"Pete C" wrote in message
...
On Mon, 8 Nov 2004 14:02:06 -0000, "IMM" wrote:


"John Aston" wrote in message
...

Look at:
http://www.landisstaefa.com/opc%5Fe/sheet/N3367e.pdf

This is a two stage controller. It requires a 24v supply so a 230v x 24v
transformer is needed. Look at the connection diagram at the bottom. A
room temp sensor (B1 in the diagram), NI 1000 range, is needed. The
outputs
are Y1 (first stage [UFH]) and Y2 (2nd stage [rads]). The output voltage
is
0 - 10V A timer (S1) can switch it on or off.

You will also require two suitable 0 -10 volt modulating valve actuators
complete with valve (22mm).

On the second stage (Y2) you could have an outside stat set to 12 to 15C,
to
hold off the second stage. I can't quite recall now, but if the Y2, 0 -
10v
line to the valve actuator is cut, the valve will move to off (0V). That
needs checking. In reality there will be no need for the outside stat as
the controller will bring in either UFH or rads and modulate either to
maintain the room setpoint temp. It may settle on UFH fully on (Y1 will
be
10v) and the rads just on (Y2 at 1V) to give an even temperature in the
room
or house.

Not cheap, but worth pricing up.

1. Polygyr RWC62 controller
1 Suitable 230v x 24v transformer to power the controller and two valve
actuators.
1. Mounting box for the controller. This is best a central box for all
the
system with all wires going in and out of the box.
1. NI 1000 range, wall mounted room temp sensor.
2. Suitable 0 - 10V actuators and valves 22mm. (Landis and Staefa will
advise on this)

Sorted on the control side.

You will need 3 pumps. 1 for UFH, one for the rads and one for the
primary
circuit.
You will need a blending valve for the UFH circuit to ensure it does not
go
over 50C.

When DHW calls for heat it switches in the primary pump, if not already
called by the UFH and rads.
Boiler temp will need to be enough to maintain DHW temp. A boiler with
integral load compensation control will modulate the burner up and down
to
the temp differential of the flow and return. It roughly works out the
heat
load of the building by doing this.

When looking at expensive UFH heating controls and the extra control for
the
rads, this may well end up a cheaper option and seamless control of the
two
systems. Polygyr is an excellent control system.

Hi,

Why not have two themostats, one for the rads (TMV) and one for the
UFH. Set the UFH one slightly higher than that for the rads so it's
preferenced.

Too crude and will not maintain the room temp accurately. Seamless
temperature control can be has by using the correct controls. In this case
a commercial controller is the only option.

"IMM" wrote in message
...

"John Aston" wrote in message
...

Look at:
http://www.landisstaefa.com/opc%5Fe/sheet/N3367e.pdf

This is a two stage controller. It requires a 24v supply so a 230v x 24v
transformer is needed. Look at the connection diagram at the bottom. A
room temp sensor (B1 in the diagram), NI 1000 range, is needed. The
outputs
are Y1 (first stage [UFH]) and Y2 (2nd stage [rads]). The output voltage
is
0 - 10V A timer (S1) can switch it on or off.

You will also require two suitable 0 -10 volt modulating valve actuators
complete with valve (22mm).

On the second stage (Y2) you could have an outside stat set to 12 to 15C,
to
hold off the second stage. I can't quite recall now, but if the Y2, 0 -
10v
line to the valve actuator is cut, the valve will move to off (0V). That
needs checking. In reality there will be no need for the outside stat as
the controller will bring in either UFH or rads and modulate either to
maintain the room setpoint temp. It may settle on UFH fully on (Y1 will
be
10v) and the rads just on (Y2 at 1V) to give an even temperature in the
room
or house.

Not cheap, but worth pricing up.

1. Polygyr RWC62 controller
1 Suitable 230v x 24v transformer to power the controller and two valve
actuators.
1. Mounting box for the controller. This is best a central box for all
the
system with all wires going in and out of the box.
1. NI 1000 range, wall mounted room temp sensor.
2. Suitable 0 - 10V actuators and valves 22mm. (Landis and Staefa will
advise on this)

Sorted on the control side.

You will need 3 pumps. 1 for UFH, one for the rads and one for the
primary
circuit.
You will need a blending valve for the UFH circuit to ensure it does not
go
over 50C.

When DHW calls for heat it switches in the primary pump, if not already
called by the UFH and rads.
Boiler temp will need to be enough to maintain DHW temp. A boiler with
integral load compensation control will modulate the burner up and down to
the temp differential of the flow and return. It roughly works out the
heat
load of the building by doing this.

When looking at expensive UFH heating controls and the extra control for
the
rads, this may well end up a cheaper option and seamless control of the
two
systems. Polygyr is an excellent control system.

If you are using modulated valves then Landis & Staefa have a wall mounted 2
stage controller with a built-in temp sensor. You can have an outside
sensor which will raise and lower the setpoint. This unit is £130, so
excelelnt value.
http://www.landisstaefa.com/opc_e/sheet/N3331en.pdf

The mixing valve is the 3/4" VMP43 at about £64
http://www.landisstaefa.com/opc_e/sheet/n4841e.pdf

The actuator is the SSB 61.00 0 -10v @ £108
http://www.landisstaefa.com/opc_e/sheet/N4891e.pdf

So, two mixing valves, 2 actuators and one controller is: £474. Not bad,
for what it will do.

"John Aston" wrote in message ...
"Aidan" wrote in message
om...
"John Aston" wrote in message
...
Could you expand a little bit on why it would be impractical
to modulate the radiator output with a boiler reset?

It's not practical, on it's own. You could use the boiler reset to
supply the higher flow temperature required by the rads, and then have
a mixing valve to supply the lower flow temperature required for the
UFH. My background is in commercial systems, so I've never dealt with
a boiler reset system. I'd be inclined to have 2 mixing valves to
minimize the amount of control circuitry in the boiler.

Aidan, please could you explain the purpose of the vessel and pumps.

The vessel's similar to a section of the primary header pipe, but with
a big diameter and so a large water content. The primary circuit would
contain 50 or 100 gallons, rather than 5 or so gallons. The buffer
vessel's temperature will change gradually in response to heat inputs
or outputs and the mixing valves won't be motoring up & down
continually to compensate for a rapidly fluctuating flow temperature.
A modulating burner will also help minimize the temperature
fluctuations, but there will still be mismatches between the heat load
and boiler output. Most 32 kW boilers will modulate down to about 9kW.

You need a primary pump for the boiler. If you've got a mixing valve,
serving the UFH, then it has got to have it's own secondary pump. You
could use the boiler pump to supply the rads with a boiler reset
temperature control, or you could have another mixing valve & pump
set. Decision time.


Why would you do this instead of just using the boiler pump and one
zone valve per circuit?

Just my preferred method. The use of 2-port zone valves will cause
changes in the other zones' flow rates when they close.

Is "system reset" as efficient as the "boiler reset" method that you
talked
about? For most of the year, a primary flow temperature of 55°C will
be
sufficient to heat the house.

Probably less efficient, but not much in it. A modulating condensing
boiler with a 0-10V burner control input would be ideal. The flow
temperature would be the minimum required, i.e., the maximum required
by the rads, the UFH OR the DHWS.

A condensing boiler will be operating more efficiently at 55°C than at 82°C. It seems a shame to heat the flow on/off at 82°C and then modulate the u.f.h. circuit down to 55°C. Wouldn't it be better to heat the boiler flow continuously at 55°C. I may be missing something here...

I had a non-condensing on/off type boiler in mind. The heating would
operate at less than 55°C for much of the time. With boiler reset,
you'd still have to boost the temperature when there was a DHWS
demand. You'd then have to tolerate overheating of the rads, or stop
them temporarily. If you had a mixing valve serving the rads, it would
maintain a constant mixed flow temperature by just modulating down to
compensate for the higher flow temperature. Again, my preferred method
from commercial experience. You're not missing much.

Although, on warm days, the "boiler reset" method would result in
lower flow
temperatures than the thermostatic mixer setpoint, which seems
desirable.

Unless the users had turned the thermostatic control down. I only
mentioned the thermostatic mixer as a control device which works
adequately, for most people, despite it's inherent lack of
sophistication, i.e., electronics and motorized actuators.

What part of the control loop would make the radiators respond
rapidly but then drop off when the u.f.h. gets up to speed?

The value of the PID constants you've programmed into the control
loop.
For an explanation see
http://www.eurotherm.co.uk/NR/rdonly...Dknowledge.pdf

This gets technical. The loop compares the sensor input with the
setpoint and processes the output. The proportional output term is the
error times the gain.
So if it's 20°C and the setpoint is 21°C, the error is 1 °C. You could
have a 10% output from one (proportional only)control loop to the UFH
(gain = 10). At the same time, with the same sensor input, you could
have a 50% output to the rads (gain = 50) from another loop. You
programme in the proportional gain, the Integral & Derivative
constants into each loop to get the response you want, depending on
the system characteristics. My control theory isn't up to much, so
you'll have to research it on Google if you want a more detailed
explanation. I'm not going to even try to explain Integral and
Derivative constants. You could program two loops to get one to react
like a hare and the other like a tortoise.

You should tune the control loops (Ziegler and Nicholls method?) to
get the optimum response. Most commercial control contractors take an
educated guess at the initial PID values but most HVAC systems still
work well with these.

Are they used commonly in domestic situations, too? What advantages
do they offer over the standard boiler pump and zone valves
arrangement?

Not commonly used in domestic installations. They give much better
control but cost much more.

"Aidan" wrote in message
om...
"John Aston" wrote in message
...
"Aidan" wrote in message
om...
"John Aston" wrote in message
news

Could you expand a little bit on why it would be impractical
to modulate the radiator output with a boiler reset?

It's not practical, on it's own. You could use the boiler reset to
supply the higher flow temperature required by the rads, and then have
a mixing valve to supply the lower flow temperature required for the
UFH. My background is in commercial systems, so I've never dealt with
a boiler reset system.

A boiler reset system as you call it is known as weather compensation, or
just compensation. This is fully commercial, and if you are in commercial
controls you would have come across this as an everyday thing.

I'd be inclined to have 2 mixing valves to
minimize the amount of control circuitry in the boiler.

Aidan, please could you explain the purpose of the vessel and pumps.

The vessel's similar to a section of the primary header pipe, but with
a big diameter and so a large water content. The primary circuit would
contain 50 or 100 gallons, rather than 5 or so gallons. The buffer
vessel's temperature will change gradually in response to heat inputs
or outputs and the mixing valves won't be motoring up & down
continually to compensate for a rapidly fluctuating flow temperature.
A modulating burner will also help minimize the temperature
fluctuations, but there will still be mismatches between the heat load
and boiler output. Most 32 kW boilers will modulate down to about 9kW.

You need a primary pump for the boiler. If you've got a mixing valve,
serving the UFH, then it has got to have it's own secondary pump. You
could use the boiler pump to supply the rads with a boiler reset
temperature control, or you could have another mixing valve & pump
set. Decision time.


Why would you do this instead of just using the boiler pump and one
zone valve per circuit?

Just my preferred method. The use of 2-port zone valves will cause
changes in the other zones' flow rates when they close.

Is "system reset" as efficient as the "boiler reset" method that you
talked
about? For most of the year, a primary flow temperature of 55°C will
be
sufficient to heat the house.

Probably less efficient, but not much in it. A modulating condensing
boiler with a 0-10V burner control input would be ideal.

I know of no domestic boiler tha will take an external control signal to
modulate the burner.

The flow
temperature would be the minimum required, i.e., the maximum required
by the rads, the UFH OR the DHWS.

A condensing boiler will be operating
more efficiently at 55°C than at
82°C. It seems a shame to heat the
flow on/off at 82°C and then modulate the
u.f.h. circuit down to 55°C. Wouldn't it
be better to heat the boiler flow continuously
at 55°C. I may be missing something here...

No. Best to raise and lower the boiler temp to suit the UFH demands. This
can be set via an outside weather compensator. The unit you need is the
Seimans BLC1.A:

Boiler Load Compensator is a heating controller that can be used as either
a:

1. Weather Compensator
2. Load Compensator.

The BLC1.A can be set up to control conventional or underfloor heating
systems and tuned to condensing boilers.
http://www.landisstaefa.co.uk/prd/Res/prd_res_blc.asp

Data on unit.
http://www.landisstaefa.co.uk/prd/resofacts/blc1a.pdf

Price from Newway:
01905 794242. About £200.


This is ideal to have on the UFH circuit. Have one condensing combi boiler
do the UFH and this unit controls its temperature output. Have another
combi do the rads and this need not be under outside waether contro,a s it
is just a boost. The two combi's combine to give high flow hot water.

You will still need a two stage controller to seamlessly combine the UFH and
booster rads and maintain the internal temperatures.

What are your DHW needs? How many baths, showers etc?

"IMM" wrote in message
...


You will still need a two stage controller to seamlessly combine the UFH
and
booster rads and maintain the internal temperatures.

What are your DHW needs? How many baths, showers etc?


1 bath and 3 showers for a family of five.

Thanks for your thoughts. I'll take a look at those controllers you
suggested.

"John Aston" wrote in message
...
"IMM" wrote in message
...


You will still need a two stage controller to seamlessly combine the UFH
and
booster rads and maintain the internal temperatures.

What are your DHW needs? How many baths, showers etc?


1 bath and 3 showers for a family of five.

Thanks for your thoughts. I'll take a look at those controllers you
suggested.

There are a number of routes you can take. You obviously are installing a
new system(s) and boiler. Are you keeping the same cylinder, or is it a
full new system? How is your cold water mains. Can it cope with all of the
house?

Thanks, Aidan, for taking the time to compose that informative reply.
I appreciate the help.

"Andy Hall" wrote in message
...
On Mon, 8 Nov 2004 00:35:02 -0000, "John Aston"
wrote:

snip

Isn't the problem, though, that the radiators have a faster response than
the UFH. Assuming it's cold enough outside for the radiators to be on,
they
will raise the room temperature relatively quickly. The UFH will see that
the room temperature is rising and throttle back on its output. The
eventual
"steady state" position will be determined by how quickly the radiators
and
UFH respond to the demand for heating.

snip

TRVs are still needed because it's desirable to have different
settings per room. However, they only start closing near the set
point for the room quite gently because the average flow temperature
has fallen quite a bit anyway.
For example on my radiator based system, the flow temperature can be
around 40 degrees sometimes with the boiler running at very low
output.


I had a thought further thought about controlling UFH as a primary heat
source and using radiators as boost heaters only.

The UFH is controlled by room thermostats. My problem is that when the
weather is cold, the UFH output is not sufficiently high to heat he rooms.
At this point the radiators come on. Rather than put a room temperature TRV
on each radiator, though, I could use a *water temperature* valve (Danfoss
FJVR). That means that the maximum kW output of the radiator will be fixed
at a user-defined level whatever the room temperature. From my thermal
calculations, I know the kW shortfall for each room when the UFH is at its
maximum output and the outside temperature is at -2°C. I can adjust each
radiator output to exactly match this shortfall on a room-by-room basis.

As the outside temperature increases, weather compensation will reduce the
radiator output as the boiler flow temperature falls.

This seems a better solution than using TRVs. With TRVs, I would have two
parallel heating systems fighting to reach the same setpoint.

John Aston wrote:

As the outside temperature increases, weather compensation will
reduce the
radiator output as the boiler flow temperature falls.

Summat along these lines?

http://www.pmengineer.com/CDA/Articl...,21624,00.html

The article uses BTU/hr, degF, etc., but I'm sure you'll make sense of
it.

I'm not sure that you're taking account of transient heat gains, e.g.,
3 or 4 people in one room with the lights and TV on will provide a
substantial heat gain. Similarly, east-facing rooms may get big a.m.
solar gains through the windows, west facing may get big p.m. solar
gains and they'll all have fairly constant heat losses overnight.

The radiator TRV's, on a 'normal' system would compensate by reducing
the flow rate to the rads as the room temperature went up. With your
system, the response time of the UFH would be too slow to compensate
for this, so you'd probably need some control on the rads, which I'm
not sure you've got.
Not picking holes, I haven't read the proposals in detail so you may
already have got this covered. I'm not familair with the workings of
the Danfoss valve, I'll have to read up on it.

In article .com,
"Aidan" writes:

John Aston wrote:

As the outside temperature increases, weather compensation will
reduce the
radiator output as the boiler flow temperature falls.

Summat along these lines?

http://www.pmengineer.com/CDA/Articl...,21624,00.html

Oooh, magic. I'm in the middle of designing a control system to
do just this. I'll have to read the article in detail to see if
there is anything I've not taken into account.

My father installed what was originally coal-fired central
heating in late 1950's, and he used this scheme for the
temperature control. It was being pushed by the Coal Board at the
time. It was called BMT -- no idea what it stands for. It used an
outdoor temperature phial on a very long capilliary tube which
operated a bellows in a rather complicated valve which set the
radiator water temperature by mixing the boiler water with the
return water to create an automatically adjusting flow temperature.
The unit was powered by the water pressure across the pump, which
had to run continuously. The BMT unit continued to be used with a
later gas fired boiler up until 2000, when the whole lot was
replaced with a small wall mounting low volume boiler. In that
40 year period, I think the only thing that ever went wrong with
it was an O-ring went hard and started leaking.

--
Andrew Gabriel

Aidan wrote:
John Aston wrote:

As the outside temperature increases, weather compensation will
reduce the
radiator output as the boiler flow temperature falls.

Summat along these lines?


http://www.pmengineer.com/CDA/Articl...,21624,00.html


Yes, exactly along those lines. Thanks for the link.

The article uses BTU/hr, degF, etc., but I'm sure you'll make sense
of
it.

I'm not sure that you're taking account of transient heat gains,
e.g.,
3 or 4 people in one room with the lights and TV on will provide a
substantial heat gain. Similarly, east-facing rooms may get big a.m.
solar gains through the windows, west facing may get big p.m. solar
gains and they'll all have fairly constant heat losses overnight.

The radiator TRV's, on a 'normal' system would compensate by reducing
the flow rate to the rads as the room temperature went up. With your
system, the response time of the UFH would be too slow to compensate
for this, so you'd probably need some control on the rads, which I'm
not sure you've got.

Agree with you, Aidan.

I suppose that any house with underfloor heating (whether or not there
are radiators installed) will have this response problem. There don't
seem to be many unhappy UFH users though so I guess that it's all
relative. My house is mid-terrace with a south-facing wall partially
shaded by trees and a north facing wall which is fairly well sheltered
from the wind. Hopefully, the external influences with be small.

My UFH will be installed on a suspended timber floor, which I'm told
has a faster response that a screeded floor. Don't know how much
faster, though!

The problem with TRVs is that the radiators could take over from the
UFH as the primary source of heating, which would lead to a less
efficient heating system.

Basically, if the UFH can respond fast enough (or I can live with the
fluctuations), I'm sorted.

Not picking holes, I haven't read the proposals in detail so you may
already have got this covered. I'm not familair with the workings of
the Danfoss valve, I'll have to read up on it.