Frost

Heating Plant.

Frost protection is a feature which is enabled to prevent damage to the building and plant. There are three stages which we would use in a heating system.

The first stage is based on a room temperature around 10°C. This is intended to provide protection of the building fabric against condensation. The operation overrides the timeclock to provide heating to the building until the room temperature has risen by 1oC. In buildings such as factories or warehouses the setpoint may be determined by a product requirement.

The second stage of frost protection is based on an outside temperature of around 2°C. This stage is intended to provide protection of any external or exposed pipework which may be present in the system - including buried pipework. At this setpoint the pumps will be enabled to circulate water through the system to prevent freeze up. This stage may not be included if there is only pipework fully contained within a building. This stage would be disabled once the outside temperature has risen by 1°C.

The third stage of frost protection is based on a boiler return water temperature of around 4°C. At this temperature the boilers would be operated to prevent freeze up of any pipework within the building.

Air Handling Plant.

Air handling plant hase the same requirements for frost protection to prevent freeze up. 

A duct mounted frost protection thermostat is placed downstream of the air heater battery.  In the event of a frost condition the fan is disabled.  A control strategy would also open valves under low abmient conditions to ensure circulation is maintained through all pipework.

Chilled Water Plant.

Chilled water plant and pipework is usually designed to operate at around 5°C.  There is usually a mix of glycol in the system to prevent freeze up.  This reduces the freeze up temperature and frost protection measures may still be required at a lower setpoint.

Static Water.

Static water (for example water mains) presents a problem.  There is no form of heat generation or motive power.  In these instances an electrical heater tape - "trace heating" - is applied to the exposed pipework to heat the water.  Trace heating is usually controlled by a thermostat.