new central heating system

[axamus]

hello guys,
Ive just bought old 3 bed house which is 1950s. The central heating system is an old gas fired back boiler with 15mm copper running throughout the house.
Im going to be ripping it all out and fitting 33 kw baxi duo tec combi,my questions are as follows;
Do i need to replace the existing pipework due to new pressures?
If so, what size throughout the house and can i use hep20?

Im wanting to know peoples opinions on this boiler for efficiency and are there better models that would be cheaper to run.

Thanks guys

all comments are welcome

 

[tamz]

A 3 bed house, presumably 1 bathroom, why the need for a 33kw?
Apart from that the Baxi is a decent boiler.....they are all quoted as 90 odd% efficient, in an ideal world, but rarely get near that in reality.
Do i need to replace the existing pipework due to new pressures?
Generally no. But if as you say the whole house is piped in 15mm you will have to change it about some.
If so, what size throughout the house and can i use hep20?
As a general rule no more than 18000 btu max (just under 6kw) should be fed through 15mm. (more will work but flow velocity and noise will increase).
So this usually means 2 to 3 max from 15mm tails. The rest is 22mm on this size house.
Hep....whatever turns you on. Minimum 1m copper from boiler though.

 

[axamus]

The reason for 33kw is allowing for possible 2 storey extension on back with 2nd bathroom.
Will i get good strong pressures for mixer shower for upstairs shower and if not is there any way of improving shower pressure?? run it in 22mm from boiler perhaps?

cheers guys

 

[tamz]

The pressure at your shower will depend on the incoming mains. The flow rate from the boiler is around 13.5 litres/min at a 35deg rise. More than enough for any shower.
Running a 22mm hot pipe would make no difference. The flow rate is restricted on the boiler.

 

[axamus]

thanks for advice mate, will look into it!!

 

[Centralheatking]

There are some vital questions you need to pose before you start, especially if your going to fit a combi.

1.How many bathrooms/ensuites in the final plan more than one and a combi is only as good as the mains water supply. Combis are great for flats and small houses but
anything larger forget them
2.hep is fine and easy to fit but it is difficult to make look good and does not take traffic well - from floor level to rad valves and under boiler copper is strong, straight and neat
3. My outfit only fits Vaillant cause they do not go wrong and start up 1st time but
they are a bit more expensive
4. Do not underestimate flushing out and water conditioning for the new system

We have been at this almost 30 years and we have learnt alot from our mistakes

Centralheatking

 

[axamus]

hello mate, right there are 3 bedrooms upstairs and bathroom at mo, with extension 4 bedrooms with ensuite making 2 bathrroms total.
do you think 33kw baxi will be up to task? if not, what instead?
when you say hep having problems with traffic, do you mean restricted flow?
when you say flushing and conditioning system, can you give me some tips.

as you have guessed im new to the plumbing as im brickie by trade. ive recently done me level 3 in plumbing but limited on experience!!!
thanks!!

 

[Rodreguez]

hello mate, right there are 3 bedrooms upstairs and bathroom at mo, with extension 4 bedrooms with ensuite making 2 bathrroms total.
do you think 33kw baxi will be up to task? if not, what instead?
when you say hep having problems with traffic, do you mean restricted flow?
when you say flushing and conditioning system, can you give me some tips.

as you have guessed im new to the plumbing as im brickie by trade. ive recently done me level 3 in plumbing but limited on experience!!!
thanks!!

Combi will only feed 1 hot tap at once. using 2 bathrooms you mite find urself having a cold shower. personally ide go unvented but there are other systems like thermal store.