Hot water thermostat with Nest

ctlsleh

All,
I am Installing 2 nests for 3 zones - downstairs, upstairs and hot water (have motorised values in place for each zone)

I understand I need to have a thermostat on the hot water tank so that it doesn't overheat. That's a requirement for the heating control grant

Can anyone advise me how that should work in conjunction with the nest and should be wired?

I don't have any wiring between the hot water tank and the boiler itself, also, not sure how it should work with the nest which just opens the valve and turns on the boiler.

If I turn on the nest and it turns on the heat to the tank, how does the thermostat then turn it off? Maybe I'm misunderstanding so any guidance is appreciated.

Pete67

You will need to get a small wiring job done, the Nest is basically just a timeswitch for the domestic hot water, so an additional thermostat is required on the hot water tank. If the zone valve for the DHW is close to the cylinder, then it will be very straightforward. The switched live from the nest goes to the thermostat on the cylinder, and then on to the DHW motorised valve so that the valve is only energised when the cylinder is below the setpoint on the thermostat (usually 60 degrees).

You also need a boiler interlock, usually done by utilising the microswitches built into each zone valve, these are wired back to the boiler to enable it when any one of the three zone valves is open. Your installer should be very familiar with this setup.

ctlsleh

Thanks Pete,

My hot water tank is upstairs and my boiler is downstairs with no wiring in between so wondering if there are other options......? Also no mains power where my hot water tank is

Can you help me understand the interlock statement?......each of the valves can already turn on the boiler independently as it's currently wired.........?
Cheers

Pete67

You already have the boiler interlock sorted then, so probably no need to do anything further with that. There is one thing I would check though, especially if you have a modern gas boiler. Most gas boilers require a permanent 230V mains supply so check that that the zone valves are not simply removing all power from the boiler when there is no heat demand. If wired correctly the boiler should remain powered on in standby when all zones are off, and then fire on demand as one or more zones call for heat. Not so important for oil boilers, but check the the manufacturers instructions.

I guess your zone valves are located close to the boiler? If so you have a couple of options, run a cable from the location of the HW zone valve to the hot water tank, or use a wireless solution. If possible, running the cable would be the best option as it is less complex, avoids need for battery replacement etc etc.

ctlsleh

Yes, the valves are beside the boiler. Running a wire between upstairs and downstairs would be difficult, lots of floorboards would need to be lifted, the tank is very far away from the boiler so it's not an option really. How do the wireless ones work?

Getting power into the hot press is easy as there's a switch on the wall.

Using Ethernet powerline technology would be another option if that's possible...? Or are there wifi versions that can connect through my router?

Pete67

There are many wireless solutions, probably best to stick to tried and tested manufacturers. Here is one solution by Danfoss that looks suitable for your application, but isn't your installer looking after this for you? You will need an SEAI approved contractor to do the work in order to be eligible for the grant.

ctlsleh

Yes, I have a seai approved guy, but he doesn't seem to k ow much about it.....! Are there wifi options?

ctlsleh

Just wondering if there are any smart hot water thermostats that integrate into a nest eco system and basically tell the nest to turn off the hot water once the temperature is reached (over wifi)........anybody seen anything like that?

Doodoo

ctlsleh wrote: »

All,
I am Installing 2 nests for 3 zones - downstairs, upstairs and hot water (have motorised values in place for each zone)

I understand I need to have a thermostat on the hot water tank so that it doesn't overheat. That's a requirement for the heating control grant

Can anyone advise me how that should work in conjunction with the nest and should be wired?

I don't have any wiring between the hot water tank and the boiler itself, also, not sure how it should work with the nest which just opens the valve and turns on the boiler.

If I turn on the nest and it turns on the heat to the tank, how does the thermostat then turn it off? Maybe I'm misunderstanding so any guidance is appreciated.

Just wondering if you got sorted as I have a similar setup