The right solenoid valve for the job

[Aelita Sophie]

So basically, I want to control the temperature per room by controlling every single heating radiator with a Solenoid Valve.

Some specs of the heating system that I know:

- Runs between 1.7 to 2.4 bar

- Peaks to 75-80 Celcius (167F - 176F / 348.15 - 353.15 Kelvin)

- 3/4 inch tubes.

 

I prefer a solenoid operating at 5v or 12v. Power consumption isn't a big deal. I'm on a budget. So the cheaper the better, as long the quality is good enough and well within spec.

It will be controlled by an ESP8266 or ESP12-E to be precise in combination with a Temperature sensor somewhere else in the room and a relay to switch the solenoid on/off.

 

I've been looking at these solenoid valves. Which should be good enough or do I need to search for better ones.

 

https://www.banggood.com/DC12V-Two-Way-Solenoid-Valve-Water-Valve-p-1196614.html

https://www.banggood.com/34-inch-12V-DC-VDC-Slim-Brass-Electric-Solenoid-Valve-NPSM-Gas-Water-Air-NC-p-1161984.html

https://www.banggood.com/34-Inch-Electric-Solenoid-Valve-12V-DC-VDC-Slim-Brass-NPSM-Gas-Water-Air-NC-p-1192177.html

 

Feel free to link other Solenoid valves.

[Dujith]

Only the first one will be able to keep handling those temps. Are the latter 2 are rated for 80C Max. And i would never use anything at its limit if it needs to run for a long time.

Any reason you have to use 12-5V? Higher voltage is always better for longer distance to the solenoid. (voltage drop due to resistance on wire)

I am saying this because solenoids have 1 major drawback: if you do not engage them fully they burn out.

 

You might have 2-3 Ohms of resistance to one of your solenoids and the coil on that is 26.

With 12V and a total of 29Ohm you will have a current of 0,414Amps which will put just 10,7V on the coil.

I cannot find a datasheet but that might be just enough or just to little.

 

Using a higher voltage like 24V will solve most of those problems

[Dujith]

Also: While these might seem cheap you need to add the cost of fittings to get it to work on CV tubing (22mm/15mm)

And that will add up quickly  and you will be introducing alot more connections where leaks can occur.

[Aelita Sophie]

6 minutes ago, Dujith said:

Only the first one will be able to keep handling those temps. Are the latter 2 are rated for 80C Max. And i would never use anything at its limit if it needs to run for a long time.

Any reason you have to use 12-5V? Higher voltage is always better for longer distance to the solenoid. (voltage drop due to resistance on wire)

I am saying this because solenoids have 1 major drawback: if you do not engage them fully they burn out.

 

You might have 2-3 Ohms of resistance to one of your solenoids and the coil on that is 26.

With 12V and a total of 29Ohm you will have a current of 0,414Amps which will put just 10,7V on the coil.

I cannot find a datasheet but that might be just enough or just to little.

 

Using a higher voltage like 24V will solve most of those problems

The powersupply and ESP12-E will be placed right next to the solenoid. So the cable run would only be a few inches/centimeters. That shouldn't deliver to much resistance. Point being is that I am using 12v supplies in general for every room for the ESP's (with buck down converters to 5v)

[Aelita Sophie]

1 minute ago, Dujith said:

Also: While these might seem cheap you need to add the cost of fittings to get it to work on CV tubing (22mm/15mm)

And that will add up quickly  and you will be introducing alot more connections where leaks can occur.

I'll be using plumbers tape (which is mostly used with gas tubes) to avoid leaks. I've also been thinking about soldering it shut. So far I've changed out a few radiators etc, and have not seen any leaks so far. I might be just lucky, or maybe I just got a feel for it. That I don't know xD. CV fittings aren't to costly. Few euro's a piece.

[Dujith]

I realize they are cheap  but you will need 2 for each solenoid. And depending on how many solenoids you use it can add up

Having said that i have a few questions:

- How many solenoids are you going to use?

- Where will they be placed? near to the radiator? if so wouldn't an electric knop be a better option? 

[Aelita Sophie]

2 minutes ago, Dujith said:

I realize they are cheap  but you will need 2 for each solenoid. And depending on how many solenoids you use it can add up

Having said that i have a few questions:

- How many solenoids are you going to use?

- Where will they be placed? near to the radiator? if so wouldn't an electric knop be a better option? 

I'll be using 7 solenoids, as I have 7 radiators. (One per room/corridor)

They will be placed right after the T-split to the radiator. An electric knob would probably make it easier. (Just replacing the mechanical knob right?) But I haven't found anything like it for around the same price that I can control with an ESP12-E. If you have any suggestions, by all means.

[Dujith]

Most cheap one will be 230V (10Euro off brand, 20-30Euro honeywell/ect)

I take it the powersupply will be used in a 230V socket so you'll just need to switch a relay for the radiator knob.

Something like this: 12V Finder relay

 

For the knob something like this: Danfoss or Offbrand

 

[Aelita Sophie]

2 minutes ago, Dujith said:

Most cheap one will be 230V (10Euro off brand, 20-30Euro honeywell/ect)

I take it the powersupply will be used in a 230V socket so you'll just need to switch a relay for the radiator knob.

Something like this: 12V Finder relay

 

For the knob something like this: Danfoss or Offbrand

 

Wouldnt a normal relay work as well? (Obviously with an octo-coupler) I've got a few laying around that can handle a 3.3v or 5v control input. And can handle a few amps on 230v.

[Dujith]

The finder is a normal relay  But yeah, any relay would work if they are rated for switching 230V (ofc check the amps allowed)

 

Edit: I just realized i linked a pulse relay

[Aelita Sophie]

Just now, Dujith said:

The finder is a normal relay  But yeah, any relay would work if they are rated for switching 230V (ofc check the amps allowed)

Alright. I'll definitely check the electric knob. As this seems WAAAAY easier and cheaper to accomplish. (And a bonus is that I don't need to cut tubings. As this is a rental house xD)

[Dujith]

Just make sure that the knob matches the system used by the normal knob. There are a few different sizes depending on the age of the system.