instant hot water...

Page 1 of 3  
ie as soon as you turn the tap on. i read some time ago that some hw systems were designed to allow natral constant flowing of hot water through the pipes in order to gurantee hot water instantly at any tap in the house. i know its likly to be energy inefficent...but ...id still like to know how to do it!
steve
--
Remove the word 'SPAMTRAP' from email address to reply to me direct.



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There are some combi boilers that contain a tank of hot water in them... not quite as instant... but better that an normal combi.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 4 Dec 2003 22:23:58 -0000, "R P McMurphy"

You can get bronze circulating pumps that do this. Basically you put in an extra (small) pipe in parallel with the normal one and create a small circuit, with the taps coming off of the main run.
Grundfos make them.
Regarding energy efficiency, when it's used at the same time as the heating in the house and the hot water is heated in the same way, it doesn't make a lot of difference.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Hall wrote:

Its worse, because instead of the hot water losing its heat just once, in the pipe from tank to tap. it loses it all the time.
Its more efficient on WATER usage tho.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

No, I was careful to say "when it's used at the same time as the heating".
Think of it this way. Radiator/UFH system is connected to boiler, water is circulated and the emitters are designed to deliberately emit heat. Boiler also heats hot water in cylinder. Separate small circuit with small pump circulates water from cylinder and emits some heat into the same space (i.e. the insulated envelope of the house) as the radiators/UFH. In effect the HW loop contributes to the house heat. Since the energy to do so costs the same each way, the efficiency is broadly the same.
If this HW circuit were run in places which would be unheated then the efficiency would be less, but OTOH, they would also be highly insulated.
Obviously in the summer when the house is not heated, it can be argued that more heat is being released than otherwise would be......

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A pipe stat can be fitted at the furthest part of the loop. this will stop the pump until the water in the pipe cools.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.542 / Virus Database: 336 - Release Date: 18/11/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Hall wrote:

Not true. It is standard pactice to run water pipes to bathrooms through the roofspace. Ok they have to have little foam sleeves over them, BUT on an icy january day I know from my experience the first flush of water is warm, then it goes ICY cold, then it gets hot, so those pipes are definitely *not within the insulatione enevleope* - or at least not within a very good one.
Which is why I spent a fair amount of money this week on getting may favorite chippes to build boxes full of fiberglass around them.

Mostly in winter, unless teh HW pipes are fully inside the house living space. Chances are they are not.
It always makes me laugh when peopel go n about energy saving bulbs and full kettles though, which ARE inside the house, all of which contribute to burning less oil. This (home) office, with its two computers, two monitors, two people, router, telephone PABX, radio etc etc. hardly EVER needs any extra heat...OK, I have to pay more ofor the lectricity...
Likewise the upper landing equipped with three 50W LV lamps, is always warm after dark..

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

In all of the notes that I have read regarding good practice, the recommendation for hot water or heating pipes run outside the envelope is to use pipe insulation with a thickness of at least the pipe diameter. One could easily work out from the temperature of the pipe, the surround and the U value, what the loss will be, but I suspect that it's negligible if the thickness of insulation is adequate.

That depends on the arrangement of the plumbing.

I agree with you there.

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Hall wrote:

Let me inform you, that the heatloss- at least to the water in question - is NOT negligible, even with such isulation, because I have such, and the hot water runs bloody cold in winter. Until the pipe gets warm and the cold water is run out. You can put yoir hand on the insulation and feel the heat.
It will almost certainly stop them from freezing, but it won't keep them warm overnight.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

With the water stationary in the pipe, over a period of time of course it will cool. That wasn't really my point, though, it was more the energy loss.
Let's look at an example.
I'll take 19mm Armaflex insulation and 22mm tube which is a typical combination used domestically.
The heat transmission through a piece of material is given by
Q = (K x A x dT)/d
where K is the coefficient of thermal conductivity in W/m.K A is the area dT is the temperature difference.
If we take a 1m length of copper tube, its area is given by
pi x 0.022
Armaflex has a K value of 0.039
I'll assume that the water temperature is 60 degrees and the ambient temperature is 10 (a reasonable average over a year).
If you do the sums this works out to 7.1W per metre run of pipe.
In the context of the energy used to heat the water or the house, and your earlier comments about heat from IT equipment (I have that issue as well) this is not a significant amount.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy Hall wrote:

Well...If I take the runs around here...Ive got about 60m of central heating pipe, and probably about half that on hot water running through the loft space.. Say 90m in all to be conservative. So the average loss is 630W when all that is circulating. Heat loss to OUTSIDE the insulation envelope. About what the Aga kicks out to heat the whole kitchen, and, if averaged over a year, probably about 300 quid?
The point about electrical heat is that it is inside the insulation envelope, so, although expensive, it does heat the house.
The HW and CH stuff running in a cold roof is money thrown away.
If your figures are accurate, it is very instructive to see ho wthe practice of running CH pipes in a cold roof can lose a lot of heat, even when insulated to 'standards' and that additional boxing in and insulation is no bad thing.
Going back to the original point, it would seem that running HW continuosuly circulation could not only watse in a large house a couple of hundrd watts of heat AT LEAST , but also of course the pump is continously drawing what - 50W? to circulate it. Plus teh extra are of how water pipe and its capital cost...? So I have to say that as far as I am concerned the heat loss and installation costs outweigh the water savings. My major water usage is probably in loos and baths anyway, an baths always need cold water added.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It depends on how good the insulation is. The heavier the better. Also having a boiler on a gable end wall with associated cylinder cam be boxed in with cheap ply or MDF to make a large insulated cupboard. Not a real problem, when you consider the space it saves in the house below and the noise reduction too.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
IMM wrote:

If its in insulation it isn't in a cold roof dummy!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You put bare metal pipes in a loft without insulation? My God!
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Tripe!
By burning more coal. Electricity is the dirtiest of fuels, and the least efficient from power station to point of burn.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.542 / Virus Database: 336 - Release Date: 18/11/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
IMM wrote:

No, its true. It is the area where distributoin of services is easiest.

That is true tho. Electricity is the stupidest way to make heat. Power stations run at 60% thermal efficiency at best, and the distribution network knocks that down to maybe 50% overall.
However there are very few COAL powered stations left in the UK. Most are natural gas or oil IIRC.
And it is a LOT easier to clean up a power station flue than e.g. a car exhaust, or a domestic burner.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's quite unrealistic -- 35% is more typical.
--
Andrew Gabriel
Consultant Software Engineer
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andrew Gabriel wrote:

No, its not. Look it up.
Eevn fairly old stations are running well up towards 50%.
Car engines are able to get better than 30% these days, and some diesels up over 40%.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It is not, and be told!!

Les than 40% in many cases, and some lower than that.

Domestic burner? It is cleaner to burn natural gas at point of use. far cleaner overall.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/2003
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.