Hi

I am currently looking into replacing my radiators as part of a central
heating upgrade, we currently have single panel and single convector of
assorted sizes around the house, the style that has been chosen only
comes in single convector and above. I have work out that these can be
accommodated depth wise, and would like to keep close to the existing
width as they sit neatly under the window sill.

Q. What are the drawbacks if I oversize a radiator (fitted with TRV)
based on room calcs?

TIA

--
Mark

On Tue, 21 Mar 2006 06:42:26 GMT, Mark
wrote:

Hi

I am currently looking into replacing my radiators as part of a central
heating upgrade, we currently have single panel and single convector of
assorted sizes around the house, the style that has been chosen only
comes in single convector and above. I have work out that these can be
accommodated depth wise, and would like to keep close to the existing
width as they sit neatly under the window sill.

Q. What are the drawbacks if I oversize a radiator (fitted with TRV)
based on room calcs?

TIA


None particularly. If you are going to do this, it would be a good
idea to take a look at the manufacturer derating tables.

If you are using a conventional boiler at 82/70 degrees, the usual
figure is to take the actual heat output as 90% of the data sheet
value (which is based on 90 degrees).

If you are going to go for a condensing boiler, then you can gain some
efficiency advantage while you are doing this exercise by running the
system at 70/50 degrees. To do this, you would use 60% as the factor
on the radiators.

In other words, let's say your calculations show a heat requirement in
the room of 600W, you would use a radiator of 1000W nominal data sheet
rating.

I did a similar exercise to this a couple of years ago and it's very
effective. In fact, the boiler flow temperature seldom needs to go
above about 55-60 degrees.


--

..andy


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In article ,
Andy Hall writes:

I did a similar exercise to this a couple of years ago and it's very
effective. In fact, the boiler flow temperature seldom needs to go
above about 55-60 degrees.

Same here. Actually, I can run my heating with a flow temperature
of 45C once the house is heated up (which means there was a fault
in the program I used to do the calculations, Myson's Java calculator
when in beta, and it did warn about this I must admit).

However, on reflection this is great. I can heat the house up from
stone cold in about 1/4 hour by setting the boiler up high, and run
the boiler (Keston C25) in super-efficent mode at at 45C flow temp
at all other times.

--
Andrew Gabriel

In an earlier contribution to this discussion,
Andrew Gabriel andrew@a17 wrote:

In article ,
Andy Hall writes:

I did a similar exercise to this a couple of years ago and it's very
effective. In fact, the boiler flow temperature seldom needs to go
above about 55-60 degrees.

Same here. Actually, I can run my heating with a flow temperature
of 45C once the house is heated up (which means there was a fault
in the program I used to do the calculations, Myson's Java calculator
when in beta, and it did warn about this I must admit).

However, on reflection this is great. I can heat the house up from
stone cold in about 1/4 hour by setting the boiler up high, and run
the boiler (Keston C25) in super-efficent mode at at 45C flow temp
at all other times.

As a matter of interest, how do you heat your DHW to an acceptable
temperature?
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.

On Tue, 21 Mar 2006 15:17:45 -0000, "Roger Mills"
wrote:

In an earlier contribution to this discussion,
Andrew Gabriel andrew@a17 wrote:

In article ,
Andy Hall writes:

I did a similar exercise to this a couple of years ago and it's very
effective. In fact, the boiler flow temperature seldom needs to go
above about 55-60 degrees.

Same here. Actually, I can run my heating with a flow temperature
of 45C once the house is heated up (which means there was a fault
in the program I used to do the calculations, Myson's Java calculator
when in beta, and it did warn about this I must admit).

However, on reflection this is great. I can heat the house up from
stone cold in about 1/4 hour by setting the boiler up high, and run
the boiler (Keston C25) in super-efficent mode at at 45C flow temp
at all other times.

As a matter of interest, how do you heat your DHW to an acceptable
temperature?

I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power. Flow temperature is up
to 85 degrees in that mode. The HW temperature setting is also on
the boiler controller and it stops when that is satisfied.

After that, it returns to CH mode and responds to room temperature
from room sensor, weather compensator and max temperature setting for
CH flow.



--

..andy

In an earlier contribution to this discussion,
Andy Hall wrote:


As a matter of interest, how do you heat your DHW to an acceptable
temperature?

I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power. Flow temperature is up
to 85 degrees in that mode. The HW temperature setting is also on
the boiler controller and it stops when that is satisfied.

After that, it returns to CH mode and responds to room temperature
from room sensor, weather compensator and max temperature setting for
CH flow.

Thanks. Sounds like a fast recovery cylinder is fairly necessary.

Does this method of control have a 'plan' name? It pretty certainly isn't
standard S-Plan because that would allow HW and CH to run concurrently.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.

On Tue, 21 Mar 2006 19:16:18 -0000, "Roger Mills"
wrote:

In an earlier contribution to this discussion,
Andy Hall wrote:


As a matter of interest, how do you heat your DHW to an acceptable
temperature?

I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power. Flow temperature is up
to 85 degrees in that mode. The HW temperature setting is also on
the boiler controller and it stops when that is satisfied.

After that, it returns to CH mode and responds to room temperature
from room sensor, weather compensator and max temperature setting for
CH flow.

Thanks. Sounds like a fast recovery cylinder is fairly necessary.

I have that, but the reheat cycles are fairly fast anyway. The
temperature detection on the cylinder is done with an analogue sensor
connected directly to the boiler controller. Therefore the boiler
knows the actual temperature as opposed to being told when to fire as
would be the case in a typical thermostat/programmer setup.
If the temperature is gradually drifting downwards because of the use
of small amounts of water, then nothing happens until it reaches a
configurable number of degrees below the DHW set point. If the
temperature drops more rapidly because the shower is turned on, for
example, then the boiler fires much earlier.


Does this method of control have a 'plan' name? It pretty certainly isn't
standard S-Plan because that would allow HW and CH to run concurrently.

The boiler controller does all the work. It has analogue temperature
inputs from the cylinder and outside temperature sensor.

The room controller signals to the boiler using PWM (effectively
providing the boiler with analogue room temperature information as
well). It has the program time settings, desired setback and so on.
However, the boiler is doing the calculation of when to fire up for
optimised start etc.

There are also internal sensors for flow and return temperatures in
the boiler.

The controller is able to control the power level of the boiler, the
pump speed and to open motorised valves.

There are a whole variety of different soft programmable operating
modes that can be set. For example, I could have opted to have
conventional external controls running the boiler with a switched live
and using an external programmer opening the valves in Y or S Plan.
I could also have the boiler operate one diverter valve and do Y plan.

It would also be possible to configure for S Plan with both valves
open, but that would create the issues with temperature that you were
alluding to because either the radiator temperatures would have to be
run all the time at 80-odd degrees or during water heating or the
cylinder would not be able to be heated to required temperature. It
would also have been possible to force the boiler to behave more like
a conventional one and always run at 80 degrees or off.

In essence what I have is most closely described as S-plan plus (since
there are several heating zones) with HW priority.


--

..andy

On Tue, 21 Mar 2006 15:43:24 +0000 Andy Hall wrote :
I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power.

Presumably you've got a boiler with two call for heat inputs and two
stats? The Keston Celsius only has one.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

On Tue, 21 Mar 2006 20:48:32 GMT, Tony Bryer
wrote:

On Tue, 21 Mar 2006 15:43:24 +0000 Andy Hall wrote :
I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power.

Presumably you've got a boiler with two call for heat inputs and two
stats? The Keston Celsius only has one.

It's really the other way round, Tony.

The boiler has sensor inputs for the cylinder and outside temperatures
and a digital PWM input for the (special Siemens) room controller.

This means that it figures out what needs to be done and opens valves
and runs burner and pump as required.

I suppose that to achieve something equivalent on a Celsius, one would
need to modify the control electronics in order to be able to set two
different flow temperatures.

Even better would be if manufacturers had two switched live inputs and
each had a separate control setting inside the boiler


Better still would be if manufacturers would adopt a standard
interface between controls and boilers etc. Opentherm seemed to be
an attempt at that but I'm not sure where that has gone.


--

..andy

In article ,
Andy Hall writes:
On Tue, 21 Mar 2006 15:17:45 -0000, "Roger Mills"
As a matter of interest, how do you heat your DHW to an acceptable
temperature?

A separate Multipoint Gas water heater. It was almost brand new
(having been replaced in an emergency -- see FAQ Humour section)
when I installed the central heating. Also, there was a lot
less choice of good quality condensing combi's back then than
there are now. So I kept the hot water heating quite separate.

I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power. Flow temperature is up
to 85 degrees in that mode. The HW temperature setting is also on
the boiler controller and it stops when that is satisfied.

After that, it returns to CH mode and responds to room temperature
from room sensor, weather compensator and max temperature setting for
CH flow.

Keston C25 doesn't come with any such facility. However, I
have built a replacement facia PCB which allows remote control
of the temperature setting and remote monitoring, and I could
easily do it using that. (Actually, other than some initial
prototype testing, I haven't had time to write the software
and deploy this yet.) Someone posted a much simpler mod to
the facia board just to switch output to max temp by addition
of a relay and resistor IIRC. Obviously, such mods are not going
to be within the capabilities of most people, and if you need
such a feature, you would be better advised to get a boiler
which includes it as standard.

--
Andrew Gabriel

In article , andrew@a17.?
writes
In article ,
Andy Hall writes:
On Tue, 21 Mar 2006 15:17:45 -0000, "Roger Mills"
As a matter of interest, how do you heat your DHW to an acceptable
temperature?

A separate Multipoint Gas water heater. It was almost brand new
(having been replaced in an emergency -- see FAQ Humour section)
when I installed the central heating. Also, there was a lot
less choice of good quality condensing combi's back then than
there are now. So I kept the hot water heating quite separate.

I'm not sure what the Keston does, but on mine the boiler receives
room temperature and cylinder temperature information. When a HW
reheat is required, it opens the valve for the cylinder coil, closes
those for the CH and winds up to full power. Flow temperature is up
to 85 degrees in that mode. The HW temperature setting is also on
the boiler controller and it stops when that is satisfied.

After that, it returns to CH mode and responds to room temperature
from room sensor, weather compensator and max temperature setting for
CH flow.

Keston C25 doesn't come with any such facility. However, I
have built a replacement facia PCB which allows remote control
of the temperature setting and remote monitoring, and I could
easily do it using that. (Actually, other than some initial
prototype testing, I haven't had time to write the software
and deploy this yet.) Someone posted a much simpler mod to
the facia board just to switch output to max temp by addition
of a relay and resistor IIRC. Obviously, such mods are not going
to be within the capabilities of most people, and if you need
such a feature, you would be better advised to get a boiler
which includes it as standard.


Yep, the Celsius 25 isn't that clever in this respect, I found out the
hard way after installing mine. The mod you mentioned was mine, the post
ref is below but I've quoted the content too as I'm not sure how google
will handle the ascii art and most newsreaders will offer a fixed pitch
font option which is what's needed to make sense of it.

As Andy says this mod isn't for everyone and it's a pity Keston didn't
think of doing it for themselves, their larger 40 has it built in.

http://groups.google.co.uk/group/uk....read/fef9273bb
b60c814/

quote
For Ed Sirett and anyone else who's interested, here's the mod I made to
the control panel of my Keston Celsius 25 system boiler to create full
heat demand for hot water operation.

The circuit is not the simplest one possible but for reliability it
avoids having a relay in the high impedance signal path to the boiler
demand level. The 4k7 resistor means that there is always a small
current flow on the relay contacts which is something I prefer. The
worst that can happen if the relay contacts fail is that the mod ceases
to function rather than the whole c/h packing up.

The relay is mains powered and must have gold plated contacts (which is
rare on mains relays), I used RS model 394-9116.

The mod is straightforward to implement but requires some soldering
skill. The 10k resistor needs a cut in the boiler demand level signal
which I made by cutting the control pot wiper lead (middle connection)
and putting the 10k res in its place. The diode & the 4k7 resistor can
then be soldered to the pot terminals on the back of the board and the
relay connections wired up.

Full demand for the Celsius 25 is when the demand control level is at
0V; I have not found that the diode drop affects the operation
significantly.

Control board mod:

+5V
---
|
ctrl / 10k modified
panel \----/\/\/\----------------------- demand
pot / | level
(100k) \ +5V |
_|_ --- |
0V | |
\4k7 |
h/w / |
demand ----- \ 1N4001 | 240V~
| |--||---| ---
- | |
| | o o
RL1 | | RL1a / RL1b /
coil | | o o
- | |
| --- |
--- 0V c/h --------- boiler
240V RTN demand demand


Against my better judgement, here's a version that doesn't involve a mod
to the control board but places a cut in the loom instead. Lots simpler,
just a relay and wiring, but with the relay in the signal path so beware
of dirty contacts affecting operation in the years to come. Again, relay
contacts must be gold plated.

Loom based mod:

Control Board Loom

+5V
---
|
ctrl / RL1a modified
panel \--------------(#---------o |------ demand
pot / \o----| level
(100k) \ o
|---------------(#---------|-------------
_|_
0V

h/w
demand ----- 240V~
| ---
- |
| | o
RL1 | | RL1b /
coil | | o
- |
| |
--- c/h --------- boiler
240V RTN demand demand


I both cases, be careful to separate the wiring on the two relay
contacts as one is low voltage and one is mains, neat soldering is
required and best to sleeve the joints or gloop with hot melt glue.

/quote

I posted some pics at the same time, let me know if anyone needs these
again.

HTH
--
fred
Plusnet - I hope you like vanilla