Baxi Duotech boiler pressure getting too high

[PULLMYFINGER]

Hi,

Hopefully someone could tell me how to sort this problem out or if i need to call out a service engineer. Basically i came home from work 2 days ago to a cold house so i checked the boiler as a starting point and noticed that the pressure was at zero and the cupboard was soaking. I quickly found the source of the water as my Magnaclean leaking from where the big cap screws on. I gid a bit of googling and found it was quite a common problem and possibly just the O ring washer. Some information mentioned taken the cap off and looking to see if the o ring had degraded and replace it. I found information from Magnaclean about servicing and cleaning so i did what is said - found a bit of sludge build up so cleaned it of rinsed the Lid with the o ring washer as it felt a little gritty. Put the Magnaclean back together turned on all the valves and power etc....re pressurised the system as instructed via the filling loop valve to get up in the morning and the heating is off. Pressure is back at zero but Magnaclean is bone dry and hadn't leaked as i even left a pan under it just to check for random drips. and that was bone dry too. o re-pressurised the system via filling loop again bleed radiators to check no air was trapped but again it was at zero this morning and everything bone dry, so i re pressurised it again and watched as the heating kicked in and the pressure rose quickly to over 3 bar so i tuned the thermostat down heating knocks itself off and returns back the the green zone - around 1.5 bar. If i run hot tap water its fine and pressure dial doesn't move only when central heating is on.

Any tips or assistance would be great before i call someone out and spend a small fortune.

Thank you.

 

[TeaTime]

Is the pressure still dropping to 0bar, even after the over pressure?

Also, what modle of duotech is it...28 ...40?

 

[PULLMYFINGER]

Hi,

I'm not sure as it happens over night when heating is on or i'm at work. I did watch it for around 15 mins this morning after i re pressurised it and it rose to 3 bar once heating kick in as house was cold and like i said turned the thermostat down so it knocked itself off and it slowly dropped to around 1.5 bar. i tried again turn the thermostat up and it rose to just over 3 bar again so left it for around 4-5 mins running and it just sat at the 3 bar location so i knocked the thermostat back off so it didnt fire up while i was at work. Then wore lass jumped in the shower and it stayed at 1.5 bar while hot water was being used with no issues so seems its just the central heating

Its a Baxi Duotech he 40

 

[PULLMYFINGER]

If left for longer it may well drop to 0 bar as i assume thats whats happening overnight.

 

[TeaTime]

Are you pressurising to 1.5 bar?

 

[PULLMYFINGER]

yes 1.5 bar every time that what the manual said.

 

[TeaTime]

Well, the pressure dropping completely may be due to the PRV not seating back down after it has blown. I assume you have noticed the PRV has lifted?

Any fault codes noticed?
Have you diconnected your filling from the double check valve, to make sure it isn't passing?

It could be a mixture of your PRV not sealing when it re-seats, due to crud being in the mechanism & your expansion vessel needing repair / replacing.

Get an engineer round!

 

[PULLMYFINGER]

I have no idea what a PRV is (sorry)


Engineer it is then...cheers for your help

 

[TeaTime]

PRV is a pressure relief valve, stopping your central heating sealed system from becoming dangerously over pressurised and potentially causing you and your family a load of heart ache. When the pressure get's to a certain level, they are designed to lift and let the excess pressure out of the system.

Good choice on the engineer.

 

[PULLMYFINGER]

So i'm guessing (be gentle as i'm not clued up) when the PRV goes off does it dump water outside via the bit of copper pipe poking out my wall in the garden? so i should be able to see evidence of water on my wall.

Still getting an engineer out though..

 

[TeaTime]

I doubt you will see evidence of water on your wall, since it will be heated water and most likely disappear by the time you get there, but yes, that is how the PRV works on your boiler.

 

[PULLMYFINGER]

Just an update in case anyone has read this and thought Oo that description is the same as my boiler. British gas has been round and had to re pressurise the expansion vessel inside the boiler as mine was flat as a pancake apparently. Didn't see how he did this but it didn't take him long. Plus I got the boiler serviced too.

This post is for informaton only as I have no idea I this is a simple DIY fix or more involved.