Testing Smart Homes

[PEG]

I remember a project of 5 new-build "smart homes",with a right arrogant pair of nouveau cool developers...

One was up to DPC,with temp electric,water,and gas,drains to connect.

I spent a few hours,checking the layout,and had spotted a few issues,and had questions to ask. The pair had a problem with my asks,and responses varied from "not your problem" to "i think others will have considered that...."

One my questions,i decided to keep to my self....it concerned the fact that on the drawings,it had a direct connection to the combined waste,pavement side,but a quick lid lift,showed the invert at that position to be 300mm higher than the properties....oops...

They were going to need either a house jack....or a non-specified pumping station....

The other 4 are now built,the original pair having gone bump,and they are 1M higher than the first

My point is that you can aspire to the most smart,eco friendly hi-tech house in the world,but the obsession with these ideals,can sometimes take ones eye off the fundamentals ...and gravity is better for the planet than two pumps cycling day and night...

 

[EricMark]

To cure a problem with the sun on bay windows causing room temperature to shoot up, but radiators were still hot, I fitted some electronic heads on the TRV's.

Since these had the option for geofencing I thought why not, however they were too clever for their own good, they have anti-hysteresis software, and this means at 12 degs and set to 20 degs first 6 degs is fast, but last 2 degs it takes hour and a half designed to stop it over shooting.

However in coolest days, temperature would rarely drop more than 3 degs in 8 hours, so unless you worked 2 hours from home it was rather pointless.

Also idea was rooms can be set to different temperatures, however insulation to outside was very good, but room to room rather poor, so even with one bedroom switched totally off, it was only 2 degs cooler than other rooms.

The electronic valves were faster acting to over temperature and they reduced the spike by 4 degs, however having a TRV set to deg C rather than * to 6 one was aware when it allowed the room to over heat, and it was found the setting of lock shield valve could be critical, however it was not the same with all radiators, then realised why, with TRV on supply the sensor heats up quickly, but if on return whole radiator can get hot before the sensor gets any heat.

It is all well and good saying the valve is bi-directional but unless fitted on supply side, they over shoot rather easy.

So it was found the main advantage of the electronic head was not wifi, or geofencing but having the temperature displayed in degs C, so one knows if the lock shield valve needs opening or closing to get the temperature set same as actual temperature, with TRV on return by turning down the lock shield valve the radiators heats up more gradually so the TRV has time to act.

So in most rooms setting lock shield so electronic head gets correct temperature then swapping back to wax, and the wax worked nearly as well as the electronic.

But even a simple wireless thermostat instead of hard wired can cause health and safety issues, when living with Mother I would realise when some thing had gone wrong, but when we only visited I had changed the Honeywell wireless thermostat for a Horstmann programmable wireless thermostat so at night the house would not get too cold, with Mother living down stairs the ground floor rooms get a lot colder over night.

However I visited to find room at 28 degs C, it seems the Honeywell had a fail safe, if no signal in 30 minutes it switched off, however that was not case with Horstmann, happened a few times, placed in a draw, to flat batteries result was same, and 28 degs C far to hot for a 90 year old.

I am sure Horstmann do make better models, but looking on the sales info neither say about fail safe, you have to read deep into the instructions.

Be it closing a window, or heating a room, as the installer we need to consider health and safety, with a Velox window in the roof it is unlikely any one will get their fingers in the works for a blind closer, but the same device on a patio door, and it could injure a child.

But do we have the skill required? We can't know everything, once pointed out is seems simple common sense, but until pointed out you do not see the problem.

An example is disabled parking bays, just look how many have a post in the centre so car rear door can't be opened and ramp dropped, so people have to be unloaded and loaded into the traffic, unless you are involved with some one in a wheel chair, you simply don't see the problem.

Be it a security gate, or window blind, we simply don't have the training to identify danger, and that raises the question should be even try? If it complies with electrical regulations, should we worry about the others? Clearly in some cases yes, location of sockets for use by disabled for example, but again as installer yes, as part of an EICR should we say when a socket it too near to corner of a room, too high, or too low?

 

[Simon47]

... it was not the same with all radiators, then realised why, with TRV on supply the sensor heats up quickly, but if on return whole radiator can get hot before the sensor gets any heat.

It is all well and good saying the valve is bi-directional but unless fitted on supply side, they over shoot rather easy.

Actually, the sensor getting heat from the pipework is a "fault". It should only be sensing the air temp - and in that respect, an electronic head can (depending on the software) react much more quickly since the wax device needs time and temperature difference to absorb/lose heat.
That is why it is recommended that TRVs are on the return, and the heads are horizontal so as to be away from radiant heat from the rad and warm convection from the pipe.

The way you've described it with the TRV on the supply so it's affected by heat from the pipe, it means the TRV always operating with an offset since the pipe will (nominally) always be the same temp other than when the TRV is completely closed.
So when the room reaches temp and the TRV closes off, the pipe will cool, the TRV head will cool a bit - and so open slightly and leave the rad slightly warm.
A TRV can't work magic, it's important that the system is balanced - the combination of flow temp, flow rate (lockshield setting), rad size needs to be appropriate to the room. As you've found, if the lockshield is too open, then the rad can fill quickly with more hot water than is needed for the heat demands of the room.

But at the end of the day, it's a control loop. Without careful tuning (and a PID control function) then it's going to struggle - especially when subjected to a step change in setpoint.

This will be why your electronic heads have this "slow down as we approach the setpoint" feature. It gives a quick resonse to a large error, but slows things down where it matters. It's the ONLY way to make a generic electronic TRV that will "just work" for the majority of users - few users could cope with PID tuning..

 

[EricMark]

Actually, the sensor getting heat from the pipework is a "fault". It should only be sensing the air temp.

The eTRV has two sensors, one for air and one for water, the water one compensates the air one for the heat it gets direct from the radiator, this is part of the design, not a fault. At least for the MiHome Energenie I have fitted.

But there is a limit to how fast it can open or close,

After 5 seconds the motor will start up to exercise the valve stem. You may need to wait several minutes for this process to complete.

this is from the instructions to fit batteries, and if as clearly can happen the boiler is not running, the valve can open over the required amount, when boiler starts and it detects the heat, it starts to close, so flow is modulated rather than simply switched off/on.

However if fitted on the return it starts to modulate slower than on feed, I know as I have used them both on feed and return, so when fitted on feed clearly the lock shield valve still requires trimming, but it is no where near as critical as when fitted on the return.

 

[Simon47]

The eTRV has two sensors, one for air and one for water, the water one compensates the air one for the heat it gets direct from the radiator, this is part of the design, not a fault. At least for the MiHome Energenie I have fitted.

That's specific to the brand of eTRVs you have. It doesn't apply to all eTRVs, and AFAIK it doesn't apply at all to any non-electronic TRV heads. It does demonstrate that you need to understand the specifics of whatever you are installing/using.

 

[EricMark]

I note the cheaper TRV £10 or £15 with bluetooth eqiva has an offset temperature to allow for the heat from the radiator, +/- 3.5 degrees C max, mainly I think for when multiple valves fitted in one room.

With electronic heads down to £10 one wonders why people still use the old wax type, I suppose don't want to change batteries?

However it means paying £40 for a head, £30 is just so you can adjust it remotely, so is it really worth £30 to adjust from your phone when away from home?

OK there are other advantages, the Hive TRV states "If you also have a Hive thermostat you can enable Heat On Demand to automatically boost your heating when a radiator needs heat." it also says "Note: Hive Hub 1 does not support Hive Radiator Valves." but be it Tado, EvoHome, Hive or Nest much depends on how far you going with the installation, boiler type, and local wiring which will work within a reasonable price.

But how does one compare the options, take Hive and Nest as an example, Hive wall thermostat is cheaper than Nest, but the TRV's are much more expensive, and Nest will work with OpenTherm, Hive will not, but Nest the TRV simply follows the wall thermostat where Hive TRV switches on the boiler through the thermostat. Nest both Gen 3 and e are volt free, Hive only single channel is volt free, so both have plus and minus features which take a lot of reading to find out.

I like the ability to connect Nest thermostat to heat link hard wired so not relying on wireless link, but it often depends what wiring is already installed.

But back to question, how do you test? Or even should it be tested? Well the Nest heat link instructions say the earth is only required when the thermostat is hard wired, so I read that as earth is required when hard wired thermostat is used.

At the heat link easy to test the earth, but at the wall thermostat, first problem is how do you gain access, I know the round lump simply pulls off, but unless you have fitted one, you would be a brave man just to tug. Then you need to find another earth to test it to.

So the box of adaptors gets larger and larger, where do you stop? This house I had to dig out the living room ceiling rose to change it, OK to change it, but just to test? It now has a Maestro plug in ceiling rose, so all you need to do is unplug the chandelier, and plug in your test adaptor, if you have one, otherwise you have to remove plug from chandelier, now a Hager Klik ceiling rose is only £4 so a spare plug for them OK, but the Maestro is £23 having one of them in tool kit is unlikely.

And how many instruction manuals are you going to read? As said Nest is class II unless thermostat hard wired, so what about the rest, just because there is an earth terminal does not mean it has to be earthed.

When I did my C&G 2391 all those years ago, it took me around an hour to test the board used for the test, at that rate it would take a day even for the simplest of house. To just test one ceiling rose earth one needs a set of steps, and if using an electronic switch getting power not easy.

If I said to test a house it will take 12 hours at £15 an hour I don't think I would get much work?

So big question, is the boiler, thermostat, programmer etc part of the installation, or is it an appliance? Does it come within the remit of doing an electrical installation condition report? Supply to boiler yes, everything supplied from the boiler, not so sure.