TRV's and Boiler Query

[pinheadplanet]

Hi

Who can explain this to me as I don't quite see how it works?

What's the point of having TRV's on all my rads except 1, as when the heating is switched on the boiler is always burning (at full power, boilers don't automatically vary their output do they?) to supply that one radiator without the TRV.

If I have the TRV's set on 3, so they automatically close when they get to about 20ºC, the boiler remains alight anyway supplying the 1 radiator in the bathroom (without the TRV).

Surely it doesn't make any difference if I put all the rads on MAX as the boiler is always on supplying that single Bathroom rad.

Do you see what I'm saying?

 

[kevplumb]

Hi

Who can explain this to me as I don't quite see how it works?

What's the point of having TRV's on all my rads except 1, as when the heating is switched on the boiler is always burning (at full power, boilers don't automatically vary their output do they?) to supply that one radiator without the TRV.

If I have the TRV's set on 3, so they automatically close when they get to about 20ºC, the boiler remains alight anyway supplying the 1 radiator in the bathroom (without the TRV).

Surely it doesn't make any difference if I put all the rads on MAX as the boiler is always on supplying that single Bathroom rad.

Do you see what I'm saying?

most boilers now will modulate down to match the load
the point of trv's is to set the room temp independently
the boiler will only fire till the bathroom rad temp matches the set boiler temp then it will close down

if you put all the rads on max it will be a bit warm as your only temp control is the boiler stat

 

[pinheadplanet]

When the TRV'd rad's have reached temp they close off, but the boiler definitely stays on full whack supplying the bathroom, so if I turn down the boiler temp I should see a change whereby the boiler turns off when the bathroom rad reaches the set boiler temp?

I'll try it today.

I assume that'll change my Hot Water temp too.

 

[pinheadplanet]

Actually thinking about it I don't really want to reduce the temp in the Bathroom as it's the coldest room in the house.

Instead of a 'proper' rad in the Bathroom it's got one of these Chrome Towel Heater type rad's. It's quite big though, see pic.

The bathroom's only about 9'x5'.

What would you recommend?

Untitled

• pinheadplanet
• 9 Nov 2010
• 1

 

[D_Hailsham]

What's the point of having TRV's on all my rads except 1, as when the heating is switched on the boiler is always burning (at full power, boilers don't automatically vary their output do they?) to supply that one radiator without the TRV.

The room with a rad and no TRV is supposed to have a wall thermostat in it, usually the hall or living room. When this room is up to the temperature set on the wall thermostat, the boiler will turn off.

If I have the TRV's set on 3, so they automatically close when they get to about 20ºC, the boiler remains alight anyway supplying the 1 radiator in the bathroom (without the TRV).

TRVs rarely close completely, they open and close just enough to provide the required flow through the radiator so the room stays at the temperature set on the TRV. (Output is proportional to flow rate.)

If the bathroom rad has no TRV, it's usually like that so the towels get nice and warm!

As KP says, modern boilers automatically adjust their output. They do this by measuring the flow and return temperatures and the rate at which they increase.

 

[pinheadplanet]

if you put all the rads on max it will be a bit warm as your only temp control is the boiler stat

If I put all the rads on Max then surely I'm still using the same amount of energy as the boiler's on anyway and therefore it'll be costing me the same.

See what I'm saying? I can have the house WARM as opposed to 'nearly warm' for the same money. Is that right?

 

[JohnD]

no, it's completely wrong. I'm not sure if this is a wind up

the more heat you use, and the longer you use it, the more it will cost you, and the hotter the house will be. Ye cannae change the laws o'physics, cap'n.

The higher you turn your radiators, the more heat they will use, so the boiler will run longer, and turn up its gas, to provide that heat.

the boiler has a thermostat so it will turn itself off, or down, when it reaches, or approaches, its preset temperature. The more heat the radiators are using, the longer this will take, and the more gas it will use.

What sort of boiler have you got?

 

[pinheadplanet]

What's the point of having TRV's on all my rads except 1, as when the heating is switched on the boiler is always burning (at full power, boilers don't automatically vary their output do they?) to supply that one radiator without the TRV.

The room with a rad and no TRV is supposed to have a wall thermostat in it, usually the hall or living room. When this room is up to the temperature set on the wall thermostat, the boiler will turn off.

If I have the TRV's set on 3, so they automatically close when they get to about 20ºC, the boiler remains alight anyway supplying the 1 radiator in the bathroom (without the TRV).

TRVs rarely close completely, they open and close just enough to provide the required flow through the radiator so the room stays at the temperature set on the TRV. (Output is proportional to flow rate.)

As KP says, modern boilers automatically adjust their output. They do this by measuring the flow and return temperatures and the rate at which they increase.

OK the boiler should adjust automatically then according to the flow rate, that sounds good and would make sense. Should I be able to notice this adjustment as as I say the boiler just seems to be fired up all the time when the heating's on?

 

[pinheadplanet]

no, it's completely wrong. I'm not sure if this is a wind up

the more heat you use, and the longer you use it, the more it will cost you, and the hotter the house will be. Ye cannae change the laws o'physics, cap'n.

The higher you turn your radiators, the more heat they will use, so the boiler will run longer, and turn up its gas, to provide that heat.

the boiler has a thermostat so it will turn itself off, or down, when it reaches, or approaches, its preset temperature. The more heat the radiators are using, the longer this will take, and the more gas it will use.

What sort of boiler have you got?

Hi John,

It's not a wind up, I'm just a dullard!

Let me put it like this:

The heating is set to come on for 3 hours in the evening. The TRV's are set at 3 and those rad's remain warm (not hot) as the the TRV's close and modulate the rads, HOWEVER the boiler will be fired up for the entire 3 hours obviously supplying the rad in the bathroom as there's no TRV on it and I've no wall thermostat.

So I'm paying to have the boiler run for the full 3 hours!

 

[pinheadplanet]

MOD 11 - Sorry, point noted.

 

[JohnD]

What sort of boiler have you got?

 

[pinheadplanet]

Halstead - Ace High Combi

 

[JohnD]

I gather that this boiler has an output of 11kW to 30kW

http://www.halsteadglendimplex.co.u...sHCHqxj81))/downloads/SEBoiler/AceAceHigh.pdf

That means it will adjust the size of the flame, and the amount of gas used, depending on demand. I will guess that your funny bathroom radiator might have an output of 2kW. That means it cannot possibly use enough heat to keep the boiler burning continuously. Even though it is switched on, the boiler will adjust itself to its lowest flame setting, then turn off for half an hour or so until the radiator has cooled a bit and can absorb some more heat. You may find the boiler getting louder and quieter as it turns itself on, down, and off. You will also observe the gas meter getting faster, slower, and stopping.

BTW you really ought to get a room stat fitted. You are tipping money down the drain without one.

 

[pinheadplanet]

Ok - I'm gonna try to monitor the boiler adjusting the flame, hopefully I'll hear it as there's no window to the flames as in other boilers. I'll try to watch the gas meter as well.

What will a Room Stat do for me? We never have the heating on so much that the house gets too warm.

 

[JohnD]

a room stat will ensure that the heating brings your home to your chosen tempertature, then stops.

It will not turn the heat on if it is warm enough

it will turn it on if it is too cold

iy will do this automatically without you getting up and turning it on and off. By being more efficient it will improve comfort and economy. You can let it bring the home to a comfortable temperature for getting-up time and getting-home time without any risk that it will waste gas by making it too warm.

Move forward into the 1960's and get a stat!