Laars Heating Systems · Mini-Therm JX
Laars JX150
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.
Key figures
- Max input
- 150 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Laars JX150 in practice
The JX150 is the 150 size column of the Mini-Therm JX line in Document 1478C — one step below the JX200 and above the JX125, and the size many larger homes need before the top of the non-condensing range. The manual's parts sections cover its natural-gas and propane parts sets with altitude groupings.
Diagnostics remain fully analog: Section 11.C numbers the recurring symptoms with causes and remedies — including the gas-pressure checks of 5.5-10.5 in WC natural gas and 10-13 in WC propane inlet, and 4.0/9.0 in WC NG/LP manifold pressures — and Section 11.D's flow charts work each case through the control's LEDs.
Best suited to
- Larger homes whose heat-loss calculation approaches the 150 size step
- Systems with radiators or in-floor loops served by a non-condensing boiler
- Owners who want the JX envelope near the top of the range before the JX200
Applicability and support
- Model number
- JX150
- Canadian availability
- available
- Production status
- current
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Not verified
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Specifications
Published specifications
Values as published by Laars Heating Systems. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Maximum input (as printed) | 150 MBH | 150 size step of the Mini-Therm JX — the manual's parts tables list the 150 size (Document 1478C, cover: sizes 50-200 MBTU/h). |
| Domestic hot water | ||
| Domestic hot water | None built in — a DHW relay kit and DHW panel assembly are listed in the manual's replacement-parts sections | |
| Operating limits and other | ||
| Fuel | Natural gas or propane | NG and LP orifices, pilot parts and regulator springs are listed in the manual parts sections with altitude groupings. |
| 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) | |
Alerts documented for this model
None documented yet.
Frequently asked questions
Is the JX150 the largest Mini-Therm JX?
No — the line tops out at the 200 size (JX200). The JX150 is the second-largest of the six size steps documented in the manual's parts tables.
What should I do if the JX150 short cycles?
Section 11.C of Document 1478C lists the causes — thermostat heat anticipator set too low, low water flow through the boiler, or a low high-limit setting — with the remedy for each. Boiler adjustments belong to a qualified service technician.
Why does my JX need anti-condensing piping?
The JX is non-condensing, so at low water temperatures flue-product moisture can condense in the boiler. The manual's troubleshooting table calls for proper anti-condensing wiring protection and a low-loss-header or equivalent piping arrangement to keep return water warm.
Questions about the Laars JX150?
Describe what the boiler is doing and get a straight answer about the next step.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- Laars Heating Systems — official site · accessed September 7, 2026
- Laars — contact (Laars Canada, 9 Brigden Gate, Halton Hills, Ontario) · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.