Replacement of Worcester Bosch Greenstar 40 CDi Conventional boiler - system or regular - or what?

uffington

It's coming to the end of its life I suspect, after more than 16 years, but where to start with the replacement?

It will be another Worcester Bosch - that's for sure - but which one? It's a sealed system with a Megaflo hot water 'cylinder' about 19 years old. No cold water tank.

I'm guessing that the replacement needs to be a Greenstar 8000 Life or Style - Life probably, because Style looks to have limited benefit for the extra cost.

But regular or system?  Or doesn't it matter which?

And is that Megaflo worth replacing at the same time? It's never had any attention over its entire life, but it's not going to last for ever.

macman

Why a WB 'for sure'? Look at Viessmann as an alternative.

ThisIsWeird

What do you mean 'regular or system'?
Isn't your current one 'system'? On the chance it's vented, then def change to system boiler, def - get rid of all cold storage tanks.
Do consider the best type of CH controls, tho' - Opentherm or similar. Get the max efficiency out of your boiler control, and lowest output temp. An issue is that you will want your DHW output at 60+, but your CH often lower than this, so ask each manufacturer how they can achieve this.
As macman says, don't dismiss alternatives to WB.

uffington

macman said:

Why a WB 'for sure'? Look at Viessmann as an alternative.

Vaillant might be an option, but as 'Which?' put it recently for Viessmann:

".....after parts supply issues and unsatisfactory manufacturer support dragged its score down."

I've always found WB support to be absolutely first rate.  Highly unusual these days!

uffington

ThisIsWeird said:

What do you mean 'regular or system'?
Isn't your current one 'system'? On the chance it's vented, then def change to system boiler, def - get rid of all cold storage tanks.
Do consider the best type of CH controls, tho' - Opentherm or similar. Get the max efficiency out of your boiler control, and lowest output temp. An issue is that you will want your DHW output at 60+, but your CH often lower than this, so ask each manufacturer how they can achieve this.
As macman says, don't dismiss alternatives to WB.

The current one was/is described as 'regular' (it's a sealed system, as explained) and WB still sell the same boilers as either 'regular' or 'system'.  I may be wrong, but I suspect the difference is that the system boilers have small internal expansion tanks. Not, I think, necessary for my system.

FreeBear

macman said:

Why a WB 'for sure'? Look at Viessmann as an alternative.

Or a heat pump - Octopus are currently giving quotes that are coming out very close to the cost of a replacement gas boiler. If you are fortunate to have 22mm or even 28mm feed/return and relatively short runs of 15mm to the radiators, you may not need much additional plumbing work. Certainly worth a look.

Unfortunately, the incentives were not available last year when I had my boiler fitted (Viessmann combi)... Went from a vented system to fully sealed with new plumbing & radiators.

ThisIsWeird

uffington said:

ThisIsWeird said:

What do you mean 'regular or system'?
Isn't your current one 'system'? On the chance it's vented, then def change to system boiler, def - get rid of all cold storage tanks.
Do consider the best type of CH controls, tho' - Opentherm or similar. Get the max efficiency out of your boiler control, and lowest output temp. An issue is that you will want your DHW output at 60+, but your CH often lower than this, so ask each manufacturer how they can achieve this.
As macman says, don't dismiss alternatives to WB.

The current one was/is described as 'regular' (it's a sealed system, as explained) and WB still sell the same boilers as either 'regular' or 'system'.  I may be wrong, but I suspect the difference is that the system boilers have small internal expansion tanks. Not, I think, necessary for my system.

Ah, I see. 
An expansion vessel will be required somewhere, so that will be internal to the boiler or external, the latter usually means mounted in the hot cylinder cupboard.
In essence, internal to the boiler means neater. External means it's easier and cheaper to replace if it fails.
AfaIk.

Albermarle

In the title you say you have a 40KW boiler, and I think with the Greenstar 800 you have a choice of 30Kw or 35Kw.

Unless you have a very large house, you do not need even a 30KW boiler, with the system you have. Although many heating engineers seem to like to overspec boilers for some reason.
For example I have a megaflo system and a WB boiler. We have 13 radiators of various sizes and our 18Kw boiler copes easily, even in an older, slightly draughty house.

As said also worth researching a heat pump instead. With the grant on offer installation will have a similar cost.
However there can be a lot of extra costs, if the house needs a lot of improved insulation/new radiators etc

uffington

Albermarle said:

In the title you say you have a 40KW boiler, and I think with the Greenstar 800 you have a choice of 30Kw or 35Kw.

Unless you have a very large house, you do not need even a 30KW boiler, with the system you have. Although many heating engineers seem to like to overspec boilers for some reason.
For example I have a megaflo system and a WB boiler. We have 13 radiators of various sizes and our 18Kw boiler copes easily, even in an older, slightly draughty house.

As said also worth researching a heat pump instead. With the grant on offer installation will have a similar cost.
However there can be a lot of extra costs, if the house needs a lot of improved insulation/new radiators etc

Thanks - I do need to get the size of the boiler checked. The 40kW was put in because the original 29kW couldn't cope, but there may have been other reasons for that.  It is a large house though, with several double height rooms increasing the overall volume.

Our underfloor heating should make a heat pump even more viable, but I'm pretty sure one wouldn't cope. Doubtless there are larger ones though, or maybe it's a case of doubling up.  A neighbour had one installed a couple of years back - with a load of top-up electric radiators following soon after!

Food for thought, and the decision would probably be a lot clearer two or three years down the line.  

sheslookinhot

Why don’t you ask WB for technical support in helping you chose which boiler to purchase ?