Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The JX125 and JX150 are the upper-middle Mini-Therm JX steps — 125 and 150 in the 50-200 MBTU/h range of Document 1478C — the same non-condensing boiler at two size columns with identical LED diagnostics and no numeric codes on either.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Laars JX125 | Laars JX150 |
|---|---|---|
| Maximum input (as printed) | 125 MBH | 150 MBH |
| Fuel | Natural gas or propane | Natural gas or propane |
| Domestic hot water | None built in — a DHW relay kit and DHW panel assembly are listed in the manual's replacement-parts sections | None built in — a DHW relay kit and DHW panel assembly are listed in the manual's replacement-parts sections |
| Error reporting | No digital display or numeric codes — Section 11.C troubleshooting table and Section 11.D flow charts use the control LEDs (TEMP ACTIVE, LOW WATER, HI TEMP, TARGET) | No digital display or numeric codes — Section 11.C troubleshooting table and Section 11.D flow charts use the control LEDs (TEMP ACTIVE, LOW WATER, HI TEMP, TARGET) |
Both models sit at the upper end of the Mini-Therm JX line, one manual apart in the parts tables of Document 1478C: the JX125 at the 125 column and the JX150 at the 150 column. The design, the natural-gas and propane parts sets, the troubleshooting table and the LED flow charts are shared line-wide.
With no digital display, both models are serviced through Section 11.C's twelve numbered symptoms — from a boiler pump that will not operate and pilot outage through flame roll-out, insufficient heat, knocking, relief-valve opening and short cycling — with the Section 11.D flow charts reading the control's LEDs.
The JX150's larger column matters when the heat-loss calculation plus any accessory hot-water duty approaches the JX125's capacity. Above the 150 column the line has one more step — the 200 size — before its ceiling, and homes beyond that leave the non-condensing residential range entirely.
Laars Heating Systems
The Laars JX125 is the upper-mid Mini-Therm JX boiler: a non-condensing gas-fired residential hydronic boiler at the 125 size step of the 50-200 MBTU/h range, with LED-based analog diagnostics and no digital display.
Laars Heating Systems
The Laars JX150 is the second-largest Mini-Therm JX boiler: a non-condensing gas-fired residential hydronic boiler at the 150 size step of the 50-200 MBTU/h range, with LED-based analog diagnostics and no digital display.
One size column: 125 versus 150 in Document 1478C's parts tables. Everything documented about operation, fuels and diagnostics is the same.
When the calculated heating load needs the extra 25-class step of ceiling. If the load never approaches the 125 column, the two boilers perform identically and the smaller entry point wins.
No — every Mini-Therm JX is non-condensing. The manual's troubleshooting table reminds installers to protect against condensation with anti-condensing wiring protection and low-loss-header or equivalent piping.
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 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.