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Comparison
Verdict in brief
Both the HTP Elite XL ELX-500FBN and the HTP Elite XL ELX-650FBN belong to the HTP Elite XL Commercial Condensing Boiler line of condensing boilers. Published ratings: HTP Elite XL ELX-500FBN at 50–500 MBH input, 485 MBH heating capacity and Up to 97% thermal efficiency; HTP Elite XL ELX-650FBN at 65–650 MBH input, 630 MBH heating capacity and Up to 97% thermal efficiency. HTP Elite XL ELX-650FBN lists 150 MBH more input than HTP Elite XL ELX-500FBN (650 MBH against 500 MBH). Both list the same published thermal efficiency of Up to 97%. HTP Elite XL ELX-650FBN lists 135 lb more shipping weight than HTP Elite XL ELX-500FBN (680 lb against 545 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | HTP Elite XL ELX-500FBN | HTP Elite XL ELX-650FBN |
|---|---|---|
| Input rate, minimum | 50 MBH | 65 MBH |
| Input rate, maximum | 500 MBH | 650 MBH |
| Heating capacity | 485 MBH | 630 MBH |
| Thermal efficiency (page and submittal claim) | Up to 97% | Up to 97% |
| Turndown | Up to 10:1 | Up to 10:1 |
| Boiler water content | 4.3 gal | 5.6 gal |
| Shipping weight | 545 lb | 680 lb |
| Dimensions (W x H x D) | 26" W x 41" H x 40.7" D | 26" W x 41" H x 56.5" D |
| Minimum flow rate at 20 °F ΔT at low fire | 5 GPM | 6.5 GPM |
| Power supply | 120 V / 60 Hz, less than 12 A | 120 V / 60 Hz, less than 12 A |
| Flow switch activation | 4 GPM | 4 GPM |
| Gas connection | 1" NPT | 1" NPT |
| Supply / return connection | 2" NPT | 2" NPT |
| Vent size and maximum combined run | 4" adapter — 4" (125 ft) max combined, 10 ft minimum | 6" adapter — 6" (125 ft) max combined, 10 ft minimum |
| Packaging dimensions (W x H x D) | 32.25" W x 49.625" H x 48" D | 32.25" W x 49.625" H x 64" D |
| Gas supply pressure | Natural gas or LP: 3.5"–14" w.c. | Natural gas or LP: 3.5"–14" w.c. |
| Heat exchanger | 316L stainless steel water tube, 160 PSI ASME stamped, National Board listed, gasketless | 316L stainless steel water tube, 160 PSI ASME stamped, National Board listed, gasketless |
| Water pressure | Heat exchanger MAWP 160 psi; ASME 50 psi relief valve | Heat exchanger MAWP 160 psi; ASME 50 psi relief valve |
| DHW indirect setpoint range | 70–185 °F | 70–185 °F |
| Control | 928 digital operating control with color touchscreen; HTP Link Wi-Fi standard | 928 digital operating control with color touchscreen; HTP Link Wi-Fi standard |
| Approved vent materials | PVC, CPVC, polypropylene or stainless steel | PVC, CPVC, polypropylene or stainless steel |
| Safety devices | Flame rectifier probe, dual water supply temperature sensor/high limit (210 °F), freeze protection, condensate trap with float, dual flue sensor (210 °F), blocked vent pressure switch, integrated UL 353 CSD-1 low-water cut-off, high-resolution flow switch | Flame rectifier probe, dual water supply temperature sensor/high limit (210 °F), freeze protection, condensate trap with float, dual flue sensor (210 °F), blocked vent pressure switch, integrated UL 353 CSD-1 low-water cut-off, high-resolution flow switch |
| Warranty | Five (5) year basic / ten (10) year extended limited warranty on the heat exchanger | Five (5) year basic / ten (10) year extended limited warranty on the heat exchanger |
Published ratings: the HTP Elite XL ELX-500FBN is rated 50–500 MBH input, 485 MBH heating capacity and Up to 97% thermal efficiency; the HTP Elite XL ELX-650FBN is rated 65–650 MBH input, 630 MBH heating capacity and Up to 97% thermal efficiency. HTP Elite XL ELX-650FBN lists 150 MBH more input than HTP Elite XL ELX-500FBN (650 MBH against 500 MBH). Both list the same published thermal efficiency of Up to 97%.
HTP Elite XL ELX-650FBN lists 135 lb more shipping weight than HTP Elite XL ELX-500FBN (680 lb against 545 lb). The boiler water content differs: the HTP Elite XL ELX-500FBN lists 4.3 gal, while the HTP Elite XL ELX-650FBN lists 5.6 gal. The dimensions differs: the HTP Elite XL ELX-500FBN lists 26" W x 41" H x 40.7" D, while the HTP Elite XL ELX-650FBN lists 26" W x 41" H x 56.5" D. The minimum flow rate at 20 °F δt at low fire differs: the HTP Elite XL ELX-500FBN lists 5 GPM, while the HTP Elite XL ELX-650FBN lists 6.5 GPM.
Both records print the same thermal efficiency (Up to 97%), turndown (Up to 10:1), electrical requirement (120 V / 60 Hz, less than 12 A) and flow switch activation (4 GPM), per the cited sources.
The HTP Elite XL ELX-500FBN is the 500 MBH class model of HTP's current commercial condensing line: 50 to 500 MBH input, 485 MBH heating capacity, a 316L stainless steel water-tube heat exchanger and up to 10:1 modulation in a 545 lb floor-standing cabinet.
The HTP Elite XL ELX-650FBN is the 650 MBH class model of HTP's current commercial condensing line: 65 to 650 MBH input, 630 MBH heating capacity, a 316L stainless steel water-tube heat exchanger and up to 10:1 modulation in a 680 lb floor-standing cabinet.
The HTP Elite XL ELX-650FBN lists 650 MBH, against 500 MBH on the HTP Elite XL ELX-500FBN, per the cited documentation.
Both list the same thermal efficiency of Up to 97%.
It ships at 680 lb against 545 lb for the HTP Elite XL ELX-500FBN, per the cited sources.
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.