How to set up system with a TRV on ALL radiators?

[ChristopherBBB]

Hi,

I am wanting to have 'smart' heating so that ALL rooms are individually thermostatically controlled but I do not want a central house thermostat.

I want this logic :
- If a one or more TRV requires heat I would like the boiler to turn ON and pump hot water around the flow/return to provide heat to that radiator.
- If non of the TRV require heat I would like the boiler to turn OFF.
- I don't want the concept of multi room 'zones' or a 'house thermostat'.
- I want this logic to work 24/7, not just the few hours either end of the day.
....can I do this?

Heating Engineers I have spoken to have not been very technological minded and can't see the point in spending lots of money on the new fan-dangled smart heating systems with all the apps, geo presence, smart learning and logs of historic temperatures - "it only takes a second to twist a manual valve" etc etc so I am not getting any help with my challenge.

I DON'T want a hall that has the 'dump radiator' and I DO want a TRV in the bathroom as I want to control the temperature there too.

I think that these systems provide the technology
- Novo (https://www.kickstarter.com/projects/313176179/novo-the-smartest-radiator-valve)
- Tado (https://www.amazon.co.uk/tado°-Smart-Thermostat-Starter-Kit/dp/B01MG5BION/ref=sr_1_2?s=diy&ie=UTF8&qid=1511313045&sr=1-2&keywords=tado)
- Honeywell EvoHome (https://www.amazon.co.uk/Evohome-HR...coding=UTF8&psc=1&refRID=ZAJT8ZQJQMR4053C2PG8)

But how do I get around the problem that when all TRV are SHUT the boiler will bang/whoop/pop/struggle/blow attempting to push water around a closed loop ?

Thanks in advance,
Christopher

 

[ianmcd]

fit an automatic by-pass and use a boiler with a pump over run

 

[ChristopherBBB]

Hi ianmcd,

Thanks for the quick reply ... sorry to be such a newbie / amateur ... but what do those expressions "automatic by-pass" and "pump over run" mean ?

Do you have a suggestion for appropriate boilers to chose from ?

Thanks

 

[John D v2.0]

Would be against building regs to have it running through a bypass when there's no heat demand, also wear out your pump.
You'd need some kind of boiler interlock, surely these fancy smart systems have a switched live or a volts free terminal to control the boiler?
Better still would be the ability to vary the boiler water temperature so your shiny condensing boiler actually condenses.

 

[Dan Robinson]

What you are describing is Evohome.

 

[fezster]

EvoHome will do what you want, but there may be a delay between a TRV turning off and the signal to the boiler. So when the last TRV turns off, the boiler will need somewhere to dump it's heat, hence an ABV will achieve that. Regardless, an ABV will ensure minimum flow through the boiler and should be fitted anyway. Zone valves will still be required, if you have a HW cylinder.

 

[John D v2.0]

Agree with the above, although specifically the bypass isn't for dumping heat, it's just to allow water to flow through the heat exchanger, the heat stays in the water. But as above most boilers require a bypass as they have pump overrun - to prevent hot spots in the heat exchanger.

 

[ianmcd]

Would be against building regs to have it running through a bypass when there's no heat demand, also wear out your pump.
You'd need some kind of boiler interlock, surely these fancy smart systems have a switched live or a volts free terminal to control the boiler?
Better still would be the ability to vary the boiler water temperature so your shiny condensing boiler actually condenses.

John there wouldnt be a demand for heat as the individual thermostats send a request for the boiler to fire, when they are all satisfied and closed the boiler shuts down but a by-pass and a pump over run will protect the boiler and wont cause any extra wear on the pump

 

[John D v2.0]

John there wouldnt be a demand for heat as the individual thermostats send a request for the boiler to fire, when they are all satisfied and closed the boiler shuts down but a by-pass and a pump over run will protect the boiler and wont cause any extra wear on the pump

Indeed, the thermostats sending a request to the boiler is basically what I meant by boiler interlock.
Dumping heat is when the heat source can't be controlled and the heat needs to be dissipated eg solar heating

 

[gasbanni]

Make sure one rad doesn't have a thermostatic rad valve or simply take the head off one. No matter the set up I'd always have 1 rad which couldn't close.

This is not to say don't fit a bypass.

 

[Gary_Funwick]

Either Tado or Evohome will do what you want on the control side. Any TRV/zone of TRVs can call for heat. In the absence of any TRVs calling for heat the boiler is off.

I would say that you need a bypass circuit to handle any pump overrun or leave one radiator/towel rail uncontrolled and permanently open. If you're replacing the boiler you need one that can modulate down over as wide a range as possible for the occasions when a single radiator calls for heat.

Even better (if you're installing from scratch or doing a big remodel) install a thermal store so the boiler is controlled just to keep the thermal store up to temperature and the store (being just a tank of water) has no problem when a single radiator calls for heat.