would unvented cylinder work with normal boiler system

[momer79]

We are doing a loft conversion and need to replace the water tank and hot water cylinder with other system. We have been thinking about installing a indirect unvented cylinder.

First Question: Would 210L - 250L indirect unvented cylinder work with our existing worcester boiler which is 18kw?

Second Question: All the radiators pipe are 15mm in the house, do we need to change the radiator pipes ? I heard that unvented cylinder can bust the pipe because of high pressure ?

 

[oldbutnotdead]

1 Yes, no difference to your existing cylinder in terms of boiler connection.
2 No. The primary circuit can stay open vent if you want and have space for the F & E tank (the small one). If your boiler does allow pressurised operation it should still be ok long as the pipework is in good condition but that's down to someone looking at it.

Before looking at unvented cylinders you need to make sure your mains cold water supply is adequate- 20 litres per min at 2 or more bar dynamic (that's the pressure in the pipe while taps are delivering 20l/min) is about the minimum.

 

[momer79]

1 Yes, no difference to your existing cylinder in terms of boiler connection.
2 No. The primary circuit can stay open vent if you want and have space for the F & E tank (the small one). If your boiler does allow pressurised operation it should still be ok long as the pipework is in good condition but that's down to someone looking at it.

Before looking at unvented cylinders you need to make sure your mains cold water supply is adequate- 20 litres per min at 2 or more bar dynamic (that's the pressure in the pipe while taps are delivering 20l/min) is about the minimum.

Thanks for your reply.

I don't know the dynamic pressure but the static pressure was once 3 bar in the garden tap and other time its was around 2.1. The water flow rate was once around 20-21l/m and other time it was around 16-18l/m.

We live in 1950-1960 build house so I believe the water pipes going in radiators are pretty old. We have not had any issue in last 10 years.

 

[momer79]

The dynamic pressure is around 1.4-1.5 bar.

The static is around 2.7 bar