Takagi T-H3M-OS-N
The Takagi T-H3M-OS-N is the natural gas outdoor 120,000 BTU/h condensing tankless water heater in the T-H3 Series — a DHW-only appliance, not a boiler, rated 0.91 UEF with up to 6.6 GPM maximum flow.
Key figures
- Max input
- 120,000 BTU/h
- Max CSA output
- —
- AFUE
- —
- Min input
- 15,000 BTU/h
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Takagi T-H3M-OS-N in practice
Per Takagi's official specification sheet (TRGSS01713), the T-H3M-OS-N fires from 15,000 to 120,000 BTU/h on natural gas, is rated 0.91 UEF, and delivers up to 6.6 GPM maximum flow. It connects on 3/4" NPT hot/cold water lines and a 1/2" NPT gas line, measures 22-7/8 × 13-7/8 × 10-13/16 in and has an approximate shipping weight of 52 lb.
The T-H3M-OS-N is an outdoor model with a commercial-grade copper primary heat exchanger and a Type 316L stainless-steel secondary exchanger, Ultra-Low NOx combustion below 14 ng/J (< 20 ppm), and an outdoor configuration that vents directly. It ships with an integrated temperature controller on indoor models and a wall-mount remote controller on outdoor models.
Takagi's official T-H3 page documents the family for space-heating, hydronic and radiant applications as a water heater; it is not a boiler. Sizing, venting design, gas-supply capacity and any hydronic or recirculation integration are engineering decisions that belong with a licensed contractor following the current installation manual and local code; Boilers.ca reproduces Takagi's printed figures and does not size appliances from floor area.
Best suited to
- Outdoor domestic hot-water service at up to 120,000 BTU/h input
- Projects needing 0.91 UEF condensing efficiency with Ultra-Low NOx combustion
- Manifolded systems: Easy-Link up to 4 units, or Multi-Link up to 20 with a controller
Applicability and support
- Model number
- T-H3M-OS-N
- Canadian availability
- unknown
- 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 Takagi. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input, maximum | 120,000 BTU/h | As printed in Takagi specification sheet TRGSS01713. |
| Input, minimum | 15,000 BTU/h | As printed in Takagi specification sheet TRGSS01713. |
| Efficiency | ||
| Uniform Energy Factor (UEF) | 0.91 UEF | 0.91 UEF as printed in Takagi specification sheet TRGSS01713. |
| Domestic hot water | ||
| Maximum flow rate | 6.6 GPM | Factory-tested maximum; 0.4 GPM required for continuous fire after ignition. |
| Physical and connections | ||
| Hot/cold water connections | 3/4" NPT | |
| Gas connection | 1/2" NPT | |
| Dimensions (H × W × D) | 22-7/8 × 13-7/8 × 10-13/16 in | |
| Approx. shipping weight | 52 lb | |
| Heat exchanger | Commercial-grade copper primary + Type 316L stainless-steel secondary | |
| Operating limits and other | ||
| Installation | Outdoor | |
| Technology | Condensing tankless water heater | |
| NOx | Ultra-Low NOx < 14 ng/J (< 20 ppm) | |
| Manifold capability | Easy-Link up to 4 units; Multi-Link up to 20 units with controller | |
| Warranty | 15-yr limited HX / 5-yr parts residential; 5-yr HX / 5-yr parts commercial | As printed by Takagi for the T-H3 family; TCT-199 commercial warranty is 6-yr HX / 5-yr parts. |
Frequently asked questions
Is the Takagi T-H3M-OS-N a boiler?
No. It is a condensing tankless water heater (DHW-only). Takagi's catalogue contains no boiler line; where the T-H3 family is used with hydronic or radiant systems, the appliance is still a water heater and the system must be designed by a licensed contractor.
What is the input range of the T-H3M-OS-N?
Takagi's specification sheet prints 15,000 BTU/h minimum and 120,000 BTU/h maximum input on natural gas, with up to 6.6 GPM maximum flow and 0.91 UEF.
Can the T-H3M-OS-N be used for space heating?
Takagi's official T-H3 page states the unit can supply hydronic heating systems and radiant floor systems, and that it suits heavier residential usages such as space heating. That is an application of a water heater; a licensed contractor must confirm the design against the installation manual and code.
Questions about the Takagi T-H3M-OS-N?
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.
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- T-H3 Series series hub
- Buying guide
Sources and verification
- Takagi — T-H3M-OS-N product page · accessed September 9, 2026
- Takagi — T-H3M Specification Sheet · TRGSS01713 · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.