Are room thermostats out of fashion?

[Andy Hall]

.. but it doesn't - it merely suggests it as good practice.

That's simple enough to do.

If the boiler manufacturers were doing their job properly, it would be a non issue anyway.

Of course not, because there are sound engineering reasons to back up the practice or the use of calculation.

I didn't say that it was optional. However, some of the methods described as "best practice" fade into inignificance if a properly designed modulating boiler is used. The best practice has been thought out assuming the simplest and least efficient boiler is used. Even the slothful UK heating industry is gradually moving beyond that point and the return from using systems appropriate for older technology heating equipment becomes less and less.

True, but there is no specific legislated requirement. It states that very clearly at the start of the Approved Document.

One can always refer back to the statutory instrument.

The boiler is going to fire numerous times during the day anyway at full power output to recover the hot water cylinder, even in the summer.....

In comparison to everything else that can be done, preventing a boiler from firing for a minute or two an hour on a few days of the year is not a big winner in terms of energy saving.

.andy

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[Christian McArdle]

I still don't understand the objection to adding a simple flow switch to the radiator circuit. It costs very little, makes the system explicitly compliant with approved document L1, is simple to wire and prevents your primary circuit being hot 24/7/365. (Unless you sit by the controls and act as a manual room stat, turning your system on when it gets cold outside).

I read the document as being suggestions of what might be considered reasonable provision, rather than best practice. You are required to make reasonable provision. If it considers system 'A' explicitly with feature 'B' to be reasonable, then I can't see how system 'A' without feature 'B' or an alternative to it can be considered reasonable.

The system without this feature depends on user intervention to remain efficient. This appropriate user intervention may not be apparent when you sell the house to someone else. It relies on the user to understand that the system uses considerable energy even when the house is not being heated.

Christian.

[Andy Hall]

Yes, but it's a recommendation, not a requirement.

Mine does exactly that, and modulates the pump.

That was my other main point. Since a modern boiler already has to have "intelligence" by way of a microprocessor to handle modulation etc. it is possible to sense all of the operating parameters and to control all of the devices like pump and motorised valves.

Not really. My point was that there are much more substantial savings that can be made by using modulating and condensing technology than can be saved by this corner case.

Part L1 also discusses having some low energy lights, but it can't make the householder use them.

.andy

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[Andy Hall]

Easily. If I can demonstrate that I can substantially exceed the energy saving of adding room stats to old technology boilers by using a newer technology boiler, then that is more than reasonable.

That assumes that the boiler is a simple on/off type which is the assumption of the whole document and those referenced by it.

If the game is changed by using a newer and better technology, then those assumptions are no longer the case in the overall scheme of things.

It's only considerable in the case of an older style simple on/off boiler.

.andy

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[Christian McArdle]

But most "building regulations" are recommendations. If you don't follow the recommendation, you have to prove your alternative is just as good.

In which case, the systems within the boiler provide sufficient interlock and the boiler is directly compliant with Approved Document L1 without further external controls.

However, it becomes much more than a corner case if you can't rely on the user to turn the system off during warm weather/over summer. Didn't someone suggest around 700W to keep a typical primary circuit warm? At 16 hours a day on the timer from May to October, that's around 2000kWh over summer, completely wasted. Over winter, the savings are much less, as the primary circuit will need to be warm for at least half the time, but savings are more likely to occur, as people will probably turn off the heating over summer, if they can work out the controls.

This part of L1 is totally ridiculous. I only use low energy bulbs, but refuse to install the ugly and expensive fittings that are mandated. A more reasonable solution to the low energy bulb fitting problem is to allow normal pendent fittings, but put a ten pound tax on each incandescent light bulb, to ensure they retail at considerably more than the cost of a proper bulb. The bulbs should also come with a health warning on the side, saying that you are causing irreparable and needless damage to the environment.

Christian.

[Andy Hall]

Right, and all of this is easy for manufacturers to implement at low cost.

At 80 degrees possibly, but at 40?

I don't think that that would fly somehow. Until the appearance and colour temperature of these can be made to match tungsten lighting or at least be in the area, and be dimmable people, I don't think that they will become that popular.

I don't mind having fluorescent lamps in a workshop or even for outside lights but not for living areas. They are too cold.

.andy

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[Christian McArdle]

I don't get that assumption at all. Why do you think that turning off the boiler when no heating appliance requires heat is specific to an on/off type boiler? It is simple to do, cheap and effective to turn off the burner when no heat is required, whether it is a modulating type or not. OK, an old open flue boiler suffers more from short cycling than a modulating condensing fanned flue boiler, but the primary circuit losses are the same for both.

Obviously, with analogue TRVs and a modulating boiler you have the advantage that the system can modulate down and bumb along nicely. However, there are still savings to be made when the system really doesn't require heat, and by a very simple, cheap and effective system, too. The cost of a flow switch is very small, and it is wired up in the same way as a room stat, just requiring to be inserted into the correct bit of pipe. (i.e. after the bypass). The pulsing pump system is optional (but could save quite a lot of cash, if you run an 80W pump 24/7).

Christian.

[Andy Hall]

I didn't say that it was specific, only that it is much more worthwhile.

On a conventional on/off boiler, especially one with large thermal mass heat exchanger and with natural draught flue, there are numerous inefficiencies:

- It isn't modulating

- It isn't condensing

- Heat convects through the flue after firing

- There is a lot of hysteresis in the water temperature coming up once the burner starts.

- It operates at a consistently high temperature.

All of these add up to an overhead each time the boiler is fired up, so I agree that for that scenario, preventing firing when there really is no heat demand is desirable because the energy saved may be significant.

They are not because the operating temperatures are different.

During the winter heating season the system will be operating in a condition when some level of heat is required to compensate the building heat losses during the timed heating period. There is always a demand for heat, so there is no reason to interlock firing. The burner may turn off because its minimum heat output is less than required, but there remains a demand. At this stage, the flow temperature may well be in the 40s.

During the spring and autumn the duty cycle of on time gets less and less as the heat requirement reduces and with a properly designed modulating boiler you end up with very short burning periods and very low circuit temperatures except during hot water cycles.

Exactly.

There are still *some* savings perhaps, but I think that it is a matter of keeping these things in proportion. There is really no point in saving 50W of energy if there are other factors that result in the waste of hundreds of watts or more elsewhere.

Flow switches are cheap, I agree, but they are not very accurate or sensitive. If you consider that TRVs around the set point should be partly open because they should be allowing some amount of water through how do you determine the cut off point? A bypass around the switch could be used, but I still wonder about the sensitivity.

I suppose a flow sensor would be better, but then that's a lot more expensive. In any case, the boiler should be able to deduce the flow because it knows how much energy is going in and the temperature drop across the heat exchanger...

.andy

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[Christian McArdle]

Certainly, if the boiler can work it out in software, all the better.

Christian.

[Christian McArdle]

Not if my shower pump was anything to go by. The flow switch activated even for a couple of drips. For the CH application, you would want it at the sensitive end, to take full advantage of the TRV's analogue nature.

The alternative is to put the flow switch on the bypass. However, I reckon this wouldn't be as good. Firstly, it makes the control wiring more complicated. Secondly, a correctly configured bypass would actually operate slightly when TRVs were mostly closed, in order to reduce noise in the system. You wouldn't want to cut the burner under these conditions.

Christian.

[Owain]

"Andy Hall" wrote |"Christian McArdle" wrote: | > ... put a ten pound tax on each incandescent light bulb, to ensure | > they retail at considerably more than the cost of a proper bulb. | > The bulbs should also come with a health warning on the side, | > saying that you are causing irreparable and needless damage to | > the environment. | I don't think that that would fly somehow. Until the appearance and | colour temperature of these can be made to match tungsten lighting | or at least be in the area, and be dimmable people, I don't think | that they will become that popular.

They'd become much more popular very quickly if incandescents cost a tenner each!

However, the price of CFLs is kept down because they are in competition with very cheap GLS. If GLS were taxed to be a tenner each then CFL manufacturers could creep their prices up and we'd all end up paying more to the manufacturers or the government either way.

Perhaps we should simply tax energy more; at full 17.5% VAT, and possibly with a tax on top of that for larger bills to go towards paying for new and greener power stations (because we're going to need new power stations 'real soon now'). At the moment large and inefficient users actually pay less per kWh because they get discounted rates.

Owain

[The Natural Philosopher]

So, you think people sit there dripping with sweat, with the boiler churning away, in teh summer? I don't think so.

Even the most stupid user can work out how to s3itch the boiler ON and OFF. FAR more than they can get the hang of adjusting 14 TRV's and a main thermostatt.

[The Natural Philosopher]

Ah, but that was averaged over the year. Its MUCH less in summer.

AND asummes long runs of pipework with full flow through them, and not insulated particularly well.

IF all TRV's are off, then the bypass loop will be the only thing getting heated. Basically thet is so small as to be almost irrelevant.

Anyway, the biggest savings in fuel are to be had by working from home.

Transport eats about 5 times what domestic heating does.

When I was commuting I was burning something like 70 liters a week in fuel. Times two for two people. That's 3500 liters a year to be saved.

[Christian McArdle]

Maybe not. But many will turn the heating on in October and off in May. For much of this time, no heating will be required.

Why bother, when a flow switch can turn the boiler on and off for them? There is no need to have room thermostats fighting with TRVs. A simple flow switch is fine.

Christian.

[The Natural Philosopher]

Ok, given that I have very few TRV's, and instead a series of fan assisted convectors, how do you think I should control THAT lot :-)

Wire OR all the room stats together to control the pump? And then what about the rads with TRV's on?

Blimey, the installation cost in both cash and energy would exceeed savings over the lifetime of the system...

[Christian McArdle]

That depends on what your bypass is. A tiny bypass internal to the boiler is likely to be small. However, a permanent bypass through a bathroom radiator is likely to be much larger.

I'm still not sure why you are so resistant to having a ten quid flow switch in the system. Over the lifetime of the system, it will definitely save many times that in gas and isn't much of a risk.

Christian.

[Christian McArdle]

I'd have thought that fan convectors would have simplified matters.

If I had several fan convectors and several TRVs and didn't want a room stat in the radiator part of the house, I would:

1. Have a programmable room stat for each fan convector (basically because you can, and it gives separate timing for rooms likely to be used differently, such as kitchens and conservatories, where such heaters are typically installed).
2. Put all the convectors on a separate convector zone (or unzoned, if the convector has an internal valve to prevent water circulation when off).
3. Put all the TRV radiators on the unzoned circuit, with flow switch. Any bypass is before the radiator circuit
4. Run boiler when either HWC or convector zone valve (internal or external) opens, or when flow switch activates.
5. Run pump either continuously, or when any zone valve or flow switch opens and pulsed every ten minutes when not.

Alternatively, if the convectors have internal valves, an alternative is to just treat them like a TRV radiator, in that they would cut the flow when off and can activate the boiler using the flow switch, just like the radiator. This would be very simple to wire, as the signalling to the central heating from the convector is simply through the water pipework. No electrical connection is needed.

Christian.

[Dave Plowman]

With an overall stat, it won't come on...

[Andy Hall]

It's counterintuitive of course. Utilities are already charged in this way in California.

Of course if light bulbs were heavily taxed, there would become a black market in them......

Perhaps the government would then introduce colour temperature detector vans.

Owain

.andy

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[Christian McArdle]

Tax them at source. Then people can ship in loads from France, except, of course, they are for 220V and will blow twice as often.

On the other hand, would people bother, particularly as the hassle of importing them illegally just isn't worth it, as the alternative is cheaper overall than what they're used to.

Another technological solution (easily bypassed, of course) to the silly fittings rule in Part L1, is to introduce a pendent fitting that only allows

25W to be drawn. Any more and it should flash the light. i.e. stick a 100W light bulb in and it has 1 second on and 3 seconds off. BTW, I'm not actually serious here, except maybe if I renting out a house and wanted to stop the tenant flogging the bulbs.

Christian.