BAXI 105E Problems:

[LincolnHandyman]

Not sure if this is the right place to post this...

Hi and thanks for reading: We have the above boiler installed in our garage, it is approximately two years old and is operated using a wireless Towerstat RF. I have noticed that the boiler fires up on its own accord. I have checked the timer and this is set in the off position (moon). The boiler fires up for approximately 30 seconds to 1.5 mins then switches off. The boiler delivers good hot water and the heating works well on timer. Just can not understand why the boiler should run for short seconds and then switch off. It does this several times an hour. I was maybe thinking that there might be a problem with the Towerstat RF unit but am unable to find anything negative about this unit on the internet. With fingers crossed i look forward to hearing back with some helpful ideas. If only to save on my gas bill.... the last being in excess of £420.00
Many thanks for reading
Christian

[Charlie2]

Does the boiler have a pipe stat on it ? or a stat in the garage ? it is common practice to install these when the boiler is fitted in a garage ...its to prevent the pipes freezing.... if you see a unit on one of the pipes near to boiler...then this is what it sounds like......

[LincolnHandyman]

Hi many thanks for the reply - Yes the boiler does indeed have a stat in the garage for control of freezing pipes.... when you say it sounds like this could i please ask you to elaborate a little.... many thanks
Christian

[neilball]

Sounds like you have 2 stats - your room stat (Tower RF version) and a frost stat in your garage. The short cycle could point to the frost stat if it uses a pipe sensor as this would warm up very quickly when the boiler fires. You could try temporarily turning up this stat to see if that stops the problem - unless your garage gets very cold then it would rarely need to operate and maybe it is already switching on while the pipe temperature is quite high. I would expect it to be no higher than 10 degrees and if not too exposed then you could proabably et away with closer to 5 degrees especially if the pipes are porpoerly insulated with climaflex or similar pipe insulation.

If the frost stat is not the problem then it could either be the RF stat or a boiler fault. Can you safely electrically isolate the RF recevier power so it cannot operate? If this stops the cycling then you know there is something wrong with the stat and replace it. If the problem occurs with the stat disconected then it could be a boiler fault and you could then talk to Baxi tech support to see what they can suggest.

[dalethecaptain]

Pipe thermostats are usually set to run when the water temp in the pipes is below 20 degrees, you should make sure if you have one fitted that its not set too high.

Are the two large bore outer pipes (left and right outer most as you look at the boiler) staying warm all the time? (by this I mean are that at normal operating temperature) It could be that the hot water diverter is sticking, which will also cause the boiler to short cycle. These pipes are the flow and return for the central heating, do they pipe get noticeably hotter when you run the hot water?

[fredd500]

I have the Baxi 105HE - not sure whether there is a difference or the lack of H on yours is a typo.

Anyway, my boiler has a pre-heat circuit which keeps the hot water temperature up so there is less delay when turning on a hot tap. The boiler fires up every so often for about 30 seconds or so. You can switch this off by turning the hot water temperature control knob right down on the front. I suspect this is what you are seeing. If your boiler is the same as mine, check the LED's on the front - the tap LED should flash and the flame LED should light.

The boiler also seems to circulate the water in the heating loop every so often too when it should otherwise be off - I sometimes hear it in the middle of the night (due to crap floating around in the radiators and making a noise). I am guessing this is part of the anti-freeze mechanism or something to ensure the pump doesn't seize up.

I don't have any external thermostat connected to the boiler at all, just a time switch and thermostatic radiator valves on every radiator so the on/off cycle is purely determined by time rather than temperature.

Hope this helps