Problem with Modena 102 Central Heating - DHW fine

[Mazellett]

Hi all,

I've just tried to used my central heating for the first time since April, only to find that it will not fire up.

DHW works fine and dandy, when running it is telling the boiler to put CH to standby but when trying to get the CH to work nothing happens.

I know the room thermostat was a little dodgy so I've disconnected that aspect of the external controls, tonight I'm going to bypass the timer to see if that will make it kick in.

My next point after that is to remove the pump to make sure that it spins freely. Before I do that though, I'd like some advice on the boiler CH process if anyone can help.

My question is basically, if the pump has failed does the boiler recognise this and just not engage the CH? The reason I ask is that the boiler appears to think it's working normally (no error led) but just doesn't fire up for CH at all.

Anyone seen this before?

Thanks,
Mark

 

[Billy Bob Bob]

your pump has failed on the modena you will get hot water but not heating when the pump dies

 

[Mazellett]

That was going to be one of my checks. My boiler was peaking at 4 bar in the depths of last years -10 winter and I know the pump shouldn't exceed 3 bar.

Thanks for the advice, I'll check the pump head today

 

[Mazellett]

Right, I think I can rule out the pump, it spins ok but I'm not counting it out just yet.

No problem with the fan or anything, that's running ok as far as I can tell. Does anyone know how to test the CH sensor for fault?

 

[Billy Bob Bob]

it wont be your ch thermistor,the ferroli wont work at all if this has failed when you say it spins ok have you tried it with the power on? if its not the pump you have not said if you have a roomstat or time-clock they will need to be eliminated first

 

[GrahamM]

You mention disconnecting the room stat. in your first post. Did you link the proper terminals? Just want rule the stat. out completely.

 

[Mazellett]

I've bridged the 2 connections in the 4-block in the panel underneath the boiler and it made no difference.

To rule out a problem with the clock do I bridge connections 3 and 5 on the clock to rule this out?

Due to illness I haven't managed to test the pump with the power on yet to rule out the magnets the drive the pump failing.

 

[Mazellett]

I tested the pump last night while the boiler was powered up, it still seems to turn ok with the power.

I might have to completely disconnect the timer (seems it is optional) and see if that works

 

[Mazellett]

Afternoon people, I've worked my way through everything I can think of so far with this boiler.

Disconnected the external control, checked pump spins (with and w/out power).
Ran through the fault finding, no flashing LED5, with DHW running LED3 is on LED4 not flashing but RY100 is on, fan is running and air pressure switch activated, so the chart suggest the CH sensor.

It's been said that if the CH sensor is faulty on one of these then nothing works but everything else seems to be working fine.

Any ideas?

 

[Billy Bob Bob]

on the ferroli it looks at the ch sensor first then the dhw before anything can work

 

[GrahamM]

Had a bit of a think about and some time back was at a Modena 102. HW fine, but would not fire for CH and was going to lock out.
Replaced both thermistors and solved the problem.

Or, was it the other way about? Anyway, it probably worth replacing both thermistors to rule them out if all the other usual suspects are looking ok.

 

[Mazellett]

I appear to have been a slight imbecile when performing my checks and removing external controls on the boiler. After completely removing the clock the CH fired up fine. There was a sound of air pockets clearing themselves from the pipes, then it sounded like someone dropping a bag of spanners downstairs.

So it's starting to look like the initial mention of the pump failing could well be the ultimate problem. Money is tight at the minute so I guess I'm going to have to drain the system and remove the pump to guarantee that's the problem before I throw £70 at it.