What is a flue on a boiler?

Asked By: Doncho Zanoni | Last Updated: 11th April, 2020
Category: home and garden home appliances
4.4/5 (224 Views . 29 Votes)
A flue is a duct, pipe, or opening in a chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. Historically the term flue meant the chimney itself.

Click to see full answer

Beside this, is boiler flue gas dangerous?

The gases that the boiler flue disperses outdoors, including carbon monoxide, are potentially harmful, which is why the regulations surrounding them are getting stricter. Boiler flue regulations ensure that the gases being expelled don't re-enter the home, which would instantly make the flue redundant.

Furthermore, what happens if a boiler flue is blocked? A blocked utility flue serving a gas water heater, furnace, or boiler can mean serious problems. A blocked flue can cause deadly Carbon Monoxide back up into the home, and is the primary reason for shutting down the system when this occurs.

Similarly, should a boiler flue be sealed?

The flue should be properly sealed on both sides It should be sealed using sand cement or equivalent material. It must be sealed properly so no exhaust fumes can come through into the building.

What is the maximum length of boiler flue?

The design and diameter of the flue will determine its maximum allowable length. For example, a 60/100mm concentric flue fitted to a system or combi boiler can be a maximum of 10m long.

37 Related Question Answers Found

Should boiler flue smell of gas?

The smell of gas is actually added in as a safety feature because gas itself is odourless. So what they were smelling was the unburnt chemical that was coming from the flue. This is actually fairly normal. So if you want a professional gas boiler engineer to check over your boiler system, give JSL Heating a call today.

Why is my boiler flue dripping?

weargas. The flue should rise from the boiler to outside so any condensate falls back into it and not out onto the floor. If your boiler has a huge plume then it's probably because the ch is turned up high. This stops the boiler from condensing and increases plume size.

Can I extend my gas boiler flue?

The flue terminal is about 850 mm long and is normally cut shorter when installed. If yours exits behind the boiler then all that is likely to be needed is a new terminal. Otherwise if 850 mm is not long enough then an extension can be fitted to lengthen the existing terminal unit.

Does carbon monoxide come out of boiler flue?

Boilers can produce carbon monoxide naturally, but the gas is usually carried out of your house via a flue. If your flue is blocked, the carbon monoxide has nowhere to go and will escape into your home. Carbon monoxide can also be present as a result of a leak in your appliance.

How do you tell if your boiler flue is blocked?

Step 1 - Check Inside the Heater
Wipe around the edge of the pipe using a cloth. If it appears oxidized, or there are white stains around the mouth of the flue, this can indicate that it is blocked. You may also notice a bad smell, or have your carbon monoxide alarm sound, if you have one.

How far should a flue be from a boundary?

With regard to proximities to boundaries, a flue duct outlet of a gas appliance needs to be sited so that it is at least 600mm from the boundary line when facing it and at least 300mm from the boundary line when running parallel to it.

How do you seal a flue?

Vacuum around the seal to remove any residue dust and fire cement pieces etc. Ensure that the stove lid and collar, as well as the flue pipe, is protected before you apply the new fire cement. Use masking tape around the top and bottom of the seal so that the fire cement can be applied with a neat straight edge.

How many bends can you have in a flue?

A chimney cannot have more than four bends and no bend can be more than 45 degrees (except if you use a 90 degree “T” off the rear of the stove). If you are are going out through a wall then you will be using two 45 degree bends straight away and have two left if you need them.

Do you need a new flue with a new boiler?

Yes, you do need to replace the flue when replacing any boiler even if the same brand. This is to keep it in line with manufacturers specifications and Building regulations. The washers on the combustion side of the flue (inner section) perish over time and can leak and cause damage to the rest of the flue.

Can you use expanding foam around a boiler flue?

It should be ensured in all installations that the wall is sealed to the flue inside the property by using expandable foam, by pointing with sand and cement or using any other suitable material. Providing the wall is flat and in good condition, It is not required to point around the flue on the external wall.

Do you need planning permission for a boiler flue?

You don't usually need planning permission to replace or install a new boiler. However, if it needs an external flue this needs to be: No more than 1 metre above the highest part of the roof if it's on the rear or side of a property.

Can you insulate around boiler flue?

Insulating the flue is not commonly done. They do make double-wall pipe that would reduce the temp of the outside pipe wall. If you worry that the hot flue pipe is wasting energy, that is not the case.

Can I paint my boiler flue?

Many people spray their flue pipe with matt black heat resistant spray paint to match their stove. Our heat resistant spray paint is designed for working temperatures of up to 600°C. You should not paint flue pipe before it is in situ. This is because the paint goes through it's final curing process when it gets hot.

Does boiler have to be on external wall?

It should be positioned on or next to an outside wall because by regulation all new boilers installed in a property have to be condensing, which means they generate condensation and a discharge pipe is therefore necessary.

Is it safe to leave boiler on all the time?

You could leave your central heating on all day, controlled by the thermostat. Leaving the central heating on all day means that your boiler has to constantly burn gas to keep the temperature of your house at the required level that you have set.

What can go wrong with a combi boiler?

1. Low boiler pressure. If your boiler pressure is below 1, your central heating system is likely not able to function properly. Low pressure can be a result of various potential reasons, such as a water leak in the system, the pressure relief valve needs replacing or a cause of recently bleeding the radiators.

Why is there black smoke coming out of my boiler?

Improper burning is the cause of black smoke coming from a boiler. It can also be caused by oil building up in the combustion chamber due to delayed ignition. This is known as "puff back" and is dangerous as the excess oil can suddenly ignite, causing a shooting flame and potentially splattering oil out of the boiler.