# Wiring/symbol help...

#### cpu888

Joined Sep 17, 2021
12
I want to power a small heater 2kw in my bedroom with this wireless thermostat. I'm having trouble understanding how to wire it correctly.

https://salus-controls.com/uk/product/rt310rf/

https://salus-controls.com/files/RT310RF-Quick-Guide-V018.pdf

Question 1)
Is this able to be wired directly to the heater? its a 2kw heater so would need 10a 230V UK mains.

Question 2)
For example I can't understand what this means:
16 amp relay switching
RX Rating Max: 16 (5) A SPST

Question 3)
following this wiring diagram attached
attached

to have the heater powered maybe I use the bottom image. But...
It says Max 16 (5) A . I dont know what voltage it handles/outputs, what is the (5) ???
The black triangle in circle & M in circle with two arrows. What do both these symbols mean???

Question 4)
In other words I'm confused about the (5) - maybe it means 16A 5V
And maybe the symbols are a low voltage 5V switch for a larger Volt appliance.
So basically can this be wired straight through or would it require an extra switch before the heater ???

Replies appreciated.
Thanks.

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Joined Jul 18, 2013
23,907
You need a 230vac coil relay who's contacts can handle the load of the heater. 2Kw?
The thermostat switches the coil, as shown.

#### bertus

Joined Apr 5, 2008
21,667
Hello,

The 16 (5) A probably means that it can switch an 16 Amp resistive load (like a heater) or an 5 Amp inductive load (like a motor).

Bertus

#### cpu888

Joined Sep 17, 2021
12
You need a 230vac coil relay who's contacts can handle the load of the heater. 2Kw?
The thermostat switches the coil, as shown.
Do you mean I need an 'extra separate' coil relay or you mean the 'RF thermostat' switches the 230V coil that is in the 'receiver' that comes with it, as shown?

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#### ericgibbs

Joined Jan 29, 2010
14,136
hi cpu,

Rating Max: 16 (5) A SPST

Means 16Amps AC or 5Amps DC.
As its in Bonnie Scotland its 230Vac At 16 Amps maximum, so its fine for a 10Amp 230Vac Heater circuit.

E

Joined Jul 18, 2013
23,907
Do you mean I need an 'extra separate' coil relay or you mean the 'RF thermostat' switches the 230V coil that is in the 'receiver' that comes with it, as shown?
I would hesitate to switch 2kw with the internal relay, most room temperature thermostats i am familiar with use the internal contacts to pick up an external relay when operating the typical furnace fan/input, etc.

#### cpu888

Joined Sep 17, 2021
12
I would hesitate to switch 2kw with the internal relay, most room temperature thermostats i am familiar with use the internal contacts to pick up an external relay when operating the typical furnace fan/input, etc.
Thats my concern and why I am posting my questions. It seems usually they would have an external switch also. But what others have said seems this is ok and rated at 16A 230V. Why would you hesitate? Could this overheat, even though rated at 16A 230V? I think i'll email them also before. It depends on what those two symbols on the diagram mean. Do you have any idea? The 'black triangle in circle' & 'M in circle with two arrows below'. What do each of these symbols mean?

Joined Jul 18, 2013
23,907
The symbols appear to be either a fan or a solid state circuit.
Or a low voltage input to a electric furnace

#### LesJones

Joined Jan 8, 2017
3,570
My guess would be that the triangle is a solenoid valve and the M is a motorised valve. (This would be where separate zones are controlled.)

Les.

#### cpu888

Joined Sep 17, 2021
12
My guess would be that the triangle is a solenoid valve and the M is a motorised valve. (This would be where separate zones are controlled.)

Les.
So maybe it would be best to look for a simple affordable boiler/heater external elctrical switch valve rather than connecting a 2kw heater directly?

Joined Jul 18, 2013
23,907
Whatever you are switching at 2kw, personally i would use an external relay to switch it, rather than the thermostat take the brunt of the load, and more  to replace.

#### SamR

Joined Mar 19, 2019
3,607
Not to pick too fine a nit... I usually use a relay to switch control signals and a contactor to switch power to lights, heaters, and small motors where overloads are not required. If overloads are required, I use a starter. IE The thermostat should have a set of relay contacts to energize the coil of a contactor for the heating element. Contactors have Arc Chutes for arc suppression & extinguishing that a relay does not.

Joined Jul 18, 2013
23,907
Generally an ordinary house HVAC thermostat switches the gas valve on for gas heating, and starts the heating element start sequence for the electric furnace.
Or the compressor relay for cooling.

#### ericgibbs

Joined Jan 29, 2010
14,136
hi cpu,
You do not need an auxiliary relay for the RT310RF unit, its Contacts are rated for 230Vac 16Amps Max current,

Your 2kWatt heater at 230Vac will draw only ~9Amps.
Thats only 56% of its Rated maximum.

The 13Amp Mains fuse should be in the 13Amp Plug, that plugs into your UK Mains Socket.
E

BTW: your electric kettle, Rated at 2.3KWatt draws 10Amps, would you fit a relay to a Kettle circuit.??

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#### MisterBill2

Joined Jan 23, 2018
9,794
The symbols appear to be either a fan or a solid state circuit.
Or a low voltage input to a electric furnace
That symbol in the attached drawing is for a LIGHT. So the remote can switch either fan or a light. Some places get creative with symbols and the result is a lack of communication.
The claimed current rating for the switch is 16 amps and so your heater should be OK switching directly from the thermostat receiver. 10 amps through contacts rated for 16amps is an adequate safety margin.
BUT you do need to use wire sized for that current and with suitable insulation. And you need to be sure that the wires are adequately secured into the terminal connections when you do the installation.

#### cpu888

Joined Sep 17, 2021
12
Well I now understand its supposed ratings and symbols thanks to online forums. I have at least learned something valuable and new...

Quote
" Yes 16A max. resistive (heating) load or 5A max. inductive (motor or transformer) load. That is a standard way of representing relay switching capability on a control device. "

Someone guided me to this webpage - I had never seen those symbols and could not easily find them. They are HVAC system symbols.
https://stoutmep.com/electromechanical-ethos-blog/6uaxlxrm1pzyu06dr3ygg3c1k4xmg2

So with those two things learned. Thats good.
But I am still getting mixed opinions to weather I can use this directly with a convector heater. Maybe like me some see it is usually installed by heating electricians for heating systems, so more than often there will be auxillary switches before the big heating system. But technically that would mean if this was an extremely large huge heating system, like to heat a few aircraft hangers with turbo jet heaters in the sub zero frozen north pole, ... which would need a huge '16A relay switch/contactor' to swich on the massive heating system.... some are saying this Salus RT310RF could not be used.

I'm not an electrical engineer so I'm not itelligent on the detail of the subject but isn't a huge 16A relay/contactor the same as a 16A convector heater?

#### ericgibbs

Joined Jan 29, 2010
14,136
hi cpu,
If this 2KW heater is for Home or Office use, the Contacts in the Unit are more than adequate for the job.
You are over thinking the problem, just wire as I described in my last post
E

Joined Jul 18, 2013
23,907
Yes you most likely can control it directly But,
You most likely have one of those small PCT relays inside that unit, and although most claim fairly high current rating, they can be a source of failure in many appliances, also Is the PCT the relay is soldered to capable of 16A?
Personally for the cost of an external relay, i would prefer to play it safe.

#### ericgibbs

Joined Jan 29, 2010
14,136
Hi Max,
It is not the just the cost of the relay, it requires some form insulated enclosure etc, and the associated inter-wiring from Thermostat to Relay box etc,

IMO the unit is suitable for its purpose as supplied.
E

#### MisterBill2

Joined Jan 23, 2018
9,794
It should be possible to mount a relay inside the heater. Use a mains powered relay with adequate contacts that would be controlled by the wireless t-stat. That would cover all corners. OR, I have seen rather high powered baseboard heater control relays all in a nice package that allow a small thermostat to switch 50 amps of heater power.