10 ms·

The Nest comes in two parts - the "smart" bit with the USB charger & battery & wifi, and the Heat Link - the actual radio control for your boiler. The Heat Lin

by mattbee 11y ago

The Nest comes in two parts - the "smart" bit with the USB charger & battery & wifi, and the Heat Link - the actual radio control for your boiler. The Heat Link has a big button on which lets you turn the heating on and off, overriding what the Nest is telling it. That's not as economical as a regular thermostat, but it means you won't freeze: https://nest.com/uk/support/article/How-do-I-turn-the-heat-on-if-the-Nest-Thermostat-isn-t-working https://nest.com/uk/support/article/How-do-I-turn-the-heat-o...

mattbee 11y ago
Oh, OK, you don't have that in the US apparently. Why's it necessary?
- HillRat 11y ago
  Almost all US central heat and air systems are "forced air" -- gas or electric heaters (furnaces) that blow conditioned air through ducting. Boiler-radiator systems wouldn't work with the standard US thermostat, not least because US thermostats use low-voltage signaling.
  - ghaff 11y ago
    I don't claim to be an expert but I have a forced hot water system (converted at some point from steam) and AFAIK it uses a "standard" thermostat. At least when I upgraded to a Honeywell programmable thermostat 15 years or so ago, I don't remember it being anything unusual. I bought a thermostat at the home improvement store and an electrician who was doing some other work installed it.
  - quicklyfrozen 11y ago
    Boiler + hot water circulation through radiators is also pretty common in US and will also use a low voltage thermostat. The only exception I can think of is older gas-powered steam boilers which may use a millivolt thermostat (which have the advantage of working when the power is out). (Or electric baseboards...but who can afford to heat that way?)
  - quesera 11y ago
    You must be from a warm part of the U.S. Forced hot water systems are very common in the colder parts, and they use the same thermostat wiring as forced air. Some parts of the U.S. even use diesel fuel for heat (it's called #2 heating oil, but it's really just diesel fuel with pink dye added so they can fine you for using it as a vehicle fuel...it's taxed advantageously). Also, boiler-radiator systems can absolutely work with standard thermostats. The classic design has no electrical control at all, just bimetal valves (like car thermostats) to regulate the flow of heated water. But the modern revision uses the same kind of electrically controlled valves (24VAC, IIRC) that forced hot water does. All low-voltage thermostats with standardized wiring layouts. I didn't know the UK ran high voltage to ordinary thermostats though, that seems crazy if it's just a control circuit. Presumably the full mains voltage? Old U.S. "radiant" (electrical, non-hydronic) heat ran 220/240 VAC to big rheostats in each room, but that was actually the supply to the heating elements. It feels like something that wouldn't meet code today, but it used to be popular in some parts of the country where electricity was inexpensive.
    - Aloha 11y ago
      It still is popular, even in new construction, in the Pacific Northwest.
    - makomk 11y ago
      Yeah, UK central heating systems in homes use the full 240V for all their control wiring. It's worth bearing in mind that this isn't just signalling - the thermostat and timer directly switch the power to the pump and valves.
- jsight 11y ago
  It looks like the UK version is a lot different: http://www.cnet.com/news/nest-thermostat-finally-arrives-in-the-uk-for-179-partners-with-npower/ http://www.cnet.com/news/nest-thermostat-finally-arrives-in-... https://nest.com/blog/2014/04/02/the-uk-just-got-a-little-more-comfy/ https://nest.com/blog/2014/04/02/the-uk-just-got-a-little-mo...
- jauer 11y ago
  US thermostats usually use low-voltage wiring for signalling to the furnace or boiler. We usually only see line/mains voltage thermostats (that work by limiting current supplied to a electric heater) in cheap apartments. https://nest.com/support/article/How-can-I-tell-if-my-current-thermostat-is-low-voltage https://nest.com/support/article/How-can-I-tell-if-my-curren... The US version won't work with line voltage systems. It looks like the UK version only works with line voltage systems. This also explains why in the US changing a thermostat is something pretty much anyone can do but the UK version requires a Nest Pro to hook up. Nest US: "It's easy to install the Nest Thermostat. Everything you need comes in the box" Nest UK: "A Nest Pro installer should install your Nest Thermostat. They will identify cables from the boiler, zone valve or junction box to connect to the Heat Link."
jedberg 11y ago
That must be a UK thing or something. I only have a single device. I know because I installed it myself -- there is definitely no manual override button, and I've never even heard of this Heat Link before.

by mattbee 11y ago

mattbee 11y ago

Oh, OK, you don't have that in the US apparently. Why's it necessary?

HillRat 11y ago
Almost all US central heat and air systems are "forced air" -- gas or electric heaters (furnaces) that blow conditioned air through ducting. Boiler-radiator systems wouldn't work with the standard US thermostat, not least because US thermostats use low-voltage signaling.
- ghaff 11y ago
  I don't claim to be an expert but I have a forced hot water system (converted at some point from steam) and AFAIK it uses a "standard" thermostat. At least when I upgraded to a Honeywell programmable thermostat 15 years or so ago, I don't remember it being anything unusual. I bought a thermostat at the home improvement store and an electrician who was doing some other work installed it.
- quicklyfrozen 11y ago
  Boiler + hot water circulation through radiators is also pretty common in US and will also use a low voltage thermostat. The only exception I can think of is older gas-powered steam boilers which may use a millivolt thermostat (which have the advantage of working when the power is out). (Or electric baseboards...but who can afford to heat that way?)
- quesera 11y ago
  You must be from a warm part of the U.S. Forced hot water systems are very common in the colder parts, and they use the same thermostat wiring as forced air. Some parts of the U.S. even use diesel fuel for heat (it's called #2 heating oil, but it's really just diesel fuel with pink dye added so they can fine you for using it as a vehicle fuel...it's taxed advantageously). Also, boiler-radiator systems can absolutely work with standard thermostats. The classic design has no electrical control at all, just bimetal valves (like car thermostats) to regulate the flow of heated water. But the modern revision uses the same kind of electrically controlled valves (24VAC, IIRC) that forced hot water does. All low-voltage thermostats with standardized wiring layouts. I didn't know the UK ran high voltage to ordinary thermostats though, that seems crazy if it's just a control circuit. Presumably the full mains voltage? Old U.S. "radiant" (electrical, non-hydronic) heat ran 220/240 VAC to big rheostats in each room, but that was actually the supply to the heating elements. It feels like something that wouldn't meet code today, but it used to be popular in some parts of the country where electricity was inexpensive.
  - Aloha 11y ago
    It still is popular, even in new construction, in the Pacific Northwest.
  - makomk 11y ago
    Yeah, UK central heating systems in homes use the full 240V for all their control wiring. It's worth bearing in mind that this isn't just signalling - the thermostat and timer directly switch the power to the pump and valves.
jsight 11y ago
It looks like the UK version is a lot different: http://www.cnet.com/news/nest-thermostat-finally-arrives-in-the-uk-for-179-partners-with-npower/ http://www.cnet.com/news/nest-thermostat-finally-arrives-in-... https://nest.com/blog/2014/04/02/the-uk-just-got-a-little-more-comfy/ https://nest.com/blog/2014/04/02/the-uk-just-got-a-little-mo...
jauer 11y ago
US thermostats usually use low-voltage wiring for signalling to the furnace or boiler. We usually only see line/mains voltage thermostats (that work by limiting current supplied to a electric heater) in cheap apartments. https://nest.com/support/article/How-can-I-tell-if-my-current-thermostat-is-low-voltage https://nest.com/support/article/How-can-I-tell-if-my-curren... The US version won't work with line voltage systems. It looks like the UK version only works with line voltage systems. This also explains why in the US changing a thermostat is something pretty much anyone can do but the UK version requires a Nest Pro to hook up. Nest US: "It's easy to install the Nest Thermostat. Everything you need comes in the box" Nest UK: "A Nest Pro installer should install your Nest Thermostat. They will identify cables from the boiler, zone valve or junction box to connect to the Heat Link."

jedberg 11y ago

That must be a UK thing or something. I only have a single device. I know because I installed it myself -- there is definitely no manual override button, and I've never even heard of this Heat Link before.