Laars Heating Systems · Mini-Therm JX
Laars JX100
The Laars JX100 is the mid-range Mini-Therm JX boiler: a non-condensing gas-fired residential hydronic boiler at the 100 size step of the 50-200 MBTU/h range, with LED-based analog diagnostics and no digital display.
Key figures
- Max input
- 100 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Laars JX100 in practice
The JX100 is the 100 size — the middle column of the six Mini-Therm JX sizes in Document 1478C — and the step many detached homes land on when a heat-loss calculation is applied to the non-condensing line. The manual lists natural-gas and propane parts sets, with altitude groupings printed for both fuels.
Diagnostics are handled without a display: Section 11.C numbers twelve recurring symptoms and gives causes and remedies for each, and Section 11.D's flow charts read the control's TEMP ACTIVE, LOW WATER, HI TEMP and TARGET LEDs plus the ignition and limit lights to steer the check. The boiler is heating-only, with the optional DHW relay kit and panel listed in the parts sections for DHW-demand applications.
Best suited to
- Detached homes whose heat-loss calculation lands near the 100 size step
- Heating-only systems where a non-condensing boiler is the chosen technology
- Owners who want the JX line's simple LED diagnostics at a mid-size input
Applicability and support
- Model number
- JX100
- 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) | 100 MBH | 100 size step of the Mini-Therm JX — the manual's parts tables list the 100 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 JX100 condensing?
No. The Mini-Therm JX is a non-condensing gas-fired hydronic boiler line; Laars' condensing residential lines are the FT Series and NeoTherm. Non-condensing operation is why the manual stresses anti-condensing piping protection at low water temperatures.
How do I troubleshoot a JX100 with no error codes?
Work the symptom through Section 11.C of Document 1478C — for example a boiler that short cycles points to the thermostat anticipator, water flow or high-limit setting — then confirm with the 11.D flow charts and their LED checks.
What sizes surround the JX100?
The JX line runs 50, 75, 100, 125, 150 and 200 across its parts tables, so the JX100 sits between the JX075 and JX125 steps. A heat-loss calculation picks the correct column.
Questions about the Laars JX100?
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.