intergas

[anz]

No pump over run so i wouldn't see it being an issue not having one.

I think that the instructions state that you must fit one.

 

[Killy Bing]

Got the instructions here

"If all radiators are equipped with thermostatic or radiator valves, an auto bypass must be fitted in order to guarantee minimum water circulation. The auto bypass must be as far as possible from the applience in order to prevent over heating of the applience."

one rad on just lockshields should be alright in my view.
fit one for good measure.