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Thread: What happens non trv radiators with evohome?

  1. #1
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    Default What happens non trv radiators with evohome?

    Hi, I have recently installed evohome, fantastic I must say and so easy to move from a cm927 controller. Two quick questions though. I have a trv in the hall where I also have the thermostat plugged in. I have 3 non hr92 trv radiators, are these controlled by the thermostat, hence the hall? The reason I ask is that the bathroom radiator, a large metal style radiator for towels (non trv) always seems hot regardless of hall temperature. would it be wise to install trv on this and if so how as it has 2 manual trv at the minute.
    Other question is that my hot water has continued to work as normal during the transition. Is this because it's a combi boiler, I was trying to get thermostat to display water temp but can't find any option for it?
    Any support or advice would be greatly appreciated

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    Quote Originally Posted by FUNKYDADDIO View Post
    Hi, I have recently installed evohome, fantastic I must say and so easy to move from a cm927 controller. Two quick questions though. I have a trv in the hall where I also have the thermostat plugged in. I have 3 non hr92 trv radiators, are these controlled by the thermostat, hence the hall? The reason I ask is that the bathroom radiator, a large metal style radiator for towels (non trv) always seems hot regardless of hall temperature. would it be wise to install trv on this and if so how as it has 2 manual trv at the minute.
    Other question is that my hot water has continued to work as normal during the transition. Is this because it's a combi boiler, I was trying to get thermostat to display water temp but can't find any option for it?
    Any support or advice would be greatly appreciated
    I've got a couple of radiators in the house which don't have the HR92 attached. They just pump out heat whenever there is a heat demand from an HR92 equipped radiator which then causes water to circulate. They would only turn off if they reach the heat setting for the non HR-92 TRV.

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    You won't get a hot water temperature unless you have a HW kit with sensor fitted. My understanding is that this only works with hot water cylinders - not combi boilers.

    If your boiler has a pump over-run then you need to have either an open radiator in the circuit or an ABV/ gated pump bypass fitted to the system to protect the boiler from an overheat situation. It also makes best use of residual heat.

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    Quote Originally Posted by wg100 View Post
    I've got a couple of radiators in the house which don't have the HR92 attached. They just pump out heat whenever there is a heat demand from an HR92 equipped radiator which then causes water to circulate. They would only turn off if they reach the heat setting for the non HR-92 TRV.
    Quote Originally Posted by HenGus View Post
    You won't get a hot water temperature unless you have a HW kit with sensor fitted. My understanding is that this only works with hot water cylinders - not combi boilers.

    If your boiler has a pump over-run then you need to have either an open radiator in the circuit or an ABV/ gated pump bypass fitted to the system to protect the boiler from an overheat situation. It also makes best use of residual heat.
    So does that mean that the non hr92 radiators will heat if even only one hr92 is calling for heat? Thanks..

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    Quote Originally Posted by FUNKYDADDIO View Post
    So does that mean that the non hr92 radiators will heat if even only one hr92 is calling for heat? Thanks..
    Correct. The non HR92 (call it a manual valve) is a thermostatic valve, so provided the ambient temperature at the manual valve is lower than the dial setting (say 2 or 3), the valve will open and allow the circulating hot water from the boiler to pass through the radiator. It will close when the ambient temperature has risen above the dial setting on that valve. It will only work provided the boiler (and pump) is on and heating the water.

    Many Evohome users start by installing some rads with HR92s and some on the existing manual TRVs.

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    Quote Originally Posted by FUNKYDADDIO View Post
    So does that mean that the non hr92 radiators will heat if even only one hr92 is calling for heat? Thanks..
    Exactly that; with the caveat, that if the manual TRV is set below the actual room temperature then the radiator will not get hot. This is why it makes no sense to mix HR92s and manual TRVs in the same zone. Manual TRVs are fine in rarely used bedrooms. They can be turned down to a low setting so are effectively off.

    Sorry - crossed with the above.

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    Quote Originally Posted by FUNKYDADDIO View Post
    The reason I ask is that the bathroom radiator, a large metal style radiator for towels (non trv) always seems hot regardless of hall temperature. would it be wise to install trv on this and if so how as it has 2 manual trv at the minute.
    You say your towel rail is non-TRV then say later it has 2 manual TRV.

    Often, towel rails are left with the existing manual valves, so that the towel rails (or at least one of them) act as an "overflow" or Automatic Bypass Valve [ABV]. One side of the towel rail will have a manual lockshield valve used to regulate the flow or volume of CH water passing through. The other side is probably just a matching elbow with the same décor gate wheel matching the other side (it might be a freely rotating wheel).

    I use three rails, none of which have TRVs or HR92s. The location of the towel rails may have a bearing on how effectively it can act as an ABV but you will be able to tell from the temperature. If it's hot - its working fine. Ultimately, a full system using HR92s is the way to go but cost might delay installing your full set.
    Last edited by killa47; 3rd January 2017 at 04:52 PM.

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    Quote Originally Posted by FUNKYDADDIO View Post
    Hi, I have recently installed evohome, fantastic I must say and so easy to move from a cm927 controller. Two quick questions though. I have a trv in the hall where I also have the thermostat plugged in.
    What do you mean by "the thermostat" ? Are you referring to the evotouch controller itself ? And when you say you have a TRV on the radiator in the hallway, do you mean an HR92 ?

    If so then you can choose to either let the HR92 use its own built in temperature sensor for the hall - in which case the evotouch temperature sensor is not used, or you can choose to make the evotouch be the room temperature sensor for the hallway and thus control the hallway radiator - which is what I do as mine is wall mounted in the hallway.

    It's up to you and depends on how you set things up during the binding and zone creation process, but its easy to change it later.
    I have 3 non hr92 trv radiators, are these controlled by the thermostat, hence the hall? The reason I ask is that the bathroom radiator, a large metal style radiator for towels (non trv) always seems hot regardless of hall temperature.
    On an evotouch system instead of there only being one central thermostat that can call for heat from the boiler, all HR92's are able to call for heat and thus fire the boiler when they require it. Therefore if you have some manual TRV's that are turned up high enough they will heat up when ANY HR92 controlled radiator is calling for heat, not just your hallway. That's why your bathroom radiator is getting hot often - some other room besides the hallway is still calling for heat. Only when all HR92 controlled radiators stop calling for heat would that bathroom radiator cool down with the system as you have it at the moment.
    would it be wise to install trv on this and if so how as it has 2 manual trv at the minute.
    It won't have two manual TRV's, you never fit two TRV's to one radiator. It will have either two lockshield valves (with a cap you can lift off to reveal a slotted shaft you can turn with a spanner or pliers) or it could be just be a "handwheel" valve, which is just a knob that works like a tap. Either way the result is the same - they're designed to be left open and you can't mount an HR92 on one.

    To fit an HR92 you'd have to get one of the handwheel/lockshield valves (preferably the one on the colder return side) replaced with a TRV valve body - to do this the system would have to be drained down and later refilled with new inhibitor, so best left until scheduled maintenance is needed.

    If your system has an automatic bypass valve then you can potentially fit HR92's on ALL radiators so that no bypass radiators are needed, however if you don't have an automatic bypass valve in the system, then generally you must have at least one radiator that stays open all the time as a bypass - often this is the hallway or the bathroom. So if you were contemplating fitting HR92's to all radiators including the bathroom you would need to check a bypass valve was present in the system or that the boiler has a variable speed pump and specifically says it doesn't require a bypass. (A few modern boilers can do this)

    Personally I think a bypass radiator that always gets hot when the system is running is wasteful, and I like being able to schedule my bathroom radiator - I have it quite hot in the morning for a shower (23) but in the evening when people get home it is only scheduled to 18, then mid evening it drops to 16 then finally to 5 at bedtime.
    Other question is that my hot water has continued to work as normal during the transition. Is this because it's a combi boiler, I was trying to get thermostat to display water temp but can't find any option for it?
    If you have a combi boiler then your hot water will continue to operate as before - the Evohome won't have any influence on your hot water and won't be able to display or set hot water temperature - the evohome can only control hot water if you have an S-Plan or Y-Plan system and have the Evohome hot water kit installed to control it.
    Last edited by DBMandrake; 3rd January 2017 at 09:32 PM.

  9. #9
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    Quote Originally Posted by DBMandrake View Post
    What do you mean by "the thermostat" ? Are you referring to the evotouch controller itself ? And when you say you have a TRV on the radiator in the hallway, do you mean an HR92 ?

    If so then you can choose to either let the HR92 use its own built in temperature sensor for the hall - in which case the evotouch temperature sensor is not used, or you can choose to make the evotouch be the room temperature sensor for the hallway and thus control the hallway radiator - which is what I do as mine is wall mounted in the hallway.

    It's up to you and depends on how you set things up during the binding and zone creation process, but its easy to change it later.

    On an evotouch system instead of there only being one central thermostat that can call for heat from the boiler, all HR92's are able to call for heat and thus fire the boiler when they require it. Therefore if you have some manual TRV's that are turned up high enough they will heat up when ANY HR92 controlled radiator is calling for heat, not just your hallway. That's why your bathroom radiator is getting hot often - some other room besides the hallway is still calling for heat. Only when all HR92 controlled radiators stop calling for heat would that bathroom radiator cool down with the system as you have it at the moment.

    It won't have two manual TRV's, you never fit two TRV's to one radiator. It will have either two lockshield valves (with a cap you can lift off to reveal a slotted shaft you can turn with a spanner or pliers) or it could be just be a "handwheel" valve, which is just a knob that works like a tap. Either way the result is the same - they're designed to be left open and you can't mount an HR92 on one.

    To fit an HR92 you'd have to get one of the handwheel/lockshield valves (preferably the one on the colder return side) replaced with a TRV valve body - to do this the system would have to be drained down and later refilled with new inhibitor, so best left until scheduled maintenance is needed.

    If your system has an automatic bypass valve then you can potentially fit HR92's on ALL radiators so that no bypass radiators are needed, however if you don't have an automatic bypass valve in the system, then generally you must have at least one radiator that stays open all the time as a bypass - often this is the hallway or the bathroom. So if you were contemplating fitting HR92's to all radiators including the bathroom you would need to check a bypass valve was present in the system or that the boiler has a variable speed pump and specifically says it doesn't require a bypass. (A few modern boilers can do this)

    Personally I think a bypass radiator that always gets hot when the system is running is wasteful, and I like being able to schedule my bathroom radiator - I have it quite hot in the morning for a shower (23) but in the evening when people get home it is only scheduled to 18, then mid evening it drops to 16 then finally to 5 at bedtime.

    If you have a combi boiler then your hot water will continue to operate as before - the Evohome won't have any influence on your hot water and won't be able to display or set hot water temperature - the evohome can only control hot water if you have an S-Plan or Y-Plan system and have the Evohome hot water kit installed to control it.
    Quote Originally Posted by killa47 View Post
    You say your towel rail is non-TRV then say later it has 2 manual TRV.

    Often, towel rails are left with the existing manual valves, so that the towel rails (or at least one of them) act as an "overflow" or Automatic Bypass Valve [ABV]. One side of the towel rail will have a manual lockshield valve used to regulate the flow or volume of CH water passing through. The other side is probably just a matching elbow with the same décor gate wheel matching the other side (it might be a freely rotating wheel).

    I use three rails, none of which have TRVs or HR92s. The location of the towel rails may have a bearing on how effectively it can act as an ABV but you will be able to tell from the temperature. If it's hot - its working fine. Ultimately, a full system using HR92s is the way to go but cost might delay installing your full set.
    Quote Originally Posted by HenGus View Post
    Exactly that; with the caveat, that if the manual TRV is set below the actual room temperature then the radiator will not get hot. This is why it makes no sense to mix HR92s and manual TRVs in the same zone. Manual TRVs are fine in rarely used bedrooms. They can be turned down to a low setting so are effectively off.

    Sorry - crossed with the above.
    Quote Originally Posted by killa47 View Post
    Correct. The non HR92 (call it a manual valve) is a thermostatic valve, so provided the ambient temperature at the manual valve is lower than the dial setting (say 2 or 3), the valve will open and allow the circulating hot water from the boiler to pass through the radiator. It will close when the ambient temperature has risen above the dial setting on that valve. It will only work provided the boiler (and pump) is on and heating the water.

    Many Evohome users start by installing some rads with HR92s and some on the existing manual TRVs.
    Quote Originally Posted by HenGus View Post
    You won't get a hot water temperature unless you have a HW kit with sensor fitted. My understanding is that this only works with hot water cylinders - not combi boilers.

    If your boiler has a pump over-run then you need to have either an open radiator in the circuit or an ABV/ gated pump bypass fitted to the system to protect the boiler from an overheat situation. It also makes best use of residual heat.
    Quote Originally Posted by wg100 View Post
    I've got a couple of radiators in the house which don't have the HR92 attached. They just pump out heat whenever there is a heat demand from an HR92 equipped radiator which then causes water to circulate. They would only turn off if they reach the heat setting for the non HR-92 TRV.
    Many thanks to everyone for your help. This is the towel rail I was talking about. I closed off both valves (as such) yesterday and it dropped a few drips of water from the left hand side. I`m really not sure if my system has a bypass, is there a way to check? Its only been installed 4 years. I really wanted to maximise savings and having the bathroom warm pretty much frustrates this.

    When you mention using the evotouch controller to control hall temp does this mean I could set it up as a zone effectively without a hr92 and use the controller hence giving me a spare hr92?

    Thanks again..DSC_0425.JPGDSC_0424.jpgDSC_0425.JPGDSC_0424.jpg

  10. #10
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    Quote Originally Posted by FUNKYDADDIO View Post
    This is the towel rail I was talking about. I closed off both valves (as such) yesterday and it dropped a few drips of water from the left hand side. I`m really not sure if my system has a bypass, is there a way to check? Its only been installed 4 years.
    I have same or similar towel rail. Both valves are manual, no thermostat. Sometimes, I also get an odd drip. If you're capable, you could prise off the disc cover on the valve collar which should reveal a screw which holds the collar on to the valva body. Try tightening the nut (say 1/4 turn) to see if drip stops. If not, will it tighten a bit more. Otherwise, you might need to use some PTFE tape around the thread. After that, if it still drips, you need a plumber of a friendly DIYer.

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