Ludicrously interesting boiler question

Eric999

Anyone any good with boilers?

We've got a Vaillant boiler that's been pretty good, the shower used to be proper hot, especially in the summer when it was too hot but some of the radiators weren't great so I bled them about 6 weeks ago and since then the water has gone proper tepid.

Thought it was the pressure in the system as that was way too low so I put more water in it and the pressure goes up to about 2 bar when the heating is on. The water though is still not warm enough even when it's up full.

The tap in the kitchen is right next to the boiler so that's usually pretty fine, it's the shower that's not.

When the heating is on and the boiler says like 80 degrees or something, the instant you turn the water on it plummets to around 35-42 degrees, even when it's turned up to full.

I can't find a model number or anything for stuff to specific and the only real instructions I found just said turn the dial up.

Here's a picture of the boiler.

Anyone have any ideas?

Cheers

AndyPK

Do u have a hot water tank in airing cupboard

AndyPK

Try turning top knob to the 3 o'clock position

rds60h

The mistake you have made is that you have bled the radiators, you should only bleed radiators if you have the old style back boiler.
With a Combination Boiler like you have you do not touch the radiators, you need to re-pressurize the Boiler.
This is done by using the mains water pipe on the boiler and connecting the filling loop, there should be plenty of videos on the net showing how to do this. Your pressure should be between 1 and 1.5 Bar.

CashStrapped

It is a combi, so as others have posted you do not always have to bleed the radiators in the traditional way. If you do, you have to re-pressurise the system. It does sound like you have attempted this.

When did you last get the boiler serviced? If it has been a while or never, you should consider getting it checked over by a Gas Safe engineer. You may cause more issues than you solve by trying to dabble and attempt a fix yourself via information from a forum.

stator

rds60h wrote: »

The mistake you have made is that you have bled the radiators, you should only bleed radiators if you have the old style back boiler.
With a Combination Boiler like you have you do not touch the radiators, you need to re-pressurize the Boiler.
This is done by using the mains water pipe on the boiler and connecting the filling loop, there should be plenty of videos on the net showing how to do this. Your pressure should be between 1 and 1.5 Bar.

So how do you get trapped air out of a radiator if not by bleeding it?
It sounds like he did reperssurise the system using the filling loop?

Eric999

rds60h wrote: »

The mistake you have made is that you have bled the radiators, you should only bleed radiators if you have the old style back boiler.
With a Combination Boiler like you have you do not touch the radiators, you need to re-pressurize the Boiler.
This is done by using the mains water pipe on the boiler and connecting the filling loop, there should be plenty of videos on the net showing how to do this. Your pressure should be between 1 and 1.5 Bar.

I've bled them now and the radiators are a lot hotter. I did follow some guides and stuff on bleeding them and I didn't come across that anywhere.

This video looks to have almost the exact same issue, don't bother watching it as it's useless and offers only some cryptic clues about what might be wrong with it but in the comments it says the 'Aqua Sensor' was what needed replacing. Does that sound like it might be what's wrong with it?

Ours definitely does what the one in the video does, gets up to 80+ degrees when the heating is on and then just plummets as soon as you turn any of the taps on.

Eric999

CashStrapped wrote: »

It is a combi, so as others have posted you do not always have to bleed the radiators in the traditional way. If you do, you have to re-pressurise the system. It does sound like you have attempted this.

When did you last get the boiler serviced? If it has been a while or never, you should consider getting it checked over by a Gas Safe engineer. You may cause more issues than you solve by trying to dabble and attempt a fix yourself via information from a forum.

The landlord came and did his thing with it in the past year, think it was more of a safety check than a service. I have no idea what that entails though so I couldn't say.

It looks like he's going to have to send someone round though this week so hopefully that guy will know if it has been serviced recently.

I agree completely with not dabbling but I suppose that depends on the recommendation. I didn't know about the pressurisation until after and that turned out to be a 3 second fix.

stator wrote: »

So how do you get trapped air out of a radiator if not by bleeding it?
It sounds like he did reperssurise the system using the filling loop?

yeah I did, it's now back up around 1.5bar.

Robwiz

If the radiators are cold at the top then it's trapped air. If they are cold in the middle or at the bottom then that's a build up of sludge, which needs flushing out.

When you draw hot water, the full power of the boiler goes into heating the water and not the water in your radiator circuit. If the heating thermostat is calling for heat the pump should still be running so the temperature will fall as the circulating water returns to the boiler.

As others have posted though, probably worth getting a gassafe engineer in to check it.

ollski

What does it do if you run the hot water tap at a slower speed?, does it get warmer?

CashStrapped

Eric999 wrote: »

The landlord

You said the L word!

Not your responsibility, if there is a problem, it is theirs. I appreciate not all landlords are good or will respond quickly to repair requests etc. However, it is not your boiler to try and attempt a repair on. The cheapest option is to contact the person who is responsible and get them to fix it.