Occurs if manual or automatic reset limit opens
The LIMIT OPEN error code on Weil-Mclain boilers indicates occurs if manual or automatic reset limit opens.
Weil-Mclain LIMIT OPEN means: occurs if manual or automatic reset limit opens. The usual cause is occurs if manual or automatic reset limit opens. You can safely reset the boiler once — if LIMIT OPEN returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does LIMIT OPEN Mean
The LIMIT OPEN code is shown by the boiler’s control board when it detects occurs if manual or automatic reset limit opens. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows LIMIT OPEN and the boiler stops until the fault is cleared |
Common Causes
Causes documented in the Weil-Mclain service literature published by weil-mclain.com, cross-checked against the manufacturer’s fault-code table.
| Cause |
|---|
| Occurs if manual or automatic reset limit opens |
Safety Warning
LIMIT OPEN involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
How to Fix It
Is there an external safety device connected? If yes, trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections
Remove the top right Control tray cover and inspect the connector. Ensure a jumper is installed across the MAN LIMIT terminals if not using a manual reset external limit. Ensure a jumper is installed across the AUTO LIMIT terminals if not using a automatic reset external limit
Automatic external limit will reset 2½ minutes after external limit device closes
Manual limit fault must be reset by choosing Manu
Refer to the Weil-Mclain service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Weil-Mclain models that can display fault code LIMIT OPEN:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Weil-Mclain models | — | Possible |
Frequently Asked Questions
Is there an external safety device connected? If yes, trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections. According to the technical documentation, this is the first check on the list for LIMIT OPEN.
LIMIT OPEN is not classified as a high-severity fault, so the boiler can be reset once. If LIMIT OPEN comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.