Combi boiler supply temperature questions in Greater Vancouver

Supply temperature is simply how hot the water leaving your combi boiler is when it heads out to your radiators, baseboards, or radiant floor. Homeowners ask about it because it affects comfort, efficiency, and how often the boiler cycles. Here is a practical look at what the right supply temperature is and why it varies through a Greater Vancouver heating season.

There is no single right number

The ideal supply temperature depends on your heat emitters. Cast iron radiators and baseboards may want water around 140 to 170 F on a cold day, while radiant floors want it much cooler, often 90 to 120 F. A combi boiler with outdoor reset varies its supply temperature automatically, sending cooler water in mild weather and hotter water as it gets cold outside.

Lower supply temperatures let a condensing combi boiler condense, which is where it earns its efficiency. So a well tuned system runs as cool as it can while still keeping you comfortable.

• Radiant floors: low supply temperature, very efficient.
• Modern panel radiators: moderate supply temperature.
• Older baseboards and cast iron: higher supply temperature on cold days.

What homeowners can and cannot adjust

You can comfortably manage your thermostat and make sure emitters are not blocked, which influences how the system behaves. The actual supply temperature target, the outdoor reset curve, and any high limit settings live in the boiler control.

Those settings should be set by a licensed technician matched to your emitters and home. Setting supply temperature too high wastes gas and can cause short cycling; setting it too low leaves you cold on the coldest days. HeatLand can confirm your supply temperature is right for your system.

Frequently Asked Questions

Why does my supply temperature change on its own?

Most modern combi boilers use outdoor reset, which automatically raises supply temperature as it gets colder outside and lowers it in mild weather. That is normal and helps efficiency.

Lower supply temperature is more efficient, so should I just turn it down?

Lower is more efficient only up to the point where your emitters can still heat the home on a cold day. Push it too low and rooms go cold during cold snaps. A technician finds the right balance.

What supply temperature is right for radiant floors?

Radiant floors typically run roughly 90 to 120 F, far cooler than radiators. A mixing station usually tempers the boiler water down to that range.

Does a high supply temperature wear out the boiler?

Running hotter than needed keeps return temperatures up, prevents condensing, and can encourage short cycling, all of which reduce efficiency and add wear. Right-sizing the supply temperature helps.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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