told by plumber that a whole house mixing valve wont work?

[mpooley]

Funny how when OPs get told something they don't like, it can't possibly be true.

...and sometimes they mysteriously disappear, presumably to see if they can get the answer they want on another site.


OP - from the TMV installation code of practise
"When one valve is used to supply mixed water to a number of outlets the length of the pipe run and the volume of mixed water after the valve should be kept to a minimum.

The maximum pipe run after the mixing valve should be such that the required mixed temperature, at the furthest outlet, is reached within 30 seconds"

Nothing Mysterious about my "Disappearance" Just unable to sit at the computer all day.
And as far as "Funny how when OPs get told something they don't like, it can't possibly be true"
If you seriously think That water kept at 45c in the tank and then fed to taps is any different to water kept at 60c mixed down to 45c and fed to the same taps I'd like to know your reasoning? The only difference is that any legionella have been killed in the hotter tank, so what he told me is downright stupid.

I do see what some people are saying about water in long runs. What I don't understand is why it is better (according to this Plumber) to just lower the temp in the Tank?
That makes things worse as far as I can see. I don't want high temps at taps as it's dangerous for kids especially and I don't want to lower the tank temperature.
So I am at fault for trying to improve the safety in my house? or just questioning a 'Plumbers' opinion?

thanks for all helpful suggestions

Edit
I have been looking into legionella transmission and although extremely rare in domestic properties it seems that if water is supplied to taps at 50c there is virtually no risk at all.
unfortunately the blender I was looking at has a fixed max 48c output.
I wonder why? although the makers say that the recommended temp to taps and baths is 44c.

 

[muggles]

Blending valves have a mac temperature of 48c because there are no situations in which a TMV should be fitted where a higher temperature is permitted under the installation regulations.

Storing the water at a lower temperature presents a greater risk due to increased volume and stagnation, hence your plumber was correct in suggesting that a TMV should be used on every outlet; IE whole house blending is not recommended

 

[Dan Robinson]

The whole thing is a load of horse's rectal discharge.

48 degrees is rubbish for a bath fill. 44 even worse. The tmv on my thermal store is set to 51 which more or less gives a perfect temperature Bath as well as usable hot water at the kitchen.


My son does stock his hand in in mixed hour water because he knows is hot.

The first thing he learned to say in both his languages was "hot".


So no, you are not making your house any safer in my opinion. You're making it worse. In the long run. By not only allowing an environment for legionella to breed further downstream in your system, but by giving your children the understanding that a hot tap isn't hot.


Just my opinion of course, but then I don't believe in nanny stateism.

 

[ALEC1]

Dan mixing down overheated water is what happens in thermal stores and is a perfectly acceptable way of conserving heat...

what distance are the taps from the tank...

and why the hell do manufacturers of solar equipment and the regs specify and supply ONE mixing valve for the outlet of a solar thermal tank, not several...

 

[Dan Robinson]

There is a clue in my reply.

 

[mpooley]

Blending valves have a mac temperature of 48c because there are no situations in which a TMV should be fitted where a higher temperature is permitted under the installation regulations.

Storing the water at a lower temperature presents a greater risk due to increased volume and stagnation, hence your plumber was correct in suggesting that a TMV should be used on every outlet; IE whole house blending is not recommended

Perhaps you should read the original Post.
"My" Plumber who has never seen my house said It was Best just to reduce the temp of the water in the Tank.

I have been reading what I can find online and it seems that if you have taps
take less than 30 seconds to get hot water then in a domestic situation 1 main blender should be ok
My kitchen tap takes 3 seconds My bathroom takes 4 seconds the longest run takes about ten seconds

 

[Dan Robinson]

Do you have a link to those figures?

Cheers.

 

[mpooley]

Do you have a link to those figures?

Cheers.

http://www.google.co.uk/url?sa=t&rc...qLnOiMBN4HRXwaQ&bvm=bv.67720277,d.ZGU&cad=rja

I think that will work! it's a PDF it's in section 4.1
I also found in a couple of other places but I had closed the tabs and can't find them now - I'll have a look later

Edit that's section 4.21

 

[Norcon]

I just asked a plumber for a quote for fitting a whole house thermal mixing valve because our hot water is sometimes too hot.
He told me I would need separate mixers on every tap as a mixer by the tank would not work.
specifically he said water would get too cold by the time it got to the taps!

he said this without seeing my house or asking me any questions about my system.
I can't believe this is true.

is there any problem with a whole house mixer, I can't see any difference with water heated too 42c or blended to 42c I think the guy just doesn't want the job.

Just use a single mixer at the cylinder. That's what ACV recommend and supply one with their cylinders.
Then put a sticker on the hot taps saying "All numpties beware, hot water flows forth from the orifice of this tap".

 

[EFLImpudence]

From another thread:

Like the new guy who scalded his hands under the hot water tap.

"...at the last place I used to work there was a sign saying "caution hot water!", but not on these sinks".

Hilarious. You have to wonder how these people cope once they get home every night.


Gawd 'elp us.