Combi boiler working on 30s on/off cycles

[LeoCh]

Hello

I recently moved to a new rented flat, with a combi boiler. So far we only used it for hot water and it has been working very well, strong hot shower pressure.

However it's been very cold the last few days so I decided to turn the central heating on. Pressure looks ok at 1 bar, no room thermostat only the temp control dial in the boiler. Initially the boiler refused to fire until I put the temperature control in the boiler to max.

Now the boiler fires for 30s, turns off for 30s, then fires again and so on. Water pump seems to be on all the time. Pressure gauge goes up to 1.5 bar.

The rads are warming up ok but very slowly, but do get hot to the touch.

Is that normal? Doesn't fell like the boiler should be going on and off so quickly. The boiler is also extremely loud when fired (not the water pump, which is constantly on, only when the flame is on).

Any ideas before I ask the landlord so send someone in or not to look at it?

 

[Dan Robinson]

And the boiler is a ???????

 

[LeoCh]

It's a Vaillant, but there's no model or any other markings on it, there's no booklet in the flat... I googled around and from the pictures it looks like a Turbomax Pro.

I noticed now when the boiler was fired that the hot water out was going out at 55c or so and coming back in at 45c. The rads were also at 55c. This is with the boiler's temp control at maximum. All the rads in the flat are warm except one which for some strange reason is not warm at all. They all have very old metal thermostat valves.

The fan is also extremely noisy when it kicks in, I don't think I ever heard such a noisy boiler before because of the noisy fan.

 

[Dan Robinson]

Sounds like it is in need of some extreme TLC.

 

[Terry lambert]

I take it all of the thermostatic valves are fully open? Are they obstructed by curtains etc

Also check the other end is open with a small spanner