"Onetap" wrote in message
...
On Friday, February 14, 2014 3:29:00 PM UTC, Derek F wrote:
On 14/02/2014 08:31, harryagain wrote:

"Andrew Gabriel" wrote in message

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In article ,

Vir Campestris writes:

On 12/02/2014 19:37, Derek F wrote:

We live in a Block with a communal heating and hot water system.

It has been suggested that residents at their own expense have TVR's

fitted to their radiators to cut down on the communal heating bill.

Some have previously replaced their radiators and have TVR's.

To my very simple mind I'm not convinced that it will work.... but I

will soon be corrected. At the moment if I have a valve full on or
turn

it down to barely on the radiators stay at the same heat.

Derek

(cross-posted)



It seems to me if the radiator doesn't cool down the valve isn't off.



TRVs should cut down the costs - you won't get people having to open
the

windows to control heat.



A very common misunderstanding is that a TRV is a *radiator*
thermostat.

It is not - it's a *room* thermostat.



The radiator will variously go hot/warm/cold, as the TRV maintains the

*room* temperature.



The big problem with communal heating systems is that people just throw

the windows open when it gets too hot. With my home automation, the

heating in that zone is switched off if an outside door or window is

opened for 5 minutes or more.





The big problem is they don't work very well.

They are more influenced by the nearby radiator temperature than the
room

temperature.

Unless you have one with a remote sensor.





We have 51 flats. The penthouses and ones in an annexe have their own

systems as do a few others. Probably about 35 use the communal heating.

This year the estimated gas cost is £38,500. Less than when we had the

old oil fired boilers.

Now my Thicko bit again. I don't understand how the water flows between

the ones in our flat or round the building. How does an individual

thermostatic valve reduce a radiator heat when water of a certain

temperature leaves the boiler?

If does it by reducing the flow would not less water be leaving the rad

to go on to the next rad as it must be continually flowing round this

huge building.

Mind you I didn't understand it when we had our own system in a house

and a flat but at least then I could hear our pump going.

Answers and diagrams n the back of a fag packet please:-)

Derek

Quick answer there would typically be a pair of flow and return pipes,
usually in a services duct in a central stairwell. From that there would be
flow and return branches to each flat. Each radiator would connect between
the F&R, a TRv would restrict the water flow as the room temperature reached
the setpoint.

You should be able to turn all your rads off, or just have one or two on
without affecting the rest of the block.

Here's the thing though. As TRVs close down, the volumetric flow rate
decreases and the pump differential pressure increases; look at a pump
curve. Hopefully the new boilers had intelligent pumps that throttle back to
maintain a constant differential across F&R. If not, it can cause much TRV
whistling since they can only cope with a limited pressure differential
across them.


There are various designs.
Different ideas from different times and different fuels.
Normally in large systems there is a pump in the boilerhouse that circulates
constant temperature water round a single pipe loop/system that is in a
central position
The individual flats probably each have their own pump abstracting water
from this loop and individual control sytems.

Not popular these days, inefficient and expensive to install.
It's more usual for each flate to have it's own boiler with a gas supply
running round the building.
(This can bring it's own dangers though.)