NTI Trinity Lx400
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.
Key figures
- Max input
- 399 MBH
- Max CSA output
- —
- AFUE
- 94 %
- Min input
- 75 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
NTI Trinity Lx400 in practice
The Lx400 reaches a 399 MBH ceiling at 94% AFUE — the top of the sizes NTI's introduction describes as able to mount wall-hung (up to 399 MBH), and the last size with a wall-hung kit included per the features list. It weighs 225 lb, connects on 1 1/4" NPT female water and 3/4" NPT female gas, and vents in 4" pipe to 100 ft per side.
The 400 is also the largest size for which the I&O manual gives DOE AFUE, which is one of the points where NTI's documentation switches treatment: beyond 400 MBH the manual rates the larger sizes by combustion and thermal efficiency instead. In BC, the Lx400 suits large multi-zone residences and light-commercial plants whose load calculation approaches 399 MBH.
Best suited to
- Large multi-zone residences and light-commercial plants up to 399 MBH
- Projects at the boundary between NTI's wall-hung-capable and pure commercial Lx sizes
- Mechanical rooms with 4" vent routes within 100 ft per side
Applicability and support
- Model number
- Lx400
- Canadian availability
- available
- Production status
- current
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Not verified
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Specifications
Published specifications
Values as published by NTI Boilers. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input, minimum | 75 MBH | Per the NTI product page. |
| Input, maximum | 399 MBH | Per the NTI product page. |
| Efficiency | ||
| Efficiency (AFUE) | 94 % | Per the NTI product page; the manual also gives DOE AFUE for this size. |
| Domestic hot water | ||
| Domestic hot water | Heating-only; pair with an indirect tank or separate water heater | |
| Venting and air | ||
| Max. equivalent vent length | 100 ft | 4" pipe per side; maximum equivalent run per the NTI product page. |
| Physical and connections | ||
| Weight | 225 lb | Per the NTI product page. |
| Water connections | 1 1/4" NPT female | Per the NTI product page. |
| Gas connection | 3/4" NPT female | Per the NTI product page. |
| Operating limits and other | ||
| Fuel | Natural gas or propane | NTI publishes LP conversion instructions for this series. |
Manuals
- Trinity Lx 150–800 I&O Manual, 99986573, V.2024-06-2899986573 · 2024-06-28
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Frequently asked questions
Is the Lx400 the largest residential Lx?
The NTI page lists the Lx under commercial products while noting smaller sizes suit residential use. The 400 is the last size with the wall-hung kit and the largest for which the manual gives DOE AFUE.
What efficiency does the Lx400 have?
94% AFUE per the NTI product page. The I&O manual's DOE AFUE coverage ends at this size; from 500 MBH it rates by combustion and thermal efficiency.
What are the Lx400's connections?
1 1/4" NPT female water connections and a 3/4" NPT female gas connection, with 4" venting to 100 ft per side, per the NTI product page.
Questions about the NTI Trinity Lx400?
Describe what the boiler is doing and get a straight answer about the next step.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Compare and explore
- NTI Trinity Lx300 vs Lx400Comparison
- NTI Trinity Lx400 vs Lx500Comparison
- NTI Trinity Lx150Same series
- NTI Trinity Lx200Same series
- NTI Trinity Lx300Same series
- NTI Trinity Lx500Same series
- NTI Trinity Lx600Same series
- NTI Trinity Lx700Same series
- NTI Trinity Lx800Same series
- Trinity Lx series hub
- Buying guide
Sources and verification
- NTI — Trinity Lx Series product page · accessed September 7, 2026
- Trinity Lx 150–800 I&O Manual, 99986573, V.2024-06-28 · 99986573 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.