Soot on fake coal cause?

brie27 · 20-03-2025 10:37AM #1

Hi everybody,

I have a gas fire in my living room with the fake coal that the gas heats to throw out heat into the room. It's costing me about 120Euro a month to run, sometimes even more. lately I've been getting a soot build up on the fake coal, and every few days I've to uninstall the coal, clean it (hoover) and re-install the coal, but I am always concerned about the placement of the pieces for optimal heat, and I don't think there is an answer for this. Can anybody help me here? - Why is the soot building up, where in the past there was no soot, or it formed over a year or so, now it's days. Is there a perfect fake coal placement set-up? or a gas dispersing design of insert that increases the efficiency of the fire? - There are a few questions here, so ALL replies are greatly appreciated.

Here are the images of the soot on the fake coals. Can anybody explain why this would be happening more often, almost weekly now. Is it the gas?

The soot hoovers off easily enough, but it I've to lift and replace he 'coals' every time. It's also a messy job. Thanks for the advice in advance.

mickdw · 20-03-2025 10:48AM

If its the gas unit in an open fireplace with chimney, they are hopelessly inefficient and really are only for occasional use. Everyone I know who had them got rid due to running cost.

I would get it checked by qualified gas plumber cause the sorting doesn't sound right if it's now more frequent.

brie27 · 20-03-2025 11:06AM

https://www.boards.ie/discussion/comment/123280635#Comment_123280635

It's in daily use 2pm to 10pm most days. I don't want to engage with a gas plumber until I know what to get because my experience has been, they are (for he most part) selling me something, and I am hoping the community will provide a good advice.

10-10-20 · 20-03-2025 11:14AM

Bearing in mind what mickdw said, it's likely to be the log placement causing it. The logs are supposed to be around or on the periphery of the sources of the flames and not directly in the path of the flames as otherwise they cause incomplete combustion of the gas due to their lower temperature than the flame. The gas itself needs to mix with air through the full distance of the flame, and the logs prevent that in places, so you end up with localised deposits where the flame runs coolest and where the air didn't manage to reach the inner part of the flame.

So turn off the gas at the isolator and dismantle the logs and any vermiculite on the base. Sieve the vermiculite to rempve broken down pieces (or replace it) leaving larger chunks in a thin layer around the fireplate. Then place the logs back on as per the original layout (yes, annoyingly, the manufacturer will have chosen where you should place the logs). Then turn it on and make any small adjustments after that.

Finally, while you're at it, have a check of the room vent to ensure that it's present and still open, take down the internal over and clean it out if needed. Keep safe!

brie27 · 20-03-2025 11:23AM

https://www.boards.ie/discussion/comment/123280710#Comment_123280710

Thanks 10,10,20. This is the kind of outcome I was hoping to avoid. I have been cleaning the coals when the soot builds up, and its been after a yearly clean and re-placement that the soot started to increase. Your explanation makes sense, but with the flame burning high it seems I am loosing a lot of heat, and this is probably just how it is with these fire to chimney flu gas fires. I am seriously considering changing form this fire to a flueless gas fire, but they have a lower heat output. I realise I should try to see what the gas consumption per hour is of my existing fire. Hopefully I can find that out.

mickdw · 20-03-2025 12:47PM

We looked at these fires as price wise they are quite reasonable but the efficiency with chimney is just too low to run it all day every day. Very handy versus solid fuel but the costs are high.

10-10-20 · 20-03-2025 03:35PM

https://www.boards.ie/discussion/comment/123280743#Comment_123280743

https://www.boards.ie/discussion/comment/123281027#Comment_123281027

Agreed, they are a waste of energy. You only benefit from the very small amount of radiated heat as all of the convected heat is lost up the chimney. I think efficiency of around 10 to 15% would be reasonable for them. A gas stove would be a much better investment especially if it was run off a balanced flue or air external air inlet.

brie27 · 20-03-2025 04:43PM

https://www.boards.ie/discussion/comment/123281027#Comment_123281027

Mick, when you say these types of fires, what types of fires do you mean? because there's a wide range of gas inlet and venting combination options. From what I've read, and considering our situation, which is a traditional fireplace and block flue lined chimney, the bumph says the glass fronted High efficiency gas fires can be up to 94% efficient, and will deliver 3-5kw which is good enough for our 4.2x4.2x2.6H room. I have to find a comparison between the open flame style gas fire vented via a traditional chimney and a Glass Fronted High Efficiency Gas Fire. OK, I just checked this and traditional gas fires with an open flame and chimney vented would be 60% efficient. If these efficiencies translate into cost savings it would result in 350 euro saving a year, possibly up to 450. It's not a no brainer because fires can cost up over 1000, but it might be worth considering if over 10 years the saving add up, even over 5 years the savings add up.

mickdw · 21-03-2025 11:55AM

Im referring to those units that go into an existing open fire and draw air from room and exhaust to open chimney. They have very low efficiency.

The More efficient are flueless open fires or room sealed stove type arrangements.

Soot on fake coal cause?

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