Boiler & Furnace Combustion Chamber Liners

Refractory ceramic fiber combustion chamber liner inspection & replacement for oil fired heating equipment

Oil Heater Combustion Chamber Refractory Liner Inspection & Replacement

Modern oil fired forced hot air furnaces have heat exchangers that are shaped similar to a metal trash can turned on its side. The burner is on one end of the exchanger and combustion exhaust leaves through an opening on the opposite end at the top of the exchanger.

Oil fired boilers also require a combustion chamber liner that typically covers the floor and sides of the combustion chamber. Older boilers and some older furnaces used fire-rated fire bricks or clay as a liner while modern boilers use a non-combustible liner material that is shaped to fit the chamber.

Modern chamber liners, also called "refractories" are made from a non-asbestos ceramic fiber material that can stand high heat and glow when heated (orange color) as the oil burner is running.

This combustion chamber liner is replaceable if damaged.

The combustion chamber liner repair kit above, specifically designed to fit Bard models D36C, D48C, D60C, F81, F86C, F86H, F97, F100CF, FC085, FH085, FH110, FLF085, FLF110, FLR085 and FLR110, would require some disassembly of the heater to get this liner in place.

For that reason, installers often prefer a combustion chamber liner kit that is sold either in pieces to custom-fit a boiler or furnace exactly, like the kit shown below for some Weil-McLain boilers,

Once the refractory is heated it becomes brittle as is used and ages. It's important not to vibrate the furnace excessively when cleaning or repairing once a refractory has been 'fired' (used with the oil burner).

Watch out: Avoid banging on or shoving the furnace or boiler heat exchanger to prevent damaging a 'fired' refractory.

A damaged refractory allows the fireball from the oil burner directly contact the metal of the heat exchanger and can cause problems because of overheating which can distort the thin metal. This can lead to cracks and leakage of combustion gas into the forced air heating system.

The refractory interior should be inspected yearly. Here is an example text excerpted from a New Y0rker boiler manual:

Inspect flueways at least once a year - preferably at the start of the heating season.

The inside of the combustion chamber, the vent system and boiler flueways should be cleaned if soot or scale has accumulated.

When cleaning this boiler, do not damage combustion chamber liner and/or rear target wall.

If damaged, combustion chamber insulation must be replaced immediately. - source: New Yorker CL WATER CAST IRON OIL BOILER IO MANUAL Pre-2012 [PDF] (2011)

This means the oil burner needs to be removed to gain access and look at the inside of the refractory for cracks and holes.

Temporary patches of refractory material called 'wet packs' can be used to repair cracks or holes until the original refractory can be replaced.

A repair during the cold weather of the heating season is one reason to use a temporary 'wet pack' patch. These patches shouldn't be relied on as a permanent fix.

or we might use a wet pack roll of ceramic fiber material that is cut to fit in place in an existing boiler or furnace, like the Lynn combustion chamber wet pack liner shown below.

One sign of a long-term refractory problem that's gone un-addressed is discoloration on the side of the heat exchanger opposite the oil burner.

It's best to check the heat exchanger for cracks since grossly uneven heating of the heat exchanger can cause stresses to build resulting in metal cracks.

Also see these COMBUSTION CHAMBER or CHAMBER LINER DAMAGE FAQs

Watch out: burn marks on a heating boiler or furnace might (among other causes like a blocked exhaust flue and inadequate venting) be due to collapsed or damaged combustion chamber liner - a serious fire hazard needing immediate attention.

Notice that in our photo the brown burn marks around the oil boiler combustion chamber inspection port (that rusty round door above the oil burner) have been cleaned-off., suggesting that someone (me?) has inspected and cleaned this heater.

Boiler or Furnace Combustion Chamber Damage FAQs

Boiler combustion chamber damage - repair urgency

I looked on the inside of the furnace (boiler) and there is a piece of the fire wall laying on the inside is there any danger and can it wait until Monday to call someone (Mar 28, 2015) thomas tate

Reply:

Thomas

While indeed I've sometimes found boilers or furnaces chugging along and heating the home with a damaged combustion chamber liner, there is also a risk that the boiler overheats something nearby and burns the house down. So ...

Watch out: Sorry but yes what you described is unsafe - the risk is that the burner burns through the boiler wall and starts a fire in your home.

Leave the system OFF

Combustion chamber liner repair kits are readily available in both a generic form that is fitted to your boiler or as an exact-fit combustion chamber liner kit sold for many boilers and furances, like the Weil-McLain boiler chamber kit I'll show below.

Below: a Replacement Combustion Chamber Kit for Weil-McLain WTGO, WGO, SGO, & 386-700-355, 1072 boilers and sold at supplyhouse.com. The cost is about $150.U.S. This is NOT a repair that a homeowner should undertake.

Is it possible to replace the heat shield in my oil burner combustion chamber?

The heat shield in my oil boiler burner box is damaged, dan it be repaired? it is a foam type shield. - Bob 10/9/12

Reply: yes and it is a critical safety feature that needs to be fixed

Bob, I've never seen a foam heat shield and can 't imagine what that might be.

But there are various types of combustion chamber liners in the fire box that contains the oil burner flame, ranging from fire-brick through pre-formed factory-built combustion chamber liners to a wet-pack kit used to repair or reline a combustion chamber through the oil burner mounting opening.

The wet pack ceramic chamber liner kit is sold as a roll of combustion chamber liner material that is shaped and cut to fit in the field such as the one I show here by Lynn. I have used this combustion chamber reliner method in the field. It can work reliably if installed with care.

Alternatively, often there are exact fit pre-fabricated combustion chamber liner kits such as the one I'll show below, also from Lynn Manufacturing and sold by heating suppliers such as supplyhouse.com

And indeed, to someone not familiar with combustion chamber liners, the fireproof liner might look a bit like "foam" - it's not.

Watch out:  The combustion chamber liner is critical for safe, proper oil burner operation, serving at least two functions:

1. The combustion chamber liner gets hot when the oil burner is running, helping to assure complete combustion of oil droplets exiting the oil burner nozzle
2. The combustion chamber liner prevents the oil burner from burning a hole through the back of the boiler or furnace - a fire hazard.

Watch out: when installing a combustion chamber liner replacement or repair kit, see this

Health and Safety Warning: excerpted from Lynn Manufacturing's instructions cited in detail at the end of this article:

Ceramic fiber products are suspected of causing cancer by inhalation.

All ceramic fiber products have a hazard communication warning label and a prop 65 warning for airborne fiber inhalation.

You should minimize exposure to airborne fibers.

When handling ceramic fiber we recommend using particulate respirator mask (N95), protective gloves, safety glasses and long sleeve clothing.

For complete safety information consult the SDS sheet. https://www.lynnmfg.com/documentation/

Also see COMPLETE COMBUSTION, STOICHIOMETRIC for an explanation of complete fuel combustion and boiler or furnace maximum efficiency. A combination of proper oil burner nozzle spray pattern and angle, temperature, air supply, and combustion chamber liner all have a role in proper heating oil combustion.