Nest for elderly (first thermostat)

[lucluc]

My parents have a non-condensing Optima 701 combi boiler in the airing cupboard on the landing. There's no room thermostat. A programmer is on the boiler but is not used (they turn boiler CH on/off when needed).

I'm thinking of trying to get a Nest for them and getting it professionally installed (their gas man has refused for years to install a thermostat).

Am I right in assuming that the "receiver" fits in the airing cupboard and takes power direct from the boiler, so no extra power socket is needed to the cupboard (online manual p28 mentions 24v room thermostat)? If not, can it take power from the fused spur that powers the boiler? Effectively no redecoration/mess?

The "sender" then fits in a stand in the living room and has to connect to a 240v plug. Living room radiators then turned up to "max".

The boiler has flues go through the loft (access hatch on the stairs). When they have to replace the boiler can it still go through loft?

I have an OpenTherm system boiler in kitchen, analogue thermostat in living room, programmer in kitchen, HWC upstairs. If I wanted Nest do I need new "OpenTherm" wires from electric box next to HWC to the boiler? Or does the receiver go next to my boiler?

Thanks.

 

[stem]

Am I right in assuming that the "receiver" fits in the airing cupboard and takes power direct from the boiler.

It can go in the airing cupboard, but it doesn't have to. The receiver should take its mains supply from the boiler so that the same fused connection unit isolates the boiler and receiver. Please note though; if it is necessary to remove a room sealed cover from the boiler to access the boilers wiring terminals, then this is not a DIY project. It should be carried out by a Gas Safe engineer who can carry out the appropriate safety checks afterwards.

online manual p28 mentions 24v room thermostat

The mains supply mentioned before is to provide 230V to power the receiver. The switching contacts inside the receiver are 'voltage free' that means they are not connected to the mains supply and so can be used with any voltage. If your boiler has wiring connections the same as the diagram below, 24V is correct. The wire link between terminals 4 & 5 would be removed and the terminals connected the the Nest Heatlink receiver terminals 2 [Heating Common] and 3 [Heating Call for Heat]. (it doesn't matter which way around)

As you say the boiler has an internal timeswitch, usually (unless it is already wired to terminals 4 & 5)it will it will need to be set to be permanently 'on' and the Nest will take over the time control.

The "sender" then fits in a stand in the living room and has to connect to a 240v plug

The thermostat comes with a separate power supply and is simply plugged in. However, it is important that the thermostat itself it is sited in the best location. It may be the living room, but it may not. Here are the basic rules of thermostat location:

• It should be in a place that is the last to warm up, so that the radiators remain 'on' in all of the other rooms first to allow them to heat up before the main thermostat turns the whole system off.

• Not in a room where it will be subject to other heat sources such as cooking appliances, fireplaces & sunlight etc.

• It should be located in an open space to allow air to circulate freely around it so that it senses the true ambient temperature of the room in which it is located, not stuck in a corner, behind curtains or furniture, or subject to drafts

Living room radiators then turned up to "max".

If by this, you mean that a Thermostatic Radiator Valve (TRV) is turned up full in the room where the Nest thermostat is sited, that is correct. Ideally there shouldn't be a TRV at all, but if you don't want to remove it, setting it to max is the next best thing.

I have an OpenTherm system boiler in kitchen, analogue thermostat in living room, programmer in kitchen, HWC upstairs. If I wanted Nest do I need new "OpenTherm" wires from electric box next to HWC to the boiler? Or does the receiver go next to my boiler?

Ok, so we have swapped projects now. Where systems have central heating and stored hot water, the existing system controls operate motorised valves and are not wired directly to the boiler. In such cases the Nest Heatlink receiver usually replaces the existing programmer, and any existing room thermostat is removed, with a minor modification to the wiring. A separate cable is required between the boiler and Heatlink for OpenTherm.