when do you need a auto bypass?

[seaboat]

can anyone tell me exactly when you need a auto bypass.
i have a ideal mexico super 450ff floorstanding boiler.
cheers

 

[doitall]

On any fully pumped Y or S plan system where thermostatic valve are fitted to all the radiators.

 

[wilhelm]

ergo, a rad without a trv.

 

[spacethegas]

ergo, a rad without a trv.

this is no longer acceptable & has not been for sometime in order to comply with part l.

 

[D_Hailsham]

can anyone tell me exactly when you need a auto bypass.
i have a ideal mexico super 450ff floorstanding boiler.
cheers

To quote CHeSS:

A bypass circuit must be installed if the boiler manufacturer requires one, or specifies that a minimum flow rate has to be maintained while the boiler is firing.The installed bypass circuit must then include an automatic bypass valve (not a fixed-position valve).

The Installation Manual for a Mexico 450FF states:

When thermostatic radiator valves are used, the space heating temperature control over a living / dining area or hallway having a heating requirement of at least 10% of the boiler heat output should be achieved using a room thermostat, whilst other rooms are individually controlled by thermostatic radiator valves. However, if the system employs thermostatic radiator valves on all radiators, or two port valves without end switches, then a bypass circuit must be fitted with an automatic bypass valve to ensure a flow of water should all valves be in the closed position.

 

[seaboat]

thanks for the replies.
if a auto bypass was fitted and it was not required, is it ok and safe?
cheers

 

[ChrisR]

That would depend on its adjustment.