Combi boilers, TVR's and room stat

[Lucy1979]

Hi,

I have recently had a new heating system put in, I have a combi boiler, and 4 radiators. I live in a one person bedsit, and 3 of the rad's have TVR's fitted to them and in the livng area i have a room stat. However my bathroom is always freezing, because the room stat turns the heating off when it gets to the temperature for that room, so the others are left without heating. Should it have been set up like that?
Would it be better to have all the rad's on TVR's running straight from the boiler?
What is the most efficent way of setting up a heating system in such a small property?

Thank you for your advice

 

[DP]

The function of the room thermostat is to switch the boiler off when the ambient temperarture in that room reaches set point. It follows that other rooms (including your bathroom) will also have attained their ambient temperatres when the room thermostat shuts the boiler down.

TRVs will 'isolate' the radiator when the sensor head reaches the switch off point (will not happen if this valve is fully open) but your TRVs do not 'talk' to your boiler. In this case the boiler cycles wastefully

If you have a ladder/ towel rail in the bathroom, that could be the issue as these things hardly ever put out the heat the bathroom needs.

 

[Lucy1979]

I understand that when the room stat researches its required temperature it switches the boiler off, however the other rad's that have the TVR's are not heating up the other rooms because the room stat in the living room has turned off. so the issue i have is that the living area is a sauna and the bathroom is freezing. If I took out the room stat and put TVR's on all the rad's, adding a bypass to the boiler so that all rad's connected straight to the boiler directly, surely this would allow me to control each room more efficently?

Why do i need a room stat?
Can i have all TVR's instead?
what's the most efficent way of getting the correct temperature needed in each room?

Thank you for your responce

 

[Lucy1979]

I do not have a heated towel rail, joined to my system

 

[Hugh Jaleak]

Do the other radiators reach the same temperature (roughly) as the living room rad?

 

[D_Hailsham]

Why do i need a room stat?

Because Building Regulations say that you must have an "interlock". This means a device which switches a boiler off when heat is not required.

Can I have all TVR's instead?

No. TRVs do not provide the required interlock so the boiler will carry on running when all rooms are up to temperature.

What's the most efficient way of getting the correct temperature needed in each room?

This may sound simplistic, but the radiators in each room need to be correctly sized for the heat loss and they need to be balanced. It sounds as if neither has been done by your installer, which would explain why the living area is getting up to temperature before the rest of the flat.

Did the installer give you any heat loss calculations to show how he arrived at the sizes of radiators?

Did the installer balance the system? This would involve running the boiler for some time and going round to each radiator adjusting the "lockshield" (LS) valve. That's the one at the opposite end to the TRV.

If he didn't do that, the radiators will not be giving off the correct amount of heat.

There is an easy way of checking if the rads have been balanced:

Remove the cover from the LS valve (no water will come out) which will expose a metal spindle. Using a pair of pliers or similar tool, turn the spindle clockwise (looking down) until the spindle stops turning (valve closed). Count the number of turns you make (e.g. 1¼).

If the rads have been balanced, they should be between ¼ turn and one turn from closed.

If they are all two or more turns from closed the system has not been balanced. You can achieve a rough and ready balance by opening each LS valve about half a turn. If this doesn't achieve the desired result, close down (clockwise) the LS valve on the hottest rad an eighth of a turn at a time and recheck. If one room is much colder than the rest, open (anticlockwise) the LS valve an eighth of a turn. It will take 15 to 20 minutes for any adjustments to take effect.

You can read a detailed explanation of balancing in How to balance a CH system.

 

[sooey]

You haven't got the fire on in the lounge have you? Are the TRVs in the other rooms opened up?

 

[sherbert]

Why do i need a room stat?

Because Building Regulations say that you must have an "interlock". This means a device which switches a boiler off when heat is not required.

Can I have all TVR's instead?

No. TRVs do not provide the required interlock so the boiler will carry on running when all rooms are up to temperature.

What's the most efficient way of getting the correct temperature needed in each room?

This may sound simplistic, but the radiators in each room need to be correctly sized for the heat loss and they need to be balanced. It sounds as if neither has been done by your installer, which would explain why the living area is getting up to temperature before the rest of the flat.

Did the installer give you any heat loss calculations to show how he arrived at the sizes of radiators?

Did the installer balance the system? This would involve running the boiler for some time and going round to each radiator adjusting the "lockshield" (LS) valve. That's the one at the opposite end to the TRV.

If he didn't do that, the radiators will not be giving off the correct amount of heat.

There is an easy way of checking if the rads have been balanced:

Remove the cover from the LS valve (no water will come out) which will expose a metal spindle. Using a pair of pliers or similar tool, turn the spindle clockwise (looking down) until the spindle stops turning (valve closed). Count the number of turns you make (e.g. 1¼).

If the rads have been balanced, they should be between ¼ turn and one turn from closed.

If they are all two or more turns from closed the system has not been balanced. You can achieve a rough and ready balance by opening each LS valve about half a turn. If this doesn't achieve the desired result, close down (clockwise) the LS valve on the hottest rad an eighth of a turn at a time and recheck. If one room is much colder than the rest, open (anticlockwise) the LS valve an eighth of a turn. It will take 15 to 20 minutes for any adjustments to take effect.

You can read a detailed explanation of balancing in How to balance a CH system.

The boiler has been installed correctly and it appears that Part L of the BR have been followed from what you say

To be Honest a combi on 4 rads should not really need balancing as long as the lockshields are open it should p*ss round the system

What do you have the room stat set to temp wise ........ is the living room west facing which means yiour getting solar gain in this room

As its a bedsit I assume theres no hallway so why not turn up the room stat a smidging and open the bathroom trv to number 6

 

[Lucy1979]

The rad's are all different sizes, they are the newer kind.
So in the living/bedroom area, i have a large rad which doesn't have a TVR fitted. I have a tiny hallway which for some strange reason has a meduim sized rad in it! The other very small room has a little rad in it, and so does the bathroom which is twice the size of the hallway!

The hallway gives off the most heat, the small room is sufficient given the size, however I struggle to get 20 degress in the bathroom.

I have a temperature gauge in each of the rooms, and the only one i have an issue with is the bathroom, as it has two out side walls connected to it, like the living area does. Also there is a draught coming from the sewage pipe which needs filling in, only the housing assosiation say the sewage pipe needs room to breath!

To answer your question, yes all the rad's give out simular heat, obviously the size of the rad makes a difference to the amount of heat coming out, if you get what i mean.

i would like to add, that the room stat is approx 1.5meters away from the rad. Had the room stat been placed at the opposite side of the room from the rad, it would take longer to reach the required temperature, therefore the bathroom rad would stay on longer, allowing the room to heat up.


Hope this all helps,

Thank you for your advice

 

[D_Hailsham]

The boiler has been installed correctly and it appears that Part L of the BR have been followed from what you say.

You are making an assumption about the boiler but I agree that Part L has been followed as far as the interlock is concerned.

a combi on 4 rads should not really need balancing as long as the lockshields are open it should p*ss round the system

It doesn't matter how many rads there are (unless its only one), all systems need to be balanced. In any case, the aim of the exercise is not to have water p*ssing round the system but to have the correct flow through each radiator.

is the living room west facing which means you're getting solar gain in this room?

That's a valid point.

Why not turn up the room stat a smidgen and open the bathroom trv to number 6

But the OP is a complaining that the living room is too hot. If the bathroom is not up to temperature the TRV will be fully open in any case, so setting it to 6 won't have any effect.

The problem is that the living room is heating up faster than the rest of the flat, so the thermostat turns the boiler off too soon. The output of the living room radiator needs to be reduced so it takes longer for the room to heat up, giving the rest of the flat more time to reach temperature.

 

[mickyg]

simple, bathroom rad is too small

 

[sherbert]

The boiler has been installed correctly and it appears that Part L of the BR have been followed from what you say.

You are making an assumption about the boiler but I agree that Part L has been followed as far as the interlock is concerned.

a combi on 4 rads should not really need balancing as long as the lockshields are open it should p*ss round the system

It doesn't matter how many rads there are (unless its only one), all systems need to be balanced. In any case, the aim of the exercise is not to have water p*ssing round the system but to have the correct flow through each radiator.

is the living room west facing which means you're getting solar gain in this room?

That's a valid point.

Why not turn up the room stat a smidgen and open the bathroom trv to number 6

But the OP is a complaining that the living room is too hot. If the bathroom is not up to temperature the TRV will be fully open in any case, so setting it to 6 won't have any effect.

The problem is that the living room is heating up faster than the rest of the flat, so the thermostat turns the boiler off too soon. The output of the living room radiator needs to be reduced so it takes longer for the room to heat up, giving the rest of the flat more time to reach temperature.

Sorry for dare helping as your obviously so great

Cant seem to find where she says the living room is to hot ... she actually states that the living room stat is to close to the rad so it shuts the boiler down before it heats up the room ........ that dont sound to hot to me

Even the smallest combi (24kw) should hammer it around four rads on a bedsit and I would expect that if temps where taken of flow & return they would be well over the required temp drop and this will not be a balancing issue

Most prob eiither to small rad as Mickyg suggests or the stat is to close to the rad ... if wireless just move it
Contact your housing association and expalin the prob and they will sort it ..... we have done some new build housing work for housing associations and they are very good at get contractors back ( its called retention)

contact your housing association

 

[D_Hailsham]

Cant seem to find where she says the living room is to hot

Try this:

the issue i have is that the living area is a sauna and the bathroom is freezing

she actually states that the living room stat is too close to the rad so it shuts the boiler down before it heats up the room

She says it is 1.5 metres from the rad, which doesn't sound too close to me.

Even the smallest combi (24kw) should hammer it around four rads on a bedsit and I would expect that if temps were taken of flow & return they would be well over the required temp drop and this will not be a balancing issue

A 24kW combi on four rads is probably cycling most of the time as it cannot modulate low enough.

I don't understand your comment about large temperature drops not being a balancing issue. If the actual temperature drop is higher then the rad output will be lower, e.g. a 1kW rad at 75C/65C will only produce 928W with a drop of 15C and 854W with a drop of 20C.

Most prob either too small rad

It does sound as if the bathroom and hall rads could have been swapped over!

 

[Agile]

Lucy, all you need to do is turn living room rad down to almost off!

Simple.

Tony

 

[Lucy1979]

Thank you all for your advice.

My College tutor has said that given the issues i'm experincing if all rad's had TVR's on them, and disabled the room stat, and then added a bypass valve in the boiler so that all the rad's worked directly on TVR's from the boiler then I would be ale to regulate each room much more efficently, there for it would save me money on heating.
He also stated that i would need to change the temperature settings on the boiler for the heating as it can stay at 70 degrees and i can then just change the TRV's in each room up or down dependent on the requirements.


Is this correct?

The engineer has now added a TVR to the main rad in living area, and disconnected the room stat.

I am unsure, if he has put in the bypass valve needed?
Is there a way i can test to see if this has been done?

The engineer explained that having all TRV's on the rad's, would cause me problems with the boiler over heating, and constantly being on in the summer.

The engineer also said that i would need to change the temperature of the heating through the boiler, ie from 70 degrees to 0 for the summer, is this correct as i'm confused?

I have also been informed that its better to have the boiler on all the time throughout the year, on low in the summer rather than having the boiler constantly turning its self on and off and having to reignight each time.

Is this true?