back boiler Gravity hot water, pumped heating system with a cylinder thermostat but without a motorised valve wiring diagram

[RichardBowes]

Hello all

Have purchased a Salus TC100 wiring center and have come a bit stuck as all the wiring plan S-Y included a motorized valve.

Does anyone have a wiring diagram for a Gravity hot water, pumped heating system with a cylinder\pipe thermostat but without a motorized valve wiring diagram that they would be willing to share ?

ive seen the answer i believe ( https://www.diynot.com/diy/threads/gravity-hot-water-pumped-heating.269049/ ) but it still leaves me head scratching with what cable goes where using a wiring center

Any help gratefully received - Thank you

Kind regards
Richard

 

[stem]

The system is so simple it doesn't need a wiring centre, they are for the more complicaed systems with motorised valves but the connections need to be terminated somewhere and that can change depending upon the location of the various components in your home which will vary from place to place. I guess in your case they are already existing, so a photo of what you have in place now might be useful, and if you can describe what is on the other end of each cable, that would help too.

 

[RichardBowes]

The system is so simple it doesn't need a wiring centre, they are for the more complicaed systems with motorised valves but the connections need to be terminated somewhere and that can change depending upon the location of the various components in your home which will vary from place to place. I guess in your case they are already existing, so a photo of what you have in place now might be useful, and if you can describe what is on the other end of each cable, that would help too.

Hello
I have attached a drawing which might help
What i have is two fused switches , one turns on the boiler and heats the water , the other turns on the pump with pushes the water to the radiators. The Pipe thermostat must connect to the boiler power switch ensuring the water remains hot , turning the boiler on and off.

what i would like to do is to install a programmer ( Salus Ep210) for hot water and heating controls and a room stat (RT310RF)

 

[oldbutnotdead]

You don't need a wiring diagram.
Your cylinder stat may be causing you problems if it is connected between power and boiler (you need to verify this using a multimeter). Consider situation where hot water is switched on, cylinder is hot so the boiler is off. You switch the pump on, water circulates through the boiler but until enough heat has bled off the cylinder through reverse circulation to drop the hot water temperature below the setpoint the boiler will not fire therefore the rads will not get warm. The rads also will stop warming when the hot water has heated up again.
Traditionally with gravity systems there was no cylinder stat, hot water temperature was set by the boiler thermostat.
So, ditch the cylinder stat. And the wiring centre
On your Salus, set the top link to Gravity.
Connect boiler live to DHW ON
Connect COM on the thermostat receiver to CH ON
Connect NO on the thermostat receiver to pump live.
Connect both neutrals to N
Connect both earths to E.
Set boiler stat to 3
Turn it all on
Be aware that you cannot have heating on without hot water being heated (long as your cylinder and supply pipework is insulated not a big deal).

 

[RichardBowes]

Thank you very much
That looks a lot easier that i thought, i understand all apart from the domestic hot water - where would the DHW on be located. how would i pick that up ?
It could be possible that the Stat is connected to the pump - is it easy to describe how to connect to the system ?
The stat is currently set to 90
The boiler is a Potterton Fuego
sorry for so many direct questions - i do appreciate your help - Thank you

 

[RichardBowes]

will setting the Salus to gravity disable the the 5-2 day timer

 

[ianmcd]

will setting the Salus to gravity disable the the 5-2 day timer

No all setting to gravity does means that if you only have the CH set to come on the HW will also come on

 

[stem]

Here's the original diagram you sent the link to, but this time with a junction box and the interconnecting cables shown inside the ellipses. The wire colours are drawn to shown their functions [Brown L, Blue N] If in reality you use a blue wire as a live, then you should really fit a brown sleeve over the end to identify its true function. Earth connections are omitted for clarity but should be made as required. Some boilers as well as the switched live, also need an additional permanent live which isn't shown.

With this configuration you do not need to set the programmer to gravity mode; the changeover switch which is part of the cylinder thermostat will ensure that the boiler is also 'on' when the central heating starts the pump.

You should be aware though, that the hot water will always be heated whenever the boiler is 'on'. So, even if the hot water cylinder is 'hot' but the central heating is running, the hot water will still be being heated. This is a restriction caused by the 'gravity circulation' pipework arrangement, not the controls.

A plus point is that when both the heating and hot water are up to their set temperatures, the boiler will shut down, which is better than the current arrangement where only the pump will go off, but the boiler will still be running just to keep itself hot, even though no heat is required.

The main advantage will be in the summer when the central heating isn't required, because, the cylinder thermostat will switch off the boiler once the water is at the temperature set on the cylinder thermostat.

 

[RichardBowes]

Thank you Stem for taking the time to draw out a diagram and the additional info , very grateful . I will set to work .

What a brilliant support forum this is

 

[oldbutnotdead]

View attachment 285151

Here's the original diagram you sent the link to, but this time with a junction box and the interconnecting cables shown inside the ellipses. The wire colours are drawn to shown their functions [Brown L, Blue N] If in reality you use a blue wire as a live, then you should really fit a brown sleeve over the end to identify its true function. Earth connections are omitted for clarity but should be made as required. Some boilers as well as the switched live, also need an additional permanent live which isn't shown.

With this configuration you do not need to set the programmer to gravity mode; the changeover switch which is part of the cylinder thermostat will ensure that the boiler is also 'on' when the central heating starts the pump.

You should be aware though, that the hot water will always be heated whenever the boiler is 'on'. So, even if the hot water cylinder is 'hot' but the central heating is running, the hot water will still be being heated. This is a restriction caused by the 'gravity circulation' pipework arrangement, not the controls.

A plus point is that when both the heating and hot water are up to their set temperatures, the boiler will shut down, which is better than the current arrangement where only the pump will go off, but the boiler will still be running just to keep itself hot, even though no heat is required.

The main advantage will be in the summer when the central heating isn't required, because, the cylinder thermostat will switch off the boiler once the water is at the temperature set on the cylinder thermostat.

Ahhh, that is a good use of cylinder stat on a gravity system, like it!

 

[stem]

I realised the diagram is a bit small to see properly though, here's a larger version.