Vaillant TurboMax 242e

[wirralbret]

Hi, I have a vaillant turbomax 242e and i still have all the installation manuals. The problem I have is ever since I fitted TRVs to all but two radiators, the boiler comes on, gets the system up to temperature and as my room stat is still calling, the boiler is on for a minute, off for one and so on...

The manual says that to stop this, a timer is built into the boiler to hold it off for five minutes once it has been on.

Now, I am an electronics engineer, so the PCBs are not a problem. The truth is i've not even looked at the PCBs yet, so I was just asking if anyone had a circuit diagram they could send me please, or if not, is it a POT on the board that alters the holdoff time?

Any help would be grately appreciated,

Ivan

 

[jackthom]

Is it possible the TRVs are starting to close down too early, ie before the house has reached the sort of temperature you have set on the room thermostat?

That would explain the rapid cycling of the boiler, something which is generally to be avoided if at all possible.

Not sure about this boiler but does it display diagnostic codes by pressing the "i" and "+" keys simultaneously? The troubleshooting section of the installation manual should give you a list plus instructions on changing the values of some parameters.

d2 is usually the setting for the burner anti-cycling period.

 

[wirralbret]

hi, thanks for your reply

I have 7 radiators, 5 with trvs on, the room with the digistat on does not have a trv, but the on/off cycles are about 30 seconds, which is not even enough time to push water round. It doesnt have diagnostics on the boiler. it was installed in 1996

 

[jackthom]

Assuming the lockshield valves are all open, I'd be inclined to turn all of the TRVs up full and make sure the boiler is no longer rapidly cycling.
Just to make sure the system doesn't have some new unrelated fault

If that works OK and all rads get nice and hot, you can then experiment with the TRVs to get each room closer to the temperature you would like.

There will always be a cycling problem if the majority of TRVs are shutting down before the room thermostat is satisfied.

Sorry I don't know the answer to your original question about PCB tweaks but someone here will.

 

[wirralbret]

I have already experimented to get the rooms the right temperature.

To Quote the vaillant manual: "This boiler has a cycle holdoff function for TRVs. When the boiler has reached temperature in central heating mode, the boiler will switch off and hold itself off for a 5 minute cycle prior to starting again. this does not effect the hot water."

Mine doesnt hold off - it stops and then starts heating again 1/2 a minute later.

Does anyone have a schematic diagram of the board please? there are two pots at the bottom of one of the boards, one has a picture of a clock, the other a picture of a flame. The clock one seems to do nothing.