Recommendations - Storage combi or Normal combi?

[Del-inquent]

Our new place is a bit lacking on spaces to put tanks / cylinders, and our planned extension removes where the storage tank sits, so we can either go for an unventilated tank or a combi. Combi would save a lot of hassle with plumbing and free up the space the tank currently sits for some (much needed) storage space.

Every time we've been somewhere with a combi before, it's p****d my wife right off. Turn on a tap, shower goes cold or messes around.

New place has family bathroom, ensuite and obviously kitchen tap. 

I've got some people saying a high flow combi will be fine, others saying a storage combi would be way forward, others saying neither and go unventilated.

Thoughts of the esteemed members here? I should point out my wife is Latina, therefore my very life is in danger if she gets blasted with cold water. 😅

If a storage combi is the way forward, any recommendations? There don't seem to be that many out there. 

[JohnMo]

Gas is really the past. But if you insist on gas you have the two options you mentioned plus combi with pre heat cylinder.

 

The issue with all combi boilers in the UK is they are fitted with a flow restrictor to help with the production of hot water in winter and the required extra heating needed as the cold water coming into the house get colder. So even the best performance on paper can be an issue in reality.

 

Combi-SuperFlow-White-Paper-v1-2-4.pdfCanetis-SuperFlow-Product-Sheet-WE-050318.pdf

 

A combi storage gets around this by having a volume of water heated by the CH circuit. A pre heat cylinder does the same thing. And is more flexible space wise.

[Andehh]

Have you got a loft space you could use?

[Del-inquent]

2 hours ago, JohnMo said:

Gas is really the past. But if you insist on gas you have the two options you mentioned plus combi with pre heat cylinder.

 

The issue with all combi boilers in the UK is they are fitted with a flow restrictor to help with the production of hot water in winter and the required extra heating needed as the cold water coming into the house get colder. So even the best performance on paper can be an issue in reality.

 

Combi-SuperFlow-White-Paper-v1-2-4.pdf 960.61 kB · 9 downloads Canetis-SuperFlow-Product-Sheet-WE-050318.pdf 322.43 kB · 4 downloads

 

A combi storage gets around this by having a volume of water heated by the CH circuit. A pre heat cylinder does the same thing. And is more flexible space wise.

My house is also from the past... a neighbour (identical property) had a heat pump fitted. Then they had a gas boiler refitted when it proved entirely incapable of keeping the place warm. 

That is very interesting on the pre-heat cylinder. Nobody has mentioned that. Looking at the photo, I might just be able to squeeze that in somewhere!

[Del-inquent]

1 hour ago, Andehh said:

Have you got a loft space you could use?

I'm not saying we are tight on space, but put it this way; at the moment, the expansion tank fitted by British Gas for the previous owner, is screwed to the bedroom wall... nice touch, I thought.

[SimonD]

4 hours ago, Del-inquent said:

Our new place is a bit lacking on spaces to put tanks / cylinders, and our planned extension removes where the storage tank sits, so we can either go for an unventilated tank or a combi. Combi would save a lot of hassle with plumbing and free up the space the tank currently sits for some (much needed) storage space.

Every time we've been somewhere with a combi before, it's p****d my wife right off. Turn on a tap, shower goes cold or messes around.

New place has family bathroom, ensuite and obviously kitchen tap. 

I've got some people saying a high flow combi will be fine, others saying a storage combi would be way forward, others saying neither and go unventilated.

Thoughts of the esteemed members here? I should point out my wife is Latina, therefore my very life is in danger if she gets blasted with cold water. 😅

If a storage combi is the way forward, any recommendations? There don't seem to be that many out there. 

 

.A properly sized combi will not provide unwanted bursts of cold water, nor will a properly sized unvented cylinder, but an unvented cylinder will run out of hot water and need re-heating whereas a combi won't. But a combi also has its drawbacks, especially if it has to provide simultaneous hot water to multiple outlets.

 

First you need to sit down and figure out your hot water usage and patterns. For example, do you use lots of short bursts of hot water or do you tend to draw large amounts of hot water at a time, like for baths and showers? Also, what are your usage patterns in terms of timing for the main bathroom and the ensuite.

 

Then you need to check your mains water flow rate and pressure (both static and dynamic).

Together, this information will provide you with a more sound basis for your decision making because it will guide you in the direction of the best solution for you and the best solution might be worth the price of storage. But it's difficult to say without more information.

 

Regarding specific products likened to storage combis, Alpha Innovation provide a boiler that has storage and pre-heat for DHW here: https://www.alpha-innovation.co.uk/products/FlowSmart/FlowSmart/1836534677 which is slightly different to a normal storage combi. Storage combis are great if you draw lots of small amounts of hot water as it reduces dhw cycling but some non-storage combis have a pre heat function that can be useful for this, so as i say figure out your usage needs first.

[JohnMo]

24 minutes ago, SimonD said:

Regarding specific products likened to storage combis, Alpha Innovation provide a boiler that has storage and pre-heat for DHW here: https://www.alpha-innovation.co.uk/products/FlowSmart/FlowSmart/1836534677 which is slightly different to a normal storage combi.

That's the same as the info I provided above but in a wall mounted version, closed coupled to the boiler. Not all combi boilers will take pre heated water, Alpha , Atag, and Intergas do, most other companies are a bit sketchy on details, I suspect most would but tech support in the UK don't come across it much, so outside comfort zone, so they just say no.

[Andehh]

Combi for primary usage, electric shower for secondary?

[Adsibob]

@Del-inquent find out your mains pressure and flow rates as @SimonD mentions.

 

 We have one more bathroom than you, and still manage well with just a 300L UvC and system boiler. Unless you have lots of baths, you could go smaller than that, maybe 240L. In horizontal configuration they can be hidden in lofts quite easily.

Edited October 27, 2023 by Adsibob

[Lofty718]

If you get a boiler setup with hot water priority and use a heat pump cylinder with a large coil you could probably use a tiny 100l cylinder depending on the size of your property

 

[LiamJones]

Had an Ideal Logic Combi 35kWh boiler at my last place doing 2 bathrooms. Yeah the pressure dropped a little when using both, but that was infrequent enough that it didn’t bother me. the temperature certainly never dropped regardless. If I wasn’t going heat pump this time round I’d have no hesitation about chucking in a big combi again. I really liked that I didn’t need to think about hot water. It was just available all the time.