UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
DIY Novice
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?

I'm getting a new central heating system fitted, probably a Vaillant
Turbomax 282 combi boiler. I wanted to put the boiler in a small
utility room at the back of the house but my plumber suggested a
better location would be to put it in the kitchen as it will take less
time for the hot water to get to the shower/bath.
Is this reasonable or is he trying to make his job easier/cheaper. The
difference in distance is about 15 feet.
We will be fitting new 22mm pipes throughout, will this help to
alleviate this?
I would rather not put the boiler in the kitchen as it opens onto the
dining room and I'm worried about the noise aspect. The plumber says
this boiler is virtually silent, is this correct?.
If the total journey is about 35 feet how long will it take for the
hot water to reach my shower?
  #2   Report Post  
BillV
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?


"DIY Novice" wrote in message
om...
I'm getting a new central heating system fitted, probably a Vaillant
Turbomax 282 combi boiler. I wanted to put the boiler in a small
utility room at the back of the house but my plumber suggested a
better location would be to put it in the kitchen as it will take less
time for the hot water to get to the shower/bath.
Is this reasonable or is he trying to make his job easier/cheaper. The
difference in distance is about 15 feet.
We will be fitting new 22mm pipes throughout, will this help to
alleviate this?
I would rather not put the boiler in the kitchen as it opens onto the
dining room and I'm worried about the noise aspect. The plumber says
this boiler is virtually silent, is this correct?.
If the total journey is about 35 feet how long will it take for the
hot water to reach my shower?

As a minimum all the cold water in the 35 feet has to run out before you get
any hot.
You could work out how long this would take knowing the flow rate and pipe
diameter.
but my experience on a smaller combi over a similar distance was around a
minute i.e. similar to the gravity system it replaced.


  #3   Report Post  
fred
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?

In article , BillV
writes

"DIY Novice" wrote in message
. com...
I'm getting a new central heating system fitted, probably a Vaillant
Turbomax 282 combi boiler. I wanted to put the boiler in a small
utility room at the back of the house but my plumber suggested a
better location would be to put it in the kitchen as it will take less
time for the hot water to get to the shower/bath.
Is this reasonable or is he trying to make his job easier/cheaper. The
difference in distance is about 15 feet.
We will be fitting new 22mm pipes throughout, will this help to
alleviate this?
I would rather not put the boiler in the kitchen as it opens onto the
dining room and I'm worried about the noise aspect. The plumber says
this boiler is virtually silent, is this correct?.
If the total journey is about 35 feet how long will it take for the
hot water to reach my shower?

As a minimum all the cold water in the 35 feet has to run out before you get
any hot.
You could work out how long this would take knowing the flow rate and pipe
diameter.
but my experience on a smaller combi over a similar distance was around a
minute i.e. similar to the gravity system it replaced.

If you make the run to the shower in 15mm it will take roughly half the
time. Whether you would want to do this will depend whether you have a
healthy mains pressure. I had a similar run in 22mm which took an age to
run hot in 15mm but is now easily acceptable for bothe delay & flow. My
system was tank fed (not mains) at about 3bar, which I would hope you
should be able to get from your mains. Also, mine was not a combi.

Like yours, my preference would be not to have the boiler in the kitchen,
peoples opinion of 'virtually silent' vary greatly.

If you did all the hot in 15mm, you may suffer from hot taps being turned
on affecting the amount of hot available at the shower, but AAIU, you will
get that anyway from a combi as the maximum flow of hot water is limited
by the capacity of the boiler.

In your place, I would run separate feeds from the boiler to kitchen,
bathroom and any other large users of hot water. If this cannot be done,
take 22mm for a short run (less than 3m) then split into separate 15mm.

HTH
--
fred
  #4   Report Post  
Christian McArdle
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?

We will be fitting new 22mm pipes throughout, will this help to
alleviate this?


Quite the opposite. The throughput of a standard combi boiler is so low that
no more than 15mm is needed unless your mains water is very low pressure.
However, the 22mm pipe has twice as much water in it per unit length, so it
takes twice as long to clear out the cold, given that the flow rate is
limited to a fixed low value, around 11.5 lpm, which 15mm is very capable of
supplying at mains pressure. Gravity systems needed larger pipes because the
tank fed nature leads to very low pressures, so didn't have the "push" to
squeeze through smaller pipes.

Christian.





  #5   Report Post  
Bob Mannix
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?


"Christian McArdle" wrote in message
. net...
We will be fitting new 22mm pipes throughout, will this help to
alleviate this?


Quite the opposite. The throughput of a standard combi boiler is so low

that
no more than 15mm is needed unless your mains water is very low pressure.
However, the 22mm pipe has twice as much water in it per unit length, so

it
takes twice as long to clear out the cold, given that the flow rate is
limited to a fixed low value, around 11.5 lpm, which 15mm is very capable

of
supplying at mains pressure. Gravity systems needed larger pipes because

the
tank fed nature leads to very low pressures, so didn't have the "push" to
squeeze through smaller pipes.

Christian.


Quite so. Even without a fixed flow rate and with a gravity system you are
better off with the smaller pipe (as long as it doen't get too small!). The
volume of water in the pipe goes up as the square of the radius. The flow
rate through a pipe depends on the radius but at less then a power of two so
water at one end will be travel slower through a bigger pipe. Once the
water is hot at the outlet end, of course, it's an entirely different matter
as the big pipe will be delivering more.

This was the first question I had answered on this ng many years ago. I
fitted all 22mm hot pipe to my kitchen sink. This was a mistake as waiting
for the hot is more irritating than the speed the bowl fills when it is hot
and I made things worse rather than better. For a bath fed from a storage
cylinder, of course, you just turn the tap on and the fact it's cold for a
bit doesn't matter, you are interested in the flow rate over a longer
period, so big pipes are best - likewise old gravity CH systems.

Where you can't maximise flow rates (as with a combi boiler) you are better
off with smaller pipe.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)




  #6   Report Post  
Ed Sirett
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?

On Mon, 24 May 2004 02:33:57 -0700, DIY Novice wrote:

I'm getting a new central heating system fitted, probably a Vaillant
Turbomax 282 combi boiler. I wanted to put the boiler in a small
utility room at the back of the house but my plumber suggested a
better location would be to put it in the kitchen as it will take less
time for the hot water to get to the shower/bath.
Is this reasonable or is he trying to make his job easier/cheaper. The
difference in distance is about 15 feet.
We will be fitting new 22mm pipes throughout, will this help to
alleviate this?
I would rather not put the boiler in the kitchen as it opens onto the
dining room and I'm worried about the noise aspect. The plumber says
this boiler is virtually silent, is this correct?.
If the total journey is about 35 feet how long will it take for the
hot water to reach my shower?


You want 15mm pipe from the boiler to the kichen+shower , but it's
probably not worth taking out existing 22mm pipe especially if it's alredy
there.

The gas, flow and return will be 22mm fine.
The CW supply can be either 15 or 22mm but I'd install 15mm unless the
mains pressure was really poor (in which case the combi boiler might be a
questionable install anyway).

I reckon you mean a Turbomax 828e. This is a 33kW (input) unit would not
be a good idea to install onto an open plan living area.
It's fine for kitchen/diner say.


This model has a user selectable 'hot standby' mode which keeps the
boiler innards hot even
in summer - probably takes around 1 min of gas per hour to do this.
It will generally cut around 20s of the startup time for HW production.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html


  #7   Report Post  
derek
 
Posts: n/a
Default How long does it take hot water to get from combi boiler to shower?

Whitelist
On Mon, 24 May 2004 19:18:58 +0100, "Ed Sirett"
wrote:

The gas, flow and return will be 22mm fine.
The CW supply can be either 15 or 22mm but I'd install 15mm unless the
mains pressure was really poor (in which case the combi boiler might be a
questionable install anyway).

I reckon you mean a Turbomax 828e. This is a 33kW (input) unit would not
be a good idea to install onto an open plan living area.
It's fine for kitchen/diner say.


This model has a user selectable 'hot standby' mode which keeps the
boiler innards hot even
in summer - probably takes around 1 min of gas per hour to do this.
It will generally cut around 20s of the startup time for HW production.


I've got more or less the same set up as the OP, except my boiler's a
Worcester-Bosch 37Kw I believe, in a utility room on a long pipe run
with some 22mm pipe. As regards the shower I've had no complaints
whatsoever, the little bit of a wait is not much more than the time
needed for the thermostatic shower to stabilise.

However as regards the handwash basin it's a bit tiresome, first cold
water comes through, then the preheat water arrives, there's less than
half a basin of this it then runs flat cold again (chilling the lttle
bit of hot water in the basin), till the boiler is fully in operation
and the hot water has filled the pipes. then you're talking. I've a
mind to turn the preheat off since then the arrival of the first hot
water at the tap can then be taken as a sign to put the plug in, in
the knowledge it won't just run cold again straightaway.

If the OP has the chance to change the hot service to 15mm pipe, I
think I'd recommend it.

DG

--
Seh ich die Werke der Meister an,
So seh ich das, was sie getan;
Betracht ich meine Siebensachen,
Seh ich, was ich hätt' sollen machen. (J.W.v.Goethe)
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Near death boiler + replacing a boiler David Hearn UK diy 9 January 26th 04 01:44 PM
Contemplating unvented Indirect hot water upgrade vortex2 UK diy 21 December 4th 03 12:51 AM
Combi boiler - long wait to get hot water ChrisJ UK diy 26 November 23rd 03 02:30 PM
Hot water problem with my combi boiler Andrew Bainbridge UK diy 1 October 25th 03 11:21 PM
Condensing-combi boilers Sapient Fridge UK diy 16 September 23rd 03 02:27 PM


All times are GMT +1. The time now is 06:04 AM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"