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Would any of you knowledgeable chaps have any info on the Combi superflow by canetis, ever fitted any, know anything about them etc, I'm wondering if they could be a way to get a better shower in my place with a WB 24i ?

i cant work out if they 'work", are miracle, a duff, or if i'd still be limited by the boiler 9ltr per min flow rate?

 

SimonG

Plumber
Advent Win
Still limited to your boilers 9 litres per minute. They allow minimal flow through until up to temperature.
Waste of money if your combi has a preheat function.
 

SimonG

Plumber
Advent Win
It's not what I thought it was.

Stores water at 30 Celsius and uses that to supply the combi. In a 25 or 50 litre cylinder. Which is heated by the primary flow on the combi, which doesn't run whilst hot water demand is present.

Even at only 9 litres per minute you are going to exhaust it in a crack.

As well as the growth range for legionella is between 25 and 42 Celsius then I would say that the health risks outweigh any supposed benefit.

Bit of a non starter.

Bigger boiler or fit an unvented cylinder off the combi, leaving just the kitchen sink running off the combi.
 

king of pipes

Esteemed
Plumber
Gas Engineer
Advent Win
No it will not solve your issue only way to improve the shower is add a unvented cylinder off the combi to feed the shower as Simon has stated above leaving the kitchen sink fed off the combi , your thread seems familiar have you asked the forum for advice on a new boiler ? did you take the advice given ? and now have hot water problems regards kop
 
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ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
new boiler but tbh you wont be getting much of an improvement eg around 11-14lpm

what do you need the extra lpm for ?
 
@king, nope, not asked about this Superflow thing before, only found out about them today.
@Shaun , i'm trying to get a more powerful shower in effect, at the moment the hot water is getting hot enough but hot water alone out of the shower is a dribble really, then as soon as you turn on the cold on the mixer taps it gets more powerful but goes cold. Only other thing i've read about is maybe add a non return value on the hot water and a flow restrictor on the cold, to bring it down to 8-10lrs, same/ similar to the hot side. no clue if this work though?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
sounds like its more of a shower issue and maybe not the boiler whats the flow like out of the hot taps? acceptable
 

SimonG

Plumber
Advent Win
No it will not solve your issue only way to improve the shower is add a unvented cylinder off the combi to feed the shower as Simon has stated above leaving the kitchen sink fed off the combi , your thread seems familiar have you asked the forum for advice on a new boiler ? did you take the advice given ? and now have hot water problems regards kop
Asked about upgrading the 24 by just changing something in the boiler.
 
taps are ok ye the one quirk i can see in the hot water to the bath/ mixer tap is, its a 15mm straight run from the boiler of about 6 meters, the pipe pops up under the bath and is t'd off, 15mm to the bathroom sink, then 22mm to the bath tap. The 22mm is only about a meter to the bath tap. the bath mixer taps are Deva, one of these:
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
whats your mains pressure like poor?
 
reasonable good i think, thats part of the problem i think, the mains comes in about 3 foot away from the bath and why when you open up the cold it increases the pressure but makes the "mix' go lukewarm then. To get the shower to the best it can be, you have to open the hot full and a tiny bit of cold. If i crank the cold wide open, its well powerful.
 

king of pipes

Esteemed
Plumber
Gas Engineer
Advent Win
Hmmm thought so we all know a 24 kw will only give you 9- 10 litres a minute Max with a 30° rise so soon as the incoming cold water temperature starts dropping then you notice the drop off in pressure by having to slow the water flow down to achieve a decent shower temperature I personally fit flow limiters to give 8 litres a minute you could try that could avoid having to keep adjusting the shower mixer . Kop
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
I would be switching to a thermostatic shower you can get them so they just thread on to your existing connections eg 180mm
 
@kop, so bang one of these on basically and see what happens?

@Shaun, and recomendations for one that works well with this 8 ltrs ish of flow?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
@kop, so bang one of these on basically and see what happens?

@Shaun, and recomendations for one that works well with this 8 ltrs ish of flow?
Your problem isn’t the hot water flow is too much cold

You could try putting the above flow restrictor on the cold to the tap
 

king of pipes

Esteemed
Plumber
Gas Engineer
Advent Win
As a quick fix you could try one of these I have had some success in rental properties fitting these on the handset, it restricts the flow to 8 litres a minute on older combis with the push of a button . Kop
 

Attachments

We at Canetis, now we have seen the post on the Canetis Superflow (CSF) would like to answer the question from David Stanton and correct the misinformation from “Simon G” and “King and Pipes”. CSF can indeed address poor domestic hot water performance and is not magic rather just a logical development of engineering technology. The actual flow rate of domestic hot water (DHW) from the boiler is governed by a restrictor that is installed by the manufacturer and the only way to increase this is to remove this device. However with a CSF installed the 24KW boiler that David seems to have installed should supply adequate hot water for all but the very largest homes.

The CSF works be providing preheated water to the boiler. This allow the combi boiler to deliver water at a greater temperature than without the device thus increasing the energy value. The 25 litre CSF tests show that when heated to a temperature of 80°C it is able to deliver over 100 litres of preheated water benefit that compares well to a typical 75 litre British bath and less water for a shower. The CSF allows a combi boiler to produce hot water at its design temperature (>40oC ) even when the cold input water is lower than the assumed mains water temperature of 10oC.

Canetis suggest the use case of CSF is for multi bathroom properties, where there is low gas pressure and to achieve Silver Standard for heating systems on new build in Scotland. In an ideal world CFS could be used to promote the use of smaller boilers in the UK that are sized for space heating (SH) not DHW which will ensure boilers work efficiently without cycling more of the time. This was a key problem outlined in the paper by George Bennett entitled “The secret life of boilers: Dynamic performance of residential gas boiler heating systems – a modelling and empirical study”.

We note that David Stanton has a Worcester Bosch (WB) boiler. We provided them with a boiler to install in the house of Neil Schofield (a well known member of the WB team) to address his poor domestic hot water demand. Whilst positive test data was collected the key feedback was from Mrs Schofield who believed the hot water performance had markedly improved. As far as we are aware the system is still operational.

The issue of legionella was raised by Simon G. Many tens of thousands of CSF and the other main Canetis product GasSaver have been sold over many years and there have been no cases of legionella. Legionella is generally considered to be primarily a problem of cooling towers not domestic water systems. In domestic hot water supply it is controlled by the heat range such that cold water is generally kept below 20oC and hot water above 50oC. The water that is pre heated to enter the boiler is mixed to 30oC but then heated in the boiler to 70oC to 80oC. The legionella operating range is:

  • Above 70 °C (158 °F) – Legionella dies almost instantly
  • At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)
  • At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain
  • 48 to 50 °C (118 to 122 °F) – can survive but do not multiply
  • 32 to 42 °C (90 to 108 °F) – ideal growth range
  • 25 to 45 °C (77 to 113 °F) – growth range
  • Below 20 °C (68 °F) – can survive, even below freezing, but are dormant


In short there is no evidence we have seen that legionella is an issue with CSF just comment, largely from German manufacturers, about the potential of legionella in what appears to be an attempt to deny consumers the chance to purchase the most appropriate boiler system. There are however potential challenges that will need to be addressed as we move towards lower heating profiles with the likes of heat pumps where the system will generally produce water at much closer to the temperature of use by the consumer thus the water will be often held within the legionella growth range and will unlikely to operate above 50 °C where legionella is killed.
 
Last edited by a moderator:

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
We at Canetis, now we have seen the post on the Canetis Superflow (CSF) would like to answer the question from David Stanton and correct the misinformation from “Simon G” and “King and Pipes”. CSF can indeed address poor domestic hot water performance and is not magic rather just a logical development of engineering technology. The actual flow rate of domestic hot water (DHW) from the boiler is governed by a restrictor that is installed by the manufacturer and the only way to increase this is to remove this device. However with a CSF installed the 24KW boiler that David seems to have installed should supply adequate hot water for all but the very largest homes.

The CSF works be providing preheated water to the boiler. This allow the combi boiler to deliver water at a greater temperature than without the device thus increasing the energy value. The 25 litre CSF tests show that when heated to a temperature of 80°C it is able to deliver over 100 litres of preheated water benefit that compares well to a typical 75 litre British bath and less water for a shower. The CSF allows a combi boiler to produce hot water at its design temperature (>40oC ) even when the cold input water is lower than the assumed mains water temperature of 10oC.

Canetis suggest the use case of CSF is for multi bathroom properties, where there is low gas pressure and to achieve Silver Standard for heating systems on new build in Scotland. In an ideal world CFS could be used to promote the use of smaller boilers in the UK that are sized for space heating (SH) not DHW which will ensure boilers work efficiently without cycling more of the time. This was a key problem outlined in the paper by George Bennett entitled “The secret life of boilers: Dynamic performance of residential gas boiler heating systems – a modelling and empirical study”.

We note that David Stanton has a Worcester Bosch (WB) boiler. We provided them with a boiler to install in the house of Neil Schofield (a well known member of the WB team) to address his poor domestic hot water demand. Whilst positive test data was collected the key feedback was from Mrs Schofield who believed the hot water performance had markedly improved. As far as we are aware the system is still operational.

The issue of legionella was raised by Simon G. Many tens of thousands of CSF and the other main Canetis product GasSaver have been sold over many years and there have been no cases of legionella. Legionella is generally considered to be primarily a problem of cooling towers not domestic water systems. In domestic hot water supply it is controlled by the heat range such that cold water is generally kept below 20oC and hot water above 50oC. The water that is pre heated to enter the boiler is mixed to 30oC but then heated in the boiler to 70oC to 80oC. The legionella operating range is:

  • Above 70 °C (158 °F) – Legionella dies almost instantly
  • At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)
  • At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain
  • 48 to 50 °C (118 to 122 °F) – can survive but do not multiply
  • 32 to 42 °C (90 to 108 °F) – ideal growth range
  • 25 to 45 °C (77 to 113 °F) – growth range
  • Below 20 °C (68 °F) – can survive, even below freezing, but are dormant


In short there is no evidence we have seen that legionella is an issue with CSF just comment, largely from German manufacturers, about the potential of legionella in what appears to be an attempt to deny consumers the chance to purchase the most appropriate boiler system. There are however potential challenges that will need to be addressed as we move towards lower heating profiles with the likes of heat pumps where the system will generally produce water at much closer to the temperature of use by the consumer thus the water will be often held within the legionella growth range and will unlikely to operate above 50 °C where legionella is killed.
you can’t remove the restrictor as the flow rate will be to excessive through the plate and once the pre heated store is depleted you won’t have any hot water until this is replenished

they are not for multi bathroom houses as the boiler even without the restrictor won’t be able to pass the amount of water required through the plate let’s say 2 bathrooms that’s 20lpm required combined so around 14 lpm hot water required

now if you have 3 bathrooms that’s 30l combined 21 lpm hot

And water will always take the path of least resistance this is why if you turn a kitchen tap on when you have a shower most often the shower will show a drop in temp
 

SimonG

Plumber
Advent Win
So my "misinformation" isnt actual misinformation, glad to see German manufacturers agree 😀. Thanks for clearing that up


Wow, nearly 650 delivered for the 25 litre version and nearly 700 delivered for the 50 litre version. Plus installation.
Not small units either.

I would definitely recommend an unvented cylinder, pressures and flows withstanding, that you could run of a combi with the hot off of the combi running the kitchen sink.

Then you can have twin coil in cylinder for solar or if PV, hooked up to immersion.
 

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