I see the original poster hasn't said what he wants from his system? Perhaps we've scared him away.
The CDi condenses in hot water mode and the Vaillant doesn't (in fact very few boilers do). This is a minor performance difference, but might be important if you use a lot of hot water in proportion to heating.
The CDi has a silicon coated aluminium heat exchanger where the Vaillant has a stainless steel one. Stainless steel is good, aluminium not so good, the coated ones perhaps too new to tell. Anyone have any feedback?
The CDi heating output modulates down slightly lower which may avoid cycling in some cases where you have low heat extraction, which is very common with insulated houses and TRVs. Lower power Vaillants modulate to much lower levels. Maximum CH power is slightly higher on the 37CDi, but remember that almost any combi boiler is massively over-sized for almost any home.
The Vaillant is available with a small hot water tank (937 storage model) for faster supply of hot water. Might be important if you constantly demand small quantities of hot water. It will knock you back an extra 100 quid or more. Nearly all boilers have a feature to keep the heat exchanger permanently hot for reasonably fast hot water delivery, usually as the default setting.
Not huge differences, but something might strike you as important. Both have installation and maintenance quirks. The Vaillant ecotec plus 837 is usually a little cheaper than the Worcester 37CDi.
The CDi condenses in hot water mode and the Vaillant doesn't (in fact very few boilers do). This is a minor performance difference, but might be important if you use a lot of hot water in proportion to heating.
The CDi has a silicon coated aluminium heat exchanger where the Vaillant has a stainless steel one. Stainless steel is good, aluminium not so good, the coated ones perhaps too new to tell. Anyone have any feedback?
The CDi heating output modulates down slightly lower which may avoid cycling in some cases where you have low heat extraction, which is very common with insulated houses and TRVs. Lower power Vaillants modulate to much lower levels. Maximum CH power is slightly higher on the 37CDi, but remember that almost any combi boiler is massively over-sized for almost any home.
The Vaillant is available with a small hot water tank (937 storage model) for faster supply of hot water. Might be important if you constantly demand small quantities of hot water. It will knock you back an extra 100 quid or more. Nearly all boilers have a feature to keep the heat exchanger permanently hot for reasonably fast hot water delivery, usually as the default setting.
Not huge differences, but something might strike you as important. Both have installation and maintenance quirks. The Vaillant ecotec plus 837 is usually a little cheaper than the Worcester 37CDi.
