Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The MLX EXT 800 and 1100 share 46 MBH minimum input, 2" NPT gas, 2 1/2" NPT water, 6" venting, 30.3" depth and 45.3" height; the 1100 adds two more thermal modules (seven vs five), raises maximum input from 802.5 to 1,123.5 MBH, deepens turndown from 17.5:1 to 24.5:1 and widens the cabinet from 40.6" to 51.2", adding 192 lb wet weight.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | AERCO Modulex EXT MLX 800 | AERCO Modulex EXT MLX 1100 |
|---|---|---|
| Min. input | 46 MBH | 46 MBH |
| Max. input | 802.5 MBH | 1,123.5 MBH |
| Max. output | 762 MBH | 1,067 MBH |
| Efficiency (up to) | 98.6 % | 98.6 % |
| Efficiency range | 87–99 % | 87–99 % |
| Turndown or operating range | 17.5:1 | 24.5:1 |
| Gas connection | 2" NPT | 2" NPT |
| Water connection | 2 1/2" NPT | 2 1/2" NPT |
| Thermal modules | 5 | 7 |
| Electrical requirement (120 V) | 4.5 FLA | 6.3 FLA |
| Vent and air inlet size | 6" | 6" |
| Width | 40.6 in | 51.2 in |
| Depth | 30.3 in | 30.3 in |
| Height | 45.3 in | 45.3 in |
| Weight, wet | 634 lb | 826 lb |
| Weight, shipping | 716 lb | 924 lb |
AERCO builds both on the same 160,500 BTU/hr thermal modules: five in the 800 and seven in the 1100. The ratings table prints 802.5 MBH maximum input and 707,000–762,000 BTU/hr output for the 800, against 1,123.5 MBH and 993,000–1,067,000 BTU/hr for the 1100.
Turndown deepens from 17.5:1 to 24.5:1 with the extra modules, while electrical draw rises from 4.5 to 6.3 FLA. Both use the same 6" vent and air inlet and the same 92 psi working pressure.
The trade is floor space and weight: the 1100 is 51.2" wide versus 40.6", at 826 lb wet (924 lb shipping) versus 634 lb wet (716 lb shipping). Height and depth are unchanged, so a row of either size lines up the same way against a wall.
AERCO (Watts)
The AERCO Modulex EXT MLX 800 is a condensing multi-module commercial boiler rated 802.5 MBH maximum input and a 707,000–762,000 BTU/hr output range in AERCO's published ratings table, with 17.5:1 turndown across 5 independent thermal modules and a 634 lb wet weight.
AERCO (Watts)
The AERCO Modulex EXT MLX 1100 is a condensing multi-module commercial boiler rated 1123.5 MBH maximum input and a 993,000–1,067,000 BTU/hr output range in AERCO's published ratings table, with 24.5:1 turndown across 7 independent thermal modules and a 826 lb wet weight.
17.5:1 on the MLX EXT 800 and 24.5:1 on the MLX EXT 1100, per AERCO's TDS.
40.6" for the MLX EXT 800 and 51.2" for the MLX EXT 1100, both 30.3" deep and 45.3" high.
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.