Dimplex Optimyst e-MatriX 39" Electric Firebox, Three-Sided Bay
The Dimplex Optimyst e-MatriX (model FEF3226L3, Dimplex order number X-FEF3226L3) is the most convincing electric fire Dimplex builds, and it works on a completely different principle from the rest of the range. Ultrasonic transducers atomise water into an ultra-fine mist; LEDs light that mist from below. What rises off the log set is real three-dimensional vapour that rolls and curls the way smoke does, because it is behaving like smoke.
This is the three-sided bay configuration — glass across the front and down both returns, so the fire reads from anywhere in the room. It is the one to specify for a peninsula, a room divider or an island hearth, and it is the configuration that shows off water-vapour flame best, because from the side you can see the vapour has real depth rather than being a picture on a screen.
Also available as a single-sided front-facing unit, or two-sided left-facing and right-facing.
Read This First: It Is a Fire, Not a Heater
The e-MatriX draws 270 watts — about the same as three old light bulbs. Dimplex's technical sheet records the heat output as none, and the owner's guide puts it this way: "The heat output is minimal and should not be considered a source of supplemental heat."
That is not a shortcoming, it is the design. The flame is cool water vapour, so the glass is cool on all three faces, there is nothing to burn and nothing to vent — which is precisely what lets you put it in the middle of a room where people walk past it. But if you are buying a fireplace to warm a room, this is the wrong product and we would rather tell you now than after it is built in. Talk to us about the Ignite or BF lines instead.
Will It Fit? Rough Opening
| Overall size (W x H x D) |
39 1/8" x 37 5/8" x 20" (99.4 x 95.6 x 50.8 cm) |
| Firebox height |
37" to 37 3/4" (94.0 to 96.0 cm), adjustable |
| Firebox depth |
20 1/4" to 22 1/4" (51.4 to 56.4 cm), adjustable |
| Framed opening |
Call us — see below |
We are not going to publish a rough opening for this model, and here is why. Dimplex's three current documents for the e-MatriX do not agree with one another, and on the bay they cannot all be right:
- The technical specification sheet for the FEF3226L3 gives a framed opening of 36" wide — but the 2026 price list puts this unit at 39 1/8" wide overall. An appliance cannot go through an opening three inches narrower than itself.
- The owner's guide prints a different set again, and its rough opening is narrower than the firebox in every configuration, which cannot be right either.
- The spec sheet's figures for the bay are byte-identical to those for the single-sided front-facing model, which suggests the sheet was copied rather than measured.
A three-sided bay is the hardest of the four to build for — it is usually structural, it is finished on three faces, and it is the most expensive to get wrong. Ring us with your drawings and we will get the opening confirmed with Dimplex in writing before anyone picks up a saw. We would rather have that conversation than sell you a unit that does not fit.
Water Supply: This Fireplace Has to Be Plumbed
The flame is made of water, so the unit needs a permanent supply. Unlike the Opti-Myst Linear range there is no refillable-tank option here — the e-MatriX is designed for a direct connection to the mains and continuous operation.
| Connection |
1/4" water line, or 3/4" female |
| Water pressure |
8 to 110 psi |
| Water quality |
Normal tap water. In hard-water areas use softened or filtered water. |
On an island or peninsula installation the water line has to come up through the floor. Settle that with your plumber at first fix — it is the detail that most often derails a bay installation.
Fresh Air Inlet: Required
The enclosure has to breathe, and the opening goes below the fireplace so air reaches the underside of the unit. Here too Dimplex's documents disagree, so we will give you both figures and a recommendation:
| Owner's guide and sell sheet |
Minimum 40 in² (258 cm²) |
| Technical specification sheet |
80 in² (516 cm²) required |
| What we would build |
80 in² — it satisfies both |
Ventilation is the one requirement where over-delivering costs nothing and under-delivering voids the warranty. Build to the larger number. On a bay, remember the inlet still has to sit below the unit even though there is no back wall to hide it in.
Electrical Requirements
| Voltage |
120 V, 60 Hz |
| Power |
270 W |
| Current draw |
2.25 A |
| Heat output |
None usable — see above |
Location
This is an indoor appliance. The owner's guide states "Do not use outdoors." The water system rules out anywhere that can freeze.
Specifications
| Model |
FEF3226L3 |
| Dimplex order number |
X-FEF3226L3 |
| Series |
Dimplex Optimyst® e-MatriX |
| Configuration |
Three-sided bay — glass to the front and both returns |
| Flame |
Optimyst® water vapour with LED illumination |
| Flame temperature |
None — the glass is cool to the touch on all three faces |
| Fuel |
Electric and water — no venting, gas line or chimney |
| Installation type |
Built-in, recessed; requires a plumbed water supply |
| Location |
Indoor only |
| Remote batteries |
Two 1.5 V AA |
| Warranty |
2 years limited on electrical components |
Documents & Downloads
Warranty
2 YEAR LIMITED WARRANTY on electrical components, from the date of first purchase. Download the Dimplex warranty document.
One more disagreement to flag, because you will see it yourself: the owner's guide packed with the unit refers to a five year limited warranty, while the sell sheet and the technical specification sheet both say two years on electrical components. We have published the shorter term because two of the three current documents give it. If the longer term matters to your decision, call us and we will get it confirmed by Dimplex in writing before you order.
Dimplex excludes Hawaii, Alaska, Yukon, Nunavut and the Northwest Territories from warranty coverage.
