So here’s a dilemma where your advice would really be appreciated…
My boiler guys came down to plan the heating system.
They’ve advised against smart TRV in each room (as they say its uneconomical to have rooms going on/off demanding more use of the boiler to heat each separately). Also the the cold rooms/space will suck the heat from the warmer rooms again creating demand on the boiler to go on/off.
They’ve advised to keep all the radiators on constantly at a low temp with low flow rate at the boiler 55C.
They’ve advised to keep the wet UFH on constantly too at a low temp on ground floor, with wired heatmeiser with smart hub.
This removes the need for smart room control it seems. They say less energy is used in the boiler when it trickles constantly at 20p per hour, rather than going full whack then cold repeatedly.
I’m really skeptical but they seemed to know their stuff in detail. Their personal home heating bill per month on a 3 bed is £150 in winter. Mine has always been 2-4 times that.
Any views as this might mean not going down the smart trv with DW at all. I’ll just keep one thermostat for the whole house which is a Nest currently.
There is some truth in this… Its a tricky one and the answer is “it depends”
In my old house, wiser worked fantastically and the house was always warm where I needed it, in my new house (detacted, old 1895), my existing scheme did not work. Boiler was always pulsing ( inefficent) and generally the house was cold…
Another friend of mine also had a heat survey and they also highlighted that in a solid wall house if you have a warm room next to a cold room, the wall will be cold and suck heat out - its true in this house, not in my old (terraced house)
What did I do?
I created zones/clusters of rooms
Downstairs I heat uniformly Lounge/playroom/kitchen, second lounge is set to 18c when the others are being heated to 20
Upstairs I heat in the evening
I also have two radiators in the corridors which have NO Smart TRV , bog standard trv and Ive set the trv to 3. This way whenever any radiator calls for heat then the corridor rads heat up, heating the corridor, and keeping the walls warm.
Also given the heat loss in this old house, I also set the mins to higher than i used to, I found this meant it was quicker to heat and seamed to be more comfortable.
As for gas… well… it ironically appears to be lower…
Thats my view, I think the idea of not letting it go down too much is sound advice, but it depends on the house… Mine is 1895/solid walls, lime plaster, whereas my old place was terraced, new insulated rear and only the front , with large double glazed windows, was exposed solid walls
Definitely depends on your situation. For me, being on oil and therefore no modulation Drayton Wiser has been perfect especially I have different areas in my house with different construction methods and heat loss. In your circumstance, I think you would probably be better off going with what your installer was recommending. If you are going to continue using nest, make sure you choose a boiler which accepts 3rd party opentherm support. I believe intergas boilers work really well but I’m sure there are others. Worcester Bosch are notorious for not working well with 3rd party controls and not having good proprietary controls either so would avoid that.
they both told me to stay away from baxi, main, intergas and don’t bother with the opentherm modulation, saying its not needed if setting the flow rate temp to 55c in the boiler itself instead of hoping for a modulating curve which doesn’t work in practice great.
my new kitchen extension is fully insulated cavity. floor will be insulated for ufh.
rest of house is 1930’s brick without cavity.
2nd installer said the complete opposite of the first and advised smart trv in each room.
so difficult as a layperson when the installers say the complete opposite to each other.
Agree that “it depends” but I’d just like to comment on the myth that a cold room will “suck heat” from a warm room … yes, of course, heat will transfer from a warm room to a cold room (basic thermodynamics) but if the cold room isn’t being used then there is no merit in heating it (except to stop it being damp, and make it easier to warm up when you do want it).
Imagine a setup that goes [Outside] - [Cold Room] - [Warm Room]. The heat loss to the outside from the Cold Room will be less (proportional to temp difference) … or, to put it another way, the Cold Room is acting as a very large insulating layer for the Warm Room.
I have a large, old, poorly insulated house (cost way too much to fix!) with many rooms of which only a few are in use at one time. Over the winter that’s just ended, using the Wiser system, we used less than 65% of the gas we used a couple of years ago, with the same boiler. I think there is more to be done with tuning our schedule and TRV usage, but I’m very happy so far.
It is very confusing, but I’m really not sure about the statement concerning boiler modulation. It really can save you as boiler efficiency increases at lower flow temperatures and it can also make the heat more comfortable as the temperatures become more stable. I believe intergas are good boilers but require water softeners in hard water areas as the heat exchanger is susceptible to scaling which is why sometimes they are shunned.
As others have said, it does depend on your particular circumstances and the house construction.
However, what I will say regarding “installers” is, in my experience, most of them know bugger all about heating and thermodynamics, only being qualified to safely install a heating system, which is the only qualification they need. This is actually an industry-wide problem, as there is no formal qualification to become a “heating engineer” other than being Gas Safe Registered AFAIK.
I would suggest you find a Heat Geek near you and get them to come and take a look. They take training through the Heat Geek programme to properly understand heating, and although it is not an industry standard qualification, it does indicate they have at least got a grasp on the basics of heating. In the past I have had supposed “heating engineers” service my boiler, which I have spent time to carefully adjust the flow temperature on, crank it up to max and leave it there. It shows absolutely no undestanding of heating.
The most efficient way to heat is low and slow, with the boiler return temperature below 55C in order to recouperate as much energy as possible through condensing. This is why I said that you may want to reconsider the idea of using motion sensors as you don’t want to be constantly turning your heating on and off.
It’s true that putting smart TRVs in each room does cause more calls for heat than if you only had one central thermostat. However, the thing that you get from having smart TRVs in each room is comfort. Each room will always be at the correct temperature and you can fine tune the heating as you want to balance comfort and efficiency. The Wiser integration in Home Assistant allows you to put some TRVs into an emulated Passive Mode, to act like a dumb TRV i.e. it stops them calling for heat, unless other rooms that are actively heating are already calling for heat and you can take them in and out of Passive Mode according to your situation e.g. only passively heat a guest room unless you have guests staying.
What I can say is that we moved from a 3 bedroom house 2 years ago, before the energy prices soared, to a 5 bedroom house that is twice the size and our bills are less here than they were at the old house (even with the massive price increases since then). Granted this house is much newer and better insulated, but we have smart TRVs in every room and are not heating 3 of the bedrooms most of the time. They are placed in Passive Mode with a setback of 16C and a minimum temperature of 12C and I have spent a lot of time tweaking the setup to e.g. automatically switch off the heating in rooms where the doors and windows are open, change the heating schedule for certain rooms automatically dependent on who is at home. These are the biggest benefits of having separate room control, along with the comfort that it provides. It depends how far down the rabbit hole you want to go in tweaking everything to gain those efficiencies though.
In addition to what I already said about so called “installers”. Even if they do know something about heating, most of them will recommend what they are comfortable and used to installing and not necessarily what is best for you.
From my fairly limited research, I believe Viessmann are widely considered to be the best boilers available and play nicely with third-party OpenTherm controllers.
Anyone that’s advising against using OpenTherm would be a red flag for me.
@robertwigley yes agreed. Viessmann also good with 3rd party opentherm controls - probably higher end than intergas. Agreed also on installers re opentherm. Definitely suggests they don’t have much knowledge in the technicalities of heating design.
If you haven’t had the TRVs fitted to your radiators yet (the valves themselves excluding the head), instead of using regular ones, consider using auto-balancing ones.
Note, these may not be the cheapest prices, so shop around.
This prevents the need to labouriously balance the system and means that if a radiator is ever removed in future e.g. for decorating, you don’t need to rebalance. In any system where a TRV is fitted the system balance will be constantly changing dependent on which radiator valves are open. These dynamically adjust to that.
I started looking at Viessmann as a top end Opentherm boiler to modulate the heat from DV trv after reading these posts, but then saw their opentherm connectivity is very limited and doesn’t allow the modulating heat curve that people tell me allows the efficiency = pointless if can’t modulate via trv.
However, when connecting on OpenTherm, you have no microcontrol on, for instance, the heating pemperature. It goes to 80 degrees (Celsius), and it stays there no matter what. I would have liked to keep it on, say, 55, and then adapting the timings as such.
I’ve contacted 2 heat geeks so lets hope they don’t say the opposite to each other.
Off topic completely - has anyone tried Electric Water Scale Inhibitors (£70) instead of water softners (£1500 inc. labour).
The Worcestor Bosch installer swears by them in his own home and the Vaillant installer pooped on them - although he did want to install a water softner too!
As I said before, I personally wouldn’t use wiser for a newly installed modulating boiler, especially if you’re not going to be zoning. I would either use the manufacturer controls if they’re good or a nest as I believe nest does opentherm well as it doesn’t tend to request higher flow temps if it doesn’t need them. You would need to clarify that nest would work well with whichever boiler you end up choosing. I remember some posts on this forum saying that wiser often calculates the demand at 100% especially in the morning and hence the flow temperatures requested are unnecessarily high.
I personally use wiser in my situation and it’s great. This is because I have an oil boiler in a very old house and a modern extension - oil boilers don’t modulate. I have setup my system using the integration’s passive mode which has essentially allowed me to zone my house into 2 zones (old part and extension) and the use TRVs as temperature limiters in unused rooms.
Unfortunately, it is a very difficult topic with many differing views and a fairly poorly trained workforce. If I were in your shoes, I would try to find a really knowledgeable installer, which can be challenging, and go down the opentherm, less zoning route. In this situation, you can still use some manual TRVs to limit the temperatures in less used rooms.
What I would definitely avoid is extreme micro zoning with itrvs. I originally did this and it just leads to less comfort. By switching my system to use the passive mode in this integration and by using larger zones and temperature limits I have a much more comfortable house for exactly the same oil usage. Having said this I have reduced oil usage by 40% using Wiser compared to the terrible controls and programmer that the house had previously
I’m steering towards zone per floor, but that still requires Wiser TRV for me. But unclear which boiler speaks well to Wiser modulation and how effective it really is. Veissman seems to not speak well to Wiser from above post. All the installers shun baxi/main when I suggest it.
I have a separate consideration regarding more efficient flow temp for ufh.
Is there a combi boiler which can provide lower flow temp for wet ufh (30C?) and higher flow temp for radiators (40-50c?) - rather than a high flow temp which the ufh manifold mixer valve puts colder water into to reduce temp.
That seems really inefficient and defeats the purpose of having low flow temp for ufh.
Tldr Vaillant can and I’m sure others as well (probably viessmann) using the proprietary controls. Electronic blending valves used instead of traditional fixed ones.
