Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The FTXL FTX500 and FTX600 share 2" water connections and 4" air/vent and both weigh 504 lb, but the 600 fires 85.7 to 600 MBH (585 MBH gross) at 7:1 turndown against the 500's 10:1, with submittal efficiency easing from 97.7% to 97.5%.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Lochinvar FTXL FTX500 | Lochinvar FTXL FTX600 |
|---|---|---|
| Heating input, minimum | 50 MBH | 85.7 MBH |
| Heating input, maximum | 500 MBH | 600 MBH |
| Gross output | 489 MBH | 585 MBH |
| Net AHRI water rating | 425 MBH | 509 MBH |
| Efficiency (thermal) | 97.7 % | 97.5 % |
| Water content | 11.9 gal | 11.9 gal |
| Space-heating water connections | 2" | 2" |
| Gas connection | 1" | 1" |
| Air inlet size | 4" | 4" |
| Vent size | 4" | 4" |
| Shipping weight | 504 lb | 504 lb |
Both are FTXL Series 120 fire-tube boilers on 2" water and 1" gas connections with a 4" air intake and 4" vent, vented to 100 equivalent feet per the submittal, and both print the same 504 lb shipping weight.
The structural difference is turndown: the submittal rates the 500 at 10:1 and the 600 at 7:1, which the ratings table reflects in minimum inputs of 50 and 85.7 MBH. A building whose part loads sit near the boiler's minimum will cycle more on the 600.
Capacity steps from 500 to 600 MBH of maximum input, gross output from 489 to 585 MBH and the AHRI net rating from 425 to 509 MBH, while submittal thermal efficiency eases from 97.7% to 97.5%. Water content is identical at 11.9 gallons.
Lochinvar
The FTXL FTX500 fires 50 to 500 MBH with 489 MBH gross output and a 425 MBH AHRI net rating at 97.7% submittal thermal efficiency, keeping 2" water connections and 4" venting.
Lochinvar
The FTXL FTX600 reaches 85.7 to 600 MBH input with 585 MBH gross output and a 509 MBH AHRI net rating at 97.5% submittal thermal efficiency, with 7:1 turndown.
The FTXL submittal rates 7:1 turndown on the 600, 725 and 850 sizes against 10:1 on the 400, 500 and 1000; the ratings table minimums (85.7 MBH versus 50 MBH) match those ratios.
2" water and 1" gas connections, 4" air intake and vent, an 11.9-gallon water content and a 504 lb shipping weight — the published differences are capacity, minimum fire and efficiency.
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 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.