Boiler suddenly humming

pieroabcd

It's 9 years old.
The engineer has just left. He replaced the g10 gasket that was damaged and added that that noise shouldn't be a concern. If the pump breaks it's 370 pounds for the whole replacement 

ThisIsWeird

£370 for just the pump replacement?! Eek!

But, yes, I'd live with the noise, at least until it becomes a rumble...

If you need to get that guy in to do it, then I suspect the only option would be for a new item. Another GS might be willing to fit a pump that you provide, obviously with no ongoing warranty (other than the one provided with the part, often a year, but you'd need to pay £abour again to have it swapped). But, no harm in asking other GSs.

Personally, I wouldn't pay £370 for just this part - that is OTT, and is in the realms of 'silly' for a 9-year old boiler.

I have fitted a refurbished fan on a GlowWorm before, and this was bought from a reputable co on eBay. The supplied item was in superb condition, super-smooth (obviously new bearings), and was even resprayed - it did look 'new'. Also had a 1-year warranty. I'd happily go 'recon' from a reputable co again. 

I guess your options are to take out an annual maintenance contract, and wait until the pump deteriorates - could easily be over a year(s) - or hunt around for a happy GS. Or, there are some very good deals on boiler maintenance contracts, some with super-cheap intro-year offers, but which go up with auto renewal. These also tend to have differing levels of 'excess' charge, but the good thing about them (usually) is that they will replace everything they find that's dodgy, and not just the obviously-faulty part. One service fellow explained to me that they don't want a call-back on the same boiler within 3 months. Or, look for fixed-price repairs - usually around the £300 mark, so already a lot cheaper, and they also tend to replace any part that's 'dodge'. Vaillant themselves will offer these. Or, look for a GS that will charge only labour, and fit your part. This should be a 30-60 minute job.

To be clear, I was not suggesting that you - or anyone - should DIY this. Even tho' that is exactly what I would do/have done - and I wouldn't be breaking any law in doing so.

FreeBear

ThisIsWeird said: To be clear, I was not suggesting that you - or anyone - should DIY this. Even tho' that is exactly what I would do/have done - and I wouldn't be breaking any law in doing so.

Unfortunately, you would be breaking a law by working on a gas boiler. Specifically The Gas Safety (Installation and Use) Regulations 1998

Unless you are Gas Safe registered, the HSE will not consider you a competent or authorised person, and there is a (very small) chance that you could be prosecuted.

pieroabcd

I think that in the meantime I can search for a new part for a bargain AND for a GS that will accept to mount it.
Anyway, as long as it works I'll keep the current pump. The noise is not a concern, but I was worried that it could be the symptom of an imminent breakdown 

pieroabcd

Yesterday it did it again. I noticed that in all cases the noise and the vibrations were produced when I set a temperature higher than 1 degree more than the ambient temperature.

Another strange thing happened, too 
When I rebalanced the system one month ago and when the boiler was serviced one week ago the pressure at cold (in the morning, before turning on) was 1.3 bar 
This morning at cold it was 1.6, even though the refill taps have been perfectly close all along.
How can the pressure have raised on its own accord?

ThisIsWeird

pieroabcd said:

Yesterday it did it again. I noticed that in all cases the noise and the vibrations were produced when I set a temperature higher than 1 degree more than the ambient temperature.

Another strange thing happened, too 
When I rebalanced the system one month ago and when the boiler was serviced one week ago the pressure at cold (in the morning, before turning on) was 1.3 bar 
This morning at cold it was 1.6, even though the refill taps have been perfectly close all along.
How can the pressure have raised on its own accord?

What type of room stat do you have?
Most stats work by telling the boiler to go on and off. So if you set it one degree above current room temp, it'll come 'on'. If you set it for a higher temp than this, it tells the boiler to - yes - just come on the same amount. Ergo, for most stats, it doesn't matter what you turn it up to.
However, there are some boilers which have more sophist controls, and this might make a difference; one degree might tell the boiler, "Come on, but you are close, so only come on gently..."
So, make and model of controller?

The pressure issue may, or may not be an issue. Chances are it's just a normal variation. Eg, the system temp is not the same, even tho' you call them both 'cold'. For example, ambient temps will vary from day to day. Or, it may have fired up briefly during the night, so not as 'cold' as you think. What is your overnight temp set to?

The important thing is, does the pressure change much as it heats up? 

pieroabcd

It's a simple hive that turns on full power when it's on, not one of those that give just a kind push.
The water temperature in both cases was 26 degrees.
At night the thermostat is set at 8 degrees, so it definitely didn't turn on with the heat of these days.

When the boiler heats up the pressure raises to 1.9/2 at most, and after a while 

ThisIsWeird

If it's a Hive (like mine), then it doesn't make sense that the noise occurs if you turn it up by more than one degree, because - as you say - 'on' is 'on'. It ain't any more on.
Going up to 1.9 or 2 when hot is ok. Much more than this wouldn't be. 
If the pump bearings are worn enough to be noisy, then I can well imagine a scenario that increased pressure will affect it. The bearings tend to be 'plain' types, just a smooth sleeve to support the spinning shaft. What lubricates it is the system water, so that pressure will be 'pushing' on the bearing in some way, possibly moving the whole spinning part more in one direction = changing the contact point = more noise.
An experiment could be to reduce the cold pressure to 1 or even 0.9 - just release via a rad bleed screw.

badmemory

Are you sure it isn't the boiler cooling down after it has reached temp & stopped firing.

pieroabcd

badmemory said:

Are you sure it isn't the boiler cooling down after it has reached temp & stopped firing.

No, it was definitely still pumping