Dunnair LSFP25

[daveo222]

I have been given a job to fit 4 electric heaters each is 2.5kw to a AHU and also have to fit necessary thermostat, however i have never worked on this type of unit and never installed heaters before,

and help would be appreciated phots of jobs already done etc.

[Brian_UK]

Sadly the Dunnair website doesn't have much useful on it does it?

Any electric heater needs a control thermostat and an overheat thermostat as a safety backup. The overall control circuit for the heaters needs to be linked back to the AHU so that they cannot be switched on without the fan running.

The fan should also incorporate a run on timer so that at plant switch off, timeswitch or otherwise, there will be air blowing over the heaters to dissipate any residual heat.

Are the heaters being staged or are they being fitted in separate ducts?

[daveo222]

It is a 4 stage each stage is 2.5kw

[joneyjnr]

Hi,

most of the units I have seen have flow switchs to confrim airflow as a safetly.

[Brian_UK]

OK, so you need a four stage thermostat, airflow switch, overheat switch, fan run-on timer, four isolators and you'll be nearly there.

Some documents on electric duct heaters...
http://www.swift-air.co.uk/E%20H%20B.pdf
http://www.ehpricedartmouth.com/pdfs...terCatalog.pdf
http://xinca.com/docs/johnsoncontrols/pau-2.PDF

[install monkey]

a step controller to gradually load up the heater bank and an interlock to prevent heaters from running when cooling is enabled.