Grrr.Combi boiler in new house.

misswoosie

Just bought a new house. Combi has been in since 2015 and replaced a traditional gas boiler with hot water tank in cupboard in one of the bedrooms.
The vendors provided the Gas safe register document for the installation and a British Gas safety check and "yearly service" dated about 2 weeks before we completed.
We've noticed that when the toilet cistern stops filling and when you turn a cold tap off, the boiler comes on. Not quite sure if it's just the pump coming on, or if it's igniting. Yesterday when I turned cold tap on and off, it came on and the temperature guage ( was at about 15 as hadn't had the heating on) didn't rise. Today when the heating had been on and the temp was reading around 40 it did start to rise. Only stays on for about 30 seconds.
I have problem a understanding how people could live with a combi boiler that fires up every time the loo is flushed and not do anything about it but that's beside the point. Should this not have been picked up by the British Gas man in the inspection? I mean, he gave the boiler an energy efficiency rating which I understand goes on the boiler make and age, but it's a bit meaningless if the boiler's not functioning correctly surely? The heating seems to work well otherwise although it seems like a noisy boiler. Maybe it's because ours at the moment is in a cupboard upstairs and this one's in the kitchen and not in a cupboard or anything.

In the cupboard where the HW tank was there's 2 copper pipes sticking up through the bottom of the cupboard (which is about 4 ft above the floor, as it's over the stairs) labelled HW and CW. They're capped off, both feel cold and seem to "wobble about in the breeze". Just in front of them a copper pipe comes up through the base of the cupboard , runs along the base for about 6 inches maybe, and then goes back down through the base of the cupboard. This is HOT when the heating's on. Bit dangerous actually as it's right at the front of the cupboard where a small childs hand could easily reach. We're getting someone out to look at it, but wondered if we had any come back from the installer or John from Birtish Gas?

misswoosie

On the Annual service, No 5 says "Appliance/system controls checked" this is ticked "yes".
British Gas didn't install the system.

silvercar

In the cupboard where the HW tank was there's 2 copper pipes sticking up through the bottom of the cupboard (which is about 4 ft above the floor, as it's over the stairs) labelled HW and CW. They're capped off, both feel cold and seem to "wobble about in the breeze".

They would. If the water isn't flowing through them, the HW in it would take a long time to heat up, if at all.

Just in front of them a copper pipe comes up through the base of the cupboard , runs along the base for about 6 inches maybe, and then goes back down through the base of the cupboard. This is HOT when the heating's on. Bit dangerous actually as it's right at the front of the cupboard where a small childs hand could easily reach.

So that pipe is part of the heating system. Maybe there was once a plan to put a small rad in their, if that is the airing cupboard. Doesn't sound like it is doing any harm. If you are worried about small hands touching it, then lag it. You can buy purpose shaped lagging for heating pipes; would make the heating very slightly more efficient.

Alex1983

It could be firing for a pre heat, most modern boilers the pre heat option can be turned off. Pre heat stores a small amount of hot water at all times. What make and model boiler do you have?

daveyjp

Definately sounds like pre heat.

Look up the boiler manual on line and find how to turn it off.

southcoastrgi

You have air trapped in one of the capped off pipes, get the pipes capped off lower

misswoosie

silvercar wrote: »

They would. If the water isn't flowing through them, the HW in it would take a long time to heat up, if at all.

So that pipe is part of the heating system. Maybe there was once a plan to put a small rad in their, if that is the airing cupboard. Doesn't sound like it is doing any harm. If you are worried about small hands touching it, then lag it. You can buy purpose shaped lagging for heating pipes; would make the heating very slightly more efficient.

Well yes. I realised that the water wasn't flowing through them! I was trying to convey that they must be the old pipes to and from the old hot water tank, and that they seem to stick up rather a long way and if the cold water one is still connected to the system somewhere the boiler could be thinking that (when cold water is run) the hot water is being run.
No little hands in our house, but the people before had 2 little girls

Alex1983 wrote: »

It could be firing for a pre heat, most modern boilers the pre heat option can be turned off. Pre heat stores a small amount of hot water at all times. What make and model boiler do you have?

Well our combi has pre heat, but it never comes on just after I've flushed the loo or when I switch the cold tap off. It comes on a lot more frequently and at random times so doubt this is pre-heat

southcoastrgi wrote: »

You have air trapped in one of the capped off pipes, get the pipes capped off lower

Thanks southcoastrgi. Is it the old cold water pipe in the cupboard that's still connected to the cold water inlet pipe somewhere? I mean, how much lower do they need to be capped off? They disappear down through the bottom of the cupboard and then they must be in under the upstairs floor and then in the walls as we have no boxing in running from the kitchen. House is only 20 years old. Guess I'm wondering if they're going to have to start ripping floorboards up etc?

Alex1983

Pre heat will come on at random times, that's the ideal of it to keep it hot at all times. What model boiler is it? Turn it off if possible and see if it stops before lifting floors and altering pipes and spending money.

If it doesn't stop then as southcost says it could be the capped water supplies creating dead legs, ideally when the boiler was installed the installer should of cut the 2 pipes back too the main pipework.

J_B

We have a paid of semi's in N Wales that we do holiday lets from.

The old(ish) Worcester 'fires' every time you run hot or cold water - I asked our plumber and he said that it was to do with a pressure switch and was designed to do that.

littlerock

i have a Worcester combi installed in 2016. It fires up when i turn the hot tap on, obviously, but i have not noticed it doing so when the cold tap is turned on or the loo is flushed. I will check and report back.......

Ok just stood next to the boiler in the kitchen and ran the cold tap. It did NOT fire up.

misswoosie

Alex1983 wrote: »

Pre heat will come on at random times, that's the ideal of it to keep it hot at all times. What model boiler is it? Turn it off if possible and see if it stops before lifting floors and altering pipes and spending money.

If it doesn't stop then as southcost says it could be the capped water supplies creating dead legs, ideally when the boiler was installed the installer should of cut the 2 pipes back too the main pipework.

Yes, I know preheat comes on at random times, that's why I don'tt think this is pre heat as it's not random. It's coming on every time the loo is flushed and every time the cold water tap is turned off. It's a Baxi Duotec 33HE.