Regency U37-NG NATURAL GAS - Manual (Page 23)

U37 Regency ULTIMATE Rear Vent Direct Vent Freestanding Gas Heater 23
COPY OF THE LIGHTING PLATE INSTRUCTIONS
OPERATING INSTRUCTIONS
Again, this is normal for steel fireboxes.
Blower Thermodisc:
When this thermally activated switch turns ON
it will create a small "clicking" sound. This is the
switch contacts closing and is normal.
Pilot Flame:
While the pilot flame is on it can make a very
slight "whisper" sound.
Gas Control Valve:
As the gas control valve turns ON and OFF, a
dull clicking sound may be audible, this is normal
operation of a gas regulator or valve.
Unit Body/Firebox:
Different types and thicknesses of steel will
expand and contract at different rates resulting
in some "cracking" and "ticking" sounds will be
heard throughout the cycling process.