What size boiler

[JessieJames]

Have been advised on a Worcester CDI 34.
Its for a terraced house, 3 bed, 1 bathroom, 9 rads in total.
Im thinking this is too high for a house this size.
Worcester web site calc says just a 24i.
Any advice would be appreciated.

 

[Dan Robinson]

If it has to be a Worcester, stick with the cdi.

The hot water performance is the main thing.

Any combi boiler will be grossly oversized for the heating requirement of your house.

 

[JessieJames]

It doesn't have to be a Worcester.
Thanks for the reply

 

[Dan Robinson]

In that case, check out Intergas, Atag and Vaillant - all better boilers.

 

[JessieJames]

Thanks for the info. replacing a vaillant now, 8 years old. its been a bit of a pain. Have just found out most of the install is not to spec. So many errors. Just ripping it all out and start again. Its prob not fair but have a mental block now on vaillant.
Was advised on the Worcester CDI esp as comes with a 7 year warranty parts & labour, 10 years on the heat exchanger.

 

[Dan Robinson]

The new ecotec is better than the cdi.

Long warranties are by and large meaningless.

The best thing about Worcester is the after sales support.

I'd prefer a better boiler personally.

 

[JessieJames]

I will check those out. So is a combi not my best route?

 

[Dan Robinson]

Combi's have their place in the world, but you need to understand the pros and cons.

They take up less physical space.
High pressure hot water.
Unlimited hot water.
Few standing losses.


However....

No backup
More complicated - well not really, but for the sake of numpty repair men .
Lower flow rate.
Only one outlet can be used at a time.
Slow bath fills.
Bigger gas supply needed (not to be confused with high gas bills).

 

[JessieJames]

Think ive met them lol. So what do you advise, knowing my house size?

 

[Dan Robinson]

If the back up issue and gas pipe size issue are not problems, then I would look at the Intergas HRE18/24 or the Ecotec 824 or 831.

If the boiler is in a garage or utility room then the Atag every day.

If you are heavy bath users then for sure go for the higher outputs to get the faster bath fills. Otherwise 24kW is fine for showers.


I am not telling you to avoid the Worcester - just the 3 I mentioned are the ones we now fit out of choice as the aftersales are perfectly adequate and the warranty plenty long enough. We happen to think the boilers are better engineered than the Worcesters.

This is based in installing all of them and stripping working boilers down to the chassis and reassembling them to working order.


As I said before, heating capacity doesn't factor into things much with combis. Your house probably only need 8 to 10 kW in the darkest parts of winter.

 

[JessieJames]

Cheers Dan, you have given me plenty to think about. I read on line that if the combi boiler is too powerful, like the CDI 34, that the boiler will keep on cycling and can be a problem. Is that the case?

 

[Dan Robinson]

Cycling being a negative is under debate. I personally hate it. But others seem to not worry.

 

[Phill Peck]

Thanks for the info. replacing a vaillant now, 8 years old. its been a bit of a pain. Have just found out most of the install is not to spec. So many errors. Just ripping it all out and start again. Its prob not fair but have a mental block now on vaillant.
Was advised on the Worcester CDI esp as comes with a 7 year warranty parts & labour, 10 years on the heat exchanger.

Can I ask what is wrong with the vaillant and what model it is?
I would assume turbomax plus?

I'm very suprised an 8 year old vaillant needs ripping out

 

[JessieJames]

Its the Ecomax 828/2e.
Have had nothing but problems. PRV has been changed twice. Gauge always shows at zero. The small heat exchanger has just failed, water spraying everywhere. Have been told the fan has gone due to the spraying.
Have now discovered the guys who installed it have not followed guidelines. PRV pipe goes up. Gas pipe connection is app illegal. Its just been a nightmare.

 

[JessieJames]

Is the cycling just a cost issue or does it damage the boiler too?