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.

 

[Ermintrude]

Thanks for the reply. Thats good to know you are getting good results with the Worcester.

I telephoned Worcester and they confirmed that CH side must be hard water (due to aluminium heat exchanger I think) but DHW side can be softened as heat exchanger is stainless steel. I can isolate the water softener so that the CH could be filled with hard water. But would the boiler still need a hard water supply ?

No hard water through combi or any plate type heat exchanger causes scale. Phosphate type softness isn't best. That's why if over 200ppm you recommended to install cal mag or similar on combi!

 

[Mrs Tara Plumbi]

Getting another quote from local guy. Thanks for the replies.

Hi.
Do you want to tell us where you are - if any of the experts here might be able to give you a quote.

Back to OP - I'm a fan of combis! In my house we have a combi and 2 showers - I've never tried to use them both at the same time so I don't know what would happen.

but when I'm in the shower the kids frequently decide to come clean their teeth and flush the loo and wash hands - there is small minimal impact on the shower. But I'm sure you know incoming water pressure is important as well as the size of your boiler.

Finally, please be clear I'm not a heating engineer and the other guys on here write a lot of sense. If we had more space we probably wouldn't have a combi because my hubby also thinks along the same lines as the other heating engineers.

 

[lame plumber]

I'm not a big fan of solar on thermal stores
Simply because the householder generally just leave boiler heating store all time and solars don't get chance to work efficiently
And the pellets are made about 30 milled from where I live (ballcas)
I've fitted a couple of grant spirotec wood pellet boilers and must say very impressed with what I have seen so far

then the installer hasnt set it up correctly and explained how to use it properly, whats cheaper and better sun light or pellets made from chopping down a tree, grinding it into a mash, forming pellets and then moving the end result to the customer and burning it and producing co2. sometime the world will see snese and go for the option that relies on sunlight with a backup mechanism and not vice versa!!

 

[Dotty]

Thanks for the reply. Thats good to know you are getting good results with the Worcester.

I telephoned Worcester and they confirmed that CH side must be hard water (due to aluminium heat exchanger I think) but DHW side can be softened as heat exchanger is stainless steel. I can isolate the water softener so that the CH could be filled with hard water. But would the boiler still need a hard water supply ?

The heating side would yes, but get the filler loop tapped off before the softener and the job's a good'un!

 

[Dotty]

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

I'll leave it running Ryan, It's an interesting exchange of opposing views and doesn't come across as one upmanship. As long as it's kept friendly then I'm cool.

 

[Gray0689]

then the installer hasnt set it up correctly and explained how to use it properly, whats cheaper and better sun light or pellets made from chopping down a tree, grinding it into a mash, forming pellets and then moving the end result to the customer and burning it and producing co2. sometime the world will see snese and go for the option that relies on sunlight with a backup mechanism and not vice versa!!

No set up correctly at start explained correctly
But some customers always think they now best lol

 

[smhstu]

Why not get a combi three zones one for a cylinder coil on vented cylinder fed by tank to a pump just for showers and have instant hot water for all other outlets?

Just a suggestion to put the cat among the pedgons..

 

[nialle17]

A system boiler would enable you to make better use of the showers and baths you have. A combi would defeat the object of having numerous showers and baths if they cant be used.

 

[Howsie]

Why not get a combi three zones one for a cylinder coil on vented cylinder fed by tank to a pump just for showers and have instant hot water for all other outlets?

Just a suggestion to put the cat among the pedgons..

There are many ways to skin a cat depending on the cat. TBH if its a decent size house, it should have secondary return anyway.

 

[Gray0689]

There are many ways to skin a cat depending on the cat. TBH if its a decent size house, it should have secondary return anyway.

Agree most do just depends on location of cylinder to bathrooms

 

[Jimbob]

Combi on that lot is always going to be insufficient. Any manufacturer would also agree. Stored DHW is the only way to go. Don't be scared by BGs price, they will be much more than a decent local installer.

 

[Centralheatking]

I will not read the comments below - but really a combi will not do they are rubbish and
go wrong esp in this set up.

All the sensible tradesman below will tell you to fork out for a decent system set up
you could even be lookin at a dual boiler system in my opinion

CHK

 

[Centralheatking]

Mike is correct get a BG quote and we normally half it and still make a good wedge

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.

 

[Kev the gas]

I will not read the comments below - but really a combi will not do they are rubbish and
go wrong esp in this set up.

All the sensible tradesman below will tell you to fork out for a decent system set up
you could even be lookin at a dual boiler system in my opinion

CHK

What a fracking stupid waste of internet space.

If you cant be bothered to read the previous discussions, why bother to comment?

 

[Ermintrude]

I will not read the comments below - but really a combi will not do they are rubbish and
go wrong esp in this set up.

All the sensible tradesman below will tell you to fork out for a decent system set up
you could even be lookin at a dual boiler system in my opinion

CHK

Combi rubbish not in right application? Agree wrong for this set up, ACV cylinder and high output system boiler with water softener on DHW & DCW excluding potable water. Get cylinder with solar flanges for future?

Also possibly zone floors ?