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House Room Thermostat Wiring Help


agent_zed

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Hi,

sorry not car related but you chaps are always knowledgeable so i'm hoping you'll be able to answer this for me.

 

I bought a touch screen thermostat like this one https://www.ebay.co.uk/itm/Programmable-16A-LCD-Electric-Heating-Thermostat-Temperature-Controller-UK-PLUG/183420850951?hash=item2ab4bc1307:g:ORgAAOSw2iFbhPX6and i didn't read that it is actually for underfloor electric heating.

 

They say not to connect to a boiler as it will cause damage and whilst i havent done that i have connected it to my wiring centre for my underfloor heating which then controls actuators and turns the boiler on when needed. It is all connected and working using the number 1 connection for the load as the switched live and the L + N as indicated leaving the N (number 2 connection) of the load unused.

 

I can't see how or why this could damage anything but i also don't want to burn my house down. Can anyone see a logical reason why this shouldn't be used like this? It is only switching a live on to signal the wiring centre and it is a fraction of what the switch is designed to handle.

 

any help appreciated.

 

 

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Having recently had to spend £3k on a new boiler, I wouldn't dare touch any of the electrics involved.

 

That item probably comes from China where they have a very lax attitude towards H&S AND even they say don't connect to a boiler, so I deffo wouldn't :crazy:

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1 most thermostats are just ON/OFF contacts.

2 Modern boilers controls work at low voltage.

3 The thermostat is designed to switch mains up to a max power.

If your wiring center still works after connection then I do not see any problem as high voltage switching to low voltage inputs causes immediate destruction of the low voltage input and a puff of smoke.

I know that my under floor heating controller (a similar model) normally works on a sensor buried in the floor with a back up air sensor, in the event that the under floor sensor dies it reverts to just the air temp.

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ah ok this makes more sense then if some boilers have low voltage setups. My boiler is quite a simple one and was setup using s-plan (https://www.flameport.com/electric/central_heating/S_plan_wiring_diagram.gif) which i re-did when i re-wired the house.

 

From the diagram i have (and the connections available) there is no low voltage parts of the system/boiler (no lcd screens etc) so it wouldn't even be a problem connecting direct to my boiler (not that i intend to do that).

 

The wiring centre takes full 240v N, L to the thermostat and uses the 240v L1 switch to turn on each of the valve actuators. So this makes sense and reassures me that it's ok to do what i've done as all it is doing is turning a live on or off in the wiring centre. (wiring centre is on a fused spur 3A and on RCD protected circuit). So something would have gone as you said if it couldnt' take it, and it's definitely designed for 240v anyway.

 

I know they are chinese jobs but quite impressed so far with it, fully programmable and pretty simple to use. Feel quite well made. Ths chap has opened one up and checked it out https://hackcorrelation.blogspot.com/2017/11/floureon-byc17gh3-thermostat-teardown.htmland doesn't seem too concerned.

 

thanks both

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Hi,

Having had a look at the ebay listing, I did not see any mention of the unit being for under floor heating within the description.

 

Most central heating stats only control the water flow pump not the heating part of the system when the temp drops to circulate the water around the system.

 

The boiler comes in from it's internal temp control of the water not the external room stat.

 

Hope this information gives you a better understanding of what the room stat is controlling.

 

Regards

 

Martin

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Room stat controls nothing as such it simply tells the board in the boiler one of a number of condiotions has been met. The board then closes down the hearing cycle in a set sequence. Last thing it does is stop the pump, it kills the flame first and continues to run the pump until the heat exchanger reaches a low enough tempteture that the latent heat in there wont cause over temperature damage. The fan continues to run until a purge of gasses has taken place. Etc.

 

The switch however is exteemly simple yet is governed by many mechanical principles and many regulations and laws drawn up by governing bodies who seek to ensure the afore mentioned principles are met. Can explain more if you want to know more but its yawny.

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that's what i was thinking but i just wanted to check as they all seemed to mention possible damage. @maca further down on that listing it says

 

'NOTES TO BUY : This electric heating thermostat is NOT suitable for gas boiler, furnace, water floor heating and Air Conditioner. In order to avoid your heaters from damaging or waste of your precious time to send the unit back, please contact clearly before buying.'

 

but from what you've said above i think that just relates to boilers with low voltage parts to it, which mine isnt.

 

The way mine is setup (s-plan) it's actually the motorised valves that the thermostat (or in this case wiring centre for the UFH) opens which in turn then turns on the pump and boiler, so the pump can never run with the valve shut (Which would obviously be bad).

 

 

I'm happy now knowing that the thermostat that i've bought is pretty much a switch that is switching on a live 240v line (L1) to tell the ufh wiring centre to open the valve and turn the boiler on and doing what it should.

 

It was certainly 'fun' wiring everything up when i rewired as there about 25 wires in the connector block coming from the boiler, 2 zone valves, main power, tank thermostat and room thermostat!

 

Now i'm having to run wires everywhere for the room thermostats back to the ufh wiring centre.

 

But on the bright side it is all working and i have nice warm feet in most of my rooms, just got the do the living room floor. Oh and no radiators with pants on... i just throw them on the floor now :crazy:

 

thanks all :)

 

oh and hopefully when i'm done i can hopefully get to fit the bike carbs, new headlights, new wing mirrors, paint the nose cone and arches and a bunch of other things on the 2b!

Edited by agent_zed
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Guest gselect

I don't think the seller understands what he is selling, I think that because the rating is 16 Amp he thinks that the unit will damage items at other ratings?

Gas boilers etc work on 3 or 5 amp circuits normally so this why the warnings.

 

The unit will only switch 5 Amps if it is only fed with 5 Amps so your system should be fine . I have fitted this style of switch in to each room/area covered by the underfloor heating loop, having been supplied them by the installing plumbers (they are generally cheaper than 5 amp versions I am told)

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You dont feed amps you draw them, doesnt matter what rating the fuse (circuit protective device) the current drawn is a result of resistance (in ac circuits impedance Z). The rating of the circuit protective device must be such as to prevent undue damage and fire risk, and to remove the supply before the cable it protects reaches failure. There are tables, there are rules of thumb, there are calculations.

 

As for switching with a room stat connected to a PCB, its likely tho not guaranteed that you wont be switching more than 0.01 amps. Control circuits work on a very low level and use transistors to switch relays, the relays switch the power to the relevant hardware. Its done this way to minimise cost, size, component wear, risk to safety, all sorts. It also alows for simple programable ICs to be used to perform multiple different sequencential opperations dependant on what conditions are met without a mass of wiring and relay logic. Its all quite elegant as a solution but can be costly when it fails because youre cornered in a market. It also allows comparisons between multiple watchdog systems on a board to satisfy gas regulations to name just one, all for pennies.

 

Im not going to comment if you can or cant use this because unles you have qualifications you shouldnt be working on home electrical systems or gas. This hits both lol. But as for it causing damage, if wired correctly it would be fine. The biggest risk is from cheap components or poor workmanship in assembly but truth be told its all made in China. QC is different for known brands normally but I use much of this Chinese stuff in my home and am satisfied its ok.

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