Pipe Thermostat to turn on secondary pump

[Arjay12345]

Hi. I've had a Grundfos secondary pump installed on the CH return; I just wasn't getting the circulation across the house to heat all the rads.

The rads are brilliant now, but I have been told to only have the pump running when the heating is on, rather than 24hrs/day. To ensure this happens without any manual switches, can I add a pipe (contact) thermostat to the CH flow so that as it gets hot (say, 50 degrees) when the heating is switched on, the pump is then switched on? This way, the pump automatically runs only when the heating is on, and switches off when the pipe cools below the threshold.

The pump is powered by a standard 3 pin plug into a wall socket. At the mo, I have a manual digital timer switch that is programmed the same as my heating schedule. This is fine for now, but if I turn on the heating out of schedule then I have to manually override the timer to switch the pump on/off which will be a pain for the rest of the family.

Thanks

 

[MNW67]

Is it a combi boiler or a heat only boiler. How is the boiler connected to the current programmer/thermostat. Is there a wiring centre.

I was wondering whether you can you somehow use the signal from the current programmer/thermostat to also turn the second pump on and off.

 

[Mister Banks]

If you have a 2port motorised zone valve for the CH you could feed the pump from the switched live of the valve.

 

[stem]

In theory you can add a pipe thermostat stat as you describe but the question from @MNW67 is relevant. Particularly if you do have a heat only boiler. Depending upon the way it is installed, there could be the possibility that the additional pump will continue to circulate hot water to the radiators when it shouldn't such as when the central heating is up to temperature, but the hot water remains on.

If you have an S-Plan system with a two port motorised valve then the valve would close but the pump would continue to try and circulate water around a shut circuit until the pipe cools. Which may or may not cause it a problem.

I will assume that the pump has been installed by a suitably qualified person and installed in the correct place to avoid plumbing related issues.

Also, the entire heating system including the controls should really all be wired to the same fused spur, so that the whole system is isolated from a single point, so wiring the pump to the room thermostat instead of plugging it in would be a more suitable option.

 

[Arjay12345]

OK, so exact setup is as follows:

- Valiant ecoTec system boiler

- For hot water, the boiler hears an Ariston unvented tank. Controlled by its own zone valve. Temperature setting directly from the boiler (I think). Heating timing is controlled via a dedicated programmable timer unit

- Central heating: consists of 3 zones, each with own thermostat and zone valve. Two zones are controlled by Control4 home automation thermostats and the wiring for these is within a wiring box with a power adapter and some relays; the third zone has a manual rotary thermostat, but I'm trying to get this added to the Control4.

Aside from my suggestion below of installing a pipe contact thermostat, the other option is to add a 'module' of some form that connects directly to the Control4 programme so that it starts/stops the additional pump based on the demand status of any of the thermostats. That way, the C4 system instructs the pump to start/stop either due to the scheduled programme, or a manual override. Problem is I'm still in investigation on whether the C4 module I need is a power adapter that sits between the 3-pin plug and wall socket, or something more sophisticated. And then I still need to call the C4 engineer to add the unit to my project so call out charge there too.

Hence I was hoping the pipe contact option would be easier and cheaper to install.

Thoughts?

 

[Mister Banks]

I think its best to keep it simple. My suggestion is simple and free, just connect the additional pumps LNE to into the wiring centre and connect the pump live to the terminal in the wiring centre where the orange switched lives terminate from the motorised valves. So when the room thermostats call for heat the relevant motorised valve will open resulting in a live being fed to the boiler and the additional pump.

 

[Arjay12345]

Thanks @Mister Banks.
Freakishly, my plumber called this afternoon and said exactly the same - he too mentioned "the orange wire". I have no idea about this wire but he's certain it'll work. I thought you would need to connect each of the three CH zone valves individually, but he too is saying only one valve needs to be connected. Luckily, the closest one is only a few meters away.

I'll report back.

 

[Mister Banks]

The orange wires should all be connected together so that any zone valve can call for heat and turn on the boiler and pump.

 

[MNW67]

I'll report back.

Usually the wires from all the CH zone valves will join together in a junction box called a wiring centre which would normally be near the boiler. Then you would normally take a single wire from the wiring centre to the pump.

 

[Arjay12345]

Is this the said 'wiring centre'?

The two current Control4 thermostats, plus feeds from the zone valves (I think from the white Honeywell box) feed into it.

 

[MNW67]

Is this the said 'wiring centre'?

The two current Control4 thermostats, plus feeds from the zone valves (I think from the white Honeywell box) feed into it.

I honestly don't know. Your set up is a bit advanced for me. I was expecting something more like this:

 

[stem]

Hmmm. Advanced wouldn't be the word I would use. That's one odd installation. Methinks someone has been having a play. The room thermostats are designed to be positioned in the area where the heating zone they are controlling is, so that they can measure and control the temperature there. And there's no reason to have two side by side in the same area (especially if it's a cupboard) unless they are controlling two separate independent heating systems. (or a cannabis farm maybe ) And what are they there for when you say the heating has Control4 thermostats controlling it?

Then there's the ad-hoc power supply [Looks like a Dantech 12v or 24v] controlling something switched by a relay or relays. Not standard heating components so obviously something homemade. Without a circuit diagram showing what's going on, I suspect the only person who can tell you what's going on is either the person that did it. Or someone capable of examining the installation and producing a wiring diagram of what's there.