Gas water heater LT SERIES

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Overview
The Laars LT Series condensing tankless water heater provides up to 5.1 gpm at a 77°F rise and supports residential and commercial installations. Models can be cascaded for larger demands and configured for natural gas or propane operation.

Key Features

• Condensing design with very high thermal efficiency (UEF: 0.98 for 150 model, 0.96 for 199 model)
• Delivers 5.1 gpm at a 77°F rise
• Higher maximum outlet temperature — up to 185°F on 199 model
• Low NOx combustion system
• Stainless steel oval‑pipe heat exchanger to reduce scale build‑up and improve efficiency
• 15‑year warranty on heat exchanger
• Available in natural gas or propane versions
• Multiple venting options; cascade venting compatible with PVC or PP
• On‑board controls and rack mounting system for cascaded installations
• Priority interlock for domestic hot water when paired with air‑handler space heating
• Bottom water connections and external access to outside air and water filters for service
• Suitable for retrofit or new installations; Title 24 recirculation capable

Additional Product Notes

• Oval stainless steel heat exchanger design offers an extended service life compared to copper heat exchangers (manufacturer claim ~3.5x)
• Burner and combustion components designed to reduce dust accumulation and extend service intervals (negative pressure gas valve and metal fiber construction)
• Cascade racks, manifold kits and common vent kits available for multi‑unit installations

Documents (table summary)
Applications Manuals
2199 — LT Series Tankless Water Heater Applications Manual
2224 — 150 Recirc Model, Parts List

Brochures
2181 — LT Series Tankless Water Heater Brochure (150 MBH or 199 MBH)
9305 — Field Service Kit

Install and Operating Manuals
2182 — 199 Standard model, includes Parts
2192 — 199 Recirc model, includes Parts
2222 — LT Series Wall‑Mounted, Modulating Gas Condensing Water Heater (150 MBH) Install and Operating Manual
2222FR — French version
2223 — LT Series Wall‑Mounted, Modulating Gas Condensing Water Heater (Recirc model, 150 MBH)
2223FR — French version

Kit Instructions
7038 — On Demand Kit
7039 — Outdoor Kit
7040 — Pipe Cover Kit
7041 — Rack System
7042 — Recirc Cascade
7043 — Standard Cascade

Master Formats
5094-28 — Master Format Document

Parts Lists
2201 — Standard model parts list
2202 — Recirc model parts list
2233 — LT Tankless Replacement Parts (LT150NXX1 and LT150PXX1) / 150 Standard Model, Parts List
2234 — LT Tankless Replacement Parts (LT150NRX1 and LT150PRX1)

Start Up Guides
9307 — LT Tankless Quick Reference Guide

Submittal Data
2184 — Submittal Data, Standard model
2184_FR — French version
2198 — Submittal Data, Recirc model
2198_FR — French version
2204-FR — Non-Return Valve (French)

Warranty
8072 — LT Series Tankless Water Heater Warranty
8072_FR — French version

Models / SKUs referenced on the page

• LT199NXX1
• LT199PXX1
• LT199NRX1
• LT199PRX1

Technical specifications

• Type: Condensing tankless gas water heater
• Hot water output: 5.1 gpm at 77°F rise
• Maximum outlet temperature: up to 185°F (199 model)
• UEF (Uniform Energy Factor): 0.98 (150), 0.96 (199)
• Fuel: Natural gas or Propane
• Heat exchanger: Stainless steel, oval pipe design
• Warranty: 15‑year warranty on heat exchanger
• Venting: Multiple venting options; supports cascade venting with PVC or PP
• Installation: Bottom water connections; outside air and water filter access for service
• Controls: On‑board control; supports cascaded units and priority interlock for DHW
• Applications: Residential and commercial use; Title 24 recirculation capable