5 Bedroom House, 18 Rads, 1xBath, 3xShowers - Combi or System Boiler

[goldfrapp]

Hi

We are currently having an extension built to add a fifth bedroom and a en-suite. We'll end up with 3 showers and a bath and about 18 rads.

The existing 8 year old non-condensing boiler has to be moved and so I am considering replacing the existing 25 year old hot water tank (a weird Gledhill system that constantly heats water).

In an ideal world I know that a new system boiler and a megaflow hot water tank is the way to go but I've been quoted an horrendous amount by British Gas to install it which I can't really afford.

So I am considering replacing the Gledhill with a Worcester Bosch combi in the airing cupboard. We are happy for only one shower to be run at any one time (thats what we have to do now). But will running a hot water tap in the kitchen at the same time affect the running shower ? And what about having the central heating on in the winter and wanting to have a shower. Will a combi cope with 18 rads and a shower.

The alternative is to keep the Gledhill and connect a new system boiler to it such as a Worcester Bosch 40 Cdi.

One other problem to consider is that we have a water softener and the man from BG told me that most boiler manufacturers don't guarantee their boilers if softened water is being supplied to them. Is that true ? Is softened water really bad for boilers ?

What do you think the best way to go is ?

Any advice much appreciated.

 

[Kev the gas]

I recently took out a Gledhill systemmate hot water tank, massive rectangular box 250 ltrs of junk.

I installed a Worcester 42 cdi in its place and the flow rate to the showers has increased!

The Bg guy is correct regarding the softened water, Worcester will not allow softened water in their boiler, can a hard water supply be connected up to the boiler for the central heating side? It is ok for the domestic hot water side.

 

[mfgs]

I wouldn't even entertain a combi with that many showers. No point in having them if you aren't able to use them at the same time, an unvented cylinder is definitely the way to go in my opinion.

 

[Mike Jackson]

I agree, go for an unvented and system boiler. get alternative quotes from a xouple of local guys and the price will be a lot less than the Bg price.

 

[woodytheplumber]

an unvented is best option BY FAR! but if cost is an issue maybe a break tank and a couple of electric showers might be cheeper depending on cable and pipe runs

 

[Kev the gas]

Without starting an argument over what is best unvented /combi.

I have a 300 ltr unvented tank, incoming pressure over 6 bar on a 25mm main, over 25 ltrs flow.
3 bathrooms, all with 8 inch drench showers.
If some one else turns on another shower then the flow is poor, no different to what a combi would produce.

My tank is solar fed hence the size, if I didnt have solar I would not think twice about a high output combi, running costs
must be lower rather than heating a massive tank.

There are 2 adults and 4 kids in the house and we use sh.t loads of water.

Bearing in mind I do more repairs on cheap unvented cylinders than combi boilers in my eyes unvented isnt always better.

 

[Gray0689]

Without starting an argument over what is best unvented /combi.

I have a 300 ltr unvented tank, incoming pressure over 6 bar on a 25mm main, over 25 ltrs flow.
3 bathrooms, all with 8 inch drench showers.
If some one else turns on another shower then the flow is poor, no different to what a combi would produce.

My tank is solar fed hence the size, if I didnt have solar I would not think twice about a high output combi, running costs
must be lower rather than heating a massive tank.

There are 2 adults and 4 kids in the house and we use sh.t loads of water.

Bearing in mind I do more repairs on cheap unvented cylinders than combi boilers in my eyes unvented isnt always better.

No it's not always better both have there use
It's getting the right system for the user
And ps you may have 6bar incoming but then it's in to a pressure reducing valve then out to balanced cold supply's

 

[Ryan LPS]

Go biomass boiler with thermal store a instant hot water coil and a secondary hot return by far the best system for you in my op.... Government will pay you for the next 20yrs as well

 

[Kev the gas]

No it's not always better both have there use
It's getting the right system for the user
And ps you may have 6bar incoming but then it's in to a pressure reducing valve then out to balanced cold supply's

The 6 bar incoming was indicating that there is sufficient incoming pressure, obviously then reduced down.

I mentioned it just incase there was any doubt.

 

[Kev the gas]

Go biomass boiler with thermal store a instant hot water coil and a secondary hot return by far the best system for you in my op.... Government will pay you for the next 20yrs as well

Biomass even if mains gas is available??

Ive never heard that suggested before for a domestic property.

 

[Gray0689]

Go biomass boiler with thermal store a instant hot water coil and a secondary hot return by far the best system for you in my op.... Government will pay you for the next 20yrs as well

What's an instant hot water coil???

 

[Ryan LPS]

What's an instant hot water coil???

In thermal store you can get a coil that goes from bottom to top of buffer comes out around 76*c has to have a blending valve reli and yes why stay gas wen you can go green and still cut your normal gas bills today iv just put a small biomass pellet boiler in a small two bed cottage. Going to there vented cyclinder

 

[Gray0689]

In thermal store you can get a coil that goes from bottom to top of buffer comes out around 76*c has to have a blending valve reli and yes why stay gas wen you can go green and still cut your normal gas bills today iv just put a small biomass pellet boiler in a small two bed cottage. Going to there vented cyclinder

Lol that is the hot water coil
Instant hot water lol
It's only hot water if the store is hot lol

 

[Ryan LPS]

No they call it a install hot water coil cos it will work the same as a combi hot water on call constant. You may call it a hot water coil... Do you do many buffer systems then

 

[Ryan LPS]

Not being funny just wanted to no you views on it

 

[Gray0689]

No they call it a install hot water coil cos it will work the same as a combi hot water on call constant. You may call it a hot water coil... Do you do many buffer systems then

Yep do a few with buffer and a few with thermal stores
And never heard of a instant hot water coil
And no they don't work like a combi
As you have to have the store hot to get hot water the boiler or heat source heats the store direct
The hot water gets hot through heat transfer

 

[Ryan LPS]

Yh but most store are always kept hot as the pellets used to start boiler up and the to have on full burn to heat say a 1000L store what I installed with the hot water coil would take a fair amount of time but hence why there called a thermal store cos there always kept hot you wouldn't have a buffer system you would just have a standard unvented cylinder

 

[Ryan LPS]

Oh I said they work like a combi because through a coil it is instant hot water hence why I explained it like that maybe the wrong term of words but like I say I ment cos you can get instant hot water

 

[Gray0689]

It's only instant if the buffer or thermal store are hot yes correct to is better to keep hot all the time but in summer when no heating is required it's bad practice to keep a 1000l buffer hot all time
And a buffer tank is not the same as a thermal store
Do you fit many!!

 

[Ryan LPS]

The principal of a thermal store cylinder is similar to that of a buffer tank or accumulator. Essentially it is an efficient method of linking multiple energy inputs together, and provide domestic hot water as main pressure. Anyway I don't think it's fair to the o.p to carry this on. On his post if you wanna talk bout it mate then pm me....

croppie if you wanna remove are post up to are suggestion I think it's only fair that the o.p don't have us trying to get one over on the other