Choice Of Heater Type
The best choice of heater will depend on both the area to be heated and the use of the area. Clearly attempting to heat a whole warehouse for the comfort of a few staff may not be sensible. A decision on heating of the whole area or spot heating where it is most needed will need to be taken. With right type of heating however, adequate comfort conditions for the staff may be achieved with an alternative heating solution.
Consideration also needs to be given to the available power supply. A 3KW heater plugged into a 13amp ring main will draw 12.5amps and 2 of these heaters along with other loads will be near to the maximum load, over which the 32 amp circuit breaker will trip.
A Clearly selection of the right type and amount of heating is important in achieving the best results. Call us on 0800 1694768 to talk through the best solution for you. Here at Aircon Hire Ltd we understand heating as well as air conditioning and our advice is free.
The most suitable type of temporary heater for office areas is normally electric oil filled radiators or convector heaters. These are safe as, they cannot present a fire hazard, are silent in operation, do not cause any local draughts and can be distributed around the area to provide even heating. Where they are used to augment an installed system and heating of the office from early each day is available they will be effective. In circumstances where the installed system has failed and there is total reliance on the temporary heaters it can be helpful to use additional fan heaters to bring the office up to temperature in the morning. See below for estimating the total heating output needed.
Where a larger area is occupied by a reception desk and perhaps an achitects design with large glazed areas and/or high ceilings makes it difficult to maintain comfortable working conditions at a recepton desk, if may be appropriate to use a radiant heater. A smaller 1200 watt halogen heater to provide spot heating on the receptionist is effective. A single unit will be sufficient. Alternatively a fan heater might be used.
Workshop & Production Area Heating
In workshop, procuction or packaging areas it may not be possible to provide adquate heating. Where staff are physically active a lower temperature is required. There may be a mix af activity in the area with some staff in static locations requiring more heat. In these situations the use of 3000 watt quartz radiant heaters is very effective. These are effective up to 6 mt away and provided there are no process reasons why radiant heating should not be used, they should be considered. 3 KW cube heaters can also be employed with the warm air ducted to where it is needed.
Retail Space Heating
Most retail outlets need adequate heating to ensure the comfort of visitors and to encourage them to stay and browse. In food outlets with significant refrigerated cabinets there will be significant heating from these cabinets. Hygene may be a consideration too. In clothing stores there will be the potential for fire risk if radiant or fan heaters are used so electric oil filled radiators may be the best option for unobtrusive and safe heating. Each application will need to be assessed individually we will be pleased to assist you with advice.
Healthy Working Conditions
The Workplace (Health, Safety and Welfare) Regulations 1992 give guidance on the minimum indoor temperatures in the workplace. They are required to be reasonable without the need for special clothing to be worn. The statutory minimum is 16 deg C with a figure of 13 deg C where heavy manual work is involved. In an office environment or any location where staff are not physically active temperatures as low as 16 deg C would be unlikely to get the best performance from individuals. A temperature of 20-22 deg C would be normal in winter for offices.
The other considerations are air movement and humidity. A relative humidity of around 50% is found to be most comfortable. A lower humidity can dry the nasal passages and lead to respiratory problems whilst a higher humidity can lead to mould growth and a muggy atmosphere. All electric heating and any heating which does not discharge the products of combustion into the room, leads to a lowering of relative humidity and this leads to days lost to sickness increase, as a result. See the section on humidity below. Air velocities of less than 0.25m/s will not generally lead to discomfort.
Calculating how many heaters are needed
To assess the heating load in an office, light commercial or domestic location, the following would need to be taken into account
Full, background or supplementary heating
Number of outside walls
Temperature of adjacent areas
Other incidental gains
Use of the space
If we were installing a permanent heating system then it would be necessary to complete a full assessment of the heating requirements. The flexibility offered by temporaty heaters makes an estimate of heating load a sensible course of action. If we use values commonly found in offices for the above variables then a good rule of thumb might be to utilise 1 KW of heating for every 10 sq mt floor area for supplementary heating and 1 KW for every 6 sq mt floor area for full heating when the installed system has failed.
Where heating of the whole area is not practical, such as in warehouses and workshops, spot heating is the sensible option. The following will need to be taken into account.
The nature of the jobs, location and movement of staff in the area
Priority areas and individuals requiring improved comfort
Merits of radiant or warm air heating
Range of radiant heating effectiveness
Congestion in the work area
A 3 KW floor standing radiant heater will be effective in heating people at up to 6 mt distance. The intensity of heating is inversely proportional to the square of the distance from the heater. That is to say that the heater will feel 4 times as powerful at 3 mt distance from the heater when compared to a 6 mt distance. This principle is demonstrated in the diagram below where, at twice the distance from the radiant heat source the available radiant heat falls on 4 times the area and so is one quarter as intense.
This aspect of the performance of radiant heating needs to be taken into account in determining how many staff can benefit from each heater.
Controlling Humidity when Heating
As noted above in the "Healthy Working Conditions" section, heating fresh air from outside has the effect of reducing it's relative humidity. We can quantify this effect on a typical winter day with outside relative humidity of 70%, as follows:-
Each cubic mt of 5 deg C air with relative humidity of 70% would contain about 5gm of water.
When heated to 21 deg C without adding any water that 5 gm of water represents a relative humitiy of 27%.
To see why this is a problem refer to the adjacent chart which summarises the views of many experts in the field. Whilst high relative humidity can make the air feel heavy and sticky and encourage mould growth, low relative humidity agravates certain medical conditions particularly related to respiratory disorders.
Clearly for the best working conditions which will result in fewest health problems it will be necessary to humidify the air to achieve a relative humidity of between 40% and 60%.