I have recently moved and the living room seems to be taking an excessively
long time to heat up compared to the rest of the house.

The raditaor is a basic double panel 700 high by 1100 across without any
conventor panels or fins whatsoever. I am therefore unsure what the BTU of
such a radiator is, as Myson etc dont seem to produce a finless radiator.

The room is approx 14ft x 12ft, adjoing the linking between the hall and
kitchen. House is cavity wall (filled).Two sides are internal walls, one is
the adjoining neighbour and one is an outside. Room faces west/southwest
direction.

There is a pvcu window (double glazed window and door) that is equivilent to
about 8ftx5ft in size.

Floor is laminate on a suspending wood floor (doubt it is insulated), and
there is a Baxi gas pebble effect fire in the room (i.e chimney losses).

Is the radiator I have sufficient to heat this size room? What would be the
recommended output to change to if required?

Jim wrote:
I have recently moved and the living room seems to be taking an excessively
long time to heat up compared to the rest of the house.

The raditaor is a basic double panel 700 high by 1100 across without any
conventor panels or fins whatsoever. I am therefore unsure what the BTU of
such a radiator is, as Myson etc dont seem to produce a finless radiator.

The room is approx 14ft x 12ft, adjoing the linking between the hall and
kitchen. House is cavity wall (filled).Two sides are internal walls, one is
the adjoining neighbour and one is an outside. Room faces west/southwest
direction.

There is a pvcu window (double glazed window and door) that is equivilent to
about 8ftx5ft in size.

Floor is laminate on a suspending wood floor (doubt it is insulated), and
there is a Baxi gas pebble effect fire in the room (i.e chimney losses).

Is the radiator I have sufficient to heat this size room? What would be the
recommended output to change to if required?





Check that the radiator is getting as hot as the others - ie flow is okay.

If the room does get up to temperature eventually, the easy option is
just to replace the existing rad with a double panel convector version
of the same size.

Otherwise consider adding another physically small radiator on the
opposite side of the room to help reduce cold spots. If a quick warmup
of the living room, maybe when you get in from work, is a priority then
dont worry about having too much heat output ; TRVs will take care of
the temperature control. See what size fits in to the room layout and
unless you really need to keep the depth (off the wall) to a minimum go
for a double pamel convector.

In an earlier contribution to this discussion,
Jim wrote:

I have recently moved and the living room seems to be taking an
excessively long time to heat up compared to the rest of the house.

The raditaor is a basic double panel 700 high by 1100 across without
any conventor panels or fins whatsoever. I am therefore unsure what
the BTU of such a radiator is, as Myson etc dont seem to produce a
finless radiator.
The room is approx 14ft x 12ft, adjoing the linking between the hall
and kitchen. House is cavity wall (filled).Two sides are internal
walls, one is the adjoining neighbour and one is an outside. Room
faces west/southwest direction.

There is a pvcu window (double glazed window and door) that is
equivilent to about 8ftx5ft in size.

Floor is laminate on a suspending wood floor (doubt it is insulated),
and there is a Baxi gas pebble effect fire in the room (i.e chimney
losses).
Is the radiator I have sufficient to heat this size room? What would
be the recommended output to change to if required?

The rough rule of thumb which I use for calculating the output of double
unfinned radiators is 2170 watts per square metre at a delta-T [1] of 60
degC. That would make your rad worth about 1670 watts - but you probably
need to downrate that by up to 20% (to about 1340 watts) to allow for a
likely lower delta-T value.

In order to work out whether this radiator is adequate for supplying heat at
the rate at which is being lost to the outside world, you will need to do
some proper calculations. You *could* do that with pencil and paper or a
spreadsheet if you work out the areas of all the relevant surfaces, and look
up the U values - but an easier way is to use a heatloss program such as the
one which you can download from
http://www.barlo.co.uk/downloads_heatloss.php

If your room isn't getting hot, it will be down to either or both of 2
causes:
* the radiator isn't big enough (doing the calcs will check on this)
* the radiator isn't getting its fair share of heat from the boiler -
requiring the system to be balanced, and/or the thermostat(s) to be
adjusted.

With regard to the second possibility:
Is the radiator getting as hot as those in the other rooms? How long can you
hold your hand on it?
Is it getting hot as *fast* as the others?
Is the heating being turned off by a room stat elsewhere before the lounge
gets up to temperature?


[1] Delta-T is the temperature difference between radiator (average of input
and output) and the room. If, for example, your flow temperature is 80 and
return 70 (mean 75) and the room is at 20 degrees, the delta-T value would
be 55 - which is probably the highest you are likely to achieve
--
Cheers,
Roger
______
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With regard to the second possibility:
Is the radiator getting as hot as those in the other rooms? How long can
you hold your hand on it?
Is it getting hot as *fast* as the others?
Is the heating being turned off by a room stat elsewhere before the lounge
gets up to temperature?

Rad heats are fast as others in the house, and gets very hot (touch for
about 1 second). At the moment I am running the lounge rad without the TRV
set to max, and the house room stat in the lounge to make sure that it is
not the room stat.

I have tried the heatloss program, but I am not sure what to enter for the
Gas Warm allowance, or the Airchange rate. I have selected Gas Warm
allowance as YES and a air change rate of 1.5? This returns a value of 1866
watts. Assuming the gaswarm allowance and air rate changes are correct this
appears to show that the current rad is underated by around 25%

By using the same size rad, in a double panel 2 fin conventor should acheive
about 2150 watts, which give around an extra 650watts and should be overated
by about 15%.

Do these conclusion sound reasonable, before I buy a new rad!

"Jim" wrote in message
. uk...

With regard to the second possibility:
Is the radiator getting as hot as those in the other rooms? How long can
you hold your hand on it?
Is it getting hot as *fast* as the others?
Is the heating being turned off by a room stat elsewhere before the
lounge gets up to temperature?

Rad heats are fast as others in the house, and gets very hot (touch for
about 1 second). At the moment I am running the lounge rad without the TRV
set to max, and the house room stat in the lounge to make sure that it is
not the room stat.

I have tried the heatloss program, but I am not sure what to enter for the
Gas Warm allowance, or the Airchange rate. I have selected Gas Warm
allowance as YES and a air change rate of 1.5? This returns a value of
1866 watts. Assuming the gaswarm allowance and air rate changes are
correct this appears to show that the current rad is underated by around
25%


Maybe, but only underated by that amount at the design external
temerature, -1deg say, so if you have frequently noticed the rad ineffective
at higher external temperatures there is something else. The lack of fins
changes the balance between radiated and convected heat. I think its the
lack of convection you are noticing. From one I have done before a double
convector of the existing size will easily do in a modestly insulated room
of that size. Since it was the comparison with other rooms you complained
about its still well worth doing the whole house calcs to ensure a well
balanced design.

Jim A

In an earlier contribution to this discussion,
Jim wrote:

With regard to the second possibility:
Is the radiator getting as hot as those in the other rooms? How long
can you hold your hand on it?
Is it getting hot as *fast* as the others?
Is the heating being turned off by a room stat elsewhere before the
lounge gets up to temperature?

Rad heats are fast as others in the house, and gets very hot (touch
for about 1 second). At the moment I am running the lounge rad
without the TRV set to max, and the house room stat in the lounge to
make sure that it is not the room stat.

Not sure I understand the TRV comment. Are you saying that the TRV *is*
throttling the flow? If so, set it to max, or remove the head completely.

I have tried the heatloss program, but I am not sure what to enter
for the Gas Warm allowance, or the Airchange rate. I have selected
Gas Warm allowance as YES and a air change rate of 1.5? This returns
a value of 1866 watts. Assuming the gaswarm allowance and air rate
changes are correct this appears to show that the current rad is
underated by around 25%
By using the same size rad, in a double panel 2 fin conventor should
acheive about 2150 watts, which give around an extra 650watts and
should be overated by about 15%.

Do these conclusion sound reasonable, before I buy a new rad!

Looking at my radiator catalogue, I guess that 2150 watts for a
double-finned 1100 x 700 is based on a delta-T of 50, whereas you may be
able to achieve 55 and wring a bit more out of it.

Is your 1866 watts heatloss the steady-state value - or does it have any
bunce in it (typically 10 - 20%) to provide a fast warmup? Provided there
*is* some bunce, and provided the boiler and pipework can deliver the extra
heat fast enough, this rad may well be ok.

It's worth trying a few different values for some of the parameters in the
heatloss program to see what difference it makes. For example, what is the
effect of saying NO to Gas Warm allowance, or going for 2 air changes per
hour? [1.5 is probably ok unless you've got a lot of draughts - but it's
always useful to know how much you've got in reserve in case any of your
assumptions are wrong!]
--
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!

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Jim wrote:

The rough rule of thumb which I use for calculating the output of double
unfinned radiators is 2170 watts per square metre at a delta-T [1] of 60
degC.

Roger, this is a really useful estimated output value for older radiators.
I'm currently updating/adapting a 1970's heating system, and will need to
calculate the total load to allow for an extension as well - hopefully NOT a
new boiler for now.... Most of my current radiators are single unfinned, and
I wonder if you have a similar rule of thumb value for these?

Regards,

Charles F

In an earlier contribution to this discussion,
CJF wrote:

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Jim wrote:

The rough rule of thumb which I use for calculating the output of
double unfinned radiators is 2170 watts per square metre at a
delta-T [1] of 60 degC.

Roger, this is a really useful estimated output value for older
radiators. I'm currently updating/adapting a 1970's heating system,
and will need to calculate the total load to allow for an extension
as well - hopefully NOT a new boiler for now.... Most of my current
radiators are single unfinned, and I wonder if you have a similar
rule of thumb value for these?

Regards,

Charles F

The value I use for single unfinned rads is 1280 watts/M^2 (taking the area
as height x width, not total surface area of both sides). This is again at a
delta-T of 60 degC, and should be multiplied by 0.9 for 55 degC or 0.8 for
50 degC.

[I have arrived at these figures by taking the values which I used back in
1969 when installing central heating in my first house - and converting from
imperial dimensions, BTUs and temperatures in degF!]

For single finned rads, I use 2000 watts/M^2 at a delta-T of 60 (taken from
a recent Stelrad catalogue). Its interesting that a single finned rad
produces nearly as much output as a double unfinned one - due to the
considerable increase in surface area provided by the fins.

For completeness, values for double rads with single fins and double rads
with double fins would be about 2790 and 3575 watts/M^2 respectively (both
at a delta-T of 60 degC).
--
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!

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
CJF wrote:

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Jim wrote:

The rough rule of thumb which I use for calculating the output of
double unfinned radiators is 2170 watts per square metre at a
delta-T [1] of 60 degC.

Roger, this is a really useful estimated output value for older
radiators. I'm currently updating/adapting a 1970's heating system,
and will need to calculate the total load to allow for an extension
as well - hopefully NOT a new boiler for now.... Most of my current
radiators are single unfinned, and I wonder if you have a similar
rule of thumb value for these?

Regards,

Charles F

The value I use for single unfinned rads is 1280 watts/M^2 (taking the
area
as height x width, not total surface area of both sides). This is again at
a
delta-T of 60 degC, and should be multiplied by 0.9 for 55 degC or 0.8 for
50 degC.

[I have arrived at these figures by taking the values which I used back in
1969 when installing central heating in my first house - and converting
from
imperial dimensions, BTUs and temperatures in degF!]

For single finned rads, I use 2000 watts/M^2 at a delta-T of 60 (taken
from
a recent Stelrad catalogue). Its interesting that a single finned rad
produces nearly as much output as a double unfinned one - due to the
considerable increase in surface area provided by the fins.

For completeness, values for double rads with single fins and double rads
with double fins would be about 2790 and 3575 watts/M^2 respectively (both
at a delta-T of 60 degC).
--
Cheers,
Roger

Great set of figures. My first central heating project was around 1980, but
unlike you I neglected to keep the paperwork! Now back to the
calculator......

Thanks again, Roger

Charles F