Heating thermostat


Postby Steandkar » Mon Jan 11, 2010 10:37 pm

Is it very difficult to change the position of a thermostat. The one fitted in my hall is too close to the bathroom heater which influences the temperature of the rest of the radiators. The bathroom radiator has no thermostat so is very warm all the time.
Hope someone understands this
Steandkar
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Postby ericmark » Tue Jan 12, 2010 9:36 am

There are wireless thermostats but one must question why you have a thermostat.
With modern boilers they do not just switch on and off but vary the flame and to work correct they need a system with thermostat radiator valves and when these are used the only job of the electric thermostat is to switch off the system in summer months.
In which case the thermostat is set high.
Older systems switched on and off only and then the thermostatic radiator valves just stopped rooms over heating and the thermostat was fitted in coolest room which would not have a TRV.
One problem is where new boiler is fitted to old system or users have not been instructed on how it works.
You could move it normally 2 wires only older types have three or use radio controlled if the original has a neutral feed. Or fit from boiler.
Also you could use lock shield valve to reduce heat on close radiator.
But first ask should control be by thermostat anyway or should it be set higher? Also could you fit TRV to close radiator. Answer depends an type of boiler. Most Condensating boilers have variable output.
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Postby Steandkar » Tue Jan 12, 2010 4:20 pm

Thank you so much for speedy reply I will certainly check up on these suggestions.
By the way What is a lock shield valve and is it difficult to fit? Thanks again
Steandkar
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Joined: Mon Jan 11, 2010 10:24 pm


Postby ericmark » Thu Jan 14, 2010 3:08 am

Most radiators have two taps. One is designed for the user to control or is a TRV and the other sets maximum flow and is called "lock shield valve" not a clue why it has that name I am not a Plumber.

Years ago we would use lock shield valve to set temperature in each room then the other tap with control knob with turn radiator on and off. Both taps are same but knob on one to turn on and off with and just cap on other.

Now with TRV fitted the lock shield valve is set to give a temperature drop of around 10 degs between incoming and outgoing water. This stops the boiler from turning down too early and ensures there is pressure (so flow) on all radiators. This is only really needed when heating up. Once house is hot the TRV takes over and lock shield valve setting does not matter.

The use of condensating boilers has completely changed the way the system is controlled and all radiators should have TRV fitted as the way the boiler controls is to measure the temperature of returning water and once it returns hot then it shuts down.

So in summer it starts up and all radiators are switched off by TRV so bypass valve opens and hot water is returned straight away so anti cycle software then increases time before it tries again.

However if a radiator is still open then it will take too long for hot water to return so anti cycle software will not do it's job.

Not all boilers are the same of course.
ericmark
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Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.


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