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UNIT HEATER
Section 4. COMMISSIONING THE HEATER - ALL TYPES
Before starting to commission a heater read this section through and fully understand its contents.
Only competent engineers should carry out the work.
4.1 Pre Commission Checks
Checks before lighting the unit heater
Ensure that the heater and all controls are suitable for the gas, pressure and electrical supply that they
are being connected to.
4.1.1 Electrical Checks
A preliminary electrical check should be carried out by a qualified engineer, after completion of the
installation and before commissioning the heater as follows:-
Check that all site wiring is connected in accordance with the appropriate wiring diagram of Section 5.
Check the correct fuse size is fitted; 5 Amp must be used for all models CUHA and CUHA/A, and 10
Amp for CUHB, CUHC, CUHB/A and CUHC/A models, except for models 340 and 380 where the
fuse size should be 20 Amp. This must be connected in the live conductor (see Polarity Test below).
Earth Continuity Test
The appliance earthing must be tested using a suitable method according to local regulations. The
resistance of the earth circuit from the heater to the earth connection must be 0.1 ohm or less.
Polarity Test
Connect one lead of a suitable voltmeter to earth and connect the other lead to the live supply terminal
at the heater.
Turn on power to heater. A reading of approximately 230 volts AC 50Hz should be found.
The same result should be obtained by connecting the test leads from live to neutral.
Connecting the voltmeter between Neutral ‘N’ and Earth should give a reading of 0 volts. If these tests
do not conform to the above there is a fault which must be rectified before progressing further with the
commission. An electrician should be consulted to carry out this work.
Note: For Automatic Ignition models the burner control box will not operate with a neutral to earth
voltage above 15v and may be unreliable at any reading other than 0.
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