Using smart TRV's to zone my gas central heating.

[david101]

Having watched Heat Geeks video on why not to zone a heating system I am now wondering (confused) about whether using smart thermostats to zone my home is actually worth it.  The main message I got from the video is that the small energy savings made by turning down, or off, rooms individually are lost due to the gas boiler now running less efficiently. Its clear that zoning should be used if for example there was a UFH zone and a radiator zone but an all radiator system is not so clear.

My plan was to install Drayton Wiser smart TRV's on nearly all my radiators but now I'm wondering if just having a Wiser room thermostat is the better way to go (and cheaper!).  At present I have my downstairs radiators on smart TRV's and the upstairs radiators on manual TRV's.

I'd appreciate any thoughts on this and what peoples experiences have been that do use smart TRV's on all their radiators.

[SAtewart]

If you have a very small footprint house on one level, maybe there is an argument. Otherwise I'd take the Geek's wisdom with a pinch of salt and especially if you have manual control over the boiler's flow temperature. I'm saving £150 to £200 per winter month using this kit. That is a complete payback in two to three months (I did install myself). Unless you live in a small dwelling, take the plunge, you will not lose money and very likely make savings that eclipse the initial investment in a couple of heating seasons. BTW I have no affiliation with Schneider/Drayton, but I believe objectively the system's plusses outweigh the negatives by a significant margin. 

[SAtewart]

So if you have rooms that require a markedly different timing schedule of heating, get them on a separate stat and schedule. £40/pop - no brainer IMO.

[david101]

The house is occupied all day, every day. We use the whole house so all rooms are heated on the same schedule.

My options are.....

1. A room stat in the main lounge or the hall that controls heating everywhere.

2. Smart TRV's downstairs with manual TRV's upstairs. (I have this at present).

3. Smart TRV's on all radiators except the bathrooms, cloakroom and utility room.

I may well be over thinking this!

[PhilHornby]

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@david101 wrote:

I'd appreciate any thoughts on this and what peoples experiences have been that do use smart TRV's on all their radiators.

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Every since I encountered my first central heating system (in the mid 1980's), I've been deeply disappointed by the crudity of the controls. It seemed obvious that individual control of every room was the holy grail but it's been a long time coming.

Finally, with the Wiser system I have the control I seek. I've no idea when or if it will save me any money though - even at today's prices I could buy a fair amount of heating oil for the £1500 I spent.

So for me, iTRVs in every practical location (other than high humidity bathrooms) and Room Stats in those rooms where half-decent temperature regulation is required.

I note the issue with a hulking great big boiler firing into life, just to heat the downstairs loo - but that's a price worth paying in my book.

[david101]

In my scenario I would only have iTRV’s on 9 radiators leaving two bathrooms, one cloakroom and a utility room under manual control. This would mean if just one radiator called for heat anywhere in the house I would have 5 radiators heating up which should be beneficial to my boilers efficiency.

[PhilHornby]

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@david101 wrote:

Having watched Heat Geeks video on why not to zone a heating system I am now wondering (confused) about whether using smart thermostats to zone my home is actually worth it.

If it's this video, I think they've got themselves confused ...

...although they do some arithmetic (and call it maths), one of their premises about zoning doesn't seem right to me. User "nezhad11" replied to point out the error of their ways, but they were having none of it ("We've got 8.5K likes, so we must be right" 🤔 ).

In a nutshell, turning off the heating to a room does not affect the power output of radiators in adjoining rooms. They don't automatically start working harder or increase their flow temperature to try and maintain room temperature in the unheated room. It will have some effect, but modelling it seems quite involved, because it's dynamic - until the 'unheated' room falls to its Setpoint and starts being heated as well.

If you were heating your house with Fan Heaters and you had two adjoining bedrooms - one in use and one not - wouldn't you just shut the door of the unused one and turn its heater to anti-frost? 

Efficiency is not the same as cost; it may not cost half as much to heat one room, but it will cost less, than heating two.

(Your car probably does more mpg on long runs than short, but you wouldn't turn every short journey into an unnecessary joy ride, in the name of efficiency...)

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@david101 wrote:

This would mean if just one radiator called for heat anywhere in the house I would have 5 radiators heating up which should be beneficial to my boiler's efficiency.

I think you'd still be wasting fuel though - heating rooms unnecessarily. Since 2010, Building Regulations has  required at least two heating zones. I wonder if they will expand the requirement further?

(Just my thoughts; I've never earned a living as a Heating Engineer 😀 )

[david101]

Thats the video I watched and this one which is more to do with heat pumps

[DaveP]

I think it's about convenience for me, oh and I'm a geek!
I want my bedroom and the bathroom warming up a bit before I get up and go to bed; my back bed room is unused but don't want it getting damp; hall and kitchen low level heat for most of the day; lounge is where I want most heat. During the recent cold snap I kept the overnight temperature in the lounge higher as it was taking so long to get up to a decent temperature in the day.

Pre Drayton I had a thermostat fixed on the wall; it was fairly close to the radiator, so although I had it set to 21-22. I have discovered now that I have a portable thermostat that it's 5 degrees cooler where I sit.
Now, I can achieve a more dynamic balanced system, and when all rooms have met their targets the boiler heating flow shuts off. I am tinkering with the boiler temperature, only had the system in a couple of weeks. For the hub, room stat and 6 valve thermostats it cost £274 in the Black Friday sale, so I'm pleased.
I have Opentherm ready to go, but judging by some of the comments I may not bother.
Now having a tinker with the API to see what useful info I can glean, if any.
One thing I would like to know is how often the hub stops the boiler heating, which I've requested as a feature in the app, could be useful?