Boiler/storage guidance required

[astiling]

Hi all, I’m looking for some guidance on whether we’re planning on the right boiler solution for our house.

The house – 3 story townhouse with 3 bedrooms, 2 living areas, 2 bathrooms with showers, 9 years’ old.

Boiler – Current one is v noisily and a couple of different opinions say to replace it. The view is that strangely it seems to be older than the house. It is a combi and supplies hot water just fine. This is located on the 3rd floor. Water was tested at 3 bar on this floor adjacent to the boiler.

Heating - is an underfloor wet system with thermostats in each room and a couple of manifolds with the heads presumably connected to the room thermostats. This is currently not really working. Due possibly to the blending valve not operating (this has the flow in/out and return in/out – apparently difficult to source a replacement so maybe a slight re-design would be needed.

We’re open to replacing the boiler and thought that a bosch combi – highflow cdi model would be a sensible replacement. Accepting there is no hot water storage with this but with the claimed L/min output and decent pressure at the boiler think that could be fine.

One potential supplier/installer has said instead to use a system boiler and a storage tank. This seems to add more parts and more cost. Their reason for this is to mainly to separate the heating from hot water which they say is better.

One other complication is that we need a condensate pipe with whatever we do now but that is the same for either proposed solution.

It would be really helpful based on the above to know if we should be concerned about the hot water and heating running off a combi for a house of this size and of there is any other option we should consider.

Many thanks
Adam

 

[Agile]

You have not told us how many live there!

Or the dynamic flow rate. Static pressure means nothing to performance.

You seem to have fallen into the trap of thinking that a storage combi will give you a high flow rate continuously.

Obviously by asking here you have not been impressed by the RGIs you have spoken to. Presumably they came free to quote but you really wanted them to specify a system for you. Not really the best way to specify a system. I don't make free visits for that reason and give instead budgetary quotes by phone.

Unless there are always going to be only two living there who are happy to have showers at different times, then I would always recommend a stored water system with 50 li plus 50 li per person capacity as a guide.

Tony

 

[astiling]

Thanks Tony for your reply.

There will generally be 2-3 people in the house, more of a holiday home at the moment than full-time use but that is hoped to change in a few years so we need it working well for 2 people full time living.

You seem to have fallen into the trap of thinking that a storage combi will give you a high flow rate continuously.

I was thinking not to have any storage just a combi - the highflow says 20L/min which to me seemed great for 1 shower but of course heavily reduced for 2 but 2 at once would be less likely and not a critical requirement if that is what means we need to buy a hot water tank etc.

Hope that helps clarify a little.

Thanks again
Adam

 

[muggles]

The Highflow has a small store of hot water inside it and only gives 20L/min until the store is depleted. Once the store's gone you'll find that you get a much lower flow rate, probably around 12l/min. Also, the Highflow weighs 112kg and I think you'll struggle to find someone who's willing to carry that up to your third floor!

Your potential installer is correct, you'd be much better off with an unvented hot water cylinder and conventional boiler. I doubt the difference in cost would be very much as the Highflow is really quite expensive to buy.

 

[Agile]

With only two people then a combi will work.

But if you can afford to keep a holiday home I am sure you can afford a storage system which will be little more than a storage combi like the Hiflow series. Heat only boilers are cheaper than combis.

Its always important to install a system which would be suitable for a large family in the future. A 3 bed house can house up to six people.

Tony

 

[astiling]

Wow yes just noticed the weight, that could be a challenge to get up 2 floors with not the widest staircase

Really appreciate the input.

Many thanks
Adam

 

[Agile]

There are lighter wall mounting storage combis like the GlowWorm model.

But its a heat only boiler and storage cylinder that I would be advising you to get.

Tony

 

[astiling]

The proposal from one supplier/fitter is Worcester 18i + Worcester cylinder 250L indirect unvented + various other parts to make it all work. With the added complication of the condensate pipe - though maybe we can route that over the roof to save going through concrete floors and re-tiling part of the bathroom (aware this is not ideal but if heated and suitably pumped this I think may be more cost effective and less disruptive).

The parts add up in cost quite quickly....amazing how a boiler at <£900 ends up being a bill for >5K Though will see how the re-routed condensate pipe may help with that.

Regards
Adam

 

[Agile]

That is an ideal combination!

But ask ALL of the installers to quote for that combination so you can choose the best installer for that system.

I am always surprised how so many only quote for one system as if its all they know how to do.

Routing the condensate will apply to all new boilers and is very easy with a small pump which can pump upwards to 3m height and use a small flexible tube.

Tony