heating problems Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[douglas deay]

WE HAVE AN ISAR COMBI BOILER. THE RADIATORS ARE COMING ON WHEN THE HOUSE IS NOWHERE NEAR COLD ENOUGH. WHEN THE HEATING IS ON THERE IS A FLAME WHICH APPEARS ON THE THERMOSTATE,AT THE MOMENT THE HEATING IS COMING ON WITHOUT THE FLAME APPEARING. ALSO, FOUR OUT OF FIVE RADIATORS ARE PIPPING HOT AND ONE IS COLD. DO THEY NEED BLED DO YOU THINK THIS IS PART OF THE PROBLEM?
DOUGLAS

[htg engineer]

if all radiators are heating apart from one, check that both valves are open and vent the radiator (with the heating turned off) if still no luck, turn off all wheel head valves on the other radiators and this will push the air through and the problem radiator will then heat up as normal, remember to open all valves. Could make much sense of the rest of the post, the flame being the gas burning, or an LED flame light ?

[douglas deay]

Its an LED flame light.The heating is now coming on all the time,ragardless how warm the house is.We have to turn the boiler off so the heating will go off,but then we have no hot water.
Their should be a little flame indication on the thermostat when the heating is on,but there isnt one yet the heating its on.
Thanks for your help
Douglas

[Ideal-diag]

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.