Flow Temperature or Thermostat or TRV or Lockshield Valve?

bery_451

Hi,

I have a Worcester Bosch boiler specifically the Worcester Greenstar 32CDi Compact Combi gas fired Condensing Boiler.

I like to know the most cheapest efficient way to run this boiler to keep the house warm. Is it cheaper to keep the boiler on all the time or only use the boiler when in the house?

I am confused between the flow temp, thermostat and TRV? Lets say for example the thermostat is displaying cold 15 degrees and I set the thermostat to 18 degrees, the boiler kicks in to heat however what number between 1-6 on the TRV corresponds to 18 degrees on the thermostat? Also does my boiler use a constant supply of gas to it until desired temp on thermostat is reached? For example thermostat is displaying very cold 10 degrees and I set it to 18 degrees, will my boiler use a lot more of gas as usual to get to 18 degrees quickly from 10 degrees or my boiler uses a constant same supply of gas to get to 18 degrees at whatever rate of time it takes to get to 18 degrees?

Will using a high flow temperature get it to the set 18 degrees on thermostat more quickly or setting a high number on TRV gets there more quickly too? Getting to set desired temp quickly uses less gas or more gas?

Also if I set to high number like 5 or 6 on TRV then will this override the set desired temp like 18 degrees on the thermostat?

Its confusing or please advise the most efficient way to balance all 3 or which out of the 3 the boiler gives more priority to and what number should I set minimum on TRV to avoid air getting trapped in radiators & keep the boiler at a constant pressure?

I noticed using higher flow temp & high TRV numbers gets the room warm quicker but is this using more gas than usual or a constant supply of gas is better to get to desired temp but will take longer?

Lets say there's 2 radiators, 1 is single panel and the other is double panel. Will the single panel rad with a TRV setting of 5-6 use the game gas as a double panel rad on a TRV setting of 3?

What about radiators that have no TRV's like bathroom towel radiators?

Basically I like to know the quickest way to warm up the room with less gas used as possible.

FreeBear

Here is the output power from my boiler (a newis Viessmann 30kW combi) ->

At start up, it runs at ~10kW before dropping down to just under 5kW as the heating system gets up to temperature. As the room temperatures rise from 17°C, some of the TRVs are turning off the radiators which accounts for some of the drop in power (less radiators means less heat needs to be generated). Less heat being generated means I'm burning less gas.

I have my flow temperature set to 50-55°C which allows me to heat the house at about 1°C per hour. I could increase the flow temperature at the expense of efficiency. But my radiators are sized appropriately to use a lower flow temperature.

Depending on how long ago your central heating system was installed and whether radiators have been replaced with larger ones, I'd suggest running with a flow temperature of 60°C. See how fast the place heats up with all the TRVs set to 6. If the place isn't heating up fast enough, try setting the flow temperature to 65°C.

If certain rooms are warmer than you like, turn the TRVs in those rooms down to say 3 (that will limit the temperature to ~19°C). Playing with the TRVs will not turn the boiler on - Only the thermostat/timer will do that.

It will also help tremendously if your radiators are properly balanced and the pump speed set correctly - I'm running my pump at the lowest speed to get a decent temperature drop across each radiator (the guy that installed the boiler had left everything on max - not good for efficiency). Today's numbers suggests I'm getting 94.5% efficiency (21kW of heat generated, 22.23kWh of gas used).

Reed_Richards

The answer could depend on what thermostat you have and how it (or its control box if wireless) is connected to your boiler.  So what do you have?

The TRV valve on the radiator will set the target temperature for that radiator, so if the room has only the one radiator it will set the temperature of that room.  You should set the TRVs to maximum on all the radiators in the room with your room thermostat.  If they were set to a low value then the room would never reach the temperature set on your room thermostat so your boiler would neve turn off until it overheated. 

bery_451

FreeBear said:

Here is the output power from my boiler (a newis Viessmann 30kW combi) ->

At start up, it runs at ~10kW before dropping down to just under 5kW as the heating system gets up to temperature. As the room temperatures rise from 17°C, some of the TRVs are turning off the radiators which accounts for some of the drop in power (less radiators means less heat needs to be generated). Less heat being generated means I'm burning less gas.

I have my flow temperature set to 50-55°C which allows me to heat the house at about 1°C per hour. I could increase the flow temperature at the expense of efficiency. But my radiators are sized appropriately to use a lower flow temperature.

Hi you mean 10kW of Gas being used at the start? Only smart TRV's can turn off radiators individually or any TRV has a built in room air temperature sensor meaning if the room temp is higher than the set TRV temp then the rad will turn off automatically regardless of what is set on the thermostat or where the thermostat is?

Okay bigger rads like double panel rads are more suited for lower flower temp and smaller rads like single panel rads are more suited for a higher flow temp?

Depending on how long ago your central heating system was installed and whether radiators have been replaced with larger ones, I'd suggest running with a flow temperature of 60°C. See how fast the place heats up with all the TRVs set to 6. If the place isn't heating up fast enough, try setting the flow temperature to 65°C.

If certain rooms are warmer than you like, turn the TRVs in those rooms down to say 3 (that will limit the temperature to ~19°C). Playing with the TRVs will not turn the boiler on - Only the thermostat/timer will do that.

Central heating was originally installed 20+ years ago however boiler was installed 6 years ago. Most rads I have are big double panel ones. So to confirm larger rads are better they don't use more gas than single ones? Setting on TRV will override set temp on thermostat in the same room?

It will also help tremendously if your radiators are properly balanced and the pump speed set correctly - I'm running my pump at the lowest speed to get a decent temperature drop across each radiator (the guy that installed the boiler had left everything on max - not good for efficiency). Today's numbers suggests I'm getting 94.5% efficiency (21kW of heat generated, 22.23kWh of gas used).

What you mean by balanced, Rad is level? How you set the pump speed for each rad?

Hi quoted above ^^

bery_451

Reed_Richards said:

The answer could depend on what thermostat you have and how it (or its control box if wireless) is connected to your boiler.  So what do you have?

The TRV valve on the radiator will set the target temperature for that radiator, so if the room has only the one radiator it will set the temperature of that room.  You should set the TRVs to maximum on all the radiators in the room with your room thermostat.  If they were set to a low value then the room would never reach the temperature set on your room thermostat so your boiler would neve turn off until it overheated. 

Yes thermostat is wireless by ESi ESRTP4RF.

Yes rooms only have 1 rad in each except the the kitchen/diner that has 2 rads.

Okay to clarify a low setting set on TRV will not overide the temp set on thermostat in room meaning for e.g. I set TRV to 3, however I set my thermostat max to 35 degrees in the same room meaning my boiler will not turn off until that room reaches 35 degrees but how can it reach 35 degrees when the TRV is set to position 3?

Reed_Richards

bery_451 said:

Reed_Richards said:

The answer could depend on what thermostat you have and how it (or its control box if wireless) is connected to your boiler.  So what do you have?

The TRV valve on the radiator will set the target temperature for that radiator, so if the room has only the one radiator it will set the temperature of that room.  You should set the TRVs to maximum on all the radiators in the room with your room thermostat.  If they were set to a low value then the room would never reach the temperature set on your room thermostat so your boiler would neve turn off until it overheated. 

Yes thermostat is wireless by ESi ESRTP4RF.

Yes rooms only have 1 rad in each except the the kitchen/diner that has 2 rads.

Okay to clarify a low setting set on TRV will not overide the temp set on thermostat in room meaning for e.g. I set TRV to 3, however I set my thermostat max to 35 degrees in the same room meaning my boiler will not turn off until that room reaches 35 degrees but how can it reach 35 degrees when the TRV is set to position 3?

The answer to your last question is that it cannot reach 35 degrees, as I wrote.  That room cannot reach any temperature beyond whatever temperature position 3 on the TRV corresponds to (unless heat comes in from adjoining hotter rooms).  You should always set the TRV in the room with your room thermostat to it's maximum setting.

To get the most economical operation out of your Worcester Bosch boiler you need their own-brand controller called "Easy Control".  But with your ESI controller the operation should be very straightforward, if the room is colder than the set temperature on your room thermostat then your boiler should be on (unless it overheats the water).  

FreeBear

bery_451 said: Hi you mean 10kW of Gas being used at the start? Only smart TRV's can turn off radiators individually or any TRV has a built in room air temperature sensor meaning if the room temp is higher than the set TRV temp then the rad will turn off automatically regardless of what is set on the thermostat or where the thermostat is?


What you mean by balanced, Rad is level? How you set the pump speed for each rad?

The graph is from a heat meter that measures the flow rate of the water along with outing & return temperatures. From that, it automagically calculates how much energy is being used to heat the house. So when I say 10kW of heat, this is the amount of energy being produced by the boiler. Not being able to monitor actual gas consumption beyond what the (smart) meter tells me, I can't say what the instantaneous use is - Could fit a lab grade sensor to the gas pipe, but it would probably breach countless regulations and give a Gas Safe engineer a fit if/when I need a safety certificate issued.

A standard (non-smart) TRV reacts to room temperature and will slowly close off the radiator valve. Doesn't need smarts or batteries to do so. To change the temperature at which a radiator turns off just means picking a number (for my TRVs, No.3 is equal to about 19°C).

Balancing the radiators means setting the lockshield valves to get a consistent temperature drop across each radiator (typically, 12-20°C depending on flow temperature). This helps to ensure that each radiator in the house heats up at the same rate and can improve efficiency of the whole system. As part of the process of balancing the radiators, you may need to turn the pump speed down so that the correct temperature drop across each radiator can be achieved without shutting the lockshield right down.

Plenty of guides on the internet on balancing radiators. This one goes quite deep in to the technical aspects and can be rather confusing -> https://www.heatgeek.com/balancing-heating-systems-the-ultimate-guide/

bery_451

Reed_Richards said:

bery_451 said:

Reed_Richards said:

The answer could depend on what thermostat you have and how it (or its control box if wireless) is connected to your boiler.  So what do you have?

The TRV valve on the radiator will set the target temperature for that radiator, so if the room has only the one radiator it will set the temperature of that room.  You should set the TRVs to maximum on all the radiators in the room with your room thermostat.  If they were set to a low value then the room would never reach the temperature set on your room thermostat so your boiler would neve turn off until it overheated. 

Yes thermostat is wireless by ESi ESRTP4RF.

Yes rooms only have 1 rad in each except the the kitchen/diner that has 2 rads.

Okay to clarify a low setting set on TRV will not overide the temp set on thermostat in room meaning for e.g. I set TRV to 3, however I set my thermostat max to 35 degrees in the same room meaning my boiler will not turn off until that room reaches 35 degrees but how can it reach 35 degrees when the TRV is set to position 3?

The answer to your last question is that it cannot reach 35 degrees, as I wrote.  That room cannot reach any temperature beyond whatever temperature position 3 on the TRV corresponds to (unless heat comes in from adjoining hotter rooms).  You should always set the TRV in the room with your room thermostat to it's maximum setting.

To get the most economical operation out of your Worcester Bosch boiler you need their own-brand controller called "Easy Control".  But with your ESI controller the operation should be very straightforward, if the room is colder than the set temperature on your room thermostat then your boiler should be on (unless it overheats the water).  

Ok to confirm in a room where the rad TRV and thermostat wireless control is in the same room, the TRV has higher priority over the thermostat when it comes to air temperature for that room meaning the boiler will constantly use gas not turn off because the thermostat will sense a lower room temp than the set temp on the thermostat?

Can the same be said vice-versa, where the TRV setting is at max 5/6 position but the set temp on thermostat is lower than the TRV 5/6 position meaning it will stop the boiler using gas because room temp will get higher than set thermostat temp?

So in summary it is better to put your TRV's in max 5/6 position to stop the risk of your boiler overheating and using tons of gas doing so?

bery_451

FreeBear said:

bery_451 said: Hi you mean 10kW of Gas being used at the start? Only smart TRV's can turn off radiators individually or any TRV has a built in room air temperature sensor meaning if the room temp is higher than the set TRV temp then the rad will turn off automatically regardless of what is set on the thermostat or where the thermostat is?


What you mean by balanced, Rad is level? How you set the pump speed for each rad?

The graph is from a heat meter that measures the flow rate of the water along with outing & return temperatures. From that, it automagically calculates how much energy is being used to heat the house. So when I say 10kW of heat, this is the amount of energy being produced by the boiler. Not being able to monitor actual gas consumption beyond what the (smart) meter tells me, I can't say what the instantaneous use is - Could fit a lab grade sensor to the gas pipe, but it would probably breach countless regulations and give a Gas Safe engineer a fit if/when I need a safety certificate issued.

A standard (non-smart) TRV reacts to room temperature and will slowly close off the radiator valve. Doesn't need smarts or batteries to do so. To change the temperature at which a radiator turns off just means picking a number (for my TRVs, No.3 is equal to about 19°C).

Balancing the radiators means setting the lockshield valves to get a consistent temperature drop across each radiator (typically, 12-20°C depending on flow temperature). This helps to ensure that each radiator in the house heats up at the same rate and can improve efficiency of the whole system. As part of the process of balancing the radiators, you may need to turn the pump speed down so that the correct temperature drop across each radiator can be achieved without shutting the lockshield right down.

Plenty of guides on the internet on balancing radiators. This one goes quite deep in to the technical aspects and can be rather confusing -> https://www.heatgeek.com/balancing-heating-systems-the-ultimate-guide/

Alright I see the lockshield valve on each of the rads. To confirm the job of the lockshield valve is to control how much hot water is leaving the Radiator? Does the hot water leave the rad when air temp matches TRV setting? If I tighten the lockshield to the max then no hot water can leave the Rad meaning the Rad will retain the hot water for longer no need for boiler to use more fresh gas to supply the rad with new hot water however if I loosen the lockshield valve to the max then hot water can leave the rad more easily meaning the rad will get metal cold quicker after the TRV air temp is met?

I see no indications or settings numbers on the lockshield valve so how do you know what lockshield tight/loose setting position your at to do the balancing?

Ectophile

bery_451 said:

FreeBear said:

bery_451 said: Hi you mean 10kW of Gas being used at the start? Only smart TRV's can turn off radiators individually or any TRV has a built in room air temperature sensor meaning if the room temp is higher than the set TRV temp then the rad will turn off automatically regardless of what is set on the thermostat or where the thermostat is?


What you mean by balanced, Rad is level? How you set the pump speed for each rad?

The graph is from a heat meter that measures the flow rate of the water along with outing & return temperatures. From that, it automagically calculates how much energy is being used to heat the house. So when I say 10kW of heat, this is the amount of energy being produced by the boiler. Not being able to monitor actual gas consumption beyond what the (smart) meter tells me, I can't say what the instantaneous use is - Could fit a lab grade sensor to the gas pipe, but it would probably breach countless regulations and give a Gas Safe engineer a fit if/when I need a safety certificate issued.

A standard (non-smart) TRV reacts to room temperature and will slowly close off the radiator valve. Doesn't need smarts or batteries to do so. To change the temperature at which a radiator turns off just means picking a number (for my TRVs, No.3 is equal to about 19°C).

Balancing the radiators means setting the lockshield valves to get a consistent temperature drop across each radiator (typically, 12-20°C depending on flow temperature). This helps to ensure that each radiator in the house heats up at the same rate and can improve efficiency of the whole system. As part of the process of balancing the radiators, you may need to turn the pump speed down so that the correct temperature drop across each radiator can be achieved without shutting the lockshield right down.

Plenty of guides on the internet on balancing radiators. This one goes quite deep in to the technical aspects and can be rather confusing -> https://www.heatgeek.com/balancing-heating-systems-the-ultimate-guide/

Alright I see the lockshield valve on each of the rads. To confirm the job of the lockshield valve is to control how much hot water is leaving the Radiator? Does the hot water leave the rad when air temp matches TRV setting? If I tighten the lockshield to the max then no hot water can leave the Rad meaning the Rad will retain the hot water for longer no need for boiler to use more fresh gas to supply the rad with new hot water however if I loosen the lockshield valve to the max then hot water can leave the rad more easily meaning the rad will get metal cold quicker after the TRV air temp is met?

I see no indications or settings numbers on the lockshield valve so how do you know what lockshield tight/loose setting position your at to do the balancing?

The lockshield valve is simply a tap that doesn't have a handle on it.  Set it fully open and lots of water can flow through.  Turn it almost off and only a trickle can flow.  It has no idea what the TRV is doing.

If the radiator is full of water (and if it isn't, it needs bleeding), then the flow of water going in must equal the flow of water going out again.    So both the TRV and the lockshield valve can control how much water gets through.  In practice, the TRV turns the radiator on or off, and the lockshield valve sets how fast the water flows.

Balancing is done to ensure that all the radiators heat up evenly with each other.  A very quick and rough check is to wait for the heating to come on, give it just a few minutes, then go around the house grabbing hold of each radiator.  If one is still cold while another is really hot, then it's not balanced.

In particular, if you set the lockshield valve fully open on the radiator nearest the boiler, it will steal all the hot water flow, and the other radiators will take ages to warm up.  As I found with my kitchen radiator.

So I turned the lockshield valve on the kitchen radiator until it was fully off, then turned it on again a little.  Over the next few days, it did the grabbing the radiators trick, adjusting the lockshield valve on the kitchen radiator until it seemed about right, compared with the others.

Reed_Richards

bery_451 said:  

Ok to confirm in a room where the rad TRV and thermostat wireless control is in the same room, the TRV has higher priority over the thermostat when it comes to air temperature for that room meaning the boiler will constantly use gas not turn off because the thermostat will sense a lower room temp than the set temp on the thermostat?

Yes that is correct.  The boiler will constantly use gas until such time as the return water temperature gets so high that it triggers the boiler to cut out as a safety feature.

bery_451 said:

Can the same be said vice-versa, where the TRV setting is at max 5/6 position but the set temp on thermostat is lower than the TRV 5/6 position meaning it will stop the boiler using gas because room temp will get higher than set thermostat temp?

Yes, that is correct for ordinary TRVs.  If you have programmable TRVs linked to your heating system it could be different.  But you don't have those, do you?

bery_451 said:

So in summary it is better to put your TRV's in max 5/6 position to stop the risk of your boiler overheating and using tons of gas doing so?

Yes, if the TRVs you are referring to are the one/ones in the same room as the room thermostat.  You can set the TRVs in other rooms to whatever setting you like.