Post
by Ideal-diag »
Fri Jun 29, 2007 11:30 pm
the isar has a user display you say the heating comes on even when the room stats flame on image is not lit up .
the modes for the isar display are.
0 = doing nothing
t = temp testing . this boiler is a pre heat boiler and will monitor the temp of the dhw heat exchanger , if this temp drops below the pre set temp it will fire up the boiler to reheat the dhw hex ,when firing up this display will change to = d . once heated up the display turns back to = 0
d = domestic hot water demand
c = central heating demand
if the divertor valve or the motor head (red or grey) fails then when the temp of the dhw hex drops the boiler turns on to reheat it but as the divertor is now not working the water is now pumped round your heating system and the rads get hot even when the heating is off .
because this also takes longer to finaly heat up the dhw hex the rads maybe on for a quite a few mins every hour.
we have also had this happen if a hot water tap is driping and the divertor has failed this will result in the same problem.
as its now summer time this last reason is not likey but i'll mention it for referance , some systems can have a frost stat fitted and this will over ride the main stat so bear that in mind ok ( i dont think is that though ok)
frost stats can fire between 3 and 5 degrees on most systems , normaly this is only done to a boiler fitted externaly to the main home IE: GARAGE
or maybe a LOFT SPACE.
TO TEST THE DIVERTOR WITHOUT REMOVING ANY COVERS
run your hot water tap and feel the temp of the water is it cooler than it used to be, and feel the left hand 22mm pipe under the boiler is it warming up . if the pipe is getting very hot when the tap is run then you most likey have a divertor issue.
so check the user display when the boiler acts up if your seeing the t or d and the rads heat up = divertor issue, and check the left pipe when the heating is off and you are running a hot tap.
i hope this helps you a little.
