Hive installation help

[Graz92]

Hi Im looking to fit a hive smart thermostat system. Im looking at fitting the receiver to my boiler and ive got a few questions before I make a purchase.

First off, my boiler has a built in temperature control that tells me the temp at the radiator (see pic). Does this effect the function of the thermostat?

As far as the wiring goes it looks fairly straight forward but im not 100%. Im assuming I just run a bit of twin and earth from the boiler mains power supply input to the receiver then remove the shorting link for the thermostat but im not sure which terminals on the reciever connect in place of the link?

I have the boiler inside a cupboard would I be able to mount the receiver on the wall in the cupboard (see pic)?

Thanks in advance for the help.

 

[Graz92]

This is the reciever. Im assuming the NO and NC replace the shorting link (if so how do I tell which one is which) and im not sure about the common?

 

[ericmark]

Be it a simple thermostat, or hive and nest, they in the main only monitor one room, the Evohome does monitor every room but expensive. So unless your going the whole hog with EvoHome you have two thermostatic control systems trying to control the same house. I am not saying it will not work, it does allow you to alter the time using the phone. But the single thermostat system is designed for USA hot air central heating where every room is at the same temperature. In the UK we use a wet system and the TRV (thermostatic radiator valve) allows us to have every room at a different temperature. So with the UK system using a single thermostat is always a little hit and miss.

My first house did have a hot air system, air is pumped into every room and it returns to the central heater through vents in every door. However it was very expensive to run, most people had the hot air system replaced with a water system.

It is possible using the lock shield valve and TRV to tune the hot water system to work with a single thermostat in essence you are reverting back to a pre-TRV days, the whole idea of the TRV was linked to getting the latent heat from the flue gasses, the return water needs to be quite cool so steam in the flue gas is condensed into water.

Why there is so much push to sell the hive and nest systems I don't know, as I have said they do work to an extent, but are not really designed for a hot water system. The Evohome is designed for a hot water system and it does talk to the boiler and tell the boiler when to fire up, and every room can be set to a different program so for example bedrooms only heated at night and living rooms not heated at night, but personally I think it would take a long time to pay for its self.

 

[ericmark]

This is the reciever. Im assuming the NO and NC replace the shorting link (if so how do I tell which one is which) and im not sure about the common?

Com and NO replace the shorting link, setting the temperature high they do allow remote control of system on/off, but do not work very well at controlling temperature as only in one room, so used as a frost stat OK and putting heating on remote work OK, but the setting of the lock shield valve becomes very important.

 

[Graz92]

Com and NO replace the shorting link, setting the temperature high they do allow remote control of system on/off, but do not work very well at controlling temperature as only in one room, so used as a frost stat OK and putting heating on remote work OK, but the setting of the lock shield valve becomes very important.

I currently have no thermostat in the house and having a timer on the boiler is not ideal.

I would like a means of being able to turn my heating on prior to leaving work and hive/nest is much more suitable for my needs than a timer.

I know the temperature control is not the most accurate using a single room thermostat but its far superior than the current system in which the boiler only tells me the radiator temp and the only temp control I have is the boiler.

Also im not at home during christmas and it seems like a very good method of frost protection. Then just before I get back home in january I can turn my heating up and come back to a warm home.

If the comm and NO replace the shorting link does the NC go unused?

 

[ericmark]

If you have no TRV's fitted to radiators then yes the hive/nest system is good. And having the remote on/off is good. But in the main today the water central heating works like this.

The boiler supplies hot water which is fed to every radiator the amount of water is controlled by the lock shield valve and this means if set correctly the return water is quite cool, as the return water warms up the flame hight is reduced, so as each room gets warm the TRV switches off and the water is fed to fewer and fewer radiators until the by-pass valve opens, at this point the return water is too hot so the boiler turns completely off.

There is a variable timer in the boiler and after this time the boiler fires up again, if the by-pass valve is still open then it quickly turns off again and the re-try time is increased, however on re-try if the return water is cool the re-try time is reduced, this is called anti-cycle software. So the TRV's tell the boiler how often to fire up. So with 10 radiators with TRV's you have 10 thermostats.

If you add an electric thermostat then the anti-cycle software does not work as well as it should, add one electric TRV with clock built in and it will work, add 10 and the anti-cycle software tells the boiler not to fire up even when it is needed. So the EvoHome has all the electric TRV's connected to the main controller which in turn tells the boiler when to fire up.

But with a simple thermostat it needs to be in the room which will want the boiler to fire up the most. That does not mean coldest room, if the TRV is set lower than the electric thermostat than the electric thermostat will never turn off. And if the room does not need the boiler to run for very long then rest of house can get cold.

Adjusting the lock shield valve and the TRV one can get it to work of sorts, but simply the wind changing direction can result in very hot or very cold rooms. It is hit and miss.

It may do what you want, but be aware it is hit and miss and it can take a long time to get the valves set correctly.

And yes NC is not used for heating that is only used with air conditioning units.

 

[Graz92]

....

The majority of houses have TRVs on all radiators and an external room thermostat, whether that is the correct set-up or not ive never really noticed any problems operating with both in previous houses ive lived in or heard of people having any noticeable issues. The only major problem ive seen (which is fairly obvious considering the thermostat only monitors one room) is my parents have a thermostat in the hallway (which is massive) so by the time their hallway gets up to temp the smaller rooms are a lot warmer.

British gas website simply says to set the TRV to fully open.