mat 60 said:
"potterton ep2000 control" = low voltage controler.
Problem "the fuse in the wiring center blows if used"
Hint "If the earth wire from the control is removed the fan starts but get no spark in the boiler.if i selct the ch nothing happens."
From link below
# (R), Red, hot side of transformer.
# (Y), Yellow, Compressor activity (cooling or cooling and heating on a heat pump).
# (W), White, Heat (gas burner, oil burner , electric heat, (auxiliary heat on a heat pump including defrost output from the outdoor unit to activate electric heat and turn on the AUX. heat lamp).
# (G), Green, furnace blower fan. (needed for air conditioning, heat pumps and some electric furnaces). NOTE: on most thermostats the "G" and "Y" are connected together at all times when the fan switch is in the "Auto" mode, If you sully R to G then you will most likely energize the outdoor unit contactor!
# (O), Orange , Energize to cool (used for reversing valve on heat pumps)
# (B), Blue or Orange, Energize to heat (used on some systems, Rheem/Ruud is notorious for this).
# (C) (CC) (B) or (X), Blue, brown or Black, common side of transformer. Needed on some electronic thermostats or if you have indicator lamps. Do not confuse with (B) Reversing valve (energize to heat) above. York and Trane like to use (B) as common.
# (E), blue, pink, gray or tan, emergency heat relay on a heat pump. Active all the time when selected, usually not used.
# (T), Tan or Gray, outdoor anticipator reset.
I am asuming you are talking about the fuse for the low voltage wireing and not the breaker in the main electrical panel.
I don't think the controler is bad since it is more likey that you have a short on the "heat wire".
Was it running and this just started or are you just wireing it up now?
I would start by disconnecting the controler and going directly to the boiler and then based on the wire plan start it up manualy by jumpering it.
What is the wireing plan type?
Some links
Wireing colors
http://www.toad.net/~jsmeenen/wiring.html
Batery replacment
http://www.howtomendit.com/answers.php?id=23741