Radiator terminology: lockshield valves

[bruce_phipps]

Some basic central heating questions:

• Whats the difference between a "lockshield" valve and a thermostatic control valve -- the ones with numbers 1 to 10, say, which you turn to control individual radiator temp.

• Thermostatic control valves -- should they be turned clockwise to reduce radiator temp, anti-clockwise to increase radiator temp? Is there a standard direction in which they operate?

Bruce

[Set Square]

There are actually 3 variations - but 2 of them share many common parts.

Standard manual valves and lockshield valves are the same animal but with different plastic tops. Manual valves have a knob which you can turn - like a tap - to open and close them. Lockshield valves have a cover over the end of the spindle which doesn't rotate it. These are for balancing the system, are turned with a spanner, and then fitted with their tamper-proof cover to prevent the setting being changed.

Thermostatic valves have a wax capsule which expands when it gets hot, and pushes on a plunger which closes the valve - thus providing a degree of automatic temperature control for a room. They have a knob with numbers on to select comfort level. The higher the number set, the hotter the room can get before they shut off. I think you normally get higher numbers by turning the knob anti-clockwise - but it's the numbers which matter, whichever way it turns.

[John Rumm]

To the extent that sometimes when you buy a lockshield valve you actually get the valve with two alternate plastic tops. One that engages with the valve and acts as a knob - turning it into a conventional radiator valve, the other that is just a cover for use in "lockshield mode".