Think twice before installing a new oil boiler thay may be illegal in 10 years

(stella wood) #21


More than 40 years ago (back in UK)… we had solar panels for hot water… worked wonderfully and we could never understand why France was not “awash” with them.

(Véronique Langlands) #22

I am on the tempo electricity system from edf, it is what replaced ejp, which they stopped for particuliers as a new contract about 20 years ago.

You have 3 different rates (red white and blue) with normal and cheap rate in each. I think it is worth it.

My hot water is electric and I have 3 HW ballons because of the peculiar layout of my house, I also use a lot of electricity just washing and drying, with 5 children.

Incidentally if you want tempo they can’t refuse it but you have to insist. It is also advisable not to need electricity for cooking because on red days it is better to use as little as possible.

(Guy Marshall) #23

Really interesting thread - thanks Wozza!

Our 20 year old oil boiler is due for renewal - this makes a more responsible replacement a very good idea.

(Teresa Shipley) #24

Thanks for that information. We were told they no longer do tempo.

(stella wood) #25

This link shows what seem to be all EDF offers to individuals… and it was updated May 2018… you need to scroll right past a load of bumpf to get to the Tarifs…

(carl tunnicliffe) #26

Oh what joy - having just renewed our oil tank!! Ho hum…

Took a look at the OkoFEN range of pellet boilers and have to say I like what I see.

What I DONT see is any prices!!! I know I can get in touch etc etc etc, but I would just like an idea of what one of these systems might set us back - just for the kit, not including installation.

Anyone here be kind enough to enlighten me???

Ta muchly :slight_smile:

(Peter Bird) #27

How do you rate the pompe à chaleur Jane ?

Is it a viable system ?

(John Withall) #28

Pompe a chaleur, (heat pump) isn’t a system it’s a heat transfer device. How well it can work in a home depends on what it is coupled to (rads or under floor ) unless it’s air to air. The performance is down to what temperature the heat pump can work down to and how well sized the unit is with the radiator output.
One person’s system can work really well whereas another will be totally different.

(stella wood) #29

OK John… so, a Heat Pump… to transfer heat to rads … where does the heat come from ??

(Jacquie Clegg) #30

I’m going to be moving house in the next couple of months. The village in which I live (450 in habitants, south Seine-et-Marne) doesn’t have mains gas. Some neighbours have had great results with heat pumps, more have had very disappointing results (they use their fireplaces/woodburners very often!). Solar power doesn’t help much in the winter! A friend who has asthma is appalled at the idea of everyone converting to pellet boilers - and surely they also give off CO/CO2 emissions? Have these ideas been thought up by politicians in Paris who have no idea of what life outside big cities is like.

(John Withall) #31

It could be a ground source, via a buried pipe(s), or air source from the available air.

(Paul Flinders) #32

Either the air or the ground, as John says.

In the case of air (if I have calculated it correctly) cooling 1 cubic metre of air by 10oC gives about 13kJ of energy - which is enough to raise the temperature of a litre of water by about 3oC - the heat pump moves this heat and also allows it to flow “in reverse” from a large volume of cooler air to a small volume of hotter water. As you can see you need to move a lot of air through the system.

Ground source pumps use the fact that below about 1 metre from the surface the ground temperature is relatively constant so if you pump cold water (actually a brine with antifreeze) into a sufficiently long pipe buried 1-2m down it will come back slightly warmer, extracting heat cools the water back to its starting point and gives you heat to transfer.

Instead of using a long horizontal pipe you can use a vertical borehole.

Air source units are cheaper to install but work less well in the winter. One problem is that when the intake air is above freezing but the exhaust air is below freezing then moisture in the air freezes on the heat exchanger reducing its efficiency. Most systems include some way of melting this ice but that takes energy out of the system.

As the intake air cools below freezing icing of the exchanger is less of a problem but the gradient between input air temperature and water flow temperature starts to become impossible to achieve with the heat pump and the system may resort to using an auxiliary heater - again reducing efficiency.

Ground source pumps have the additional cost of burying the pipework or drilling a borehole but then the low temperature side of the system works at pretty much the same temperature all year round.

Heat pumps, especially air source, are less suited (than conventional boilers) to driving normal radiators as they are most efficient with a flow temperature of 35-45oC and conventional radiators do not work terribly well at that sort of temperature so they are better suited to things like underfloor heating.

(John Withall) #33

Jacquie, exactly as I said above, the system needs to be engineered to work properly, not everyone with a set of spanners is an engineer!

Again solar, depends on the system, the British antarctic team use evacuated solar for hot water in Antarctica.

Pellet burners, burn a lot cleaner than wood stoves and are generally room sealed. The pellets and wood in general is said to be carbon neutral as burning release the same amount as rotting in a forest.

(John Withall) #34

It is more to do with the area of the radiator needing to be larger as the temperature of the water flowing as you say is lower in order to provide the equivalent amount of heat, hence why underfloor is suited better to these systems.

Not withstanding that the first thing is to add lots of good insulation.

(Paul Flinders) #35

Ultimately it is because not as much heat is transferred from the radiator to the air as the thermal gradient is lower. As you say you can compensate for this by using radiators with a larger surface area such as double or triple panel designs.

Unfortunately 1950’s cast iron radiators such as I have are not great :frowning:

So, the compromise is to set the flow temp as high as possible, I also need that because the system supplies hot water - another poor match really as, ideally, the cylinder temp would be 60°C to kill any legionella but the system really does not run efficiently with a flow temperature that high - I think I set it at 56° as a compromise (just hot enough to kill legionella).

I agree with the comment about insulation.

(carl tunnicliffe) #36

The developer I work for here in the UK installs ground source heat pumps on all it’s developments as policy.

We design retirement living apartments and we find that this energy source is ideal for the owners of the apartments - they have no hot water or heating bills. The system is paid for by the company that installs it as there is something that they get in return from the UK Government. It is a very efficient system but it makes a hell of a mess when it is installed - the bores go down to a depth of some 30 metres and there are usually in the order of 10 to 15 bores per scheme. Because of the mess (mud slurry mainly) they are the first thing to go on the site before foundations are laid. As our developments are an average of 36 units each, we also have to have a fairly large plant room to house the tanks and pumps as well as the manifold that connects all the bore pipes to the equipment.

It is a fairly complex set-up!

(Paul Flinders) #37

The problem with air source systems (well, mine anyway) is illustrated in the graph below

The heat pump is a Stiebel WPL 16S, maximum output is about 16kW but you only get that if the air temperature is above about 25°C, note how the output drops sharply below an intake air temp of 10°C.

Down at 2°C, let’s say a not too chilly winter’s day and the output is about 9.5kW, down at -7°C, a reasonably hard winter’s night in Morbihan and it’s dropped further to about 8kW.

However at 150m2 I reckon 15kW is needed to heat the house even with decent insulation so I’m a bit stuffed.

The previous owner would have needed the WPL23S (or even better the 23E but I think that’s a newer model) to really have provided enough heat down to -7 outside but I guess he just balked at the price of a larger air source system or a ground source system (even though there is plenty of room to dig trenches for horizontal pipes). The system he put in cost 15k€

Ultimately, however, the point I’m making is this - John is right when he says:

You need an experienced heating engineer who will size the system properly taking into account the house, insulation, existing radiators, local weather patterns and the type of system being discussed otherwise you might end up with a heating system which is not adequate for your needs.

(stella wood) #38

We are on solid rock… so I suspect ground source is not a viable option… where can one find heat in the air… in winter - we regularly get down -10c or -15c on the other hand… it can get to 20c in midwinter at midday… ??

(Paul Flinders) #39

A borehole might still be an option.

It doesn’t matter what the air temperature is - cooling air from -20°C to -30°C gives almost the same amount of energy as cooling it from +30°C to +20°C

Even my unit produces some heat output at -15°C and the WPL23E will work down to -20°C even with a flow temperature of 60°C - it’s not crazily efficient at that temperature, CoP being about 1.5, but it does work.

However these are pretty large units (1.2 x 1.2 x 1.5m) which need, ideally, to be sited externally so you need a decent amount of space for installation.

(stella wood) #40

By the sound of it… in my situation… the external installation is out of the question… and the borehole… mmmmm… seriously know nothing about boreholes… just know all about the challenges of living on rock …