Baxi Solo 2 Overheating Problems?

[laylo]

Can anyone help, my Baxi Solo 2 PF40 boiler has started to shut down with the overheat lamp lit. This happens after the boiler has been running for at least 8 hours. Once reset, it will run again for a number of hours before tripping out again, any idea where i should start looking ?

Thanx in advance.

 

[baxpoti]

Make sure you have a bypass fitted for the pump over run to work correcttly

 

[stem]

The problem is more likley the central heating system than the boiler. Basically the hot water is not getting out of the boiler fast enough so that when the flame goes off the residual heat in the boilers internal heat exchanger causes the water to become overheated and trip the safety device.

Has the pump speed been turned down?

Do you have radiators and /or towel rail that have manual valves on (not thermostatic) to accept a flow of water when other rooms with thermostatic valves on have warmed up? If so are they open?

Have you recently insulated some pipework that is meant to be uninsulated as part of a heat sink / by pass system.

Is there a lot of air in the system preventing proper circulation?

Is the system working properly otherwise? sludge in the system may prevent proper circulation.

 

[laylo]

Thanks for the replies, ALL the radiators in the house have thermostatic valves on them but most are set to their max. My next step is going to be to replace one of these for just a normal valve and see if that makes any difference. The pump speed was turned down about two years ago as i was experencing a lot of air in the radiators which required bleeding all the time, turning the pump speed down seemed to cure it, however , if this is causing the boiler to trip out then i'll increase the speed again.
The system is fine from a sludge point of view as all the radiators where replaced approx two years ago & the system fully flushed out.
Once again thanks for all the help.

 

[ollski]

I would be suspecting that the pump overrun off the pcb is not working or possibly working intermittently. There is no point replacing the trv, just remove the head.

 

[Soggy_weetabix]

or the gas vlv letting by.

COGI territory though.

David

 

[laylo]

Problem Solved, removed four of the thermostatic radiator valve heads, (the ones that are always turned up full anyway), and the boiler has not tripped out since.
Thanks for all the help.

 

[bab]

1 should be enough on a good sized rad. U have a build up uf scale inside the heatexchanger if the system was run without inhibiter while u had the air problems. Also depending on when ya boiler wasmade the early models had the over heat sensor fixed between the flow & return ports on the boiler be4 an adaption to a clip on the flow pipe needs sliding as far from the connection as posible.

 

[laylo]

Looks like the problem has returned, even with four of the thermostatic radiator valves removed, the boiler has worked flawlessly all through summer heating up the hot water alone, but now as it is getting colder my central heating has come on and it has been tripping out on overtemp again. It runs OK for about 24 hours, heating the hot water & running the central heating, but the following morning when both the hot water & the central heating are both running together the boiler will trip out on overtemp. I then reset the boiler and it will run fine for another 24hours.

Any ideas anyone.

 

[John M]

Employ somone to come in every morning to press the reset button

 

[gas4you]

With all the air in the system you mentioned earlier, I would check that the system is not sucking air in down the open vent. After this builds up it could cause an airlock causing the boiler to overheat.

 

[laylo]

Hi, Thanks for the reply.
If air is getting into, or was in the system already, wouldn't this show itself by 1 or more radiators not getting hot? as it is at the moment, all the radiators get hot very quickly as soon as the central heating fires up.

 

[laylo]

Have just bought a replacement overtemp thermostat for my boiler just incase the one on it was faulty, was just about to swap it when i noticed that the instructions which came with the one supplied show that it should be fitted on the output pipe on the boiler, it also shows this in the service manual. However, the one on my boiler is actually built into the boiler itself, positioned between the flow & return pipes. Does anyone know if this is a design fault with the boiler as Baxi have obvously changed the design, possably to stop the boiler tripping out on overtemp? Will i be OK in fitting the new one on the output pipe via the plastic clip as shown in the service manual & replacement overheat thermostat instructions. My boiler is a Baxi Solo 2 50PF

Thanx in advance.

 

[baxpoti]

Make sure you have a bypass fitted for the pump over run to work correcttly

Have you done this?

The later stat is fine for your boiler, it was modified as it was cheaper to produce, probably.

 

[laylo]

No I haven't swapped it yet, i wanted to make sure it was safe to put the new one in the new position as the overheat thermostat is what prevents the boiler from overheating. incedentally, the new overheat thermostat kit comes with TWO new thermostat sensors, either which fit onto the output pipe depending upon what mountings you have on that pipe, ALSO the two new thermostat modules look identical to the old one which sits in the boiler itself between the input & output pipes which leads me to believe that Baxi didn't make this 'change' to reduce costs. I noticed the difference when changing the other boiler thermostat so i'll try running it with that first to see how it goes.

Cheers.