Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The Lx300 and Lx400 are the two mid-size Trinity Lx boilers in the wall-hung-kit class: the Lx400 fires 75 to 399 MBH instead of 55 to 275 MBH and is the first Lx rated 94% AFUE, weighing 225 lb against 180 lb. Both vent in 4" pipe to 100 ft and share the 1 1/4" water connection class.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | NTI Trinity Lx300 | NTI Trinity Lx400 |
|---|---|---|
| Input, minimum | 55 MBH | 75 MBH |
| Input, maximum | 275 MBH | 399 MBH |
| Efficiency (AFUE) | 93.7 % | 94 % |
| Weight | 180 lb | 225 lb |
| Max. equivalent vent length | 100 ft | 100 ft |
| Water connections | 1 1/4" NPT female | 1 1/4" NPT female |
| Gas connection | 1/2" NPT female | 3/4" NPT female |
| Domestic hot water | Heating-only; pair with an indirect tank or separate water heater | Heating-only; pair with an indirect tank or separate water heater |
The Lx300 fires 55 to 275 MBH at 93.7% AFUE and the Lx400 fires 75 to 399 MBH at 94% AFUE — the first size at which NTI's page lists the 94% figure. Both models use 1 1/4" NPT female water connections and 4" venting to 100 ft per side, while the Lx400's gas connection steps from 1/2" to 3/4" NPT female.
Weight rises from 180 to 225 lb, and the minimum fire from 55 to 75 MBH. The Lx400 also sits at the top of NTI's wall-hung-capable range: the page introduction says sizes up to 399 MBH can be wall-hung, and the features list includes the wall-hung kit through the Lx400.
Both are heating-only fire-tube boilers with the same 4" venting plan. The Lx400 is the step when the plant-demand calculation exceeds 275 MBH and approaches 399 MBH; loads within the 300's range keep the lower minimum fire and lighter 180 lb cabinet.
NTI Boilers
The NTI Trinity Lx300 is the 93.7% AFUE step of the Lx line: 55 to 275 MBH input in a 180 lb floor-standing boiler, stepping up to 4" venting at 100 ft with 1 1/4" NPT water connections.
NTI Boilers
The NTI Trinity Lx400 is the last Lx size NTI's page lists for residential-capable use: 75 to 399 MBH input at 94% AFUE in a 225 lb floor-standing boiler (wall-hung kit included) with 4" venting to 100 ft.
Input rises from 275 to 399 MBH, AFUE from 93.7% to 94%, weight from 180 to 225 lb, and the gas connection from 1/2" to 3/4" NPT female.
NTI's page says sizes up to 399 MBH can be mounted wall-hung, which puts the Lx400 at the top of that class; the wall-hung kit is listed as included through the Lx400.
Yes — 4" pipe with a 100 ft maximum equivalent run per side on both.
A consultation includes a heat-loss review so the size is right the first time.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.