to the main structure of your office, workplace, home then connecting the indoor unit to an outdoor located unit using insulated rolls or lengths of copper pipe and cable. This range can provide larger outputs, efficiently, quietly and are designed to have a longer lifespan than portable systems.

What should I consider when buying or hiring fixed split air conditioning?

Where is it required for?

Office air conditioning – If you are considering having office air conditioning installed we would always highlight the importance of buying / hiring a leading brand manufacturer. As the old saying goes, “you get what you pay for”. Low cost or lesser-known brands very often have fewer functions as standard and are very often imported without the necessary components to function reliably in UK weather conditions. The lesser-known brands also lack support and use poorer quality components therefore should anything fail on your unit it may be a while before you get replacement components to enable you to be back up and running. Leading brands generally offer a standard 3 years parts and labour warranty based on the upkeep of an annual service maintenance plan which can be provided by Cooler Air Services Ltd. If your requirements are accurately calculated, installed and maintained by our team we would hope that the lifespan of your air conditioning could last for as much as 20 years. Heat pump systems are also an ideal way to economically maintain a steady temperature 365 days of the year instead of only using air conditioning during the warm summer months.

Home and Bedroom Air conditioning – If you require air conditioning for your home or bedroom prices can vary considerably subject to the model and size of equipment you require. We would recommend the noise levels of the systems are one of your main considerations for example a whisper-quiet 25Dba indoor unit would be preferred over a standard 40Dba office quiet unit. Leading brands make huge efforts to produce units with the lowest achievable indoor unit noise levels. Aesthetics are also a prime consideration as many leading brands can offer stylish multi-coloured indoor units or replacement cover panels ideal to suit your home decor. The new breed of air conditioners produced by leading manufacturers includes heat pumps with can produce 3.8kw of heat generated from 1kw of electricity used therefore reducing your overall electricity usage.

I have an air conditioning unit that uses R22 Refrigerant – what can I do with it?

As of the 1st January 2010 usage of virgin hydrochlorofluorocarbons (HCFC’s) for example, R22 are against the law when servicing your air conditioning equipment. As of the 1st of January 2015 the sales or usage of recovered or recycled R-22 refrigerant gas will be prohibited. It is extremely important to have this unit replaced with a new R410a model in the event of operation failure as the system can no longer be legally repaired.

What should I consider before hiring an Evaporative Cooler or Air Cooler?

Evaporative cooler / Air Coolers use a method of converting hot air into a cooling breeze using the evaporation of water. It is similar to the cool refreshing effect you feel when you’re at the seaside or emerge from a swimming pool.

Our range of air-coolers utilizes the process of cold water evaporation along with an efficient air-moving system to create effective cooling. Fresh outside air is drawn through wetted filter media that cools the air through the evaporation process. A centrifugal or specially designed axial fan then circulates the air throughout the area requiring cooling. Evaporative air coolers are fairly inexpensive to purchase; Evaporative coolers use a quarter as much electricity as conventional air conditioners and do not use refrigerants that damage the ozone layer.

The range of commercial and industrial evaporative coolers available today has become extensive, Evaporative cooler hires are particularly well suited in areas where the air is hot and the humidity is low. However, in higher humidity areas, there are many proven cost-effective uses for evaporative cooling. For example, call centres, printers, retail outlets, laundries, greenhouses, warehouses, manufacturing processes, factories, construction sites, sporting events, airports, garages, plus poultry and dairy farms can all benefit from evaporative coolers.

When selecting an air cooler or otherwise known as an evaporative cooler to hire, a few important points should be considered, especially environmental conditions. As air coolers, evaporative coolers use the evaporation process to cool air they will only be efficient in hot, dry environments as long as the water temperature inside the unit remains cool and readily available fresh air ventilation supply in order to operate properly.

For further information or to arrange a fixed air conditioning installation site survey or maintenance quotations please contact CAS Hire on 01786 448862. Our experienced staff can offer knowledgeable advice and direct you in selecting the most appropriate equipment to suit your specific requirements For all hire enquiries please contact CAS-Hire on freephone 0800 525082 or email

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