vince31
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Location: Swindon or Blackpool, depends on day of the week!

Room by Room central heating control

Sat Oct 05, 2013 8:46 pm

ok, my project plan is to use my Pi to sense and control the temperature in each room or Zone of my house. This will include access via a web page so anyone in the family can change the temp in their rooms via the PC or their phone. Of course the main idea is to be more efficient in the heating of rooms as they are needed rather than heat the whole house based on one sensor in the hallway or lounge. Its a 4 bed house but sometimes there is only one person in the house during the week, and I need a challenge anyway!
Ive already got 10x DS1820 temp sensors connected in parallel to GPIO4 and they are each reporting temp sucessfully using my own python code. Ive calibrated them all by having them all next to each other and taking the avarage reading from them all, they were all within 0.3 dec C anyway. I have also run one on a 15m length of wire and it still sends data consistently to the Pi. I think I will need around 22 temp sensors in all to cover all the rooms, outside, loft, garage, hot water tank etc. So hopefully this will still work ok.
The Pi will switch each rooms standard hot water radiator on and off on demand based on the detected and selected room temperatures. To switch the radiator on and off electrically I have sourced a supply of standard nylon solenoid valves, that are good for up to 90 deg C with standard 15mm connectors. I plan to use one for each radiator feed pipe (not needed for the return pipe). These valves are controlled by 240v AC, same as in your washing machine etc. I plan to get power to these valves via remote controlled sockets plugged into the mains socket close to the radiator. Ive already got 15 of these up and running reliably commanded wirelessly by the Pi.
Im posting here to run it by you guys and halp me to understand where the issues are likely to be.
Cheers
Vince31

boyoh
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Re: Room by Room central heating control

Sat Oct 05, 2013 10:17 pm

hope you have a good circulating pump on your heating system
I'm no plumber, But will it keep handling the sudden changes
In circulating pressure,due to valves opening and closing.
You might save on gas cost, but have thought about your
Electricity bill, I hope you have great success with your project
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

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simonmcc
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Re: Room by Room central heating control

Mon Oct 07, 2013 8:16 am

Hi Vince31

I also control my central heating using a Raspberry pi, and it has been working 24/7 flawlessly for months now. Power cuts etc don't seem to have been an issue.

My system is not nearly as complex as yours (mine is just like a complicated timer) and doesn't take temperature in the rooms into account.

Do you have a link to the 240v valve you are using?
simonmcc.blogspot.com/search/label/pi

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Cancelor
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Re: Room by Room central heating control

Mon Oct 07, 2013 9:50 am

Sounds like you are nearly done! :)

My first thought was concerning expansion and contraction of the water in the pipes but as long as you just have one electric valve per radiator I'm sure you will be okay. Do you have a naturally vented system (tank in the attic) or an expansion chamber (usually a red tank near the boiler)

Even so, if all radiators are off then I would try and make sure the boiler does not come on.

The direction of water flow through the valves is probably critical, the wrong way round and water might push past the valve and/or make a lot of noise (hammering)

For safety make absolutely certain the valves can not be reached by little fingers as the electrical connections on some valves assume that they are securely inside a case of some sort.

I'd like to see a link to these valves as well; are you in the UK?
Can't find the thread you want? Try googling : YourSearchHere site:raspberrypi.org

PaulCheffus
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Re: Room by Room central heating control

Wed Oct 09, 2013 3:31 pm

Cancelor wrote:Even so, if all radiators are off then I would try and make sure the boiler does not come on.
Hi

In our central heating system one of the radiators cannot be turned off to ensure there is always somewhere for the water to go if all others are off.

Cheers

Paul
Procrastination - The Thief of Time.

vince31
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Re: Room by Room central heating control

Wed Oct 09, 2013 10:37 pm

Hi guys, thanks for the comments and hints. The valves I intend to use for the radiators are from betavalve.com, check out their plastic valve range. As you pointed out, I will have to make sure the electrical connections are safe and out of harms way.
Good points about the direction of water flow through the valves and making sure there are no hydraulic locks in the system to allow for water expansion and contraction with change in temp. My central heating system also has the standard header expansion tank in the loft.
I also intend to control the central heating pump directly from the Pi too, maybe directly via a relay on my sainsmart board rather than chance a wireless link, so I can make sure the pump is off when there is no demand and only comes on after a radiator valve is selected open.
I currently have the system under test running 8 of the temp sensors in various rooms and then wirelessly controlling 2 small fan heaters via the Maplin sockets in 2 of the rooms for now just so I can iron out any bugs in my program and chech the temp control algorithms Im setting up.
As for using too much electric driving the pump, well I dont really see that being any different to the standard timer driving the pump, just that I will be switching it on and off more often I guess but the overall run time will be about the same.
In my design I will have to make sure its all fail safe too, I dont want one of the radiator valves staying open when it should be shut and the heating to continue to run hotter and hotter whilst Im away from home, so Im trying to design in as much fail safe as I can. At the moment the project is still in test and programme development phase but all looking positive at the moment. Currently making sure the ever more complex algorithms work as I intend them to in th python code Im hacking together. Latest test tonight has been updating and testing the system responsiveness and setting up the sensitivity to temp change to make sure it works ok and the wireless sockets respond to every command.
http://www.betavalve.com/plastic-solenoid-valves

stevend
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Re: Room by Room central heating control

Fri Oct 11, 2013 12:39 pm

I'm part way through implementing a similar system, and thought I'd mention my approach to the radiator valves, which is slightly different.
I'm buying the http://www.conrad-electronic.co.uk/ce/e ... ThermostatHoneywell HR20 electronic thermostatic valve, which can operate standalone and adjusts the valve position to control the room temperature.
This valve has been reverse engineered, and open source software is available - see http://embdev.net/topic/118781. I've taken this code and modified it to support RS-485 communication, with the ability to send the room temperature (and 'window open' status) to the valve (see the forum thread for link to my code). This allows the room temperature measurement point(s) to be well away from the radiator being controlled. As with the OP, I shall be getting the temperature from one or more OWD temperature sensors per room.
I haven't yet decided whether to use the Raspi to read the temperature and forward it to the valves, or whether to use an intermediate processor for this.
One advantage of this system is that, as long as the valve has power, it falls back to a sensible mode of operation if the management processor is off-line for any reason. And the HR20 is, I think, a similar cost to alternative valves.

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simonmcc
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Re: Room by Room central heating control

Fri Oct 11, 2013 12:56 pm

I looked at these valves too, because they look promising, but for zone control I find them to be of no use because of the long cycle time, off->on is somewhere in the region of a few minutes, which is the length of time a lot of my programs are on for
simonmcc.blogspot.com/search/label/pi

PiRat
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Re: Room by Room central heating control

Fri Oct 11, 2013 1:46 pm

just a quick comment on the valves, I know that some boilers will keep the pump running after they cut the flame to stop itself over heating. So its common for a system to have some sort of bypass fitted or one rad that can't be switched off to give somewhere for the water to flow.

It's easy to see if the pump stops before the boiler as it's normally followed by a lot of banging and shaking of the pipes :D

PiGraham
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Re: Room by Room central heating control

Fri Oct 11, 2013 2:40 pm

stevend wrote:I'm part way through implementing a similar system, and thought I'd mention my approach to the radiator valves, which is slightly different.
I'm buying the http://www.conrad-electronic.co.uk/ce/e ... tHoneywell HR20 electronic thermostatic valve, which can operate standalone and adjusts the valve position to control the room temperature.
On that same site are these:

eQ-3 MAX! Wireless Radiator Thermostat

868MHz bidirectional radio controlled thermostat / valves. Has anyone tried them?

Maybe they could be Pi-controlled through one of these.
MICROCHIP - MRF89XAM8A-I/RM - MODULE, RF, TRANSCIEVER, 868MHZ

stevend
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Re: Room by Room central heating control

Fri Oct 11, 2013 4:54 pm

simonmcc wrote:I looked at these valves too, because they look promising, but for zone control I find them to be of no use because of the long cycle time, off->on is somewhere in the region of a few minutes, which is the length of time a lot of my programs are on for
Bear in mind that the 'response time' of affecting the temperature in a room, including that of potentially heating up water and circulating it round to a radiator, is measured in minutes. (IIRC the response time of a standard wax-based thermostatic valve is about 20 minutes). So everything is incredibly slow to respond, compared with, say, a robot.
And the Honeywell valves can be partially open, so the open to shut response time is not too important. Its more a matter of having a good control system to manage everything.

stevend
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Re: Room by Room central heating control

Fri Oct 11, 2013 4:56 pm

PiRat wrote:just a quick comment on the valves, I know that some boilers will keep the pump running after they cut the flame to stop itself over heating. So its common for a system to have some sort of bypass fitted or one rad that can't be switched off to give somewhere for the water to flow.

It's easy to see if the pump stops before the boiler as it's normally followed by a lot of banging and shaking of the pipes :D
On the systems I've come across, the pump and the boiler are connected in parallel, so they turn on and off together.

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simonmcc
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Re: Room by Room central heating control

Fri Oct 11, 2013 5:05 pm

stevend wrote:
simonmcc wrote:I looked at these valves too, because they look promising, but for zone control I find them to be of no use because of the long cycle time, off->on is somewhere in the region of a few minutes, which is the length of time a lot of my programs are on for
Bear in mind that the 'response time' of affecting the temperature in a room, including that of potentially heating up water and circulating it round to a radiator, is measured in minutes. (IIRC the response time of a standard wax-based thermostatic valve is about 20 minutes). So everything is incredibly slow to respond, compared with, say, a robot.
And the Honeywell valves can be partially open, so the open to shut response time is not too important. Its more a matter of having a good control system to manage everything.
I know this is true in general, and also in 'normal' systems. Mine isn't normal. We have quite a lot of radiators, and a big boiler. The boiler can give a significant amount of heat to the house in 5 minutes, so for example today, I had it programmed for 10 minutes per hour, which works out at 2x 5 minute periods, once each half hour.

Our house has poor thermostatic control, so timed control works better. What I would love is to be able to retrofit valves to the radiators that allowed me to turn specific rooms on and off.

I've also looked into some of the wireless thermostat room systems, and they *might* work for me, but it would be a lot of expense, and I'd have to make a lot of changes to my controller to work with them.

If I had my way I would have a manifold in to centralise the radiator connections, and use the standard motor valves for each zone, although they are big and relatively noisy they are almost instant.

I would even be interested in a non-wireless valve if it operated faster.
simonmcc.blogspot.com/search/label/pi

stevend
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Re: Room by Room central heating control

Sat Oct 12, 2013 9:16 pm

simonmcc wrote: What I would love is to be able to retrofit valves to the radiators that allowed me to turn specific rooms on and off.
Some of the electronic thermostatic valves might be a good basis for this, since they fit onto a standard radiator valve with M30 thread - relatively straightforward and economical to retrofit. You could then use as a simple on/off valve, since speed wouldn't be important. You'd need to find a valve that allows 'manual' control of the valve position; on a quick look the HR20/OpenHR20 doesn't currently support this, but it should be relatively straightforward to add.

patrocks
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Re: Room by Room central heating control

Sun Oct 13, 2013 8:09 am

[quote="simonmcc. The boiler can give a significant amount of heat to the house in 5 minutes, so for example today, I had it programmed for 10 minutes per hour, which works out at 2x 5 minute periods, once each half hour.

Our house has poor thermostatic control, so timed control works better. I would even be interested in a non-wireless valve if it operated faster.[/quote]

Are you not trying to fix the problem in the wrong way? Do you think the boiler oversized? If so the plan to close off rooms will make the issue of the boiler size worse.

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simonmcc
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Re: Room by Room central heating control

Mon Oct 14, 2013 8:42 am

patrocks wrote:
Are you not trying to fix the problem in the wrong way? Do you think the boiler oversized? If so the plan to close off rooms will make the issue of the boiler size worse.
I think the boiler is about the correct size for the house. What I'd need to do to really solve the problem is have each room as a zone on its own, thermostatically controlled, and also time switched. This would mean that different rooms could be different temperatures, as required, and also that if only 3 rooms are being used, only 3 rooms would be being heated.

I currently don't see any solution that allows me to reliably retrofit this functionality.
simonmcc.blogspot.com/search/label/pi

bernfriman
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Re: Room by Room central heating control

Fri Nov 01, 2013 3:21 pm

Vince,

I'm interested in how the DS1820 perform. I've read that long wires cause difficulties and the types of wire and layout matter.

In my application, I'm hoping to have 5 of the sensors within 2 metres of the Pi, but two more 8 and 15 metres away using existing 3-core 1.5mm lighting cable which is already in place. I've seen that Cat5 cable is recommended but I want to avoid running new wires. What wire are you using? Is the sensor wiring configured as a star or a bus?

My plan B is to use analogue temperature sensors for the two distant ones but I'll try it with the digital ones first as it makes the hardware and software easier.

amofok17
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Re: Room by Room central heating control

Tue Nov 05, 2013 10:19 pm

I have 5 of those DS1820 sensors connected to a clone Arduino atmega328 chip which then sends data to the Pi over serial. 4 I have connected to one digital pin via aprox 25m of 2 core doorbell/speaker wire and not had any problem, the 5th one is connected directly to a different digital pin.

Hugh Jarse
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Re: Room by Room central heating control

Wed Nov 06, 2013 3:49 pm

Interesting project. I have a couple of comments.

1. Do you intend to implement some form of hysteresis to prevent the solenoids chattering?
2. I am not sure which solenoids you have chosen but there are latching solenoids available which only require a pulse when the state is to be changed.

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r4049zt
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Re: Room by Room central heating control

Wed Nov 06, 2013 6:03 pm

My Luddite Opinion
Each room can have a self-contained bimetallic thermostat on each radiator. The effort of changing the radiator thermostat from "4" to "2" is about the same as finding an iphone app to do that with much less wiring to get it set up. == none. I suppose that you are after the data logging capability of the rPi and the cred of making a smart home.

V_1
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Re: Room by Room central heating control

Wed Nov 06, 2013 9:19 pm

bernfirman,

I have been using 8 DS1820 1-wire sensors on a long bus for well over a year now. The Bus length is up to 30 meters to the furthest sensor and they are spread along the bus dropping down on long Ts (5-6 meters depending on the location in the room) to the sensors in the various rooms.
The Bus is not Cat5 I'm using 3 cores from common 6-core alarm cable as I had it to hand and its easy to get through tight spaces. The trick for reliability I think is to use a powered 1-wire bus (I'm stealing +5v from the USB port - probably a bit cheeky and bad electronic practice :oops: ) but its been working great for me :D
I am logging temperatures from these sensors every 5 minutes for well over a year and to my knowledge I dont think the thing has missed a beat.
Before I added power to the bus and was just relying on parasite power it was quite unreliable even on short cable runs.

w_idget
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Re: Room by Room central heating control

Fri Nov 15, 2013 6:00 pm

I've been considering a similar project for far too long but haven't managed to get started yet. My overall aim is to reduce energy consumption and improve comfort with intelligent management of devices - Hot Water, Central Heating, Radiators, Curtains & Lighting. Much the same as many of the ideas above.

However, for controlling the individual radiators I've been looking at "Thermo-electric actuators", and in particular something like the series 656 from Caleffi. I've no experience of this item but it looks like it will do what I want in a neatly encapsulated unit.

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DougieLawson
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Re: Room by Room central heating control

Fri Nov 15, 2013 8:59 pm

w_idget wrote: However, for controlling the individual radiators I've been looking at "Thermo-electric actuators", and in particular something like the series 656 from Caleffi. I've no experience of this item but it looks like it will do what I want in a neatly encapsulated unit.
The biggest problem with those electronically actuated radiator valves is that they're running from a 220V supply. That means you have to build something that will use the 3V3 signal from your RPi GPIO pins to switch mains. That brings a whole bunch of safety problems along for the ride.
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simonmcc
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Re: Room by Room central heating control

Mon Nov 18, 2013 3:03 pm

DougieLawson wrote:
w_idget wrote: However, for controlling the individual radiators I've been looking at "Thermo-electric actuators", and in particular something like the series 656 from Caleffi. I've no experience of this item but it looks like it will do what I want in a neatly encapsulated unit.
The biggest problem with those electronically actuated radiator valves is that they're running from a 220V supply. That means you have to build something that will use the 3V3 signal from your RPi GPIO pins to switch mains. That brings a whole bunch of safety problems along for the ride.
Is there not a 24v version of them too? That would help with the safety aspect
simonmcc.blogspot.com/search/label/pi

borrie
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Re: Room by Room central heating control

Thu Nov 20, 2014 9:38 am

Steven,

I know this is a huge question but I hope you can help me out... :)

First of all I've never used rapsberry pi, so I'm a complete newbie, I just bought 2 Honeywell HR20's to do some basic controlling of 2 rooms and then I stumbled on the "hack the valves and put a transmitter in it page" That got me thinking :)

Now I want to create a thermostat with raspberry pi with a display to do all the "normal" thermostat things like site up a schedule for the central heating" accessible via internet and also combine the 2 HR20 on the same page so i can turn them on / off via internet

So, do you have a blog with detailed steps and maybe a hardware list to do the setup? (I imagine you have accomplished your setup?)

This would be great!

Borrie

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