The Mojo MJ22 / MJ27 from Monessen
No chimney and no household power. The Monessen Mojo is a vent-free gas log burner listed as an unvented room heater and as a vented decorative log set, in two sizes: the 22" MJ22 at 29,000 BTU/hr on natural gas (28,000 on propane) for a fireplace floor at least 29" wide at the front, and the 27" MJ27 at 38,000 (37,000) for one at least 33" wide — both 14" deep and 21" high — with IntelliFire Plus battery ignition and the RC300 remote in the box. It ships as the burner with its embers, volcanic rock, batteries and floor anchors; the eight-piece Mojo log set sized to the burner is sold separately. from $1,339.
Choose the Mojo if you already have a masonry fireplace, a UL127 factory-built fireplace or a listed vent-free firebox and want a heater-rated gas log burner without a chimney run or an electrical circuit — the 27" is the larger of Monessen's vent-free burners at 38,000 BTU/hr. Pick the 22" for a fireplace floor at least 29" wide at the front and 22" at the back, the 27" for one at least 33" wide and 26" at the back; both need 14" of depth and 21" of height. Every version lights from four AA batteries and comes with the RC300 remote, so flame height, a thermostat and a timer are in your hand from day one. Dual listing means that if a mantel or wall clearance cannot be met, the same burner runs vented with the damper open. Order it for the gas you have: each model is built for natural gas or propane and is not converted in the field.
It is not right for a bedroom or bathroom — it is barred from both, and Massachusetts bars every vent-free product from them. It is not a primary heat source, it takes its combustion air from the room and puts moisture into it, so a very tightly sealed house without added ventilation, or a room smaller than the manual's 50 cubic feet per 1,000 BTU/hr (1,450 cubic feet for the 22" at full input, 1,900 for the 27"), is the wrong place for it. It is also not a stand-alone appliance: without a masonry fireplace, a UL127 factory-built fireplace or a listed vent-free firebox that meets its minimum floor size there is nothing to install it in, and a glass-door frame or lip that rises more than 3" in front of the burner is not recommended by the manufacturer.
Specifications
The fireplace or firebox floor must be at least 29" wide at the front, 22" at the back, 14" deep and 21" high for the 22" burner, and 33" wide at the front, 26" at the back, 14" deep and 21" high for the 27"; with the logs in place the assembly itself measures 27" x 13" x 15-1/2" (22") or 31" x 14" x 15-1/2" (27"), and it sits against or as near as possible to the rear wall. A glass-door frame in front of the burner changes the depth: no restriction needs 14", a 0"-3" lip needs 16", and anything taller is not recommended. The sides of the opening stay 16" from a combustible wall and the ceiling 42" above the opening; the material directly above the opening must be non-combustible (slate or marble at least 1/2" thick) — 12" or more of it needs no hood on either size, the 22" also goes without a hood down to 8", and below that (below 12" on the 27") the material is extended or a hood installed. A combustible mantel above the 22" sits 14" above the opening if it projects 2-1/2", 20-1/2" at 6", 24-5/8" at 8" and 28" at 10"; above the 27" a mantel projecting up to 10" sits 28" above the opening; with a hood either size drops to 8" at 2-1/2", 14-1/2" at 6", 18-5/8" at 8", 22-1/2" at 10" and 26" at 12". If those cannot be met the burner runs vented with the damper open. The minimum hearth requirement is 0": the heater sits 1-3/8" above carpet or tile within 14" of the fireplace base unless 14" of non-combustible material separates them. Vinyl flooring is the exception — where vinyl runs up to the wall the manufacturer recommends a hearth extension at least 14" deep, does not recommend adhesive-based vinyl at all, and notes that floating-style flooring will reach 110°F in a 70°F room, so check the flooring's own specification. Gas pressure is 5.0"-10.5" w.c. inlet and 3.5" manifold on natural gas, 11.0"-13.0" and 10.0" on propane, through a 3/8" NPT inlet on the right side of the valve; the burner anchors to the floor with two screws and weighs 27 lb in the 22" or 29 lb in the 27".
Features
- Vent-free gas log burner in two sizes — 22" at 29,000 BTU/hr or 27" at 38,000 on natural gas — with an ODS safety pilot that shuts it down if room oxygen drops
- Dual listed: an unvented room heater (ANSI Z21.11.2) or a vented decorative log set with the damper open (ANSI Z21.60)
- IntelliFire Plus battery ignition — four AA batteries in the pack, no household power, and the RC300 remote with five flame heights, thermostat mode and a timer in the box
- Random yellow flames over glowing embers on the front burner, fed by the rock wool and volcanic rock that ship with it
- Anchors to the floor of a masonry fireplace, UL127 factory-built fireplace or listed vent-free firebox at least 29" (22") or 33" (27") wide at the front
- Sold as the burner only — add the eight-piece Mojo ceramic-fiber log set sized to the burner
Answers to common questions
What’s included, what’s required, and what’s optional?
-
Included in the box: Mojo unvented gas log burner assembly with IntelliFire Plus ODS control and battery pack; RC300 multifunction remote control and four AA batteries; One bag of crushed volcanic rock and one bag of rock wool embers; Component cover and two anchoring screws; Installation/owner's manual; UL listing to ANSI Z21.11.2-2016 and ANSI Z21.60-2017 / CSA 2.26-2017; HHT limited warranty — 5 years parts and labor on the burner.
-
Required to complete the installation, purchased separately: Log Set - the Mojo eight-piece ceramic-fiber log set sized to the burner (22" or 27"); the burner is sold without logs and is not operated without them; Fireplace or Firebox - a solid-fuel masonry fireplace, a UL127 factory-built fireplace or a listed vent-free firebox whose floor is at least 29" x 14" x 21" (22" burner) or 33" x 14" x 21" (27" burner); Gas Line - a 3/8" NPT supply with a manual shutoff valve upstream, run, purged and leak-tested by a qualified gas installer, with an external regulator for propane or a 1/2-psi natural-gas system.
-
Optional: A wired on/off wall switch, an adjustable hood where the non-combustible material above the opening is under 12" (27") or under 8" (22") and you would rather not extend it, and a damper stop or clamp for a vented installation — the burner operates fully without any of them.
Which size should I choose, the 22" or the 27"?
Match the burner to the fireplace floor. The 22" needs a floor at least 29" wide at the front, 22" at the back, 14" deep and 21" high, and runs 29,000 BTU/hr on natural gas or 28,000 on propane; the 27" needs 33" at the front, 26" at the back, the same depth and height, and runs 38,000 on natural gas or 37,000 on propane. Both share the ignition, the remote, the listings and the sidewall and ceiling clearances; the 22" is more forgiving of a short non-combustible facing above the opening (it goes without a hood down to 8" where the 27" needs 12"). If your fireplace clears the larger minimum, either burner fits — the 27" simply fills more of the opening and puts out more heat.
Where can it be installed — and where can't it?
Inside a solid-fuel masonry fireplace, a UL127 factory-built fireplace whose instructions do not exclude unvented logs, or a listed vent-free firebox — never free-standing, and never in a bedroom or bathroom. The fireplace floor must meet the minimum size for the burner (29" x 14" x 21" for the 22", 33" x 14" x 21" for the 27"), the room must not be a confined space (50 cubic feet per 1,000 BTU/hr — 1,450 cubic feet at the 22" burner's full input, 1,900 at the 27"), and it needs to be out of drafts and high-traffic areas, with curtains, furniture and clothing at least 36" from the front. Above 2,000 ft the input is derated 4% per 1,000 ft, and a manufactured home is fine where local codes allow it.
Does it need a chimney, and what does dual listed mean?
No chimney is needed for vent-free use: the burner is listed as an unvented room heater and its ODS safety pilot shuts it off if room oxygen drops; in a fireplace the flue damper is simply left unsealed. The same burner is also listed as a vented decorative log set — run with the chimney and damper open when a mantel or wall clearance cannot be met, when your state or local code requires it, or when you prefer to send the moisture up the chimney. Vented, the chimney and firebox are cleaned first, the damper is clamped fully open with a damper stop that keeps at least 29 square inches of flue open (the stop is not in the carton — order one from your dealer), the thermostat function is not used, and Massachusetts requires the damper permanently removed or welded open.
Does it need electricity or batteries?
Batteries only. The IntelliFire Plus with ODS control runs on four AA batteries in the burner's battery pack (they are in the carton), the RC300 remote takes three AAA, and the whole of the manual's wiring requirements is that 6-volt battery system — the wiring diagram is battery-only, there is no junction box, transformer or power cord in the parts list, and line voltage must never be connected to the control valve or a wall switch. One thing to know: a line in the manual's fault-finding table still tells a technician to verify that 110-120 V power is on to a junction box — a leftover from the shared IntelliFire text, since this burner has no junction box to wire. The control shuts the burner off after nine hours without a command, and adjusting the flame often from the remote shortens battery life.
How high must a mantel or shelf above the opening be?
That depends on the burner and on how far the mantel projects. The wall directly above the opening must be non-combustible (slate or marble at least 1/2" thick). Above the 22" burner with no hood, a mantel projecting 2-1/2" sits at least 14" above the opening, 6" at 20-1/2", 8" at 24-5/8" and 10" at 28", over 12" of non-combustible material; above the 27" with no hood, a mantel projecting up to 10" sits 28" above the opening, over 12" of non-combustible material. With the optional hood either size drops to 8" at 2-1/2", 14-1/2" at 6", 18-5/8" at 8", 22-1/2" at 10" and 26" at 12", over 8" of non-combustible material. The sides of the opening stay 16" from a combustible wall and the ceiling 42" above it. If a clearance cannot be met, the burner must be run vented with the chimney damper open. Send us your mantel depth and we will check the figures with you.
What does the RC300 remote do, and can I add a wall switch?
The RC300 ships in the carton, already meant for this control: on/off, five flame-height settings, a thermostat mode that reads room temperature and cycles the burner around a set point (vent-free installs only — not allowed vented), a 15-180 minute timer and a child lock, from up to 30 ft away inside the room. You can add a wired on/off wall switch as well; with the control in REMOTE it runs the burner on high and overrides the remote, so leave it off when you use thermostat mode. Never put the wall switch on a 110 V circuit.
How does the warranty work if something goes wrong?
Hearth & Home Technologies backs the Mojo with its limited warranty: 5 years on the vent-free burner and logs, covering both parts and labor, 2 years on the module, remote, valve and pilot, 1 year on other parts, and 1 year on any replacement part or accessory you buy later. Coverage starts the day it is installed and stays with the appliance if you sell the house, as long as it is not moved to another address; it is printed in full on pages 26-27 of the manual. The Torch Guys is an authorized Monessen dealer, so buying from us does not affect it — keep your invoice and the model and serial number from the rating plate in the burner's control area, and we handle the claim with the manufacturer for you.
