Noisy Baxi Duo Tech 28e

[Yani]

Fitted new condensing boiler (Baxi Duo Tech ) 4 months ago. System flushed and magnaclean fitted.
No problems for 3months. Now when system is called for full heat DHW or CH really bad rattling from boiler.
When boiler reaches it's running temp quietens down. same if you slow up DHW flow or drop CH temp.
Cleaned out magna clean when this first started and there was a bit of sludge. This didn't help magna is fitted on CH return about 1 metre from boiler.#
Could I have a fan fault or even mixture problem. If you think it's a sludge problem how can I back flush boiler?

 

[arran197]

Could well be the air/gas ratio. Did you set it correctly when you installed it? Is it a MK1 Duo Tec 28 HE A? Also worth checking is the gas valve breather pipe from gas valve to the bottom of the fan (clear hose through the burner chamber).

 

[sparra1100]

have ye checked the standing pressure coming into the house think if they drop below 16 mb the dont like it as lack of gas
thats if your an installer otherwise will have to get someone out

 

[Yani]

Thanks for the speedy reply arran197. I installed the boiler but didn't commission it. The engineer who did is at present in hospital though I'm sure he didn't alter any gas setting just checked temps and leaks. Problem being the boiler is only 5 months old and still under warranty. I just need to be certain that if I call out heat team that the problems is the boiler I can manage most jobs myself as I'm an engineer but obviously the gas side is a big no no. I did try restricting the in side of the air flow on the flue as I thought that might richen the mixture but it only cut out the boiler. I bought the boiler from Plum centre so I presume it will be the current model

 

[Yani]

Not a corgi sparra1100 so your right that would need to be "special branch". Haven't had any pressure problems that I Know of and neighbour's all seem to be OK is the Pressure problem specific to this make and model?

 

[Shaunthegas]

If the noise is coming from the chamber I'd say the gas/ air mix is wrong. Check the Operating pressure in commission mode and gas rate.
If below 17mbar OP or well below 3.1m3/hr your problem lays there.

Check the gauze in the return connection (where filling loop is connected on to)
If that's clogged then sludge would prevent good circulation.

AAVs open inside the boiler?

 

[Billy Bob Bob]

i would put money on the gas pressures being out

 

[Yani]

Ok guys I think when I get home this weekend I will drop the magna clean again and see what it's like and also check the gauze in the return connection If there is signs of sludge would it be advisable to flush again and refill with inhibitor before I involve heat team. As i said I am not corgi so the gas side will have to be left to the experts. Any more checks that I can do? Just one more thing it does seem to exhaust pretty heavily as last boiler was a potterton 80 not sure what is norm with a condenser. Cheers guys for your help much appreciate any suggestions. John

 

[Shaunthegas]

Yeah the plume from the flue will be much more visible than the older boiler, this is the same with all condensing boilers.
But if it quietens down on low flame then I would be looking at gas pressures more.
Check how long the gas run is to appliance, it should be at least 22mm from meter to the final connection.

 

[Yani]

Yes Shaun the gas is all 22mm

 

[RB PLUMBING]

where dose it sound like its coming from ?????

 

[Poxi]

Co needs to be checked with a anayliser,
Needs to be put in Flue sweep, Max Co 8.7 +/-0.2 Min Co 8.4 +/- 0.2 As per MIs

Boiler is set in the factory to fire only when first installed, Co`s have to be adjusted according to flue types and flue lengths.

Anayliser is critical on all HE boilers now days

 

[arran197]

Does it sound like it's kettling though? Or is it banging. If it does it on start up then it's almost definitely a gas/air mix wrong or the pressure. The gas valve needs adjusting to make sure the ratio of air to gas is correct to burn. It is factory set so it lights up, but will need adjusting so it is absolutely spot on. If it's set wrong you will have problems with over/under gasing and potential co risks.

 

[Yani]

Only really bad when first on full demand. Sounds like using a hammer drill on hard brick. Once it reaches operating temp and eases off not so bad but still noisier than when first fired up. All noise seems to come from burner chamber. Hope this helps. Oh through all this it has never cut out.

 

[arran197]

Well the easiest and cheapest thing to check first is the gas ratio.

 

[sparra1100]

yep cos once its got to temp its using less gas ,probs low pressure coming in the house or pipework to long or to small somewere altho you said its all in 22mm needs an analyser on it or gas rating on engineers mode you need someone gas safe to lok at it cos heatteam probs wont come out if it not registered it defo sound like a gas problem and if its factory set its unlikely to need adjusting unless its been messed with if was gas valve fault it would have done it from the start

 

[Jonwells]

The boiler needs to be re commissioned, if the original engineer is poorly, then it needs to be completely recommissioned. Using his figures on the BENCHMARK the original engineer could back track and see if any perimeters have changed, then see if it's appliance problem. All figures need to be checked, co ratios, wp, wp at meter,gas rates etc, I have only fitted about half dozen duo tech, but get it recommissioned, strange though, it has been okay for 4 months. Has the meter governor been changed. Jon

 

[Yani]

Ok I've just cleaned out the magnaclean not a lot in there just a tiny bit of silt. Bled the whole system twice and checked the condenser pipe is clear. There is loads of heat on all rads and DHW water pressure is OK on cold and hot. The only time now I'm getting the noise is when I ask the boiler for a big output. If I take the temp up in stages no problem, but if I ask for max demand from cool then it gets really noisy. As the service manual states there should be no need to adjust mixture on a new boiler I'm going to get heatteam to address the issue as a warranty problem. I hope you all agree with this course of action if not let me know your suggestions. John

 

[tipintim]

I bet its the presure gauge needle rattling.

 

[Yani]

Well I believe problem solved. My fault I'm afraid when i fitted the new boiler I was left with the problem of where to put the pipe for the condenser outlet. I thought that rather than put another hole in the wall and have the 6 foot pipe run outside exposed to the cold weather I would run the pipe along the inner wall the rear of the kitchen units and run into the sink outlet. As there was already a fitting in the pipe I used it which was before the U bend and trap. All was OK until my wife puts a bowl in the sink which covers the plug hole. Then this noise appeared. If I disconnect the pipe then the noise stops. I believe now that the condenser pipe was just pressuring up causing the unbalance. so now I will run the pipe through the external wall at the boiler and into a 32mm pipe to the outside drain. Only hope it dosn't freeze come the hard weather.