Worcerster CDI or SI

[Vincenzo]

Hi All,
I hope you will excuse my ignorance but I need to get this straight!
I need to replace my old Ferroli and I’m looking into Worcester-Bosch boilers.
I had several people in giving me quotes.. ..prices varies from 2K£ to 3K£ just for boiler and work.
One suggested the 24i Junior (British Gas guy, not sure he knew his job), one the 30 SI (South Electric guy), but I like the 27 CDI.
I’m struggling in understanding the difference between the CDI and the SI, I know is the condensing bit, but what does that mean.. ..what does it add to me?!? I also see that the CDI is bigger and heavier, do you guys know why? In 10 years time will I be better of with the CDI or SI?
As yet, I have only 7 radiators (will have 10 when the loft is converted) and 1 shower (2 with the loft done), so I guess I need only 20KW output as max needed. CDI or SI should be more than enough!
Where I get confused is here.. ..I only get 9.9L/min water from my main.. .. can I still get the 11.1 DHW (@ 35°) with the 27CDI or 12.3 DHW (@35°) with the 30 SI?!? How does that work?
I was thinking to also add a magnetic central heating filter and scale reducer, would you guys be able to suggest me the best once around?
Again.. ..Thanks for your help… Hope you guys can help…
Thank You.

 

[grahamgas]

If you only have 9.9 at the moment then you will only ever get this out of the hot.

The key thing to remember is the delta t. 35 degree rise is good in the summer when potentially the incoming cold main is say 12 degrees, this means you get 47 degree water.

Come winter when the main is 3 degrees, then you only get 38 degrees. This is when you have to reduce the flow from the taps to get the hot water.

Is your system at the moment a combi system?

Graham

 

[Vincenzo]

Thanks Grahamgas,

Yes, it is combi.

So, what you are saying is that a 30 SI will not work properly?
What do you think will be the best with what I have?

Thanks for your help.

 

[diamondgas]

Thanks Grahamgas,

Yes, it is combi.

So, what you are saying is that a 30 SI will not work properly?
What do you think will be the best with what I have?

Thanks for your help.

Hi Vincenzo,

if you're cold is supplying 9.9ltr/min then putting say a 12ltr/min boiler would guarantee hotter water in the colder months. If you install an appliance that'll only guarantee 35degC at 9ltr/min means that on maximum that is all it will ever deliver guaranteed. however if you install something with a higher output it will not have to strain as much to deliver the 35 degC rise and will most likely supply a lot more. Therefore in the colder months it'll give you more heat. Does that make sense?

 

[Vincenzo]

Thanks Steve,

it makes perfect sense.

In this case, I should be better of with the 30si as it has 12.3 DHW.

But there is anyone that can tell me the difference between the SI and CDI?

Thank You all for your help...

 

[gaspastemania]

Just go on worcesters website they have a which boiler guide to suite your property so will; give you an idea what you should have. IMO get a vaillant much better boiler than worcester , pay top whack for worcesters for what really is quite an average boiler.

 

[diamondgas]

Just go on worcesters website they have a which boiler guide to suite your property so will; give you an idea what you should have. IMO get a vaillant much better boiler than worcester , pay top whack for worcesters for what really is quite an average boiler.

Well Vincenzo I confess I do not install many appliances these days, however looking at the website speak they seem to advertise the Si as a lesser equivalent to the CDi. Personally they seem to be the same stuff in smaller or larger packages! Give or take... lol.... On replacing your original appliance choose someone who will give your original system a thorough clean out. Ask them about flushing etc! If they skip by cleansing then skip by them! MHO!

 

[Vincenzo]

Thanks Steve,
I will make sure about the clean and I guess Worcester 30SI is probably my best bet.

I was also thinking to add a magnetic central heating filter and scale reducer, would you guys be able to suggest me some good once around?

As always, Thank You.

 

[capitanpugwash]

Thanks Steve,
I will make sure about the clean and I guess Worcester 30SI is probably my best bet.

I was also thinking to add a magnetic central heating filter and scale reducer, would you guys be able to suggest me some good once around?

As always, Thank You.

Have a search on the forum for TF1 or Magnaclean. There are many threads that go into great length about the different options but these are the main two. Good luck with the reading.

 

[diamondgas]

I've heard the Fernox TF1 does the job with much less hastle than the Magnaclean. Fitted a good few Magnacleans and had some bother with water leaks on the isolation valves year or so down the line. Next installation I get to do I'll be trying out the TF1. may pay to put a post up regarding best advice on filters? Unless you're in a hard water area I wouldn't be to concerned about scale reducers... However if your water is 'hard' .... well there'a another post in the making regards advice ... 🙂

 

[stevetheplumber]

worcesters arent the best boiler nowdays id always go for a vailant or remeha first fit the 31kw vailant and then forget about it

 

[tackleburger]

Ecotech plus 831

 

[Billy Bob Bob]

i would go for the baxi duotec 33 but everybody knew i was gonna say that anyway its not just because its the bestest or anyfing