Thermostatic Rad Valves

whitelightrider

Hi folks,

We're about 6 months in our new house. Have some minor issues at the minute but we're getting there.

Currently we are running UFH downstairs and rads upstairs. However the electrician put the upstairs stat at the top of the stairs. Only problem is that it doesnt read the upstairs temp correctly as the heat from downstairs rises and although it thinks its at a certain temp, the rooms can be cold.

Im thinking of fitting thermostatic valves to the rads upstairs.
Do these kick in if the temp in a room drops below the set temp on the valve?

Mike2006

Yes, basically they automatically open and close off the hot water supply to the rads based on the 'sensed' temperature in the room.

One point to note though, if you are operating on this principle, you will have to bypass the wall stat upstairs because that controls the boiler, so if it is receiving a warm spell of air before the rooms it will cut off the supply to rads before they get hot enough to activate the thermostatic valves on the rads.

2 ways to do this:
Easy option is to turn it up fully (30 DegC) and hope that that is high enough to sort your problem or else you will have to electrically bypass the stat so that it never 'opens' and turns off the boiler. If you are not electrically competent enough to do this yourself then get an electrician to do it as there is most likely 230VAC goint through the contacts of the stat.

Mike.

whitelightrider

Mike2006 wrote: »

Yes, basically they automatically open and close off the hot water supply to the rads based on the 'sensed' temperature in the room.

One point to note though, if you are operating on this principle, you will have to bypass the wall stat upstairs because that controls the boiler, so if it is receiving a warm spell of air before the rooms it will cut off the supply to rads before they get hot enough to activate the thermostatic valves on the rads.

2 ways to do this:
Easy option is to turn it up fully (30 DegC) and hope that that is high enough to sort your problem or else you will have to electrically bypass the stat so that it never 'opens' and turns off the boiler. If you are not electrically competent enough to do this yourself then get an electrician to do it as there is most likely 230VAC goint through the contacts of the stat.

Mike.

So basically I can switch off the power to the stat on the landing and let the valves do the work?
Do they need to be wired in anyway? How do they call the boiler once the temp drops?

Mike2006

No, you actually need to bridge out the wall stat so that the boiler 'thinks' that it needs to be on all the time.

The valves will not call the boiler. This will be done thru your timer on the boiler.

You have to understand how the central heating system works to understand how the valves operate on the whole system. i will try to explain briefly:

The boiler has a flow and return line. The more rads that are on this, the more 'power' it needs to operate. When the room comes up to the set temp, the thermo valves close and now eliminate this rad from the loop, thus making the loop 'shorter/smaller'. Therefore the return line temp will rise faster as it has less work to do and your boiler will cut out at its set temp sooner...
Not sure if I explained it well enough...

Mike.

Carlow52

whitelightrider wrote: »

So basically I can switch off the power to the stat on the landing and let the valves do the work?
Do they need to be wired in anyway? How do they call the boiler once the temp drops?

The normal TRVs only work on the temp on the room and don't of themselves call the boiler. They just open and close based on room temp.

One point to watch is that one rad on the circuit should not have one unless the cir pump is intelligent as if they all close on a normal pump circuit the pump may burn out.

Come back for more if not clear:)

ps as per previous post by mike

if u have the power at the wall stat u could consider putting a timer to control upstairs instead of the wall stat: it depends on the setup

sinnerboy

Your rads - as a group are being controlled by
1. a timer
2. that landing stat

TRVs won't change that . In other words - the timer and landing stat will ( and must* ) over ride the TRVs

*You must have a timer and stat to comply with building regs .

So - can you re locate your landing stat ? Best place is the master bedroom ( away from rads / windows )

whitelightrider

sinnerboy wrote: »

Your rads - as a group are being controlled by
1. a timer
2. that landing stat

TRVs won't change that . In other words - the timer and landing stat will ( and must* ) over ride the TRVs

*You must have a timer and stat to comply with building regs .

So - can you re locate your landing stat ? Best place is the master bedroom ( away from rads / windows )

I could but it would probably mean chasing the wall. Or could the cable be pushed through the ducting for the light switch?

sinnerboy

Not sure - (I'm not a sparks) . A RECI or ECCSA registered electrician could say

whitelightrider

sinnerboy wrote: »

Not sure - (I'm not a sparks) . A RECI or ECCSA registered electrician could say

Thanks SB. Ill give the sparks a call over the weekend. He has a few snags to finish off anyway so Ill get him to look at this.

Hi. to answer your question you can't run your room stat wiring with the light cable, Gary.

John mac

best way to do is is as mike 2006 said. turn up the upstairs thermostat to max. then just let the trv's do their job.

One point to watch is that one rad on the circuit should not have one unless the cir pump is intelligent as if they all close on a normal pump circuit the pump may burn out

the pump will still pump water through the coil in the hot water cylinder. when the water gets to temp the pump will switch off.
all the rads could be off.. (thats how i heat my water in the summer.)

Carlow52

John mac wrote: »

best way to do is is as mike 2006 said. turn up the upstairs thermostat to max. then just let the trv's do their job.


the pump will still pump water through the coil in the hot water cylinder. when the water gets to temp the pump will switch off.
all the rads could be off.. (thats how i heat my water in the summer.)

I see this differently:)

sinnerboy

John mac wrote: »

best way to do is is as mike 2006 said. turn up the upstairs thermostat to max. then just let the trv's do their job.

No point in having the stat so . I would not advise this .

Best thing to do is locate the stat correctly

John mac

yea thats what i mean no point if its not sited correctly.

davidoco

Problem solved with the CM Zone set running the zone valve your stat is calling (within that zone valve you will have a relay firing the boiler).

http://www.rvr.ie/default.aspx?subj=catalog/ProductsList&catIdPath=0_47_53_159

You only need one HR80, one relay, one control panel. Fit the HR80 in the coldest bedroom and regular TRVs in the other bedrooms and upstairs landing.

Job done.

John mac

John mac wrote: »

best way to do is is as mike 2006 said. turn up the upstairs thermostat to max. then just let the trv's do their job.


the pump will still pump water through the coil in the hot water cylinder. when the water gets to temp the pump will switch off.
all the rads could be off.. (thats how i heat my water in the summer.)

It is good working practice to leave one rad with out a trv, normally the bathroom rad, this is to allow a boiler to dissipate heat and to prevent problems with whistling valves, a cylinder stat should be controlling a zone valve(in a ideal world) so as not to waste money:eek:, Gary.

davidoco

Regarding running your heating and using the cylinder as a bypass or the practice of always heating water when the heating is on the building regulations state

1.4.3.3 Hot water storage vessels should be fitted
with thermostatic control that shuts off the supply of
heat when the desired storage temperature is
reached.

1.4.3.4 Separate and independent time control for
space heating and for heating of stored water


(depending on when your house was build) You should have a time clock/zone to control the time your hot water comes on and a thermostat to shut off the hot water when desired temperature reached.

whitelightrider

Hi David.

We have a separate system to time the heat and the water in the house. Also checked over the weekend and found the stat on the cylinder which switches off when the desired temp is reached.