Baxi Duotec 40 vs Vaillant 837

diywhynot

imr4n wrote: »

Understood, thank you.

The current boiler is a 28kw and it's undersized which has been confirmed by 2 different engineers. The radiators only get hot if the heating is set to near maximum and there radiators are affected big time when a hot water tap is turned on.

Therefore I'm not wanting to pay thousands for a new boiler install that is only 10% better than currently.

How many rads on your system? What is the make and model of your current boiler?

southcoastrgi

imr4n wrote: »

The current boiler is a 28kw and it's undersized which has been confirmed by 2 different engineers.

I doubt that very much, if you need more than 28kw for the heating a combi isn't the right choice anyway

The radiators only get hot if the heating is set to near maximum and there radiators are affected big time when a hot water tap is turned on

on a combi the heating doesn't work when you turn on a hot tap

330d

diywhynot wrote: »

How many rads on your system? What is the make and model of your current boiler?

It's a 4 bedroom house with 2 bathroom and 13 radiators.

Current boiler is a Vailant eco pro 28.

southcoastrgi wrote: »

I doubt that very much, if you need more than 28kw for the heating a combi isn't the right choice anyway


on a combi the heating doesn't work when you turn on a hot tap

So how come there are 28+ kw combi boilers are available?

southcoastrgi

combi's are sized on hot water flow rate not the heating requirements, I doubt with 13 rads the heating req is anymore than 18kw

two bathrooms & 15 ltrs/min incoming supply no wonder you aren't happy with the performance

daveyjp

southcoastrgi wrote: »

I doubt that very much, if you need more than 28kw for the heating a combi isn't the right choice anyway

Agree with this and I suspect an issue with the CH circuit and not the boiler, 28kw should be more than enough. My wife's company has just had a new boiler fitted in their offices. They have 16 radiators and the boiler is a Vaillant (non combi) 18kw.

The boiler replaced an ancient Ideal Mexico, but the reason the heating wasn't good were two fold. Crud in the system, one radiator needed replacing and the Powerflush took two days. Secondly the pump was too small for the distances. A much larger pump was fitted and no one now complains of being cold.

330d

So is there any way of improving the flow rate?

I may call out another engineer for a 2nd opinion.

southcoastrgi

not without upgrading the size of the incoming supply back to the company stoptap

330d

I've got another engineer coming today to assess the property and provide a quote.

As well finding out my flow rate and pressure, what other questions should I be asking?

diywhynot

imr4n wrote: »

I've got another engineer coming today to assess the property and provide a quote.

As well finding out my flow rate and pressure, what other questions should I be asking?

Ask about suitability of an unvented cylinder and system boiler.

diywhynot

imr4n wrote: »

I've got another engineer coming today to assess the property and provide a quote.

And how did that go?