The Lemon Fool

I've had this boiler for 15 years and apart from a couple of replacement divertor valves, it has functioned wonderfully well, and still is, however, I have started to notice a surging sound from the boiler over the last week or so, it doesn't sound like the pump is surging and trying to pump harder, more like a fan trying to expel gases.

I'm not against changing it if that is what's needed, but it is a combi boiler, the replacement would need to be a condensing boiler which from what I've read can be less reliable than a simple combi.

Would anyone have an idea as to what could be causing the surging sound, if it might be terminal, and if the worst comes to worst, what to replace it with?

BluntChisels.

I can't help you with the surging sound but as you have had 15 years from your last Vaillant if you need a replacement that would be a good place to start.

Their condensing boilers are well thought of by the experts on TMF. I've fitted 3 to various properties in the last 10 years and never had a problem. The warranties are also quite good, from memory the last one had 10 years on it.

Hopefully you won't need a replacement.

I have a Vaillant boiler 25 years old, most of the water parts have been replaced over the 23 years I have cared for it. I had to replace the pump after about 18 years, but the symptoms of a failing pump is that it takes a long time for the radiators to heat up and they have a high temperature gradient (the out pipe is much colder than the in pipe). Noises from the pump may be due to low pressure in the system causing cavitation or a build up of air in the radiators causing air to bubble through the pump. The boiler has a valve that lets air seep out but it can only do so much. I would recommend bleeding any air from the radiators (generally the ones with a cold top, in our system air usually accumulates in only one or two radiators up stairs), then making sure that the system is back up to pressure. Its also possible to bleed any air out of the pump by loosening the little black disc on the end of the pump, but I've generally not found that necessary other than when I replaced the pump.

I've got a vaillant ecomax of the same age, they are very good boilers worth keeping it going if you can

Try and find a vaillant qualified gas engineer to check it out and do a service. If you are in the north east I can recomment a couple otherwise contact vaillant - more expensive but they have specialist engineers.

BluntChisels wrote:I've had this boiler for 15 years and apart from a couple of replacement divertor valves, it has functioned wonderfully well, and still is, however, I have started to notice a surging sound from the boiler over the last week or so, it doesn't sound like the pump is surging and trying to pump harder, more like a fan trying to expel gases.

This seems highly unlikely, but you're the one listening to it!

When was it last serviced? Gas boilers of this vintage rarely soot up so I very much doubt the fan is struggling. Does it make the same noise in both HW and CH modes?

MtB

Sorry for the late reply, we just got back from holiday.

To answer Mike4's questions, the boiler was serviced in January at the same time as it had a new divertor valve fitted, the noise was only apparent during the central heating cycle, for example, if the heating was set to low, so that the boiler would fire up say every 15 minutes and burn for 5 minutes, the surge could be heard during the first couple of minutes of the burn then disappear, but what is strange is, we were away for two weeks so switched the boiler off completely, when we returned the boiler was switched on and the surging sound has gone, the boiler appears to be functioning perfectly again, I think the best course of action is to have a service engineer come and look at it, we had a boiler fail two days before Christmas once and had to boil water on the cooker to take a bath until New Year.

Chisels