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!
Remove the word 'SPAMTRAP' from email address to reply to me direct.
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.
To email, substitute .nospam with .gl
No, I was careful to say "when it's used at the same time as the
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
Obviously in the summer when the house is not heated, it can be argued
that more heat is being released than otherwise would be......
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
Likewise the upper landing equipped with three 50W LV lamps, is always
warm after dark..
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
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
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
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.
To email, substitute .nospam with .gl
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.
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
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.
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.