Installing a TRV in room with central thermostat

Webbs

We have a central heating thermostat upstairs in our Master bedroom, it works great for this room but we find the other bedrooms and bathroom can be too cold.

Is it possible to fit a TRV on the master bedroom radiator and run this in conjunction with the main thermostat to get a more even temperature in the upstairs rooms,
Or would we need to run TRVs off all the radiators and have the central thermostat turned off/turned up high to control the temp.
As I am no great shakes at DIY how much would it cost to buy and get TRVs fitted? (would be 4 radiators upstairs in total)

youtheman

Not a good idea. You will have two completely separate and independant circuits trying to control one parameter (i.e. wall mounted thermostat and TRV). It would be like two guys in a car trying to control the speed with one having his foot on the brake and the other with his foot on the accelerator. Fine if they have the intelligence to speak to each other, but if they can't communicate then they could both put their foot down you have mayhem.

Your problem is your master bedroom is heating up before the other bedroom reaches the desired temperature. So you could do the following (small adjustments, and mark the system so that you can return it to its original position in case you completely screw it up).

1. Open the TRVs some more. In fact I would open them fully and see if the room reaches the desired temp before the thermostat in the master bedroom cuts off the heat.

2. adjust the flow control valves on each radiator (the ones opposite to the TRVs) such that you have more hot water flow going to the other bedrooms. Or if you gradually close the valve opposite the one on the on/off valve in the main bedroom then this will have the same effect.

Failing that you maybe looking at a bigger boiler, better insulation or bigger radiators.

Sorry if the above is confusing. Hard to get the 'auld thoughts down on paper clearly. Having read my own text, it sounds like I am speaking through my rear end (or as my father used to say " take off your trousers, I can't hear you").

Got to go.

Webbs

youtheman wrote: »

Not a good idea. You will have two completely separate and independant circuits trying to control one parameter (i.e. wall mounted thermostat and TRV). It would be like two guys in a car trying to control the speed with one having his foot on the brake and the other with his foot on the accelerator. Fine if they have the intelligence to speak to each other, but if they can't communicate then they could both put their foot down you have mayhem.

Your problem is your master bedroom is heating up before the other bedroom reaches the desired temperature. So you could do the following (small adjustments, and mark the system so that you can return it to its original position in case you completely screw it up).

1. Open the TRVs some more. In fact I would open them fully and see if the room reaches the desired temp before the thermostat in the master bedroom cuts off the heat.

2. adjust the flow control valves on each radiator (the ones opposite to the TRVs) such that you have more hot water flow going to the other bedrooms. Or if you gradually close the valve opposite the one on the on/off valve in the main bedroom then this will have the same effect.

Failing that you maybe looking at a bigger boiler, better insulation or bigger radiators.

Sorry if the above is confusing. Hard to get the 'auld thoughts down on paper clearly. Having read my own text, it sounds like I am speaking through my rear end (or as my father used to say " take off your trousers, I can't hear you").

Got to go.

Thanks for the help, pretty much confirmed what I thought, funnily enough the house is pretty well insulated its just I dont like a very warm bedroom about 19deg normally and the master bedroom has the least outside walls so is always a couple of deg warmer than the other rooms.

I will try the reducing of flow to the master bedroom first before installing TRVs

youtheman

Sorry Webbs, I thought from your original post that you already had TRVs in the other bedrooms. But the end result is the same.

If you cannot get enough heat into the other bedrooms then there is no point in fitting TRVs to those rooms as this will only restrict the flow more, and make the situation worse. TRVs are not magic wands, then cannot get extra heat into the radiator, all they can do is restrict flow to lower the heat output from a radiator. They will work if the radiator is over-sized, but they are bugger all good if the radiator in under-sized.

If you like to run your master bedroom COOLER than the other rooms then you could relocate the thermostat to an other bedroom (making it the MASTER bedroom) and then fit a TRV to the main bedroom. This will allow the main bedroom the run cooler than the other rooms.

But first you need to know if the complete system can deliver enough heat to the other bedrooms (and by the system I mean the boiler, radiators, insulation, windows drafts etc). So I suggest you do the following simple test: turn the thermostat on the main bedroom UP TO THE MAX and see if the system can deliver enough heat to the OTHER ROOMS. Keep and eye on the thermostat to see that it remains on, i.e that the room doesn't reach this set temp, and click, and turn the boiler off. If you can get enough heat into the other rooms then you know your system is o.k. it's just a matter of balancing the system.

Maybe you don't have a problem after all, it could be that you have such a low temp in the master bedroom that the other bedrooms are suffering as the are controlled by the same circuit.

Sparkpea

best thing to do is put trvs on all the radiators and turn the room stat up, use the trv's to control the temp in each room rather than the stat in the bedroom controlling the house. i personally prefer trv's on all rads but some people like to leave bathrooms/ensuites without them.

youtheman

Sparkpea wrote: »

best thing to do is put trvs on all the radiators and turn the room stat up, use the trv's to control the temp in each room rather than the stat in the bedroom controlling the house. i personally prefer trv's on all rads but some people like to leave bathrooms/ensuites without them.

If you do this then your thermostat will not work (i.e. you have nothing to tell your boiler to shutdown when it has reached the desired room temperature). So you'll be either relying on your timer, or the boiler cut-off switch, to cut the system. It will work, but not the best use of the controls available.

Sparkpea

youtheman wrote: »

If you do this then your thermostat will not work (i.e. you have nothing to tell your boiler to shutdown when it has reached the desired room temperature). So you'll be either relying on your timer, or the boiler cut-off switch, to cut the system. It will work, but not the best use of the controls available.

but the desired temp in 1 room is not necessarily the desired temp in another room? if thats the case then is it better to have all TRVs set to higher settings e.g. 4 and wait for the room stat to control the motorised valve/heating?

Sparkpea

Sparkpea wrote: »

best thing to do is put trvs on all the radiators and turn the room stat up, use the trv's to control the temp in each room rather than the stat in the bedroom controlling the house. i personally prefer trv's on all rads but some people like to leave bathrooms/ensuites without them.

Not using a by-pass rad normally the bathroom (as that's where people are normally wet and naked:eek:) can lead to noise issues from the valves closing down, burnt out pumps and boiler lock outs from over heating due to lack of movement around the circuit.

Sparkpea

Sparkpea wrote: »

but the desired temp in 1 room is not necessarily the desired temp in another room? if thats the case then is it better to have all TRVs set to higher settings e.g. 4 and wait for the room stat to control the motorised valve/heating?

In a ideal world a heating system would be balanced, heating a property evenly across all rooms, the primary heating control would be the room stat(s) and the trv's would be used to adjust the temperature downwards in the rooms that would require less heat.

Webbs

Webbs wrote: »

Thanks for the help, pretty much confirmed what I thought, funnily enough the house is pretty well insulated its just I dont like a very warm bedroom about 19deg normally and the master bedroom has the least outside walls so is always a couple of deg warmer than the other rooms.

I will try the reducing of flow to the master bedroom first before installing TRVs

The water will always take the path of least resistance, so if it's easier to ignore the other rads before the stat is satisfied then it will do, agreeing with Youtheman you need to know if it's a balancing issue or a design issue, trv's can help with balancing as when they achieve temperature they close pushing the heat to the other rads as long as the room stat is calling.

youtheman

gary71 wrote: »

In a ideal world a heating system would be balanced, heating a property evenly across all rooms, the primary heating control would be the room stat(s) and the trv's would be used to adjust the temperature downwards in the rooms that would require less heat.

Totally agree with Gary here. In an ideal world all the rooms would heat up uniformly, and lose heat uniformly so that you would need only one room thermostat and all your rooms would be at exactly the same temp.

If the system was perfectly balanced (as above) and you fitted TRVs then the rooms with TRVs could be controlled AT A LOWER TEMPERATURE.

But it's never an ideal world. Rooms heat up at different rates, and people like different temps for different rooms. So if you fit a thermostat to the room that reaches the desired temp the slowest, and TRVs to the other rooms then the TRVs will reach their desired temp first, then control the temp, and the thermostat room will then reach its desired temp and cut off the boiler. This, I believe, is the best combination.

The problem with the OP is twofold, a) he has set a low temp on the thermostat, plus b) his room is well insulated compared to the others. So its a double whammy, his master room is reaching the desired temp faster that the other rooms, the exact opposite to what you want.

So hence my recommendation about balancing the system, before fitting TRVs, to try divert heat to the other rooms so that they will heat up quicker, and divert heat away from the master bedroom so that it will heat up slower.

Of course, it could also be a problem with an undersized boiler, or inefficient boiler, of inefficient radiators (eg sludge) or improper balance.

Sparkpea

see the reason I disagree with this, and i've probably talked about it before on the plumbing forums is this.

I'm in a new build 4 months or so now, 2 zone system, TRVs on all rads except the hall and landing. Room stat in the hall at 'the coldest area of the house' apparently. However because theres a rad in the hall and landing with no trv then the heat pumps out so the room stat turns the motorised valve on. I like my babies room to be a steady temp and because his bedroom door is left open and he actually has the biggest room in the house it is sometimes the coolest. His room will cool down quicker than others with closed doors etc. but the heat on his TRV wont come on again until the hall cools down which is annoying so I'd prefer to leave the room stat up and turn off the hall rads or fit trv's to them. Theres a bye-pass on the system so it shouldnt be a problem with the water circulating round it..

danjo

Why not swap the room stat to your son's room and move the trv to the hall radiator?
Just wondering.

Sparkpea

danjo wrote: »

Why not swap the room stat to your son's room and move the trv to the hall radiator?
Just wondering.

that is an option danjo for the future, tho with it being a new build and stuff im reluctant to start messing about with moving stuff around but its for reasons like this I hate room stats but I know I've to fit them for regulation purposes.

ReadySteadyGo

I guess the risk is that the TRV never allows the master bedroom to get warm enough, for the stat to tell the boiler to switch off.

It seems wireless stats, could help here, where you can move the stat to the most appropriate room.

I have often wondered why each room is not simply fitted with a stat with a link to both the boiler and a link to a valve for the rads in that room.

Room to cold, ask boiler for heat + open valve. Room to hot, stop asking for heat from boiler, close valve.

I guess I'm describing a zone for each room.

Webbs

Thanks for all your replies, the other bedrooms heat up with no problem, its just as I said the master bedroom with thermostat heats up quicker.

So am I correct in thinking that just turning the master bed rad down incrementally should work in slowing down how quickly that room heats up allowing the others to get to desired temp.

Sparkpea

too much expense involved in that I guess and more valves/stats more problems

youtheman

Webbs wrote: »

So am I correct in thinking that just turning the master bed rad down incrementally should work in slowing down how quickly that room heats up allowing the others to get to desired temp.

I'd say it is certainly worth a go. Mark the valve such that you can restore it to its original position.

Another thing to check is that the thermostat is sufficiently distant from the radiator so that it is sampling the average room temp, not the local temp near the radiator.