Valliant Boiler 15 February at 7:47PM in Techie Stuff 13 replies 380 views

brucethefish

Hi

Got a strange problem with my boiler, I turned the heating on last night and realised the radiators wernt getting warm, and had to top up the boiler

I had a shower this morning, came home from work and it sounded like the boiler had been on all day.  I turned the heating on, and the pressure dropped, but it seemed to struggle to get past 50 degrees.  After fifteen minutes or so it had hit 70 degrees like normal. 

Any ideas?!

Grey_Critic

I suggest you get a heating engineer

RumRat

 it 'sounded like the boiler had been on all day'.   What did that 'sound' like?

brucethefish

I’ve just come down this morning, the pressure was low so topped up again and it’s fired back up, the thermostat is off and no taps are on

Ayr_Rage

brucethefish said:

I’ve just come down this morning, the pressure was low so topped up again and it’s fired back up, the thermostat is off and no taps are on

You have a leak somewhere in the heating circuit.

Newcad

As the pressure keeps dropping then you you may have a leak on your pipes/radiators.

However it's much more likely that the expansion vessel inside the boiler has failed and needs recharging with Nitrogen gas or replacing altogether.

Boiler expansion vessels will/can last for years but they do fail.

When a boiler expansion vessel fails the system will go overpressure and so dumps water out of the pressure relief valve.
When things cool down again the boiler needs topping up to replace that dumped water.

You may be able to see this, if you can see where the pipe comes out the outside wall then the dumped hot water will have run down the wall.
It's a small copper pipe that is usually bent to point back towards the wall, although older ones may just point down.

If you can see water/damp on the wall there, or if you just want to be sure, then get an engineer out to check the boiler.

Whilst a boiler can be run for a while with a failed expansion vessel it's not good for the boiler and will cause other components to fail, plus it's inefficent so increasing your gas bill.

brucethefish

Hi

It only had a new expansion vessel fitted in November 22

IM not sure (but hoping!) that comfort mode has been running since then - I spotted the "C" on the display this morning and turned it off - see how that works out now

Newcad

Have you checked the pipe outside?

Just because the vessel was recently replaced that doesn't mean it hasn't gone again.

(And you have to wonder if it was replaced or just rechared and the new gas has now leaked out, 3 months might be about right for that to happen).

brucethefish

I did last night, it had been raining but its usually obvious where it has blown out

He tried recharging it last time which worked for a week, but then he had to replace it a week later as i had the same problem (pressure constantly dropping)

Newcad

It does sound as if you have a leak then, and a pretty bad one if the pressure is dropping a lot overnight.

If it's under the floorboards then good luck finding it, you might find a phone endoscope/wifi endoscope useful for that, or your plumber may already have one.
They are not too expensive and you'll find them with an online search.

Le_Kirk

You could try posting here: - https://forums.moneysavingexpert.com/categories/in-my-home-includes-diy-moneysaving
There are some helpful knowledgeable posters there, not that the answers here haven't been helpful. I am not sure that expansion vessels are filled with nitrogen.