Probably, the 3A rating is for a "nice", resistive load, such as light
blubs, while the derated 1A rating is for a "nastier" load, such as
flourescent lamps, transformers, and other things which are likely to
produce more of a spark/arc as you interrupt the supply.
Thanks for all the replies.
I have just bought a Danfoss-Randall TP9 Programmable Room Thermostat + H/W
Although I downloaded the installation instructions before buying it, I failed
to notice that it is only rated at 3(1)A.
There is no label on my boiler to show the power consumption. All the boiler
instructions say is fit a 5A fuse, I changed this for a 3A fuse to match the
programmer. So far this has not blown.
I got out my multimeter. In round numbers the boiler draws 1.75A at for the
first 8 seconds when it starts (when the igniters are working) and 0.75A there
after when only the motor that drives the fan and oil pump is running. The
central heating water pump draws 0.25A.
The TP9 uses separate relays for the boiler and water pump.
My multimeter has a facility for recording peaks, but I suspect that this picks
up switching transients rather than any additional current that the motor might
draw at start-up.
Wouldn't worry, you're unnecessarily worrying yourself, it's designed
to switch boilers on and off, fit it, stick a 3amp fuse in the spur,
that's it. I've never come across an overloaded room stat or
Gas boilers take very little power(*) compared to a oil boiler. The OP
mentions 8 seconds and ignitors I'd take that to mean he has an oil
(*)Though the fan flued jobbies will take more than a normal open or
balanced flued thing where the only load is the gas valve. I still
doubt it matches the blower/high pressure pump of a oil boiler.
Dave. pam is missing e-mail
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