Hot walls

[gary.ellis]

Hi,

I've moved into a house and had a couple of jobs done (in this order)...

1) Got cavity wall insulation fitted 2) Replaced the electric fire with a gas fire

Both jobs have been done by "professionals".

The gas fire uses a pre-cast flue which is connected to a raised roof tile on the top of the house.

Recently, when the gas fire is on at over 50%, I've noticed the wall in front of the metal flue is getting extremely hot. So much in fact, the paint is starting to blister, and the walls are too hot to touch.

I'm a bit stuck at what to do next, other than not use the fire. Any suggestions?

Thanks in advance.

[Ian Stirling]

I assume you've paid the 'professional' that fitted the fire? Call them up. "I've got a flue the paint is blistering over, is this normal, or can you come along and fix it". "Oh, you put it in, now get here pronto before I call Trading Standards" ?

[bigcat]

Where is the problem exactly? If its the paint, you should use heat resistant paint, stripping off whats there now first.

NT

[Gaz]

Hi,

Thanks for the replies. Yep - I paid for the work to be done. I've called the company who installed the fire. Hopefully I'll be hearing from them tomorrow.

The paint is flaking off on the wall between the fire surround and the ceiling. Also noticed that in the upstairs room above the fire, the plaster has a hairline crack in it. I guess the flue is at the other side of the cracked plaster. The plaster is not new.

If worse comes to worse, I'll get the "company" to do a deal and replace the gas fire with an electric one.

[bigcat]

very odd.

[BigWallop]

If the wall is getting that hot, then something needs to be done before it gets worse. The pre-cast flue is made of what? Is it an old chimney stack?

[bigcat]

I must be in a brain warp here: as I see it, a hot stack is a _good_ thing, it means youre recovering more of the heat out of the appliance, making its heating more effective, more powerful, reducing gas cost and emissions.

If your paint cant take the heat, use some that can. The coal burner I used at one place made the metal stack roasting hot, lovely, all that heat. Luxury. It was finished in high temp paint, black to maximise IR radiation.

Its no more of a safety isseu than having a kettle, those get hot too. No idiot touches it twice. I'm assuming the house construction is in line with the 1924 build regs, with struc woodwork not touching the chimney stack. Pre 1924 properties noramlly are, as its basic common sense.

NT

[Gaz]

In the loft, the flue looks like it's made out of metal. I'm not sure if the metal goes down to the fire, or if it's something else.

The hot stack is getting too much heat. The wall above the fire surround has paint blistering off the plaster. The room upstairs has a gloss skirting board that's too hot to touch. It seems like a fire waiting to happen.

I've been having a chat with a few people at work, and it seems like the air vent at the top of the fire is too big. The vent on my fire is about A4 in size. Most people's fires seem to have smaller vents. I think the bigger the vent, the more heat is getting chucked up the flue, rather than into the room.

Does that make sense?

[BigWallop]

It all makes sense alright, but the fire was fitted professionally, wasn't it? It could be that the flue liner, the metal stack you talk about, is far to close to the surface for the type of gas fire you have, but it was fitted professionally, right?

I think it's time you showed the installer what is happening, not just talking to them on the phone. Tell them you want an engineer to come round and take a look, or have a feel in this case, and work out exactly what the problems are.

If it is getting as hot as you're saying, then the surrounding areas of the flue are, in my opinion, getting close to combusting. Get them back to have a feel.

[John]

If it is a flueblock flue then a change to "double" skinned metal flue pipe within the loft is normal

Have you posted details of what the fire actually is? Also is it suitable for the fuel in use, i.e. if it is running on LPG is it an LPG model or is it a Natural Gas model with larger injectors (jets) which would produce a much bigger flame (and heat) than it should have.

It might but your description of a "vent" requires clarification. Are you talking about an overfire flue break which will admit "lots" of cooling air and thus could be expected to actually cool the flue products rather than overheat the flue. The construction of the flue may not be to standard. Has the flue been used for a gas fire before this? I think you should speak to the manufacturers technical department

>

[bigcat]

so far so good. Check how close the woodwork gets up there if youve any doubts.

That makes little sense

so use suitable paint, or use a big metal hood.

Just how hot is it? What is the temp required for spontaneous combustion to occur? I think youll find those 2 temps are miles away. If not, you must have quite a furnace in there. Not an industrial monster is it?

I doubt it. You havent told us which air stream goes thru the vent, so we really dont know whats there.

I really think you dont know what whats going on yet, a good idea might be to draw us a diagram or pic so we know what this vent is about, and what the layout of the various bits is, including how far woodwork is from the flue.

I presume you have a single walled metal flue, not double wall as is common with gas appliances. But I've still heard nothing to indicate that there is a safety problem. All I hear is its nice and hot when you expected it to be cool...

NT

[Gaz]

Thanks for all the advice. A few answers (and a result?)

Yep - the fire was professionally fitted by a company.

I have been told a fire was originally installed. Although it's dubious why the last owners replaced the fire with an eletric one.

The wall is too hot to touch.

The fire uses natural gas, with injectors I think. Not sure if any of the previous fires used injectors.

I read the installation book that the fitter left behind last night. It appears that I have a pre-cast flue, meaning that I've got a load of concrete blocks with a hole in them going to the loft. Once it's at the loft, I've got a metal pipe going to the raised roof tile. The plaster has been applied directly to the concrete block, with no insulation.

According to the installation book, a new standard BS EN 1858 (i think) published in 2003 says pre-cast flues must have insulation between the concrete and plaster. It also says if it doesn't have this insulation, no gas fire is suitable for the flue. (does this mean no gas fire with injectors?). Looks like I'll have to opt for a balanced flue fire, or a electric fire.

As the installer fitted the wrong type of fire for our house (although it would be difficult to tell if the plaster is applied directly to the concrete during the survey), I imagine I'd be able to "do a deal" on the replacement fire.

Anyone know if it's common for pre-2000 houses to have pre-cast flues with plaster stuck directly to them?

[Gaz]

This is what the problem is... i quote...

This appliance has been tested for use in a pre-cast block flue complying with BS 1289. In accordance with BS

1289 part 1, pre-cast flues built with directly plastered faces (front or rear) are not correctly installed as to ensure proper operation with any type of gas fire. In some instances of this flue construction, temperature cracking of the surface plaster may occur through no fault of the appliance. An air gap or some form of insulation material should be installed to prevent normal flue temperatures from damaging wall surfaces.

[BigWallop]

Then you've answered the question. The flue doesn't suit any gas fire, of any type, model or structure. Either get the flue fixed, or go for an alternative means of heating.

[bigcat]

damaging

I cant agree with your conclusion. Just because a new standard says new installs should be done this way to prevent any chance of the plaster cracking doesnt mean its no good. Very little in old houses meets new build regs, and they dont need to.

The OP should stop getting his knickers in a twist and get on with life. Your plaster has a slight chance of craking. Oh no, not the dreaded small chance of using polyfilla!

You might be able to get some money back off the fitter if its not fitted to the latest regs, enough to have it 'fixed' but why youd 'fix' it I dont know. What same person chooses to have more heat go up the chimney for no benefit? Ignorant customers can be a royal pita.

NT

[John]

CORGI Registered I presume?

It may well be for the same reason as you will have to change yours

Injector is the term for the jet or nozzle which the gas passes through. In general all gas appliances have them

Therein lies your problem. You now have a decision to make. either change from a flued gas fire to one with a balanced or power flue or have the chimney breast replastered using plasterboard with dot and dab to provide an air break between the hot blockwork and the finish.

This is probably the simplest and most cost effective solution.

Good luck

Unfortunately its all too common.

[ellisgm]

thanks BigWallop & John!

[ellisgm]

Are you a retard or cowboy?

If an old granny paid =A31400 for getting a fire fitted, you can't expect her to be whipping the polyfilla out every month to repair cracks. Not to mention the having to constantly paint to the filler.

[bigcat]

no

That is not at all a realistic description of the situation.

nor is that. Lots of houses have uninsulated flues and are fine. Its silly to get knickers in a twist over it.

NT

[ellisgm]

sorry about the insult. I've just been getting it in the neck from the misses, and getting told to "stop getting his knickers in a twist and get on with life " didn't help.

Now that I know lots of other houses have similar problems, maybe I should just live with it.