Boiler notes with CAP and solar

[PITMIX]

Hello

I am looking to size the power of my future heat pump to replace my existing boiler.
I will certainly keep a boiler on standby but really in case the PAC group breaks down.
I asked myself a lot of questions to avoid making a mistake.
Well yes the PAC have a coef. performance of 3 but at the moment the electric kWh costs 0,078 € against 0,04 € for the gas . For that we must manage to calucler energy needs to the fair and make the best possible choice of equipment.

My idea is to leave on the best possible basis.
The PAC can not be sized according to the existing boiler because it is oversized. This is very often the case.
My current boiler supplied 30kW to heat a 110m² house.
The annual conso is 1200 € gas.
A heating specialist estimated the power necessary to heat my house at 16kW.
Thermal balance with the small furnace here gives me 14kW of attrition.
It seems that a PAC must be undersized from 20 to 30% compared to a boiler. The only reason for this undersizing is the starting frequency of the compressor. The less often it starts, the longer it lasts.

So with 20% less it makes me a 11kW PAC.
If I isolate the house well it falls to 7.5kW.

I left in the hypoteses:

By calculating the price of energy consumed in kWh / year compared to the power of my boiler in kW, I determined the frequency of operation of my boiler.
Boiler from 30kW to 0,04 € per kWh of gas = 1,2 € per hour.
1200 € / year divided by 1000 gives 1,2
Let 1000 hours be at 1,2 €. Which gives 41,67 days to 28,8 €.
Let's say that the heating only runs 6 months a year, ie 182,5 days, that gives 1000hours divided by 182,5 = 5,47h or 5h 28min 12sec.
The boiler thus runs 5h30 per day during 6 months of the year.

If my future PAC works with the same frequency as the current boiler, it will give an average of 5h30 per day during 6 months at 0,078 € the kWh. Either a conso annual fee of 326 € of electricity by taking an average COP of 3.

And from there I determined that to have an 1200 € electricity bill I would have to use the CAP for 21h / 24 for six months. It is very unlikely.

I calculated all that to realize the figures if I'm wrong in sizing the CAP.
Because the problem is that we must not go into excess.
Do not over size the CAP and risk the life of the compressor. Do not undersize the cap and have electricity bills too high.
I do not know if it's clear and I hope my reasoning is right.

[Woodcutter]

1200 € gas at 0.04 € / kWh equivalents gives an annual consumption of 30 000 kWh.

For a house of 110 m2, that makes us 270 kWh / m2 / year, which is really a lot ....

With good insulation (roof, walls and openings, in order of importance), you can go below 100 kWh / m2 / year, or even much less depending on what you do (65-70 kWh / m2 / an is possible).

To calculate your heating power, you can reduce to 3 months of use at 100% of the heating, or 10 "thermal" kWh per month, or around 000 kW of continuous heating power.

I don't know how much your heat pump will cost you, but you would do well to spend part of the "heating" budget towards the "insulation" budget, because your calculations are made with the current price of energy, not with future prices ...

[PITMIX]

Hi Bucheron
No worries the project is obviously the insulation of the house in the first place. I am currently calculating heat balance to estimate the power difference of losses between with and without insulation. The simulators give me 25% savings.
I am trying to make a real thermal balance to compare with the simulators.
You're absolutely right about the annual conso. It's enormous.
The boiler has more than 40 years, it has not been maintained for at least 15 years and the circuit is certainly fouled by limestone.
In addition there is a water leak on a radiator.
The roof is insulated into the attic but the ground floor is not.
Windows are new PVC db glazed downstairs. In top simple glazing frame wood.
For calculation I know that I take the current figures but there I have no choice.
Regarding the boiler itself I intend to keep it for Nothing because for me it's easier to invert in a PAC.
I am a frigologist so it helps
Normally with the tax credit it should not cost me much more than a small wall-mounted suction cup.
On the other hand, I saw an ELM Leblanc at 1000 € at casto. It's really cheap for a production of 23kW.
It makes you want to turn the old as quickly as possible.
There I will have trouble to have lower

[Woodcutter]

By the way, a question: what is your PAC as an exchange?

[PITMIX]

It will be a PAC air / water because I do not have room for a geothermal sensor.
I know that the COP is not stable at low temperatures
but it is of the order of:
4,7 to + 7 ° C
3 to 0 ° C
2,5 at -7 ° C

I also think that I could consider installing a buffer tank. It would allow to obtain more inertia and also to use the CAP at maximum in off-peak hours.

[Woodcutter]

[...] I am currently in the heat balance calculation to estimate the power difference of losses between with and without insulation. The simulators give me 25% savings.
I'm looking for a real thermal balance to compare with the simulators [...]

Can you detail your insulation project?

For your heat pump, the COP of 4.7 seems enormous to me ... it is at + 7 ° C that the "standard" COP values ​​are calculated for heat pumps that use air as a heat source, right?

[PITMIX]

Yes that's it
A + 7 ° C the COP is 4,7 for the best air cap. It falls to 2,5 at -7 ° C.
I think it's a pass-pass of the builders to take + 7 ° C to determine the COP of the machines.
If I believe what I was told the tax credit is granted for machines with a COP of at least 4,2.
Here is the example of a machine that pleases me well by its simplicity of construction

http://www.ventilation.fr/catal/geother ... .php?acces

As for my insulation project I will do in the classic.
10cm rockwool and plasterboard plates, the walls are made of 20.
Apparently the coef K of the wall will go from 1,4 to 0,6w / m². ° C
It reduces 55% losses through the walls. On the whole of the thermal blan it gives 25% of economy.
The refacing is new I do not intend to isolate from the outside.
I would also like to make solar heat exchangers for domestic hot water and eventually for heating.
Everything will depend on the efficiency in winter of the sensors that I will manufacture for the ECS.

[Woodcutter]

[..] Regarding my insulation project I will do in the classic.
10cm rockwool and plasterboard plates, the walls are made of 20.
Apparently the coef K of the wall will go from 1,4 to 0,6w / m². ° C
It reduces 55% losses through the walls. On the whole of the thermal blan it gives 25% of economy.
The refacing is new I do not intend to isolate from the outside.
I would also like to make solar heat exchangers for domestic hot water and eventually for heating.
Everything will depend on the efficiency in winter of the sensors that I will manufacture for the ECS.

It's a shame, while you plan to spend less to consume, not to do things until the end ...

Your rockwool is 650 kWh per m3 when manufacturing materials that are very energy efficient in their manufacture and which, in addition, allow to store carbon ...

In addition, by isolating from the inside, you deprive yourself completely of the mass effect provided by the cement block (which is however one of its only advantages, in addition to the fact that it is carrier).

Finally, the first post of heat losses is the roof ...

[PITMIX]

The roof is already isolated.
What do you advise me for walls other than rockwool,
cork panels ??
I have seen that cork panels cost 24,9 € per m² for 50mm thickness.
The most expensive rock wool I have found is 10,8 € m².
But most of the time it costs 7 € / m² for 75mm thickness.
Glass wool is the same price.
Not to mention that the insulation is better.
k 0,1 cork w / m². ° C
K rockwool 0,04w / m² ° C
K glass wool 0,034w / m² ° C

[arthur]

completely agree with Bucheron on the gray energy of rockwool (on the other hand, I have a value of 150 kWh / m3, local energy info space source? ...)
The expanded cork is about 90 kWh / m3, hemp wool 30 kWh / m3, cellulose wool 6 kWh / m3.

In terms of insulation, I do not have the same values ​​as you, but all depends on the source of the info (manufacturers data are they reliable ??? ...)
For the data I have (still energy info space), roughly a rock wool, a cellulose wool, a hemp wool or expanded cork, it is about the same thermal conductivity ( so even insulation at equal thickness).
So if you want to gain isolation, you have to put a thicker insulation, and if I understand correctly, you want to insulate from the inside, so it will reduce your living space.
The ideal would be outside, but it's not the same price, especially in renovations.

apart from putting a thicker insulation, I do not really see what you can do to better insulate.