Danfoss RA Plus-w wireless radiator thermostats

[MartinWilliams]

Hi, I've come across these Danfoss wireless radiator thermostats that operate on the Z-Wave frequency. I'm wandering if anyone has any experience of these.

I'm hoping that I'd be able to remotely operate them (alter the thermostat from 0 to full or somewhere in between) with my harmony 895, has anyone done that. Also what else do you need if you buy a few of these thermostats, do you have to buy some software if you want to program them using a laptop. I can't work out how much adjustment they have, the literature I've read mentions 3 degrees of adjustment but I don't understand what they mean by that. I'd like to be able to set them to off, very low, moderate and full of whatever the radiator is capable of or something like that.

I'm hoping that using a normal wireless central heating room thermostat I'd be able to control the main living areas but then use the wireless radiator thermostats to say have the bathroom rad come on quite high in the morning then be cooler for the rest of the time the central heating is on and similarly set the bedroom rads to come on before bedtime and off about an hour later then on in the morning and off an hour later, assuming that the central heating will be set to be on at those times via the normal wireless room thermostat. I understand that the danfoss wireless radiator thermostats won't be able to control the boiler, only the rads themselves so if the normal wireless central heating room thermostat has switched the central heating off then the rad RA plus-w thermostats wont do anything.

I think this set up, if it works will cost about £300, thermostats are about £60 each and I can get a central heating wireless room thermostat for about £60 and should give me the flexibility I want.

Martin

[fredd500]

I suspect the three degrees of adjustment is literally that - i.e. they will allow you to adjust them three degrees either side of their set point. Three degrees should be enough to give a noticable heat boost or cut depending on personal preference so assuming you set it to 21 deg, the three degrees will allow you to adjust between 18 and 24.

I have not done much research on this myself but am looking for some sort of zoned heating system and come across the house heat system Here. Room thermostats talk directly to radiator valves using a propriatary protocol (so your harmony is useless) and tell the radiator valve to open or close depending on the temperature within the room. The thermostats are also timers so you set a high and low temperature for different times of the day and automatically keep the room at the desired temperature - i.e. you might want 22 degrees in the living room between 0700 and 0900 and between 1700 and 2300 and 17 degrees at all other times. Meanwhile, in the bedroom, you might want 20 degrees between 2100 and 0800 and 16 degrees at all other times.

Prices don't seem too excessive - about £70 per room for a thermostat and a radiator valve.

Hope this helps

[MartinWilliams]

Originally Posted by fredd500

I suspect the three degrees of adjustment is literally that - i.e. they will allow you to adjust them three degrees either side of their set point. Three degrees should be enough to give a noticable heat boost or cut depending on personal preference so assuming you set it to 21 deg, the three degrees will allow you to adjust between 18 and 24.

I have not done much research on this myself but am looking for some sort of zoned heating system and come across the house heat system Here. Room thermostats talk directly to radiator valves using a propriatary protocol (so your harmony is useless) and tell the radiator valve to open or close depending on the temperature within the room. The thermostats are also timers so you set a high and low temperature for different times of the day and automatically keep the room at the desired temperature - i.e. you might want 22 degrees in the living room between 0700 and 0900 and between 1700 and 2300 and 17 degrees at all other times. Meanwhile, in the bedroom, you might want 20 degrees between 2100 and 0800 and 16 degrees at all other times.

Prices don't seem too excessive - about £70 per room for a thermostat and a radiator valve.

Hope this helps

Thanks Fred, that certainly is another option.

[MartinWilliams]

Originally Posted by fredd500

I have not done much research on this myself but am looking for some sort of zoned heating system and come across the house heat system Here. R

Prices don't seem too excessive - about £70 per room for a thermostat and a radiator valve.

Hope this helps

Fred, have a look at these Danfoss Randall RA-Plus Programmable TRV: Heating Controls Online they appear to be the same concept as the ones in the link you gave but are only £36 each.

Regards

Martin

[hornydragon]

I havent properly looked but these units seem to be TRV only which means the boiler still needs control, other wise the boiler will just keep runnning and wasting heat to the uncontrolled zones.

Honeywell CM Zone may be a better option about £80 a Rad for 6 including boiler control.

[MartinWilliams]

Originally Posted by hornydragon

I havent properly looked but these units seem to be TRV only which means the boiler still needs control, other wise the boiler will just keep runnning and wasting heat to the uncontrolled zones.

Honeywell CM Zone may be a better option about £80 a Rad for 6 including boiler control.

How many zones would that control? I'm thinking I would want at least 4 possibly more.

With a standard wireless boiler thermostat and several programmable rad thermostats I'd have as many zones as thermostats. Admittedly with some lack of flexibility in not being able to heat rooms without heating the room where the boiler thermostat is. I don't see this as a problem for me though (not having a large house), I'm going to want the lounge, dining room and kitchen (which will be controlled by the wireless boiler thermostat and normal TRVs) to be on in the morning along with the bathroom and bedrooms anyway, then have the bathroom drop down to a lower temp for the rest of the time that the boiler thermostat program has the boiler on for and the bedrooms off, but come on for the last hour of the night to heat up the bedrooms, earlier for the lodgers bedroom as he uses that more and have another rad thermostat for the gym which only needs to be on for a couple of hours at best.

[dalethecaptain]

You need to be careful if you are going to fit thermostats to all the rads in the house. Make sure your boiler has an internal pump bypass or you will damage the pump. You should have at least one flow radiator, i.e. a radiator that is fitted with only lock shield valves which should be left open. Ideally this also should be in the room where the main thermostat is (hallway etc). I used my towel warmer in the bathroom as the flow rad, its on whenever the heating is on which is quite practical.

The Danfoss controllers are adjustable to give you the three degree control band you require by moving a pin in the power head, you can set for example 15 min and 21 max, 21 min and 27 max etc, handy if your partner is prone to winding up the heat!

You should consider a remote controlled TRV in the room where the Boiler interlock thermostat is, this will allow you to set the local rad (remotely) to a lower temp and allow the boiler to continue firing and heat the other zones as required, but without going for a complex interlinked zone system unfortunately you will end with one space being overheated to achieve your goal.

[fredd500]

As far as I can tell, the househeat system is similar to the CM Zone system in a number of ways but does have some clear advantages:

1) The CM Zone controller can control two zones but only has a thermostat built in for zone one. That means the thermostat for zone two is on the TRV - silly place to put a thermostat, right next to the rad!! (although of course all standard TRV's are that anyway but its not a great idea). The househeat system has seperate thermostats which only control one zone but can control up to 8 rads within that zone and (I think) you can add as many zones as you like (at £70 per zone, assuming one rad per zone).

2) You are limited to four CM Zone Controllers limiting you to eight maximum zones.

3) The HouseHeat HouseMaster can centrally control up to 15 additional thermostats from a controller costing £107. With CM Zone, you would need to use the HomeTronic system to do this - sure it does more than just heating, but it is £500 for the controller alone.

4) Just about every component is cheaper!

5) If you are willing to pay for it, there is a PC control and web control system available.

At the moment, I have TRV's on every radiator - I am assuming therefore that all the rads are on one loop but haven't ripped the floor up to check the plumbing. The rads where in place when I moved in but I replaced the 20 year old Valliant boiler when it packed up on me. At the moment, when the boiler is on, the pump runs constantly and the flame is lit when the temperature of the returning water drops below the temperature set on the front of the boiler but this does mean I am using electricity on the pump if not gas on the flame. I have no central thermostat so the boiler is purely on timed control and the pump runs constantly between five pm and midnight.

The HouseHeat timer system works on a high set point and a low set point and alternating between the two up to four times a day. The reason for this makes some sense - less energy is used by heating the rooms from warm to hot than from cold to hot but because of this the system will never actually be off and the pump would be running constantly. There is a solution to this however in the form of the HouseHeat BoilerConnect which costs £89. I think this would replace my timer and only run the pump when one or more thermostats were calling for heat.

I probably need to point out here that I currently don't have any of these systems but am seriously thinking about installing one and think I will go for the househeat system. I have my first baby on the way which means the house will be occupied all day and control of the heat will be necessary 24/7 - unlike at present where the temperature is allowed to drop during the day (because we are at work) and at night (because we have a thick duvet) but I don't fancy the bills I am going to face with the current on or off system.

[MartinWilliams]

Originally Posted by dalethecaptain

You need to be careful if you are going to fit thermostats to all the rads in the house. Make sure your boiler has an internal pump bypass or you will damage the pump.

My boiler does have an internal pump, don't know if it has a pump bypass, it is a Baxi Bahama 100 combi boiler (a bit of a nightmare apparently). The pump seems to run all the time the boiler is set to be on, even when the gas isn't firing. This is one of the reasons I wanted a wireless room thermostat for the boiler as this should stop the pump running and wasting electricity when no heat is being called for.

Originally Posted by dalethecaptain

You should have at least one flow radiator, i.e. a radiator that is fitted with only lock shield valves which should be left open. Ideally this also should be in the room where the main thermostat is (hallway etc). I used my towel warmer in the bathroom as the flow rad, its on whenever the heating is on which is quite practical.

No towel rad, but I've realised that I shouldn't have a room thermostat and TRV's in the same area as there is potential for them to compete with each other, so I think I'll be removing the TRV's from the lounge, dining room and kitchen (these 3 rooms are connected and have had the doors removed, so kind of 1 room now) so these will all be lock shields I think.

Originally Posted by dalethecaptain

The Danfoss controllers are adjustable to give you the three degree control band you require by moving a pin in the power head, you can set for example 15 min and 21 max, 21 min and 27 max etc, handy if your partner is prone to winding up the heat!

Can they be set to no flow or frost protect if the rad is in a room that is not being used?

Originally Posted by dalethecaptain

You should consider a remote controlled TRV in the room where the Boiler interlock thermostat is, this will allow you to set the local rad (remotely) to a lower temp and allow the boiler to continue firing and heat the other zones as required, but without going for a complex interlinked zone system unfortunately you will end with one space being overheated to achieve your goal.

Hmm, you've lost me a bit there with the interlock thermostat, I think my boiler has a thermostat on the CH pipework where it leaves the boiler and this is used to switch the gas firing on and off and on the front of the boiler there is a control knob to alter the heat output to the rads. There is no other thermostat yet, but I my current plan A is to install a wireless room thermostat in the lounge

I'm thinking that whenever I want the boiler on I'm likely to want the main living areas on (lounge, dining room and kitchen) but I want to be able to automatically turn down/off rads in other rooms when not in use, so hopefully a wireless room boiler thermostat and remote rad controllers would achieve my aim of automatically reducing the heat in unused areas for my house and lifestyle.

But the 2 systems mentioned my Fred and Horneydragon also look interesting, albeit more expensive.

Thanks for taking the time to post.

Regards

Martin

[dalethecaptain]

In both of your situations it sounds like the pump continues to run because the CH water circuit has reached maximum temperature (controlled by the knob on the front of your boiler), but the demand for heating is only controlled by a simple on off timer. Fitting a room thermostat (boiler interlock thermostat) will have the same effect as turning the timer off when a set room temperature is reached, which will also stop the pump from running. It is about to become compulsory to use a separate timing thermostat in existing installations (for EPC's and all that)

In MartinWilliams case, this can have the undesired effect of holding the heating off in the rest of the property, as you have such a large 'zone' on the ground floor. Your solution of using remote TRV units upstairs is pretty sound, it will allow you that extra automated control and should help you cut your energy use further, and when you fit a thermostat/timer downstairs you will be surprised what a difference it will make to your energy bills.

The Danfoss units have built in Frost protection, this is however set by manually turning the power head, as is setting to the 'off' position. This over-rides the auto function.

Just to clear up a few points in fredd500's post, I would hazard a guess that all your rads are likely to be on the same circuit, its common practice in domestic installs in the UK, but I have seen interesting variations in some of my previous properties!
It is also normal in even the most efficient boilers for the pump to run on for a few minutes after the room thermostat (boiler interlock) has reached set point. This stops localized ebulation in the heat exchanger, which if its Titanium will kill it very quickly, so be mindful of altering this function. If you had the boiler fitted since 2002 your plumber should have fitted an interlock thermostat independent of the boiler front control clock as it is part of the building regulations.

I use the Siemens REV200 which allows multiple on/off programs per day and a variable set back points, e.g. when on it is set to maintain 21 degrees, and then keep the temperature at 18 degrees during the night when the timer is off, boosting back to 21 degrees for the morning before going off and controlling at 15 degrees during the day when no one is in, and so on. This unit is a bit more expensive, but it has remote relay input, built in frost protection, and a learning PID control function where the unit can adjust itself to your house characteristic to avoid over heating.

[MartinWilliams]

Originally Posted by fredd500

As far as I can tell, the househeat system is similar to the CM Zone system in a number of ways but does have some clear advantages:

1) The CM Zone controller can control two zones but only has a thermostat built in for zone one. That means the thermostat for zone two is on the TRV - silly place to put a thermostat, right next to the rad!! (although of course all standard TRV's are that anyway but its not a great idea). The househeat system has seperate thermostats which only control one zone but can control up to 8 rads within that zone and (I think) you can add as many zones as you like (at £70 per zone, assuming one rad per zone).

2) You are limited to four CM Zone Controllers limiting you to eight maximum zones.

3) The HouseHeat HouseMaster can centrally control up to 15 additional thermostats from a controller costing £107. With CM Zone, you would need to use the HomeTronic system to do this - sure it does more than just heating, but it is £500 for the controller alone.

4) Just about every component is cheaper!

5) If you are willing to pay for it, there is a PC control and web control system available.

At the moment, I have TRV's on every radiator - I am assuming therefore that all the rads are on one loop but haven't ripped the floor up to check the plumbing. The rads where in place when I moved in but I replaced the 20 year old Valliant boiler when it packed up on me. At the moment, when the boiler is on, the pump runs constantly and the flame is lit when the temperature of the returning water drops below the temperature set on the front of the boiler but this does mean I am using electricity on the pump if not gas on the flame. I have no central thermostat so the boiler is purely on timed control and the pump runs constantly between five pm and midnight.

Your system sounds very similar to mine

Originally Posted by fredd500

The HouseHeat timer system works on a high set point and a low set point and alternating between the two up to four times a day. The reason for this makes some sense - less energy is used by heating the rooms from warm to hot than from cold to hot but because of this the system will never actually be off and the pump would be running constantly. There is a solution to this however in the form of the HouseHeat BoilerConnect which costs £89. I think this would replace my timer and only run the pump when one or more thermostats were calling for heat.

Or just fit a standard wireless room thermostat with a built in timer. That way you can have the boiler off at night, or whenever you want. Although in your case with a baby on the way you probably don't want all the heat completely off, particularly wherever your baby is.

Originally Posted by fredd500

I probably need to point out here that I currently don't have any of these systems but am seriously thinking about installing one and think I will go for the househeat system. I have my first baby on the way which means the house will be occupied all day and control of the heat will be necessary 24/7 - unlike at present where the temperature is allowed to drop during the day (because we are at work) and at night (because we have a thick duvet) but I don't fancy the bills I am going to face with the current on or off system.

I looked at the Househeat system and the honeywell CM zone one in more detail last night. They both do seem to offer a lot of flexibility. The webpage for the honeywell one is atrocious, I very nearly dismissed their system out of hand because of their site, but tried to look more out of respect for hornydragon for posting the link. Later I found much better information on other web sites not connected with honeywell.

I found these links to be useful for both systems

Househeat; HouseHeat Products and http://www.house-intelligence.co.uk/..._UserGuide.pdf

Honeywell CM Zone; a good thread here talking about this system Honeywell CM Zone - basic questions - Automated Home Forums and Honeywell CM Zone - basic questions - Automated Home Forums

People can find better info on the CM Zone stuff by googling the components.

CM67z - Room Unit, can control 2 zones, would need 2 units for 4 zones
HR80UK - Radiator Controller
HC60NG - Relay module

You can buy the kit as already mentioned, which comprises 1 room unit, 1 relay module and 6 rad controllers for around £500 or the components separately, the room unit at just over £60, the receiver a little under £70 and the rad controllers just over £70

The Househeat system, as mentioned costs are

Rad controller and wireless room thermostat pack £70
rad controller only £40 & Room thermostat £45
HouseMaster control panel (for centrally controlling all the room thermostats and has built in thermostat for the room it is in) £107
BoilerConnect - switches the boiler off if there is no demand £89
plus other options including a pc control kit and weather sensors.

The only missing part for the househeat system is if you don't have wireless controllers on every rad you will still need a separate boiler timer or wireless room thermostat with programmer.

For me, I think I want up to 4 zones so with the Honeywell kit I'd need 2 room units, relay module and at least 4 rad controllers which is £410 I might want to add a normal wireless boiler thermostat to that at about £60, but I'm not sure how well it would play with this kit (nor similarly with any of the other options below) or even if you can have a wireless room thermostat and it associated receiver as well as the receiver for the honeywell kit. What would you do, wire them in in parallel?

With the Househeat I'd want similarly 4 rad/thermo packs (£280) plus 2 more rad controllers (£80) or maybe 3 rad/thermo packs and a wireless boiler thermostat (£270 ish)

or using the Danfoss Z-Wave kits, 3 rad thermo's and wireless boiler thermo (£250 ish)

I can see a couple of issues with the Househeat system, 1 the rad valves are physically not well suited to my rads where the valves are all at the bottom of the rads and these units will stick out sideways and not look very neat, this should only be an aesthetic issue. 2 the limited control over temperature, the valves seem to have only a high and low setting, I like to set a bathroom one to high first thing, then lower through the day, possibly higher than the setback temp, but this may also be the case with all the other options. The honywell CM zone one might have a greater range in the comfort and set back temps so allowing, say the bedrooms to be heated less when not in use, but still appear to be limited to only the 2 values - comfort and setback.

Are there any reasonably priced options that can allow more temp options than effectively just a high and a low setting?

Where as some normal wireless room thermostats allow for multiple values for temps so you could have a high temp in the morning, off during the day - or just a lower setting, medium high in the evening and off at night.

Still plenty to think about.

Thanks for posting Fred, some useful info there

Regards

Martin

[MartinWilliams]

Originally Posted by dalethecaptain

In both of your situations it sounds like the pump continues to run because the CH water circuit has reached maximum temperature (controlled by the knob on the front of your boiler), but the demand for heating is only controlled by a simple on off timer. Fitting a room thermostat (boiler interlock thermostat) will have the same effect as turning the timer off when a set room temperature is reached, which will also stop the pump from running. It is about to become compulsory to use a separate timing thermostat in existing installations (for EPC's and all that)

Your description sounds correct. It's good to get confirmation that fitting a room thermostat will shut of the boiler properly, saving more energy.

Originally Posted by dalethecaptain

In MartinWilliams case, this can have the undesired effect of holding the heating off in the rest of the property, as you have such a large 'zone' on the ground floor. Your solution of using remote TRV units upstairs is pretty sound, it will allow you that extra automated control and should help you cut your energy use further, and when you fit a thermostat/timer downstairs you will be surprised what a difference it will make to your energy bills.

Good to hear too.

Originally Posted by dalethecaptain

The Danfoss units have built in Frost protection, this is however set by manually turning the power head, as is setting to the 'off' position. This over-rides the auto function.

I want to like the Danfoss valves as I want more Z-wave stuff that I can control with my remote and Z-Wave in general seems to have good potential, there is just very little of it available in the UK and what there is is a bit expensive. But the Danfoss remote valves seem to have the least flexibility of the options discussed in this thread.

Originally Posted by dalethecaptain

I use the Siemens REV200 which allows multiple on/off programs per day and a variable set back points,

Dan, do you have any other suggestions for wireless room thermostat timers that have variable set back, at a cheaper cost?

Regards

Martin

[MartinWilliams]

OMG! I've been looking on a site talking about the Hometronic set up, now we've seen that for £500 you can get 6 rad controllers and 1 receiver and 1 room controller. So where is the rest of the £2500 going (assuming a typical set up will need 2 lots of the kit) with a typical Hometronic set up. Below is a quote from that website.

Typical Costs?
Hometronic typically costs a similar amount to a solar hot water installation, in other words, £3500 or more, depending on the size of the property.

LOL, I'd emailed Sensible Heat yesterday (the sole UK suppliers of Hometronic) for a quote. They did say on their site I might be surprised, well I am already!
They've not got back to me yet but now I don't have high expectations....

[neilball]

Just thought I;d post some info about the Danfoss z-wave TRV and some general pointers about the HR80UKs.

Firstly the Danfoss unit is an update on a product they made many years ago where the control was hard wired, this wired control has now been replaced by the z-wave tranceiver. The unit uses a standard Danfoss actuator and therefore is as good (or not) at controlling the room temperature as any other Danfoss TRV - a small fluid-filled capsule expands and contract with changes in temperature thereby moving the pin on the valve body. By turing the TRV head you move the "pushing" part of the TRV head further or closer to the pin thereby changing the termpature at which it operates the valve. All conventioanl TRVs are like this and the crudeness of control is entirely due to this part of the design and not the proximity to the radiator. On the Danfoss z-wave unit the temperature for normal use is set at the TRV in the normal way and the switching signal simply allows the TRV to operate either at the normal comfort temperature or at a fixed 3 degree setback. So no ability to set discrete temperatures over z-wave, no feedback to boiler plant for heat-demand control, and no adjustment on the setback for different applications.

Before I talk too much about the HR80s then I do need to declare that I run the Scotland Office for Sensible Heat so I know a lot about the technical issues of the Honeywell kit but at the same time always try to give objective advice.

The Honeywell HR80s are a very different design that uses a fully modulating electric actuator to operate the valve and the Honeywell valve bodies also seem to have a reasonably linear control characteristic. Their other advantage is that they have a built-in sensor that is very accurrate. As I mentioned above, the location of the sensor by the radiator is not a problem in most cases - we have recorded and graphed the feedback from HR80s alongside Hometronic rooms sensors fitted at a normal stat location and found that while the actual measured temperatures are different tey do track each other quite closely. In fact the HR80 often reads lower than the conventional room sensor as it is lower in the room but also when the radiator is hot it creates dstrong convection currents which means it is the coolest room air that is pasing over the TRV head before the radiator heats it and send the hot air up the wall to ceiling level. HR80s also have a 2-way radio tranceiver so can feed back it's heating demand and also be told which temperature it is meant to be at and when. The transceiver is only powered for brief periods every 5 minutes or so as it is this element that creates the largest power drain. By taking this approach the 2 AA batteries in the HR80 can last for around 2 years. Finally the HR80 is actually a self-contained controller that uses some quite sophisticated control algorithms to give close control of temerpature without the overshoot/undershoot common with simple thermostatic control, this aspect is also self-tuning so learns the thermal characteristics of the room thereby increasing it's accurracy over time. The units also offer optimum start which works out the preheat time required independently for each zone. All of these features are common whether HR80s are used in a CM Zone system or Hometronic.

Although I have not seen the Househeat units it does sound like they are a similar in concept to the HR80s. You would need to ask Housegeat for details about the control strategies used to see just how alike they are. If it is a reasonable copy then it shows that Honeywell had a great idea on how to improve room-side control and zoning when the original HR models were introduced nearly 10 years ago.

I'll not post anything specific about Sensible Heat as it may break the forum rules, but if anyone does want to ask anything specific please feel free to PM me. For anyone who emailed via the website last week then you will have waited a little longer for a response as most of us were manning our stand at the Home Building & Renovating Show.

[MartinWilliams]

Originally Posted by neilball

Just thought I;d post some info about the Danfoss z-wave TRV and some general pointers about the HR80UKs.

Firstly the Danfoss unit is an update on a product they made many years ago where the control was hard wired, this wired control has now been replaced by the z-wave tranceiver. The unit uses a standard Danfoss actuator and therefore is as good (or not) at controlling the room temperature as any other Danfoss TRV - a small fluid-filled capsule expands and contract with changes in temperature thereby moving the pin on the valve body. By turing the TRV head you move the "pushing" part of the TRV head further or closer to the pin thereby changing the termpature at which it operates the valve. All conventioanl TRVs are like this and the crudeness of control is entirely due to this part of the design and not the proximity to the radiator. On the Danfoss z-wave unit the temperature for normal use is set at the TRV in the normal way and the switching signal simply allows the TRV to operate either at the normal comfort temperature or at a fixed 3 degree setback. So no ability to set discrete temperatures over z-wave, no feedback to boiler plant for heat-demand control, and no adjustment on the setback for different applications.

Before I talk too much about the HR80s then I do need to declare that I run the Scotland Office for Sensible Heat so I know a lot about the technical issues of the Honeywell kit but at the same time always try to give objective advice.

The Honeywell HR80s are a very different design that uses a fully modulating electric actuator to operate the valve and the Honeywell valve bodies also seem to have a reasonably linear control characteristic. Their other advantage is that they have a built-in sensor that is very accurrate. As I mentioned above, the location of the sensor by the radiator is not a problem in most cases - we have recorded and graphed the feedback from HR80s alongside Hometronic rooms sensors fitted at a normal stat location and found that while the actual measured temperatures are different tey do track each other quite closely. In fact the HR80 often reads lower than the conventional room sensor as it is lower in the room but also when the radiator is hot it creates dstrong convection currents which means it is the coolest room air that is pasing over the TRV head before the radiator heats it and send the hot air up the wall to ceiling level. HR80s also have a 2-way radio tranceiver so can feed back it's heating demand and also be told which temperature it is meant to be at and when. The transceiver is only powered for brief periods every 5 minutes or so as it is this element that creates the largest power drain. By taking this approach the 2 AA batteries in the HR80 can last for around 2 years. Finally the HR80 is actually a self-contained controller that uses some quite sophisticated control algorithms to give close control of temerpature without the overshoot/undershoot common with simple thermostatic control, this aspect is also self-tuning so learns the thermal characteristics of the room thereby increasing it's accurracy over time. The units also offer optimum start which works out the preheat time required independently for each zone. All of these features are common whether HR80s are used in a CM Zone system or Hometronic.

Although I have not seen the Househeat units it does sound like they are a similar in concept to the HR80s. You would need to ask Housegeat for details about the control strategies used to see just how alike they are. If it is a reasonable copy then it shows that Honeywell had a great idea on how to improve room-side control and zoning when the original HR models were introduced nearly 10 years ago.

I'll not post anything specific about Sensible Heat as it may break the forum rules, but if anyone does want to ask anything specific please feel free to PM me. For anyone who emailed via the website last week then you will have waited a little longer for a response as most of us were manning our stand at the Home Building & Renovating Show.

Thanks for the explanation regarding the Danfoss valves, I'd emailed them some questions but you've pretty much answered them now and in doing so have likely ruled them out for me, after all I can get the HouseHeat kits for about the same amount and those will give me some more funktionality and have more options when more kit is added.

The Honeywell CM Zone option still seems the most flexible but a bit more expensive.

For me the over riding factor will have to be price as the whole point of installing this stuff is to cut costs. I'm not the heaviest user of central heating, in fact for the last few years because my boiler has had a fault that stopped it working on the timer and would cause it to switch off if I ran the hot tap I haven't ran it much. I don't have a big house either, so my gas bills have never been large anyway. But the boiler is working now and it seems nuts to be heating the whole house and the zoning concept looks like a very good one.

Thanks Neil also for the more detailed explanation of the CM Zone system (Are you the NeilUK from Automated Home forum?).

I had read somewhere that sensible heat were at the NEC over the last few days so I'm not surprised I haven't heard back. And when I mailed them I hadn't made the connection between Honeywell and SensibleHeat. I'm pretty sure a man of modest means is not a target customer for the Hometronic set up, lol.

Actually, I have a question for you Neil. I've noticed that the HC60NG Relay module is also part of the Honeywell CMT927 (CM927) Wireless Programmable Room Thermostat kit, so will I be able to integrate that room thermostat into the CM zone pack, if so that will give another zone.

Regards

Martin