How to size a gas log set to the fireplace you already have

A gas log set is not a fireplace. It is a set of ceramic logs and a gas burner that go into a fireplace you already own. It is also the purchase where sizing mistakes happen most often, because the fit depends on measurements only you can take. This guide covers the four numbers we need, why the size in a log set's name is not the size of your opening, and why the burner and the control are separate purchases.

Measure four things, not one

Fireboxes taper. They are wider at the front than at the back, so one measurement is never enough. Take these four with a tape measure:

Front width: the width of the opening at the very front, at its widest point.
Back width: the width of the firebox at the rear wall. It is almost always smaller than the front, and it is the number that usually limits the logs, because the rear logs have to fit back there.
Depth: from the front edge of the opening straight back to the rear wall, measured at the floor.
Height: from the floor of the firebox to the top of the opening, at the front.

A photo of the open firebox helps too. With the four numbers and the photo, we check the fit against the manufacturer's sizing chart before anything is quoted. Until then, nobody can tell you a set will fit.

Why a 50-inch fireplace does not take a 50-inch log set

The size in a log set's name is a nominal size class, not the footprint of the assembled logs. The assembled logs sit wider and taller than that number, so a 24-inch set does not fit a 24-inch opening. The size is roughly the length of the logs, not the width of the fireplace they go into.

Grand Canyon Gas Logs publishes minimum fireplace dimensions for every burner size: a minimum front width, back width, depth and height. Each one is a floor, and the fireplace has to clear all four, not just one. For the standard two-burner kits, the minimum front opening is the burner size plus 12 inches.

So a 48-inch two-burner kit needs a front opening of at least 60 inches, and a 50-inch opening tops out at about a 36-inch two-burner set. The intuitive answer for a 50-inch fireplace, a set of around 50 inches, is the wrong one.

Depth and height matter as much as width. A shallow firebox is the most common reason a set is ruled out, and many modern factory-built fireboxes are shallow. A slimline set is made for exactly that case. Height has to leave room for the flame as well as the logs, because flame rises, and a short opening with a tall log stack puts flame on the top of the opening.

Grand Canyon's Jumbo sets use thicker logs for large fireboxes, and the Jumbo burners call for a deeper firebox than the standard two-burner and three-burner kits. In many homes, depth is what decides whether a Jumbo set can be used at all.

Leave room on each side too. The manual gives the required space between the outermost log and the firebox walls. That space is combustion air, and it keeps flame off the masonry.

Burner size and log size go together

A Grand Canyon 36-inch burner pairs with a 36-inch log set. Burner size and log set size match one to one, and mixing sizes is not a listed configuration.

The burner sits under the logs, and the logs go in the pattern the manual shows. Their position is part of how the set was certified, so rearranging them to look better can cause soot or block the pilot.

Natural gas or propane

Gas burners are built for one fuel. The fuel type is part of the order, not a setting you change later, and a propane conversion is work for a licensed gas fitter. Every Grand Canyon burner we list is the natural gas version, so a propane fireplace needs a different configuration, which we confirm with you before quoting. Tell us whether the house is on natural gas from the street or propane from a tank.

The burner, the logs and the control are separate purchases

A complete vented gas log fire is three purchases: a burner, a log set, and a control system.

A listing marked logs only is just the ceramic logs: no burner, no grate or pan, no valve, no pilot, no remote. The burner kits we list do not include a control or ignition system either. The control is a separate kit, and its BTU rating must meet or exceed the burner's.

Controls run from simplest to most capable:

Match-lit: a key valve and a long match, with no pilot and no automatic shutoff. Some areas do not allow it, so check your local code.
Safety pilot: a standing pilot that shuts the gas off automatically if the pilot goes out.
Millivolt with a remote: the pilot flame powers the valve, so it keeps working in a power outage.
Electronic ignition with a remote: no standing pilot; it sparks on demand and has battery backup.
Modulating: the flame turns up and down through a range rather than only on and off.

Then there is the installation itself. Gas connections are done by a licensed gas fitter or plumber, and a permit and inspection are usually required, depending on where you live. We do not install, so plan on a local installer.

Check the fireplace itself

Vented logs burn with the damper open, and the damper has to be permanently clamped or locked open.
Many masonry fireplaces have no gas line in the firebox, and running one is a job for a licensed plumber.
Glass doors must be fully open or removed for most vented log sets.
Vented logs are for the look of a fire. Essentially all of the heat goes up the chimney, so if you want heat from that opening, ask us about a gas insert instead.
Outdoor fireplaces need outdoor-rated sets, because indoor log sets corrode outdoors.

Where to start

Burners and log sets are in our gas fireplace collection, including the Grand Canyon 48-inch two-burner kit, the Grand Canyon 36-inch Jumbo burner kit and the Arizona Weathered Oak 36-inch log set. Shipping is free to the lower 48 states, and freight deliveries are curbside.

Text us your measurements at (307) 317-1030, email support@hearthcourt.com, or send them through our free fit check.