Combi storage boiler - vaillant 938

[platforminc]

Hello Everyone

Just going through the design of a house with 3 showers, no bath. We are proposing to use a Vaillant 938 as there is no space for a cylinder unless we create an extension for the cylinder.

The flow rate is 20L per minute from the kitchen tap, does anyone know if Vaillant 938 is still the best storage combi boiler out there or is there a better product ?

Thanks in advance.

 

[Johntheo5]

Do you hope to run 3 showers together?, if your mains can only supply 20LPM then each shower would have to be limited to ~ 7LPM.
A normal 38kw boiler like the 838 will supply 15.56LPM with temp rise of 35C = 15.56LPM at 40C from mains at 5C, 18.16LPM from mains at 10C and 21.79LPM from mains at 15C. The 938 has, I think, a 15L "cylinder" so isn't going to boost the above flow rates for very long, it then returns to being, in effect, a 838?.
Presume you are aware of this.

 

[platforminc]

Do you hope to run 3 showers together?, if your mains can only supply 20LPM then each shower would have to be limited to ~ 7LPM.
A normal 38kw boiler like the 838 will supply 15.56LPM with temp rise of 35C = 15.56LPM at 40C from mains at 5C, 18.16LPM from mains at 10C and 21.79LPM from mains at 15C. The 938 has, I think, a 15L "cylinder" so isn't going to boost the above flow rates for very long, it then returns to being, in effect, a 838?.
Presume you are aware of this.

Thanks for this piece of valuable info, it is highly un likely that all the showers will be in use at thesame time, what may be used randomly is the kitchen tap as this could vary, the use of the shower will be at different times of the day.

Is it possible to restrict flow onto a shower and if so, how will one go about doing this ? presumably not permanent, such that this can be changed later if required.

 

[Johntheo5]

Vaillant claim some savings with the 938 when small volumes of water are drawn off like above as the boiler doesn't fire on/off each time until the store is exhausted.

Flow restrictor?, something like this maybe but depends on shower type.

https://www.amazon.co.uk/Restrictor-Silicone-Reducer-Specifications-Handheld/dp/B0BFBC9R9Q/ref=asc_df_B0BFBC9R9Q/?tag=googshopuk-21&linkCode=df0&hvadid=606682215096&hvpos=&hvnetw=g&hvrand=11963543862542182970&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007835&hvtargid=pla-1880097581896&psc=1

 

[platforminc]

Vaillant claim some savings with the 938 when small volumes of water are drawn off like above as the boiler doesn't fire on/off each time until the store is exhausted.

Flow restrictor?, something like this maybe but depends on shower type.

https://www.amazon.co.uk/Restrictor-Silicone-Reducer-Specifications-Handheld/dp/B0BFBC9R9Q/ref=asc_df_B0BFBC9R9Q/?tag=googshopuk-21&linkCode=df0&hvadid=606682215096&hvpos=&hvnetw=g&hvrand=11963543862542182970&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007835&hvtargid=pla-1880097581896&psc=1

Thanks for this, from what I can see the device will restrict hot + cold, this this the way it should work ?

 

[Johntheo5]

Yes.