Are you curious about the reason why Worcester Bosch sell a 40kW regular boiler, but not a 40kW system boiler?
It’s a good question, and one I hear occasionally from customers who have large homes and need to choose. Not everyone understands why they can’t have a 40kW system boiler, and either have to opt for a regular boiler or a system boiler with a separate expansion vessel.
Sound confusing?
As an Edinburgh engineer with over 20 years’ experience, I’m going to shed a bit more light on the subject, below.
Why doesn’t Worcester Bosch sell a 40kW system boiler?
Well, first thing’s first; the highest output system boiler Worcester Bosch sell is the Greenstar 35CDi system.
Yet, they’ll happily sell you a 40kW regular boiler – why? Well, the main reason is the output of a 40kW boiler. These are very high output boilers, and can service many radiators, and a hot water tank. Usually you’ll find these in three or four-storey homes.
Due to the amount of radiators and water in the system, the expansion vessel may have to be a larger capacity than on large system boilers. In this case, the engineer will determine the correct size of vessel for your property, and fit it separately to the boiler.
This may mean a little extra cost and labour, but it also means you can still have all the heating and hot water you’ll need for your home, with the boiler you want.
Will an unvented cylinder make a difference?
Unfortunately not. When looking at the boiler’s output, it doesn’t matter if you have a vented or unvented cylinder, as it’s more to do with the volume of water that’s to be heated.
As I mentioned above, these boilers are fitted in large family homes. So, typically they’ll have a cylinder of around 200 – 300 litres that can take 5 – 8 kW of power to heat on high fire of your boiler (this will vary depending on your individual needs).
Advice from an experienced heating engineer
Never under heat your home to save costs – or space – just because you think it’s easier. Not having that extra 5kW could mean feeling cold and not having enough power in the depths of winter.
Many clients (and some heating engineers) only look at the number of radiators to be heated, the forget about the hot water calculation. Also, some engineers seem price-sensitive and worry more about the extra cost of a larger boiler, remote expansion vessel and extra labour, instead of providing the correct solution for their customers.
Don’t fall for this trap. If possible, get 2 – 3 fixed price quotes (to see if they match up) and ask your engineer why they’re making that choice. Trust your gut.
Conclusion
Thanks for reading. I hope this blog has helped give you a better idea of why Worcester Bosch sell a 40kW regular (heat only) boiler, but the biggest output system boiler they sell is 35kW. This doesn’t mean you have to be limited to 35kW, or are forced to choose a regular boiler, however.
In fact, it just means you’ll most likely need a separate expansion vessel to make up the extra power. Just be wary that not all engineers will be willing to suggest this idea, as it can mean extra costs and labour.
Want to know more about Worcester Bosch system boilers and expansion vessel options? Just pop me a comment below. I’ll be happy to help!
