24 v stats

lucas finn

Hi all , First post here I’m an electrical apprentice , I’m wondering how do 24 volt stats work in a house that’s 230volt . Is it dry contacts in the stat that allows it to get 24v from a 230v supply I’m a bit confused about it . Thanks

2011

Yes, assuming it is a simple mechanical type of stat with dry contacts. Think of a stat as a switch.

10-10-20

There's going to be a power supply there too to supply the coils. Presume it comes off the boiler in that regards?

lucas finn

Thanks I’m afraid to say I’m a 4th year but still have a lot to learn it’s hard to get explanations on site as everything is just get it done attitude with not much information given, I did hear before someone saying think of everything as a switch , I’ve wired a lot of boilers Gas/combi type and had got my head around them , it’s just with the heat pumps and underfloor heating I get a bit lost .

lucas finn

Thanks for your reply , when you say a supply there a switch live from boiler or a permanent feed do you mean ? Does the stat call for heat and switch the boiler or heat pump etc.

2011

https://www.boards.ie/discussion/comment/121599520#Comment_121599520

Typically a "switch feed" is brought to a stat. The switch feed is what is says, it is live so it feeds the stat (or switch) with power. In your case the stat is supplied at 24V by the switch feed, when the stat is closed (just think of a closed switch) the switch wire is energised (agin in your case at 24V). This switch wire could bring power to the boiler requesting it to switch on. Once the desired temperature is achieved the stat will change state (the switch will go from closed to open), this will power down the switch wire requesting the boiler to switch off.

Does that make sense?

lucas finn

I understand most of what you’re saying , Just the part that it’s fed with 24v I’m finding it hard to understand how it’s fed with 24v is this from the time clock which is fed with 230v , how does the 24v feed the stat? Does it only become 24v when the switch wire is activated when it’s calling for heat .

Let’s assume this is a boiler we have a Timeclock being fed with 230v we have a CH zone , feeding a Room stat when calling for heat the switch wire of the stat powers the motorised valve for that zone and powers up the boiler so to me that’s 230v .

Basically just trying to figure out where does the 230v become 24v and how the process of it happens .

maybe I need a Version for dummies

2011

https://www.boards.ie/discussion/comment/121604381#Comment_121604381

now I understand the issue!

Let’s say the boiler is fed with 230V and the stat which is supplied from the boiler is fed at 24V as you suggest.

In this case the boiler would have either a transformer that steps the voltage down to 24V or a power supply unit that provides a 24V output. One way or the other some device changes the mains voltage supply to 24V.

A lower “control voltage” is commonly used to for control. This has a number of advantages primarily related to safety but also cost. Think of an intruder alarm, typically this operate at 12VDC. Again the intruder alarm panel would be supplied at 230VAC but it contains a power supply until so that detectors can be powered at 12VDC.

lucas finn

Okay thanks that makes sense now , Thanks