Hello,

I am sure I read here a post stating how many radiators you could feed
of certain pipe sizes: the bigger the pipe diameter, the greater the
number of kW. Can anyone tell me where to find this information?

We have had a new boiler, so I understand I need to oversize the rads
because the delta T is smaller with condensing rads. We used to have
two rads in the lounge (5m x 3m ish - the lounge, not the rads!) but
SWMBO would like just one long rad. I have used some rad calcs and I
think we need something about 3kW or 11-12,000 BTU. Does that sound
about right?

I was wondering whether I could feed this and the hall rad off the
existing 15mm pipe or whether I needed to upgrade to 22mm?

TIA
Stephen.

In an earlier contribution to this discussion,
Stephen wrote:

Hello,

I am sure I read here a post stating how many radiators you could feed
of certain pipe sizes: the bigger the pipe diameter, the greater the
number of kW. Can anyone tell me where to find this information?

We have had a new boiler, so I understand I need to oversize the rads
because the delta T is smaller with condensing rads. We used to have
two rads in the lounge (5m x 3m ish - the lounge, not the rads!) but
SWMBO would like just one long rad. I have used some rad calcs and I
think we need something about 3kW or 11-12,000 BTU. Does that sound
about right?

I was wondering whether I could feed this and the hall rad off the
existing 15mm pipe or whether I needed to upgrade to 22mm?

TIA
Stephen.

ISTR that 15mm is good for about 6kW - so unless the hall is large and
draughty, that should be ok.

It's impossible to comment on your 3kW requirement estimate without knowing
how many outside walls there are, whether the cavities are insulated, amount
and type of glazing, type of floor, etc., etc. Have you used one of the
usual heatloss programs (Barlo or Myson) to calculate it?

Assuming the 3kW is correct, you're going to need a very large double
radiator to achieve that. The biggest single (finned) rad I can find (2000
x700) is only rated at 2.8kW at a DeltaT of 60 - so considerably less when
downrated for a condensing boiler.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Jul 27, 1:07*pm, "Roger Mills" wrote:
In an earlier contribution to this discussion,



Stephen *wrote:
Hello,

I am sure I read here a post stating how many radiators you could feed
of certain pipe sizes: the bigger the pipe diameter, the greater the
number of kW. Can anyone tell me where to find this information?

We have had a new boiler, so I understand I need to oversize the rads
because the delta T is smaller with condensing rads. We used to have
two rads in the lounge (5m x 3m ish - the lounge, not the rads!) but
SWMBO would like just one long rad. I have used some rad calcs and I
think we need something about 3kW or 11-12,000 BTU. Does that sound
about right?

I was wondering whether I could feed this and the hall rad off the
existing 15mm pipe or whether I needed to upgrade to 22mm?

TIA
Stephen.

ISTR that 15mm is good for about 6kW - so unless the hall is large and
draughty, that should be ok.

It's impossible to comment on your 3kW requirement estimate without knowing
how many outside walls there are, whether the cavities are insulated, amount
and type of glazing, type of floor, etc., etc. Have you used one of the
usual heatloss programs (Barlo or Myson) to calculate it?

Assuming the 3kW is correct, you're going to need a very large double
radiator to achieve that. The biggest single (finned) rad I can find (2000
x700) is only rated at 2.8kW at a DeltaT of 60 - so considerably less when
downrated for a condensing boiler.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

There are some much bigger rads here...
http://www.discountedheating.co.uk/s...Radiator1.html
K2s up to 5.9KW
K1s up to 3.4KW

I've got a 2.4m x 700mm K2 rad on one wall of our kitchen which has 3
outside walls. In hindsight I would rather have installed two smaller
ones, as it's very hot against that wall!
K1s up to

In an earlier contribution to this discussion,
Swift Half wrote:


There are some much bigger rads here...
http://www.discountedheating.co.uk/s...Radiator1.html
K2s up to 5.9KW
K1s up to 3.4KW


Fair enough - my printed catalogue only goes up to 2000 mm long.

Having said that, the biggest K1 (3000 x 700) is rated at 3357 watts at a
Delta-T of 50. So if the OP runs his system at a Delta-T of 40 - which may
be more likely - the output of said rad will only be about 2545 watts, which
may not be enough.

I still think he's looking at a double - possibly a P+ rather than K2.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In article , Roger Mills
writes
In an earlier contribution to this discussion,
Swift Half wrote:


There are some much bigger rads here...
http://www.discountedheating.co.uk/s...mpact_700mm_Hi
gh_Radiator1.html
K2s up to 5.9KW
K1s up to 3.4KW


Fair enough - my printed catalogue only goes up to 2000 mm long.

Having said that, the biggest K1 (3000 x 700) is rated at 3357 watts at a
Delta-T of 50. So if the OP runs his system at a Delta-T of 40 - which may
be more likely - the output of said rad will only be about 2545 watts, which
may not be enough.

I still think he's looking at a double - possibly a P+ rather than K2.

I'm certainly a fan of the P+, seems far less obtrusive than a full
double.

I've got 2 rooms the size of the O/P heated with P+s, one with 2 rads
diagonally opposite and one with a single big rad and the temp is
noticeably more even with 2 rads
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

On Jul 27, 11:12*am, Stephen wrote:
Hello,

I am sure I read here a post stating how many radiators you could feed
of certain pipe sizes: the bigger the pipe diameter, the greater the
number of kW. Can anyone tell me where to find this information?


This is what yo uneed:

http://www.cda.org.uk/megab2/build/tn39/appb1.htm

this is also useful

http://www.elementalsolutions.co.uk/...ow%20flows.pdf

and so is this to see pump pressures

http://www.grundfos.com/web/homeUK.n...ag/DMAR-6EGDHG


The amount of heat you need to get down the pipe determines the kg/sec
flow rate. But having got that there are two things to consider. One
is the pressure drop (can the pump drive enough water round) and the
other is the noise (will the pipes make too much noise). To keep the
noise low you need to have less than 1 m/s flow velocity.

I calculated all this for our victorian terraced house and ended up
selecting 22mm for the main pipework with 15mm for the last two of
rads on each circuit. I fed each rad with 10mm tube for the last
metre or so for ease of connecting behind the skirting.

I agree about your comments about condensing boilers. You want the
return to be less than 42C to make best use of the condensation
effect. 3kW sounds about right or even generaous to me, but you
might also consider choosing radiators that one person can lift. It
makes installation much easier!

hoep this helps,

Robert

On Mon, 27 Jul 2009 13:07:43 +0100, "Roger Mills"
wrote:

ISTR that 15mm is good for about 6kW - so unless the hall is large and
draughty, that should be ok.

Thanks Roger. I was hoping you would reply. I'm sure it was one of
your old posts I was thinking of.

It's impossible to comment on your 3kW requirement estimate without knowing
how many outside walls there are, whether the cavities are insulated, amount
and type of glazing, type of floor, etc., etc. Have you used one of the
usual heatloss programs (Barlo or Myson) to calculate it?

I used the Barlow one IIRC. I don't know whether that's because I got
that first but I prefer it to Myson.

Two walls 3m and 5m internal; two walls 3m and 5m external. Inside to
out: block, blown insulation of some sort, brick. Solid concrete floor
below; plasterboard ceiling above. Double glazed window.

Assuming the 3kW is correct, you're going to need a very large double
radiator to achieve that. The biggest single (finned) rad I can find (2000
x700) is only rated at 2.8kW at a DeltaT of 60 - so considerably less when
downrated for a condensing boiler.

I divided the result from the calculator by 0.6. I must have got this
factor from a post here; possibly one of yours? I got it to be
11000-12000 BTU, which I think very roughly speaking is 3kW.

On Mon, 27 Jul 2009 15:01:06 +0100, "Roger Mills"
wrote:

I still think he's looking at a double - possibly a P+ rather than K2.

Because of the high rating, I was thinking of a double from the outset
anyway, so that's no problem. I had to look up P+ and K2; why are they
called such obscure names? What's wrong with single and double?

Before anyone corrects me, I think the P+ is halfway between the two:
a double with one set of fins? What's the point of that? To save
space? If you have two sides, IMHO you may as well have two sets of
fins and get the most heat out of it.

On Mon, 27 Jul 2009 15:18:22 +0100, fred wrote:

I've got 2 rooms the size of the O/P heated with P+s, one with 2 rads
diagonally opposite and one with a single big rad and the temp is
noticeably more even with 2 rads

Two rads would be better from a handling point of view, OTOH you only
have to lift them into place once (hopefully). The downside is that
two rads side by side would look funny, so I think you would have to
stagger them. Having them diagonally opposed is probably a logical
choice because as you say, it balances the heat output. One big rad
could I suppose heat that side of the room and leave the far side
colder.

However, SWMBO would prefer one rad and if we go with the two rad
option it means running a new set of pipes. There's a concrete floor
so that could be tricky and I can't run around the skirting board
because there are doors in the way, which only leaves going up and
down through the ceiling, which I don't like because that causes
problems further down the line with airlocks in the loops and having
to drain each loop separately.

On Mon, 27 Jul 2009 07:57:16 -0700 (PDT), RobertL
wrote:


http://www.cda.org.uk/megab2/build/tn39/appb1.htm

this is also useful

http://www.elementalsolutions.co.uk/...ow%20flows.pd=
f

and so is this to see pump pressures

http://www.grundfos.com/web/homeUK.n...ag/DMAR-6EGDHG

Thanks for these URLS and the one in the earlier reply about
discountheating. My next question was going to be where could I get a
2 metre (ish) rad from, so this may have answered that question. B&Q
only go to 600x1600 IRC and I tried a local merchant but their prices
were twice that of B&Q.

The urls above all look very technical. I haven't read them all
thoroughly yet.The grundfos one links to a page about a pump that
adapts to requirements. Is this like the Wilo Smartpump? I bought the
latter after it was recommended here.

If it is their equivalent, it looks very promising because it says it
uses 5W, whereas the Wilo, IIRC is 40W, so there's a big difference. I
have tried to contact Wilo by phone, fax, email, and post but they
never reply, so I am disappointed by their lack of customer service.

In article ,
Stephen writes:
On Mon, 27 Jul 2009 15:01:06 +0100, "Roger Mills"
wrote:

I still think he's looking at a double - possibly a P+ rather than K2.

Because of the high rating, I was thinking of a double from the outset
anyway, so that's no problem. I had to look up P+ and K2; why are they
called such obscure names? What's wrong with single and double?

Maybe Stelrad jargon? The Ultraheat Compact range I used call
them SF, HF, DF, TF for single, one-and-a-half (double with only
one set of fins), double, and triple radiators respectively.

Before anyone corrects me, I think the P+ is halfway between the two:
a double with one set of fins? What's the point of that? To save
space? If you have two sides, IMHO you may as well have two sets of
fins and get the most heat out of it.

I have a P+/HF in the bathroom, where I have limited scope for
projection from the wall, but no shortage of wall space. For
power output, as you go through SF, HF, DF, TF, you get relative
power outputs of approx 1, 1.5, 2, 2.8 for same size radiator.
I have 3 TF's (would be K3's if Stelrad did them) triple panel
radiators. Excellent where you have restricted size but no depth
restriction. (The availability of all sizes of triple panel
radiators was one of the factors in choosing Ultraheat, and that
they were manufactured just up the road and I order them in any
size at a local independant plumbers merchant for delivery in a
few hours.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Jul 30, 9:29*am, Stephen wrote:
On Mon, 27 Jul 2009 07:57:16 -0700 (PDT), RobertL

wrote:

http://www.cda.org.uk/megab2/build/tn39/appb1.htm

this is also useful

http://www.elementalsolutions.co.uk/...and%20low%20fl...
f

and so is this to see pump pressures

http://www.grundfos.com/web/homeUK.n...ag/DMAR-6EGDHG

Thanks for these URLS and the one in the earlier reply about
discountheating. My next question was going to be where could I get a
2 metre (ish) rad from, so this may have answered that question. B&Q
only go to 600x1600 IRC and I tried a local merchant but their prices
were twice that of B&Q.

The urls above all look very technical. I haven't read them all
thoroughly yet.The grundfos one links to a page about a pump that
adapts to requirements. Is this like the Wilo Smartpump? I bought the
latter after it was recommended here.

If it is their equivalent, it looks very promising because it says it
uses 5W, whereas the Wilo, IIRC is 40W, so there's a big difference. I
have tried to contact Wilo by phone, fax, email, and post but they
never reply, so I am disappointed by their lack of customer service.


We bought our rads (Biasi) from http://www.4bathrooms.co.uk/ but we
did have some problems with long delays. Biasi do rads up to 2200mm
long (3.5kW nominal for Biasi type 22K).

I found that a 1000x900 type 22k (2.3kW) is the largest I can lift on
my own, so we went for that as our maximum size. We will add more if
these are not enough.

Robert

In an earlier contribution to this discussion,
Stephen wrote:


I divided the result from the calculator by 0.6. I must have got this
factor from a post here; possibly one of yours? I got it to be
11000-12000 BTU, which I think very roughly speaking is 3kW.

Not quite sure I understand what you're saying here. Are you saying that you
calculated the *actual* heatloss and then multiplied it by 1/0.6 as a means
of down-rating the radiator?

11-12 kBTU/Hr is actually about 3.5 kW. Are you saying that the *actual*
heatloss is only 2.1kW, and that you grossed it up to 3.5kW to allow for the
difference in Delta-T?

If so, if you find a radiator which is rated at 3.5kW at a Delta-T of 60, it
will give you 2.1kW at a Delta-T of about 40. Bear in mind though that most
radiator outputs are now quoted at a Delta-T of 50, so you may need to
adjust your fiddle factors.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
Stephen wrote:

On Mon, 27 Jul 2009 15:01:06 +0100, "Roger Mills"
wrote:

I still think he's looking at a double - possibly a P+ rather than
K2.

Because of the high rating, I was thinking of a double from the outset
anyway, so that's no problem. I had to look up P+ and K2; why are they
called such obscure names? What's wrong with single and double?

Before anyone corrects me, I think the P+ is halfway between the two:
a double with one set of fins? What's the point of that? To save
space? If you have two sides, IMHO you may as well have two sets of
fins and get the most heat out of it.

Your assumption about P+ is precisely right. I've no idea why they use these
descriptions. As someone else has said, maybe it's just a Stelrad thing.

K2's are *very* fat, and P+ rads do a reasonable job without being anything
like as intrusive.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 30 Jul 2009 08:57:55 GMT, (Andrew
Gabriel) wrote:

Maybe Stelrad jargon? The Ultraheat Compact range I used call
them SF, HF, DF, TF for single, one-and-a-half (double with only
one set of fins), double, and triple radiators respectively.

Triples?! I have never heard of or seen those. Are they three
radiators sandwiched together with four sets of fins between them?
They must be huge and heavy!

Is Stelrad a good make? It's a brand that seems to have been mentioned
more than once in this thread. In the past I have just bought whatever
make Screwfix or Toolstation have sold; I wasn't aware there was so
much choice.

Does anyone know what makes SF and TS sell? I had problems with the TS
ones because they were delivered wrapped only in plastic film, so I
had one or two arrive dented. I am told SF send theirs in boxes.

Thanks,
Stephen.

On Thu, 30 Jul 2009 02:51:02 -0700 (PDT), RobertL
wrote:

We bought our rads (Biasi) from http://www.4bathrooms.co.uk/ but we
did have some problems with long delays. Biasi do rads up to 2200mm
long (3.5kW nominal for Biasi type 22K).

I hadn't heard of Biasi before; are they any good?

I presume the 22K is their terminology for a double?

The prices on that web site seem very good.


Thanks,
Stephen.

On Thu, 30 Jul 2009 15:15:49 +0100, "Roger Mills"
wrote:

Not quite sure I understand what you're saying here. Are you saying that you
calculated the *actual* heatloss and then multiplied it by 1/0.6 as a means
of down-rating the radiator?

Yes.

11-12 kBTU/Hr is actually about 3.5 kW. Are you saying that the *actual*
heatloss is only 2.1kW, and that you grossed it up to 3.5kW to allow for the
difference in Delta-T?

Yes.

If so, if you find a radiator which is rated at 3.5kW at a Delta-T of 60, it
will give you 2.1kW at a Delta-T of about 40. Bear in mind though that most
radiator outputs are now quoted at a Delta-T of 50, so you may need to
adjust your fiddle factors.

I have found the delta T problem before. IIRC Screwfix quote dT=50K
and Toolstation quote dT=60K.

I got the 0.6 factor from reading a post here but I can't remember the
circumstances now. I will double check everything before ordering a
new radiator. What correction factors would you use for different
delta Ts?

On the subject of double checking, I notice I have two spreadsheets:
one suggesting I need 11800-12300 BTUs and a second saying I only need
9000 BTUs. I loaded the Barlo program and the figures /0.6 give the
9000 figure. I wonder where I got the 11-12,000 figures from? Time to
get triple checking!

Thanks again,
Stephen.

On Fri, 31 Jul 2009 12:28:31 +0100, Stephen
wrote:

I got the 0.6 factor from reading a post here but I can't remember the
circumstances now. I will double check everything before ordering a
new radiator. What correction factors would you use for different
delta Ts?

Sorry to answer my own post but I did a google search that found the
uk diy wiki! Apologies for not reading the wiki before I posted. That
in turn pointed me towards the Myson and Quinn web sites.

Quinn states to convert dT=50 to dT=60 multiply Watts by 1.2675

Myson has a more detailed table showing lots of temperatures but for
the same dT=50 to dT=60 conversion it states a multiplication of 1.27.

These factors are the same to 3sf, so can I assume the same factor
applies to all similar makes of radiator?

Roger was talking about using dT=40 for condensing boilers. The Myson
pdf says to multiply the dT=50 figure by 0.75 to give the output at
dT=40.

So it appears the factors I need are 0.75 and 1.27. I don't know where
my 0.6 came from!

The above factors are to be used with heat outputs in Watts and eagle
eyed readers may notice I was using BTUs, so I will carefully convert
BTUs to Watts before proceeding!

Thanks,
Stephen.

On Fri, 31 Jul 2009 12:12:20 +0100, Stephen wrote:

On Thu, 30 Jul 2009 02:51:02 -0700 (PDT), RobertL
wrote:

We bought our rads (Biasi) from http://www.4bathrooms.co.uk/ but we
did have some problems with long delays. Biasi do rads up to 2200mm
long (3.5kW nominal for Biasi type 22K).

I hadn't heard of Biasi before; are they any good?

I presume the 22K is their terminology for a double?

I wish that they'd use one system to avoid uncertainty. Last time I fitted
some rads. (can't remember which make) it was simply: Type 1, 11, 2, 21, 22
for panels and fins (Type 12 ain't a good idea!), so easy to remember and
v. simple.
The prices on that web site seem very good.

Thanks,
Stephen.


--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

On Jul 31, 12:12*pm, Stephen wrote:
On Thu, 30 Jul 2009 02:51:02 -0700 (PDT), RobertL

wrote:
We bought our rads (Biasi) fromhttp://www.4bathrooms.co.uk/but we
did have some problems with long delays. *Biasi do rads up to 2200mm
long *(3.5kW nominal for Biasi type 22K).

I hadn't heard of Biasi before; are they any good?

I presume the 22K is their terminology for a double?

The prices on that web site seem very good.

Thanks,
Stephen.

the prices are very good and we have bought many rads therei nthe [ast
with no problems. however, last time we bought they kept on putting
us off "delivery expected in 3 days" for weeks and weeks so we didn't
go back again.

yes 22K is the Biasi type-name with two rads and two sets of fins
facing each other in the gap.

We bougth Biasi because we liked the look of them. They seem to work
fine. Brackets are easy to fix etc etc.

R

In article ,
Stephen writes:

I have found the delta T problem before. IIRC Screwfix quote dT=50K
and Toolstation quote dT=60K.

I got the 0.6 factor from reading a post here but I can't remember the

I've mentioned a 0.6 factor before, but not recently.
It came out of the Ultraheat leaflet, for converting their
quoted power outputs (can't recall the delta) down for 70/50
operation for use with condensing boilers.

circumstances now. I will double check everything before ordering a
new radiator. What correction factors would you use for different
delta Ts?

On the subject of double checking, I notice I have two spreadsheets:
one suggesting I need 11800-12300 BTUs and a second saying I only need
9000 BTUs. I loaded the Barlo program and the figures /0.6 give the
9000 figure. I wonder where I got the 11-12,000 figures from? Time to
get triple checking!

I used an early Myson Java calculator. It significantly over-estimated
the radiator sizes (Andy Hall thought it had wrong U-values, but I
didn't investigate where the error was). It actually means I've been
able to run the heating at 45/40 even when just below freezing outside
and get significantly better boiler efficiency than is normally expected.
I didn't actually use any Myson radiators, although on reflection I'm
rather pleased with the effect of the error.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Stephen writes:
On 30 Jul 2009 08:57:55 GMT, (Andrew
Gabriel) wrote:

Maybe Stelrad jargon? The Ultraheat Compact range I used call
them SF, HF, DF, TF for single, one-and-a-half (double with only
one set of fins), double, and triple radiators respectively.

Triples?! I have never heard of or seen those. Are they three
radiators sandwiched together with four sets of fins between them?

Yes, except 3 sets of fins - one on each panel. Think of it like
a double panel radiator with a single panel radiator added on the
front.

http://www.cucumber.demon.co.uk/radiator_tp1.jpg/
http://www.cucumber.demon.co.uk/radiator_tp2.jpg/

Those are both Ultraheat Compact 6. The 6 means they have two extra
connections into the bottom, and both these cases are using the bottom
connections so there are no side valves/pipework. The Ultraheat
Compact 4 are the same, but don't have the bottom entry connections,
although when you order a 4, you seem to get a 6 if they have no 4's
in that size already made up.

Basai also did triple panel radiators at the time, but no one seemed
to stock them or be willing to order non-stock items. The Ultraheat
came in a full range of heights and widths.

Unfortunately, Ultraheat has the most aweful web****e you ever saw.
If they'd just put up a PDF of the leaflet they supply the plumbers
merchants, that would be a big improvement over the broken flash.

If you're anywhere near Dunstable Beds, these came from Dunstable
Heating Supplies in High Street North - they get them in same day
if you call early enough, next day otherwise (well, this is going
back several years, but they're still there).
I believe the radiators are made in Leighton Buzzard, which is
just up the road.

They must be huge and heavy!

They are deeper, but they are also smaller, which is the reason
for using them.

Is Stelrad a good make? It's a brand that seems to have been mentioned
more than once in this thread. In the past I have just bought whatever
make Screwfix or Toolstation have sold; I wasn't aware there was so
much choice.

Does anyone know what makes SF and TS sell? I had problems with the TS
ones because they were delivered wrapped only in plastic film, so I
had one or two arrive dented. I am told SF send theirs in boxes.

A few people have said in the past don't bother buying single panel
radiators mail order, as they always get bent in transit. Doubles
are inherently stronger. The Ultraheat ones came wrapped in multiple
layers of strong bubble wrap (the solid plastic side was much thicker
than normal bubblewrap). None had any dents, dings, or other marks.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In an earlier contribution to this discussion,
Stephen wrote:


I got the 0.6 factor from reading a post here but I can't remember the
circumstances now. I will double check everything before ordering a
new radiator. What correction factors would you use for different
delta Ts?

These are the figures published by Stelrad - using Delta-T=60 as a
reference:
[Hope it doesn't get scrambled in transmission!]

Delta-T Factor
60 1.000
55 0.898
50 0.798
45 0.700
40 0.605
35 0.512
30 0.423

So, if you are looking at rads specified at (say) 50 and you want to know
the output at (say) 40, divide the published output by 0.798 and then
multiply the result by 0.605

[Or swap division and multiplication if you're grossing up the heat losses
rather than downrating the rads - you'll end up in the same place].


On the subject of double checking, I notice I have two spreadsheets:
one suggesting I need 11800-12300 BTUs and a second saying I only need
9000 BTUs. I loaded the Barlo program and the figures /0.6 give the
9000 figure. I wonder where I got the 11-12,000 figures from? Time to
get triple checking!

The calculation programs have many parameters which you can vary - and you
get different results if you do vary them. These include:
* Assumed outside temperature
* U-values for each type of wall, window, floor, ceiling, etc.
* Temperature in adjacent rooms
* Number of air changes per hour

In addition, some programs build in extra allowances for transitional
effects. To heat a room quickly, you need to input heat at a higher rate
than you need to maintain a steady state when it's up to temperature. So you
need to look at *all* of these things in order to make sure that you're
comparing apples with apples.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
Stephen wrote:

On Fri, 31 Jul 2009 12:28:31 +0100, Stephen
wrote:

I got the 0.6 factor from reading a post here but I can't remember
the circumstances now. I will double check everything before
ordering a new radiator. What correction factors would you use for
different delta Ts?

Sorry to answer my own post but I did a google search that found the
uk diy wiki! Apologies for not reading the wiki before I posted. That
in turn pointed me towards the Myson and Quinn web sites.

Quinn states to convert dT=50 to dT=60 multiply Watts by 1.2675

Myson has a more detailed table showing lots of temperatures but for
the same dT=50 to dT=60 conversion it states a multiplication of 1.27.

These factors are the same to 3sf, so can I assume the same factor
applies to all similar makes of radiator?

Roger was talking about using dT=40 for condensing boilers. The Myson
pdf says to multiply the dT=50 figure by 0.75 to give the output at
dT=40.

So it appears the factors I need are 0.75 and 1.27. I don't know where
my 0.6 came from!

The above factors are to be used with heat outputs in Watts and eagle
eyed readers may notice I was using BTUs, so I will carefully convert
BTUs to Watts before proceeding!

Thanks,
Stephen.


Hi,

I only read this after I had answered your previous post.

The 0.6 comes from converting from 60 to 40. All rads used to be quoted at
60, but most are now quoted at 50 - hence the difference.

If you divide all the figures I quoted by 0.798 - so as to get 1.000 at 50,
then 60 gives 1.25 and 40 gives 0.758 - which are not a million miles away
from the figures which you are now using.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Fri, 31 Jul 2009 06:23:47 -0700 (PDT), RobertL
wrote:

We bougth Biasi because we liked the look of them.

Is there a big difference between the appearances of different makes?
For standard radiators, they all seem to look the same: metal sheets
enclosing each end and plastic grill on top. Or so it appears from the
tiny photos on the various web sites.

On 31 Jul 2009 13:34:08 GMT, (Andrew
Gabriel) wrote:

I used an early Myson Java calculator. It significantly over-estimated
the radiator sizes (Andy Hall thought it had wrong U-values, but I
didn't investigate where the error was). It actually means I've been
able to run the heating at 45/40 even when just below freezing outside
and get significantly better boiler efficiency than is normally expected.
I didn't actually use any Myson radiators, altho

Would I be right to say there is no problem if all the rads are
oversized, provided they are all oversized by the same amount? I would
think that if you have an oversized radiator, you can always turn it
down but if you get an undersized radiator, you are stuck.

On Fri, 31 Jul 2009 16:49:58 +0100, "Roger Mills"
wrote:

These are the figures published by Stelrad - using Delta-T=60 as a
reference:
[Hope it doesn't get scrambled in transmission!]

Delta-T Factor
60 1.000
55 0.898
50 0.798
45 0.700
40 0.605
35 0.512
30 0.423

Thanks. I hadn't seen that before. The Stelrad pdf quoted in the wiki
has a similar table but it has been revised for dT=50, I.e. the 50 C
entry has a factor of 1.00, 60 C has a factor of 1.27, and 40 C has a
factor of 0.75. It's worth having both tables because some merchants
still quote outputs at dT=60 and others at dT=50. Using the "right"
table I would only have to multiply once, rather than twice.

The calculation programs have many parameters which you can vary - and you
get different results if you do vary them. These include:
* Assumed outside temperature
* U-values for each type of wall, window, floor, ceiling, etc.
* Temperature in adjacent rooms
* Number of air changes per hour

Yes, it is a real headache. It's easy enough to measure the rooms and
the windows but it's not always possible to know how thick the walls
are and what they are made of. I wonder how professional installers
manage? I am sure they don't go asking what the ceiling, floor, and
walls are made from!

I think I am only using half of the Barlo calculator's abilities. I
have used it to calculate the heat losses. I notice it has the water
temperature set to 60 C. Now if the room is 20C, that would mean
dT=40. I think the programme can suggest the appropriate Barlo
radiator. Can I save myself the calculations and get it to tell me
what rads I need?

On Fri, 31 Jul 2009 17:04:59 +0100, "Roger Mills"
wrote:

The 0.6 comes from converting from 60 to 40. All rads used to be quoted at
60, but most are now quoted at 50 - hence the difference.

If you divide all the figures I quoted by 0.798 - so as to get 1.000 at 50,
then 60 gives 1.25 and 40 gives 0.758 - which are not a million miles away
from the figures which you are now using.

I see:

1/1.25*0.758=0.604

I knew it had come from somewhere

Thanks again.

In an earlier contribution to this discussion,
Stephen wrote:


Yes, it is a real headache. It's easy enough to measure the rooms and
the windows but it's not always possible to know how thick the walls
are and what they are made of. I wonder how professional installers
manage? I am sure they don't go asking what the ceiling, floor, and
walls are made from!

They use a very scientific instrument along the lines of a wet finger in the
air!

I think I am only using half of the Barlo calculator's abilities. I
have used it to calculate the heat losses. I notice it has the water
temperature set to 60 C. Now if the room is 20C, that would mean
dT=40. I think the programme can suggest the appropriate Barlo
radiator. Can I save myself the calculations and get it to tell me
what rads I need?

dT is the difference between the room temperature and the *mean* radiator
temperature - not the flow temperature. So, if your rads have a 10 degree
drop (in at 60, out at 50) the mean temperature is 55, and dT is only 35.

The Barlo program (the version I have, anyway) is very old and doesn't
reflect the current range of radiators available. I only us it for
calculating the heat losses, and then do the match to individual radiators
manually.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
Stephen wrote:


Would I be right to say there is no problem if all the rads are
oversized, provided they are all oversized by the same amount? I would
think that if you have an oversized radiator, you can always turn it
down but if you get an undersized radiator, you are stuck.

Pretty much - particulartly if they are fitted with TRVs. Provided you have
sufficient boiler capacity, it will speed up getting the house up to
temperature from cold. If you have one of two which are more oversized than
the rest, you can always throttle them back a bit when you balance the
system - setting their drop a bit higher than the rest to reduce their
output and to make sure that they don't hog all the heat.

You do need to watch the rad in the room where the room stat is located,
though. If that room heats up *too* quickly, the room stat will turn the
boiler off before the other rooms are up to temperature.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Mon, 3 Aug 2009 10:14:09 +0100, "Roger Mills"
wrote:

You do need to watch the rad in the room where the room stat is located,
though. If that room heats up *too* quickly, the room stat will turn the
boiler off before the other rooms are up to temperature.

A good point, I hadn't thought of that. Thanks again.

On Mon, 3 Aug 2009 10:08:21 +0100, "Roger Mills"
wrote:

dT is the difference between the room temperature and the *mean* radiator
temperature - not the flow temperature. So, if your rads have a 10 degree
drop (in at 60, out at 50) the mean temperature is 55, and dT is only 35.

I am glad I asked. I wasn't sure what it meant by water temperature.
Flow temperature does seem the obvious choice but I wasn't sure
whether it might have been mean temperature. After all, if the rads
are balance, shouldn't the drop across the rad and the mean temp be
the same for all rads? I will have to change it to 65 C. Thanks again.

In article ,
Stephen writes:
On 31 Jul 2009 13:34:08 GMT, (Andrew
Gabriel) wrote:

I used an early Myson Java calculator. It significantly over-estimated
the radiator sizes (Andy Hall thought it had wrong U-values, but I
didn't investigate where the error was). It actually means I've been
able to run the heating at 45/40 even when just below freezing outside
and get significantly better boiler efficiency than is normally expected.
I didn't actually use any Myson radiators, altho

Would I be right to say there is no problem if all the rads are
oversized, provided they are all oversized by the same amount? I would

Correct. If you have a condensing boiler, you can turn down the
circulating water temperature, which increases boiler efficiency.
That's what I've been able to do (particularly in my case as the
boiler doesn't do the hot water, so it can be set way below normal
hot water temperatures). Another benefit of low radiator temperatures
is that the energy stored in a radiator is lower, and less likely
to cause overshoot. Indeed, I have almost no overshoot on that
system (less than 0.5C), without any need to actively control it,
and so the room temperature changes by only 0.5C as the heating
demand cycles on and off, as that's the hysterysis I deliberately
include in the control system to prevent overly frequent demand
cycling.

The only time I've had to set it above 45C is when I've been away
for days and the house has cooled down to frost protection levels
and it's minus something outside. Then I set it to 55C or 60C for
an hour or two to quickly heat the house up. It can do it at 45C
flow, but it takes many hours.

When I was commissioning the system, I tried running it at 83C
(the boiler's max), but I couldn't get it quite there, as at that
temperature the radiators would be giving off more power than the
boiler's 25kW output. (Could have covered some up or turned them
off, I suppose.)

think that if you have an oversized radiator, you can always turn it
down but if you get an undersized radiator, you are stuck.

A mixture of radiators mis-sized in different ways will always
present problems. TRV's will help, but can't cure the problems.
You can adjust the output slightly by misbalancing to create
different average radiator temperatures, but again the control
you'll have over this isn't going to cover up significant
mis-sizing.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

wrote in message ...


Thinking ahead to when I change my system boiler to a condensing one, Can
any
be set to deliver output at a higher temperature for hot water? I
currently
use mine at about 80deg to heat the hot water, and am considering a
heatbank
in order to get mains pressure hot water, and that again would require a
higher temperature than is required solely for heating.

What do you need this very hot water for?

On Aug 3, 9:33*am, Stephen wrote:
On Fri, 31 Jul 2009 06:23:47 -0700 (PDT), RobertL

wrote:
We bougth Biasi because we liked the look of them.

Is there a big difference between the appearances of different makes?
For standard radiators, they all seem to look the same: metal sheets
enclosing each end and plastic grill on top. Or so it appears from the
tiny photos on the various web sites.

With Biasi, the grill on top (and the solid sides) is metal and it
uncilps so you can dust inside the radiator between the two
sections. Some people prefer that.

Some rads also allow you to feed the pipework from behind. Some
people prefer that.

Robert

On 04 Aug 2009 18:19:40 GMT, (Andrew
Gabriel) wrote:

If you have a condensing boiler, you can turn down the
circulating water temperature, which increases boiler efficiency.
That's what I've been able to do (particularly in my case as the
boiler doesn't do the hot water, so it can be set way below normal
hot water temperatures). Another benefit of low radiator temperatures
is that the energy stored in a radiator is lower, and less likely
to cause overshoot. Indeed, I have almost no overshoot on that
system (less than 0.5C), without any need to actively control it,
and so the room temperature changes by only 0.5C as the heating
demand cycles on and off,

Thanks. I wasn't sure what overshoot was but I think you explained it.
Is it basically when the room heats up too much. The thermostat might
switch off at say 20C but because there is so much hot water sitting
in the rad, the rad continues to emit and the room becomes say 23C? I
can't believe you have managed to fine tune it to within half a
degree!

BTW, on a different topic: I now realise that the water setting in the
Barlo programme is irrelevant because the heat loss from the room is
the same regardless of the water temperature. The water temperature
only comes into play when deciding which rad will match that heat loss
and I am not using the programme to choose the radiators.

On 04 Aug 2009 18:19:40 GMT, (Andrew
Gabriel) wrote:

(particularly in my case as the
boiler doesn't do the hot water, so it can be set way below normal
hot water temperatures)

Sorry, I forgot to ask: what does the DHW?

On Wed, 5 Aug 2009 02:09:58 -0700 (PDT), RobertL
wrote:

With Biasi, the grill on top (and the solid sides) is metal and it
uncilps so you can dust inside the radiator between the two
sections. Some people prefer that.

Do the sides remove for dusting or just the grill? The cheap ones I
have bought from Toolstation allow the grill to be removed but you
cannot remove the sides without taking off the pipes.

In article ,
Stephen writes:
On 04 Aug 2009 18:19:40 GMT, (Andrew
Gabriel) wrote:

If you have a condensing boiler, you can turn down the
circulating water temperature, which increases boiler efficiency.
That's what I've been able to do (particularly in my case as the
boiler doesn't do the hot water, so it can be set way below normal
hot water temperatures). Another benefit of low radiator temperatures
is that the energy stored in a radiator is lower, and less likely
to cause overshoot. Indeed, I have almost no overshoot on that
system (less than 0.5C), without any need to actively control it,
and so the room temperature changes by only 0.5C as the heating
demand cycles on and off,

Thanks. I wasn't sure what overshoot was but I think you explained it.
Is it basically when the room heats up too much. The thermostat might
switch off at say 20C but because there is so much hot water sitting
in the rad, the rad continues to emit and the room becomes say 23C? I

Yes (although I doubt it would normally be that much).
I believe some of the more advanced heating controllers compensate,
i.e. once they've learned what the overshoot is, they switch off
earlier and use the overshoot to get the the required temperature.
If the heating controller is fully integrated with the boiler, it
can reduce the radiator temperature as the difference between current
room temp and thermostat setting is closing, to avoid overshoot,
and can also take into account outside temperature (hence heat loss
through walls). Using the outside temp is called weather compensation.

However, since I design/build my own heating controllers, I haven't
actually played with commercially available ones.

can't believe you have managed to fine tune it to within half a
degree!

I used to have gas wall heaters, before the central heating.
The dining room had a Drugasar gas wall heater with proportional
control, and that kept the room to within 0.1C, once I'd pulled
the thermostat phile out from the insides of the heater and hung
it in the air inlet underneath.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Stephen writes:
On 04 Aug 2009 18:19:40 GMT, (Andrew
Gabriel) wrote:

(particularly in my case as the
boiler doesn't do the hot water, so it can be set way below normal
hot water temperatures)

Sorry, I forgot to ask: what does the DHW?

Gas multipoint water heater (Main).
So I've basically got separates, instead of a combi!
The gas multipoint water heater was quite new when I installed
the central heating, and has a number of plus points such as it
works during power cuts, and works if the boiler goes wrong, so
it seemed prudent to keep it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]