There are basically three options regarding the choice of radiator valve:
2. Angled valves or straight valves
3. Thermostatic or manual
The size of the valve is detemined by the size of the radiator connections and the pipes supplying the radiator.
Radiator connections are mainly 1/2" BSP. BSP is a threaded connection. Some of the traditional towel rails have
3/4" BSP connections. This is a throwback to the days when these were fitted on gravity systems and bigger pipes were used.
Pipe sizes tend to be 15mm on the 1/2" valves and 22mm on the 3/4" valves. Some 1/2" valves are available with 10mm
and 8mm pipe sizes for use on microbore systems.
Valves can be purchased separately but if a radiator is being fitted it makes sense to buy a matching pair as two valves are used on a radiator. A wheelhead valve, which is the one for turning the radiator on or off, and a lockshield valve for adjusting the water flow through the radiator to balance the system. A thermostatic valve can be used instead of a wheelhead valve.
NOTE: A Thermostatic Valve must never be left with an open end unless the thermstatic element is removed and replaced with an isolation cap to ensure the valve stays in the closed position. If there is no isolation cap available a 1/2" BSP cap must be fitted to the valve tail.
ANGLED or STRAIGHT
The majority of conventional radiators have BOE, Bottom Opposite End connections. The connections come out of each end
of the radiator at the bottom and they come horizontally from the radiator, as in the picture below.
The valves shown in the above picture are angled valves and these are generally used with a radiator having BOE
Many of the designer radiators have connections which leave the radiator on the underside at each end and come vertically
from the radiator. As in the picture below. Some are positioned in the centre of the radiator but the principle is the same.
The choice is now whether angled or straight valves are needed. In the picture above, the pipes go directly from the valve
into the wall behind the radiator. In this case, angled valves have been used. The head of the valves face forward and
the valve body is screwed vertically into the radiator connection.
If the pipes come upwards from the floor straight valves would be most appropriate. As in the picture below.
THERMOSTATIC OR MANUAL
Both manual and thermostatic valves are available as angled or straight.
Thermostatic valves are intended to control the individual room temperature and save on energy bills.
They are particularly useful if the room has another form of heat, such as a room facing south which gets solar gain,
a kitchen which heats up when cooking and perhaps a bathroom. However, in a bathroom if the radiator is used for
warming towels then a manual valve is more appropriate. They are also useful if the radiator is oversized which can
happen when additional insulation is added.
The thermostatic valve regulates the flow of water through the radiator and hence reduces the radiator temperature
as the room warms up. This saves on fuel bills.
If it is intended to fit all the radiators on a system with thermostatic
valves a heating engineer should be consulted. This is because he can advise on whether or not to leave one or more radiators without a valve or alter the system pipework to protect the system.
NOTE: A Thermostatic Valve must never be left with an open end unless the theromstatic element is removed and replaced with an isolation cap to ensure the valve stays in the closed position. If there is no isolation cap available a 1/2" BSP cap must be fitted to the valve tail.
A manual valve requires the user to turn it on and off. It is recommended that quality radiator valves are used. This is even more important
if the the valve is to be operated regularly to turn the radiator on and off. Also, with Combi boilers and other sealed systems it
is of paramount importance that good quality valves are fitted.