Hi - (I hope I'm in the right forum for this - please advise if not) I have a specialised request from a customer for the following (for a bat house): 4 x 240W tube heaters to maintain a constant temperature of 30 degC in a small enclosed insulated space. The heaters are in close proximity to each other and there will be a temperature sensor in the centre, for logging and possible control (Pico EnviroMon system).

In order to maintain as smooth a temperature curve as possible, the customer has requested that each heater switch in/out individually, rather than all four being switched in/out together.

Can anyone suggest how this could be achieved? Is there a particular off-the-shelf 'heating control system' that would do this? Or does something have to be specially designed, perhaps using thermostats and relays?

I can supply more information as necessary. Thanks, John.

This sounds very similar to a problem I had some years ago with a waste oil heater which employed on/off control. The elements got so hot during the on period the impurities baked onto the surfaces.
I overcame the problem by building a proportional control based around an RS components chip which drove a triac thus as the desired temperature was approached the on periods became shorter and the off periods longer (fractions of seconds) and equilibrium was reached.
I leave it to you to investigate further.
regards

Thans seeker - I have decided to go for a fairly simple solution with a thermostat for each heater. It means that all four heaters can be adjusted to stagger the heating curves, which should, hopefully, satisfy the customer. Appreciate your input, John.

Seemed very tough.. Nice Job Seeker (Y)

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