How to Measure Your Fireplace

For Gas Logs

It's important to buy the right size log set - improper sizing can interfere with proper drafting of your fireplace. If the logs are too large, the unit will not burn as efficiently and the size may hamper the proper operation of the control system. Too small a log set will diminish the beauty of your hearth setting. Look below to see the parts of the fireplace you'll need to measure before purchasing your log set - this area of your fireplace is called the "firebox".


Sizing for installing a burner system with no valve in the fireplace.
How to measure your firebox for vented gas logs.
Use the diagram at left to determine the maximum size gas log burner that will fit into your fireplace.

The generic chart below can be used as a guide to select correct log set size. Log set sizing charts vary somewhat by manufacturer so you should check with your hearth dealer for the chart that matches the manufacturer you've selected. 

Diagram is for a match light system only.  LPG requires a safety pilot.  please use the diagram below.

Sizing for installing a burner, valve and air to cool the system.

Use this diagram to measure firebox for burner and valve.Use the diagram at left to determine the maximum size gas log burner that will fit into your fireplace if you choose to use a safety pilot control, remote millivolt control, Hi/Lo modulating control, or electronic ignition control.

If you install an on/off manual match light valve, add 2" to the width "B" of the firebox opening and front dimension of the log set.

If you install a safety pilot kit, add 3" to the width "B" of the firebox opening and front dimension of the log set.

If you install a remote millivolt system, add 4" to the width "B" of the firebox opening and front dimension of the log set. 

If you install a Hi/Lo Modulating system, add 3" to the width "B" of the firebox opening and front dimension of the log set.

If you install an Electronic Ignition system, add 4" to the width "B" of the firebox opening and front dimension of the log set.




Size
 Front Width of Fire Box Opening* Sample Gas Log Set Dimensions
(Front/Back/Depth) 		Log Set Average BTUs
12"
16" TO 22"
12"
12"
11"
25,000
25,000
16"
20" TO 30"
16"
12"
11"
50,000
30,000
18"
24" TO 30"
18"
15"
12"
75,000
40,000
20"
26" TO 32"
20"
15"
12"
75,000
40,000
24"
31" TO 38"
24"
20"
12"
90,000
50,000
30"
39" TO 45"
30"
24"
12"
90,000
65,000
36"
46" TO 51"
36"
30"
13"
120,000
90,000
42"
52" TO 58"
42"
36"
20"
150,000
105,000
48"
59" TO 65"
48"
42"
20"
150,000
105,000
54"
66" TO 71"
54"
48"
20"
150,000
105,000
60"
72" or more
60"
54"
20"
150,000
105,000

*Front widths are provided as a general guide for selecting proper log size.
Gas Log Sizing and Specifications
 

The Main Benefits of Gas Logs:

  • Can operate without electricity
  • Functional room decor
  • Leaves no smoky odor
  • No cleaning ashes
  • Added source of space heating
  • Environmentally friendly
magnificent oak log set
Main Components of a Gas Log System:
  1. Gas logs (the number of logs included in a log set will vary by style and manufacturer)
  2. Fireplace grate (stand on which the logs are installed, sized according to the log set size)
  3. Gas burner system (burner type depends on fuel type and log style)
  4. Fuel injector (natural gas only)
  5. Sand (natural gas only)
  6. Vermiculite (propane gas)
  7. Damper Clamp (vented logs)
  8. Stabilizer clips
  9. Safety pilot (mandatory for vent free and propane gas, optional for natural gas)
Gas Requirements
Is a gas line currently installed?

If no, then a gas line or propane will need to be installed upon installation on the logs. A licensed gas installer should install your gas line.

If yes, please verify the following information: Is the natural gas line currently in place for a log lighter? If so, a larger gas line will most likely need to be installed. Again, any licensed gas installer can supply this service.
Vented or Vent Free Style Logs
aged cedar log set
 Gas logs are sold in vented and vent free or unvented styles. Vented logs require an open damper in the fireplace to allow the heat to flow upwards and out of the chimney. Vented logs mirror the action of a wood-burning fireplace with the damper open.

While the vented logs do produce heat, vent free logs function more like a space heater because they do not require an open damper and the heat is confined to the room. However, vented logs are more aesthetically pleasing and not only supply some heat, but double as room decor.
Vent free logs require an Oxygen Depletion Sensor (ODS), a device that senses the amount of oxygen in the room and automatically shuts off the log set when oxygen level drops below 18%. The pilot on a vent free set that has been automatically shut off by the ODS can only be re-lit when fresh air is available. This may require opening a window or a door to another room or cracking the damper open slightly.
Gas Log Efficiency Ratings

On average, vented gas logs are 47% efficient (2 times more efficient than wood-burning fireplaces).

On average, vent free gas logs are 99% efficient (4 times more efficient than wood-burning fireplaces).
Fireplace Requirements for Vented Gas Logs

Vented gas logs are to be installed only in a fully, vented, noncombustible fireplace with an open damper. The chimney must be free of any obstructions. The fireplace must be designed and approved to burn wood. Like burning natural firewood, your gas log set is designed to burn with yellow, smoky flames. For this reason, it must be adequately vented. The fireplace flue must be at least 8" at its smallest dimension.

Your fireplace must have a gas supply line that has been installed by a qualified technician in accordance with all local codes. The gas supply line must be 1/2" minimum interior diameter. If the gas line to your fireplace is longer than 20', a larger diameter line may be necessary.

Before installation, be sure to clean your fireplace floor of any ashes or other foreign materials. It is recommended that a chimney sweep or other qualified person inspect the fireplace and chimney before having your log set installed.
Gas Log Valves

The Standard ON/OFF Valve - This valve is controlled manually and the logs will need to be lit each time they are burned.

The Safety Pilot Kit - This valve may be installed with the logs to allow the pilot to burn constantly, which does not require the logs to be lit each time they are burned. It is possible that additional installation costs may be charged for installation of a safety pilot.
Gas Log Accessories

Remote Controls - Allow for the automatic turn on/off of the log set from anywhere in the room. Styles vary from allowing the customer to turn the flame up/down, installation of a wall switch or simply turning the set on/off.

Other available accessories include: branches, sand, embers, lava granules, pine cones, bonus logs and wood chips to help customize the look of your fireplace.
Certifications
RADCO certification is the standard for vented logs. The installation, including provisions for combustion and ventilation air, must conform with local codes, or in the absense of local codes, to the latest edition of the Natural Gas Fuel Code (ANSI Z223-1 and NFPAA54). Vent free or vented logs should be C.S.A. certified to the unvented room heater standards (ANSI Z21.11.2) and as a vented decorative appliance (ANSI Z21.60).
 

Propane Gas Logs
Gas log sets are designed for use for either natural gas or propane fuels. Sets designed for use with propane gas must be installed with a safety pilot system. In most gas log sets, the safety pilot is included. Never use propane gas in a log set designed for use with natural gas or natural gas in a log set designed for use with propane gas.