New boiler combi or open vented

[Bippycat]

We have a 19 year old five bed house with three bathrooms - two showers. We need a new boiler as the current one isn't large enough to heat the house properly after being extended. There are 18 radiators in the house.

Should we stay with our current open vented system or go for a combi boiler. Also do we need a pressure test before installing the new boiler or is this not necessary.

 

[Agile]

All matters to be discussed with your preferred heating installers.

Tony

 

[JohnD]

With three bathrooms, it won't be a combi.

It is unlikely to be open vented.

A lot depends how many litres per minute come from your incoming water main. You can get an idea by seeing how long it takes to fill a bucket at the kitchen cold tap or garden tap.

 

[Bippycat]

Although we have 3 bathrooms, there are only two showers and we don't tend to run these at the same time. With 3 teenagers we do have a problem with having enough hot water which is why we were considering a combi.

We get just above 13 litres per minute from the kitchen tap.

 

[Agile]

Is that a dynamic flow rate or an open pipe flow rate?

Either is going to make a break tank a likely necessity.

Tony

 

[Bippycat]

Sorry not sure what you mean (I have no idea about plumbing as you can probably tell!).

I turned the kitchen tap on full for one minute and measured what came out so don't know it that is a dynamic flow rate or open pipe flow rate.

What's a break tank?

 

[dcawkwell]

Glow worm ultra power a cross between combi and unvented cylinder.
Will never run out of hot water and gives fast delivery of hot water.
Immersion heater backup should boiler fail.

 

[Agile]

Yes, perhaps about 6 litres per minute through the shower or taps then!

Break tank and pump then!

 

[Bippycat]

Sorry if I'm being really thick but what is a break tank? And would that be installing a combi boiler?

 

[D_Hailsham]

I turned the kitchen tap on full for one minute and measured what came out so don't know it that is a dynamic flow rate or open pipe flow rate.

Some taps, particularly mixer types, restrict the flow considerably.

If you have garden tap check the flow rate there. Another option is the cold fill for the washing machine or dishwasher - provided it is fed from the cold main.