Lochinvar Low System Flow / Piping Restriction

Boiler frequently reaches setpoint very quickly and shuts off, with very hot supply but cool returns

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Closed valves, clogged strainers, undersized piping, partially closed balancing valves

Safety first: Use caution around hot pipes.

Verify all valves open: Check isolation, balancing, and zone valves to ensure they are fully open where required.
Clean strainers: If Y-strainers or dirt separators are installed, isolate and clean them to remove debris.
Check pump performance: Ensure the primary pump is not airlocked and is spinning freely.

Professional help: If restrictions are not obvious, a technician may need to measure flow and evaluate piping design.

Medium 3/5

System Y-Strainer

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