New Boiler too powerful??

[mastersc]

Just have my old Ideal (17kw) boiler replaced with a Worcester 24ri.

Never had a problem with the old system, OK pipes creaked on start up buts thats the house(wooden frame) install rather than the boiler. however on the new boiler when I turn the temp gauge on the front of the boiler to over half way, the noise really increases and the expansion tank in the loft starts to steam as the system vents.
I believe the wiring controls to the thermostat in the hall are fine, both back up to the cylinder/pump in the airing cupboard and to the programmer is in the kitchen by the boiler but I will get these checked.

So can the new boiler really be too powerful, or should the system still work fine even with the boiler temp control turn up high? Its a 4 bed detached.

 

[petertheplumber12]

Boiler should be fine but the plumbing is the problem. You must have the air vent and cold feed in the wrong places. They should both be on the flow in airing cupboard before the valve or valves that feed the heating or hot water. And preferred way is to have the flow rising from the boiler and before it goes horizontal it tees into a vertical air vent of 22mm going to F7E tank. then a cold feed teeing into the same feed pipe before it branches to any valves and within 150mm of the vent.

 

[Agile]

If tbe old boiler was adequate then why did you choose a 24 kW when an 18 kW would have been adequate?

Tony

 

[mastersc]

I'm not a plumber just the owner, to be honest every firm said I should fit a 40kw for the size of the house, I said the old one heated the house OK, but all the online say 4 beds, 2 baths 13rads is 32-40kw.

Peter, would the plumbing have been like that for the old boiler then and I might not have noticed it or likely to be an install error, was only the boiler in the kitchen changed, no pipework in the airing cupboard touched.

With the dial turn down to near minimum it heats the house up fine. What I don't understand is what difference turning the temp dial does an why it boils over as surely its not that hot. I read 35deg min to 82deg , I reckon its about 1/5 of the way round, probably 40-45ish at a guess as its a crappy dial with no numbers.

 

[McCombi]

System fault. Pump,cold feed, open vent problem. Was the pipe work changed, or has the height of boiler or feed and expansion tank been altered?

As tony said why did you go for a bigger boiler size, more rads or plan to?
To work efficiently the boiler should be rated to the required kw rating to suit the property.

These boilers need a system bypass and have pump over-run, maybe it's pumping over into tank as pump not been wired correctly to the boiler (not the wiring centre) or there isn't a suitable bypass circuit.

Could be anything, I advise getting your installer back or one who knows what they're doing if its been like that from the start.


Edit,, just saw your post.
Where is the pump wired to?

 

[McCombi]

Maybe I'm being cynical but sounds like it was fitted by someone who has no idea what they're doing. It would have been tested at max rate if commissioned correctly, and sized correctly also. (Hope it wasn't me.....)

 

[mastersc]

cheers,

the boiler moved up the wall prob 10cm max.

Tanks haven't moved.

Bigger boiler on plumbers advice, had 3 quotes + BG all said I needed bigger than the 24 I got, which just having checked http://www.boilers.org.uk/ and done their calculator it comes out at 18.8kw.

I know the wiring isn't great to the controls(something about switched lives plus moving the programmer to the airing cupboard so its out of the kitchen, got a sparky coming next week to rewire and put in the pump overrun cable which it doesn't have, so this may fix it as you suggest.

Not sure where the pump is wired to, I guess the controller downstairs?

Unit was only changed yesterday so its still work in progress. Cannot see how the wiring would alter how its working at the moment.

 

[gas112]

if it was only changed yesterday why are you not speaking to the installer instead of asking on an internet forum

 

[mastersc]

if it was only changed yesterday why are you not speaking to the installer instead of asking on an internet forum

Helpful thanks.

I am talking to them don't you worry , as I am not a plumber is it not best for me to get some knowledge so I can ask them sensible questions and not get taken for a ride.

 

[petertheplumber12]

It is always a good idea to know what sort of question to ask, and enlightening yourself with a bit of clued up nohow. Get them to check the vent and cold feed arrangement anyway. The pump overrun should be done before a final judgement is made.

 

[mastersc]

Thanks Peter, I think it needs balancing aswell some rads are hot at the top and cooler at the bottom.

If I posted pix could you seen the things you mention about the vent and cold feed.

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[petertheplumber12]

I need to know where the air vent is that takes the air out before it goes into the pump. And is the cold feed on the same pipe within 150mm of the vent? When rads are hot at the top and cooler at the bottom it is sludge not balancing you need to take them off tale them into the garden and turn them upside down push a hose on one end and at full flow run water until black stops coming out then still sunning water tap the top on the side which is now the bottom and use a composition mallet or lump of wood rapped in cloth hitting them until black stops squirting out.

 

[mastersc]

I need to know where the air vent is that takes the air out before it goes into the pump. And is the cold feed on the same pipe within 150mm of the vent? When rads are hot at the top and cooler at the bottom it is sludge not balancing you need to take them off tale them into the garden and turn them upside down push a hose on one end and at full flow run water until black stops coming out then still sunning water tap the top on the side which is now the bottom and use a composition mallet or lump of wood rapped in cloth hitting them until black stops squirting out.

Thanks Peter. I will read up, have a look and also ask the plumber tomorrow.

I also noticed tonight whilst washing up that when I empty the sink(ie as soon as the last bit of water goes down the plug and the plug is now exposed) the boiler seems to gurgle. Looking at the condensation pipe from the boiler its been added under the sink. I have the 2 sink traps coming into one pipe then the boiler drain pipe is connected before it hots outside.

Sinks > U bends > Boiler Pipe > Outside.

I looked at the install manual that was left and I think this looks right

Is this causing the water to be pulled from the boiler? This is new as the old boiler that was replaced was 12 years old and didn't have the drain pipe.

 

[petertheplumber12]

It would be possible for a ventury effect to occur especially if the condensate extends too far inside the fitting so that the water that falls past it is causing a negative pressure on the condensate trap inside the boiler. If the gurgling is only heard when the water drains away then that problem MUST be resolved because that trap inside the boiler must not be left empty at any time, The installer is supposed to put water into the boiler to make it run from the condensate before firing it. The reason is that the drain for condensate comes from the combustion chamber direct and if the trap in the boiler is empty then boiler fumes can pass thro' the condensate drain pipe. It is much better to install the 22mm drain into a horizontal section of waste pipe. Or take it outside direct from boiler in 32mm pipe so that it can't freeze. Also I hope the external drain know as B I G is cover with a plastic cover not cast iron as steel is not allowed because the condensate is acidic and rusts steel.

 

[mastersc]

ah thanks, thats worse than my other problem! oh fun!

Going to be a good day tomorrow trying to sort this out on the phone as I expect the installers will be booked up. Never have one fitted on a Friday!!

I think the drain is all plastic with a cover over it. Will check in the AM.