Riello oil pump is there more than one type

[Inverness]

Riello oil pump is there only one style of pump? Reasons asking as I removed a oil pump from a two pipe system but there wasn't a bypass screw in the return? But boiler had worked no problems until I touched it.

 

[Brambles]

Yes there are several different types, I think around 5 for domestic sized burners. Single pipe, twin pipe and one ( maybe two) that can be used on either system.

By far the most common one in use is the ....7800 ( the dots are all the preceeding numbers) - but they are commonly known at the merchants as a “7800”. The multi type pump ( for twin or single pipe systems) . ....953 is the one to use If you need the ability to manually tweek the flow on older burners.

 

[Best]

Might have been a very old Riello pump?

 

[Inverness]

Would this be the reason to why I couldn't see the bypass screw on the return port?