Combi Boiler Pressure Increasing

cwcw

We have a condensing combi-boiler. We had filled the system up enough for a pressure of around 1.75 when not in use. It had stayed steady at this, dropping very slightly over time, and going up to just under 2 when the heating is on.

However, over the last couple of weeks the pressure has crept up, and is now up at about 2.2 when not in use and approaching 2.5 with the heating on. This is starting to get worrying since we don't want to cause a burst in the system with the pressure too high.

Neither of us know anything about DIY. I don't even know how I can temporarily relieve some pressure to make it go down a bit. We have also noticed one of the radiators in the spare bedroom is stone cold, even at the pipes, when the heating is on. All the other radiators get warm. Could it be blocked? Could this cause pressure to rise?

Thanks in advance. :money:

UPDATE: Please go to Post #20 at the bottom of this page

espresso

Have you tried bleeding the radiators? see here
I think that 1.75 is a bit high for a cold system see here

ariba10

Make sure the valve or tap on the filling loop is closed.

economiser

It could be a failure of the hot water supply heat exchanger in the boiler. A leak in this will cause mains water from the the hot water supply piping to increase the heating system pressure. You won't "burst the system" as there is a pressure safety valve which will vent water to an overflow when the pressure gets too high, usually about 3bar.

cwcw

Thanks for the replies. I am going to try bleeding the cold radiator when I get a key later this week.

The failure of the hot water supply heat exchanger sounds expensive. We're just recovering from an obscene £400 plumber's bill for 1 and a half day's mending a leaking waste pipe in the bathroom. How much would we be looking at? And is it likely with the boiler only being a year or so old?

Canucklehead

How much would we be looking at?

Some obscene amount probably.

And is it likely with the boiler only being a year or so old?

Anything is possible.

Corgi Guy.

derrick

ariba10 wrote: »

Make sure the valve or tap on the filling loop is closed.

This could be the case, although under water regs, the filling loop should be removed after pressurising;-

"A gauge is usually provided to indicate that the CH system is under pressure. It will need occasional re-pressurising from the mains water supply so a facility for a filling loop (flexible braided pipe) is provided. To comply with the water regulations the loop must be physically removed upon completion."

IDEAL BOILERS

PasturesNew

If the system is working fine at the moment - and you're worried about the cost, sign up to the British Gas £12/month Gas Boiler service.

They come out and service it before they take it on (it works, it'll be reet)
You could mention it to the guy at the time, or you could wait another 6-8 weeks if it's not urgent, then put a call in about this



I loved the BG service because I had no more worries about the boiler packing up - and, more importantly - the minute it went wrong I knew WHO I was going to call. And how much I'd be charged .... £0.

I definitely saved money within 3 months on my boiler and over the 2 years I had the service it was pretty much break even, with me being a bit ahead.

But I gained in: knowing the system was safe, not being ripped off, knowing who to call, getting a yearly service done (included).

gasmanmartin

agree with the post above,

could be a number of things wrong, but first thing first, check the expansion vessell, with pressure rises this is the first port of call.

If you have the user instructions have a look to see what it says

cwcw

I've now bled 3 of the radiators, mainly the one remaining stone cold. I deliberately let out some water too and the pressure has reduced to 1.3 cold. After running for an hour it went up to 1.5 so it should drop back down to 1.3. The 'cold' radiator got warm. Fingers crossed it has fixed it.

The only other point of concern was that I tried disconnecting the filling loop from the tap. I did this at the end nearest the tap, not the boiler. I left it disconnected for a while but it was dripping (slightly), so I've put it back on. Is this worrying?

espresso

cwcw wrote: »

The only other point of concern was that I tried disconnecting the filling loop from the tap. I did this at the end nearest the tap, not the boiler. I left it disconnected for a while but it was dripping (slightly), so I've put it back on. Is this worrying?

So the tap is not sealing correctly and you are slowly but continuously pressurising the system, hence your problem of building pressure