Aircon Frequently Asked Questions

Q How do I calculate the cooling or heating capacity of my room ?
A Multiply the length x width x height of the room in metres multiply the total by 40, this will give you the answer in "watts" (please note this calculation is only a guide, solar heat gain, occupancy etc all need to be considered)

Q How cold can I make my room?
A The lower limit for comfort cooling is 21 degrees but most units will cool to 19 or 18 degrees C.

Q How much will it cost to run?
A Take the "input power" (normally around 30% of the output of the unit) multiply this figure by the cost per unit of electricity allowing for diversity (thermostatic control)

Q Where does the heat go?
A It's transferred through the refrigerant gas and expelled by the outside condenser.

Q Can I put the outside condenser in another room?
A The ideal place is outdoors, however some applications are suitable for the condenser to be located indoors, an example being a small room/office with a large warehouse area adjacent.

Q What is the maximum separation I can have between the indoor and outdoor unit?
A This can be up to 50 metres dependent on the size of the unit and the manufacturers specifications, also the amount of "lift" involved (see below) Units under 3.5 kW normally have a maximum of 10 — 15 mtrs.

Q Can my outdoor unit be mounted higher or lower than the indoor unit?
A Yes, this will again vary dependent on make and size, but as a rule of thumb, small units are capable of up to 5 mtrs of "lift" but after this oil traps need to be inserted into the pipe runs to stop starvation or slugging back to the compressor.

Q What about fresh air?
A Normally on small wall type and ceiling type units there is no provision for fresh air on the actual unit, on the ducted and cassette type provision is made in most cases.

Q What is a heat pump unit?
A A heat pump unit is a reverse cycle air conditioner, modern Inverter heat pumps are very efficient and one of the most cost-effective methods of heating a given space.

Q Will a heat pump work in severe weather conditions, e.g. in temperatures of -5 degrees C and below?
A An " air to air" heat pump will not perform at 100% efficiency during these conditions, the system should be" sized" using a higher calculation method to compensate for adverse low temperature ambient conditions.

Q What about noise?
A The noise of the indoor unit is less than a PC base unit in most cases, The outdoor units are also extremely quiet in operation.

Q What about refrigerant, which one do I go for ?
A The Refrigerant R22 has been in use for many years, it is now illegal to import heat pumps into the EEC with this type of refrigerant, although it will be around for some time yet for servicing existing systems. Most A/C systems now use R410A

Q What refrigerant do I now use in my old R22 system?
A There are "drop in refrigerants" available now that will replace R22 without modifications to the system, an alternate is Isceon 59 (R417A).

Q Can I use the new refrigerants in my existing R22 air conditioner?
A No.! The oil in a R22 refrigerant compressor is mineral oil and in the new types like R410A, it is synthetic.

Q Can I buy "too big" a system for my room?
A Yes, too large a system will result in short cycling of the compressor and in extreme cases lead to internal damage.

Q Can I get Legionnaire's disease from Air Conditioning systems?
A Not as a general rule. This disease has, in the past been traced to poorly maintained Water Chiller commercial cooling systems, which can be used for big installations. Generally though 'Direct Expansion' Refrigerant systems pose little threat to health.

Q What is "latent heat" ?
A Latent heat is sometimes called "hidden heat"

Q What size unit(s) would I require?
A An approximate guide to working out cooling loads is as follows:-

For most offices, homes or shops:
Take the floor area of room or rooms in m2 (sq. m.) and multiply by 200 watts.
This will give you an approximate total cooling load in watts.

e.g.3m x 4m = 12m2 x 200w = 2400w or 2.4 kW

Server or telecoms rooms will have a much higher load, for budgeting we suggest you allow 400w/m2.

e.g.3m x 4m = 12m2 x 400w = 4800w or 4.8 kW

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The Enhanced Capital Allowance (ECA) Scheme provides upfront tax relief for businesses that invest in energy saving equipment, to qualify for ECA the equipment must be listed on the Energy Technology list.

Air Conditioning - FAQ
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How do I calculate the cooling or heating capacity of my room? Multiply the length x width x height of the room in metres multiply the total by 40, this will give you the answer in "watts"...

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Mitsubishi Electric has developed a comprehensive 'end of life' recycling programme with Overton Recycling Ltd of Stourbridge with a free of charge collection of air conditioning equipment to Mitsubishi Electric customers