Control of boiler and hot water.

joebre

Some time ago, I got a PLC and cylinder stat installed with a view to bringing the boiler back on if the temperature fell below a certain level.
PLC was LAE AC 5.
Guy is used in not around.
I managed to mess up the settings and am now using the boiler on timer only.
My question is can I use the PLC to bring on the boiler when the temperature in the cylinder falls bellow the set temperature (Set Point Low)
A friend thought the boiler would only come on within the time range settings or manual override.

Doolittle51

This can be achieved with just a cylinder stat (or 2), a PLC is a bit overkill for this type of control, unless it's used for other things too?

joebre

Doolittle51 wrote: »

This can be achieved with just a cylinder stat (or 2), a PLC is a bit overkill for this type of control, unless it's used for other things too?

Didn't think a cylinder stat would work. Tell me more.
What I really want to do is turn the boiler back on when the water falls below a certain temperature, outside of the set times.
Don't want the boiler to be on all the time.
We run a small bed & breakfast and the usage times can be irregular and the last thing you want is to have no hot water.

Doolittle51

joebre wrote: »

What I really want to do is turn the boiler back on when the water falls below a certain temperature, outside of the set times

To achieve that without a PLC is a bit tricky alright, but it is possible. You'd need 2 cylinder stats, a double pole relay and a latching relay. And another relay if your timeswitch doesn't have both NO and NC contacts.

joebre

Doolittle51 wrote: »

To achieve that without a PLC is a bit tricky alright, but it is possible. You'd need 2 cylinder stats, a double pole relay and a latching relay. And another relay if your timeswitch doesn't have both NO and NC contacts.

Sounds as tricky as my PLC.
I think my PLC was working but that the electrician had set SPL too high.
Since I changed it, I can get to to come on again, when the temperature goes below SPL and it's outside it's timer settings.
Guy that looked at it didn't think boiler would come on when it was outside the set times !

2011

joebre wrote: »

Didn't think a cylinder stat would work. Tell me more.
What I really want to do is turn the boiler back on when the water falls below a certain temperature, outside of the set times.

A cylinder stat and a time clock can achieve this quite easily.

If you want to get a bit more fancy you can do what I did. I stalled a number of Sonoff TH16 devices to control my heating system. For small money this achieves the following:
1) Each zone (I have two but it will work for many more) can be controlled on a timer.
2) The temperature of rooms or hot water can be viewed on my smartphone via a free app.
3) The boiler can be switched on or off from my smartphone.
4) Heating can be controlled by temperature, time or both.
5) Timers, schedules and temperature set points can all be configured from the app.

Lenar3556

Is that thermocouple effective to monitor the cylinder temp? - are you using a thermostat pocket of some description?

How do you find Sonoff in terms of reliability? Does it need ‘minding’? Occasional rebooting or anything like that?

Switching differential seems to be one of the needs in this case - can that be adjusted on the until linked?

One other query on Sonoff - Can you have devices on other networks all feeding into the same app. i.e heating controls at another house?

2011

Lenar3556 wrote: »

Is that thermocouple effective to monitor the cylinder temp?

They are not great for this type of application for a number of reasons. Generally thermocouples (such as K type) are used for far higher temperature ranges (I last used them on a furnace) or when a rapid response time is a requirement (which is not a requirement in this case). The ideal temperature sensor for this type of application would be something like a PT100.

- are you using a thermostat pocket of some description?

No, that would be best but I don't have that option. This would reduce the response time which is a "nice to have" rather than particularly important. I simply strapped the sensor to the outside of the hot water tank. It works quite well.

How do you find Sonoff in terms of reliability? Does it need ‘minding’? Occasional rebooting or anything like that?

No reliability issues ever. Once I had an issue pairing but once it paired it has been solid ever since.

Switching differential seems to be one of the needs in this case - can that be adjusted on the until linked?

Yes, I can programme the switch off temperature and the switch off. This allows hysteresis adjustment.

One other query on Sonoff - Can you have devices on other networks all feeding into the same app. i.e heating controls at another house?

I believe that this is possible but I have never attempted this. Devices can be grouped per home on the app.

Lenar3556

Thanks for the above!

Stoner

Lenar3556 wrote: »

Thanks for the above!

Agreed with 2011

Zero issues with sonoff. You can do a lot more with them if you hack them. However they download their settings and work away off line too.

Yes you can add items from other networks

You are really just pushing commands down to to them from their cloud service

I've my mother's heating on mine, I share that device with others so that they can turn her heating on if she's out with them

Sonoff allows to to have have guest access to devices too.

tweek84

Stoner wrote: »

Agreed with 2011

Zero issues with sonoff. You can do a lot more with them if you hack them. However they download their settings and work away off line too.

Yes you can add items from other networks

You are really just pushing commands down to to them from their cloud service

I've my mother's heating on mine, I share that device with others so that they can turn her heating on if she's out with them

Sonoff allows to to have have guest access to devices too.

Sonoff devices are a great bit of kit for the price, i am hoping to make up a demo board with their devices before the summer.
I have only had one issue with them that was phantom switching i had mine controlling my heating, i checked the logs it was switching on at night, (talked to wifey she hadn't touched it :eek: we has this conversation before and it had turned out it was her ) so i set up a camera near the device and sure enough it was switching itself on and off at random times on different nights so just disconnected rebooted it and no problems since.

2011

tweek84 wrote: »

I have only had one issue with them that was phantom switching

I never heard of this. I think you were just unlucky and got a faulty device. Certainly not the norm.

tweek84

2011 wrote: »

I never heard of this. I think you were just unlucky and got a faulty device. Certainly not the norm.

Yes it is unusual out of the 5 devices I have it only happened to 1, It was mentioned on one sonoff user groups that is where I got the solution