Programmable TRVs

[polygonum]

Fitting ordinary ceiling fans can move air around quite effectively - and also make the room more comfortable in summer. OK, so they are even more expensive, but they look better IMHO.

[Robert]

This is what I also need in a couple of low use rooms - ability to call for heat. While programmable by itself would improve things in a couple of rooms, I need an economical way for TRVs to call for heat in 2 other rooms without having additional thermostats.

[Chris French]

In message , harryagain writes

lots of people are probably mostly insulated up now anyway.

[CB]

No you don't have to change them for GMT/BST they do that automagically

- doesn't everything these days (the change always occurs first weekend in March and last weekend in October)

Then I'd need 15

Batteries are supposed to last 2 years - I cant vouch for that as I have only had mine 18 months but they are still on the first set of batteries. If you are away for periods you can save battery by turning them to manual and fully on or fully off (a couple of button presses)

or fit 15 wallwarts in very

You do need to have a fairly predictable routine to "set and forget" but that will apply to anything that is not internet accessible, but one off manual changes are very easy (then reverts to the auto programme at the next switch point)

a bonus is that once a week they exercise the TRV from fully on to fully off and back to minimize the chances of sticking during the summer.

[Capitol]

That improves life until we get rid of GMT. (I can but hope!)

[Andrew Gabriel]

Boilers are not efficient when trying to drive a load of only a couple of radiators. It will be a massive mismatch between the minimum boiler output power and radiator load.

When you split into lots of little zones, you need a more intelligent system to call for heat from the boiler, which needs to factor in a minimum radiator loading, and then decide which zones to activate to achieve that. If you simply have each radiator independently calling for heat, one at a time, each able to handle less than 20% of the boiler output, most boilers will run inefficiently, defeating the object of the excercise.

[Robert]

Maybe not the most efficient use of a boiler, but the object for me is to heat a cold room up when most of the house is already up to temperature ; an issue in larger old houses.

[CB]

But surely given an installed system (not starting from scratch) it would use less gas to drive a boiler inefficiently at low output than to drive it "efficiently" at high output if the heat energy is not needed in the rooms.

It then becomes a cost balance as to how long it would take to pay for a major change to the system compared to a couple of programmable TRV

[Tim Watts]

Good point.

So rather than trying to be clever and diving to a zone per room, it might be better to go for:

Zone 1 All bedrooms

Zone 2 Day areas

(Maybe) Zone 3 Sitting room if not part of 2

In the case of only having Zones 1+2, one could save money on the RF TRV systems by assuming Zone 2 is on when Zone 1 is (but not vice versa)

and only equip the bedrooms with RF-TRVs, leaving plain TRVs in the main rooms plus an RF room stat.

In other words, bedrooms calling for heat heat the day areas implicitly.

[john james]

That isnt going to work very well with only

1 or 2 people who have the same bedroom.

[GMM]

I'm guessing something like this will be the ultimate way to go, but I do have a vision of £51 x 19 rads + lots of other bits being rather more than the benefit of not having to turn a trv down manually. On closer inspection of the Pegler controller, it appears it can be controlled remotely, albeit with an RF controller that is undoubtedly their very own 'standard', so unlikely to be long-lived. Nonetheless, at less than

20 quid a unit by shopping around, it doe seem attractive.

[GMM]

I had spotted that deal as well, whih is quite tempting, especially compared to 30-odd quid at Screwfix. Looking at these a bit more closely, it seems they can be controlled remotely. Have you tried that or is it not much of an issue in practice?

[Fredxxx]

Boilers have a specified minimum flow that should be ok with a single radiator that does not have a TRV.

Even a boiler that has modulated to a minimum and idling is still cheaper to run than an electric fire. When a fan is off, the boiler is off with minimal air circulating in/out of the boiler to lose heat.

Maybe not ideal, but when the output is low, efficiency matters less.

[Tim Watts]

Or you have kids who telnd to be away all day at school but be in the later afternoons and evenings.

If you work from home, you don't need to heat the bedrooms when you heat the day areas.

[Tim Watts]

It depends...

Ignoring the fancy controller (which is self adaptive on occupancy), it might pay back if you can consistently save by having certain rooms turned down at regular times - how many people remember to run around and tweak manual TRVs.

But it is expensive and the obvious cost reductions are the RF TRV heads

- at £60-50, I think these are way over priced for an RF enabled microcontroller, a motor, a few gears and a rotation detector/shaft encoder.

Fair enough - there's a small market and a lot of R&D to recoup, but I could see this part halving in value over time and as a flat needs several and a house maybe 10 or more, this will make a big difference.

[CB]

I have 1 radiator controller that is buried behind my computer desk so I bought the remote control for that one - very easy to operate and works well.

Single button press to select "day" or "night" default setting or current setting can be tweaked up or down 1 Deg per button press.

All my other devices are very easy to get to and operate so I have no need for the remote on them.

As far as I can see there is no way to select the RF channel used and haven't experimented with the range of the thing (remote just sits by my computer monitor). If I had set up both lounge and study devices to accept remote commands, I don't know if instructions to my study device would be received in the lounge. The manufacturers might give advice if you thought you needed it.

[Andrew Gabriel]

It depends heavily on the boiler design. I've done this with two boilers - a newer modulating condensing boiler (Keston 7-25kW), and a 25 year old fixed (Potterton Profile 18kW).

The Potterton handles this just fine because it's designed to vary it's power output by cycling on and off, and does so very efficiently without wasting energy.

The Keston on the other hand is designed to modulate down, but if the radiators can't dissipate 7kW (which no one radiator ever will), it will initially allow the circulating water to go up to 10C above the set level, and will then cycle off. The cycling off is not at all efficient - it wastes significant energy then cooling the heat exchanger for 2 minutes, and it won't come back on until the water has dropped 10C below the set limit. This is just poor firmware design, but it comes about because that's not how such a boiler expects to be operating.

[GMM]

I guess it's the standard dilemma: It's hard to estimate the eficacy before trying it all out, so I'm reluctant to splurge a great deal of dosh in case it doesn't give me anything useful while, on the other hand, the good gear is more likely to work better. You might hope for a reduction in price over time but these things have been around for a while now, so one might imagine they have hit their equilibrium.

I'm coming to the view that it would probably be over-kill to put these things on every radiator as some parts of the house (various spare bedrooms etc) are used only intermittently and it's not too hard to simply turn their TRVs down manually. That still leaves around 12 radiators though, so it's a significant cost to do the whole thing.

[Tim Watts]

Well, you don't have to do the whole place.

If you leave the bathrooms on plain TRVs, they will take heat opportunistically based on their local temperature setting.

And I am going to price up for 2 bedrooms (my bedroom doubles as a workplace in the day) on fancy RF with a wall stat only in the living room and everything apart from the bedrooms will take heat if the living room controller OR the bedrooms call for heat.

On that basis I need 2 fancy TRVs, one wall stat and one controller and

3 PIRs. But I will not be heating 1/3 of the place when the kids are at school but I'm working at home (in theory).

Of course this does also rely on people shutting doors!

[Andrew Gabriel]

You can still have a zone per room, but they need to go through a broker which decides which zones come on when, and they don't get to directly drive the boiler demand signal.

Some of the logic I have played with runs along the following lines. A zone drops below its set point, so you bring that zone on. You can initially keep just that zone on, as it will take a minute or so to get that radiator up to temperature. By monitoring the flow temperature and knowing when the boiler will cycle off, as the boiler starts getting near, you look for another zone which is getting colder and is near its set point, and you bring that on too. You can keep repeating this until you have no more that are getting colder or near their setpoint. Another 'zone' you can consider is the hot water cylinder if you have one - you can bring that on too. The boiler may cycle off anyway, but you have significantly delayed it doing so, and you have also now delayed all the zones which were soon to drop to their setpoints from doing so, so you have significantly reduced the boiler cycling. When it has cycled off, clear all the demands for heat from zones which are above their set point. You will often find that the original zone now reaches its setpoint anyway.

You can also be more wooly about the initial set point - e.g. only one zone dropped to its set point - let it drop half a degree further first unless/until another zone also drops to its set point first.

If you are actually designing a heating system to operate this way from the outset, make sure you well oversize your radiators compared with conventional radiator sizes. This is also important if you intend to keep parts of the house unheated - the heat loss calculations should be done using higher heatloss figures to the unheated rooms. An example of this is where I have an upstairs zone which I might turn on by itself when I'm due to arrive home late at night and go straight to bed (no point in heating the downstairs). However, traditional heating calculators will assume that half the heat input to the upstairs comes from the radiators and the other half comes through the downstairs ceiling. If the downstairs is cold, it will take much longer to heat the upstairs with just the upstairs radiators - you need to factor in that there will be times you want to heat the upstairs without any contribution from downstairs. Same thing with heatloss through an internal wall to an unheated room.

Large radiators are a bonus with condensing boilers anyway - when heating the whole house, I can do it with central heating flow/return running at 45/38C (when blow freezing outside), which makes the boiler just about as efficient as it is possible to be. Furthermore, if you have children or elderly people in the house, it's pretty much impossible to burn yourself on a radiator at 45C. (We did have an elderly relative burn her face when she fell asleep against a radiator on a conventional heating system some years ago.)