changing to combi


Postby redkev » Thu May 27, 2010 2:14 pm

hi their. i have not longed passed my gas safe test and about a year fully qualified.

i am looking to install a combi into my flat, i have a back boiler just now and would like some advice on how to installa a combi into original pipework.

i would like to know what is best to do with the zone valves and pump. obviously hot water cyclinder expansion needs to be blanked and the new hot teed into the hot pipe work. gas upgraded to 22mm pipe. cold teed into cold,

do u just take back boiler out and blank pipes. remover pump and valves and comment straight through.
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Postby htg engineer » Thu May 27, 2010 7:20 pm

Basically, to you boiler you need:
Hot
Cold
Gas
Flow
Return
Pressure relief
Condensate discharge

The flow and return are the pipe to the radiators, as you've suggested you have a 3 port valve the pipe from the boiler to the three port and from the three port to the cylinder can be ripped out.

The return can be done away with from the back boiler to the cylinder.

All you will have left is the flow and return to the radiators - connect to flow and return on combi.

The gas as you say - depending on pipe length has to be 22mm MINIMUM.

The hot and cold can be tee'd into the hot and cold anywhere in the house, just remember to blank hot draw off at cylinder and cold feed to tank.

Pressure relief to outside - best fitting a cowl, or a elbow with a bit pipe pointing down, towards the wall will do.

Condensate - overflow/25mm solvent weld to internal waste pipe - if it goes outside it must be 1.5" solvent weld.


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