Air2water kw usage

[Marvin]

Hi @Moggaman

I've just re read this thread  and to be clear, our home is a 104m2 floored bungalow.

So we have about the same rate of usage per m2?

 

[Iceverge]

21 hours ago, Moggaman said:

surface area is 190m2

 

Sorry, I was wondering what the total outside area of the building was. 

 

The total of the ground floor slab, walls and roof and ceiling. 

 

This can make a big difference as a bungalow will have more walls and floor and ceiling exposed to the cold than a two or three story of the same floor area. 

[Moggaman]

Thanks all. I’m a little puzzled by how the system operates still . My plumber is a bluffer if you ask me.

so, I’m using 40kwh a day average, my stats are set to 20 downstairs, it reaches the temp and clicks off… yet my main kitchen living room polished Concrete floor is never warm!…so the temp in the stat stays at 20… I’m assuming the compressor kicks in every now and then to keep it at 20, yet the floor remains cold… the plumbers advice, turn up the thermostat…. I said to him there is nothing wrong with the air temp in the kitchen living but the floor is always cold / not warm… in my head I’m think that’s because the house in keeping the heat so well, the stat doesn’t call for heat so often , therefore it doesn’t get the chance to warm up…if that was the case tho… I wouldn’t be using 40kwh a day!!!!

[dpmiller]

what temperature is/ do you expect the floor to be at?

[Moggaman]

On 16/12/2022 at 09:18, Iceverge said:

 

Sorry, I was wondering what the total outside area of the building was. 

 

The total of the ground floor slab, walls and roof and ceiling. 

 

This can make a big difference as a bungalow will have more walls and floor and ceiling exposed to the cold than a two or three story of the same floor area. 

House is 1.5 storey .. 9 roof lights upstairs…rooms in roof…

Total outside area …. That’s ground floor slab …95m2… back wall - approx 12 x 4.5  - 54m2 … front wall— 12x 3.7 — 45m2.. gables — 30m2…ceiling —- 50m2…

so approx 285m2… I think that’s what you asked?..

[Moggaman]

2 minutes ago, dpmiller said:

what temperature is/ do you expect the floor to be at?

Never had UFH before so I presumed u would feel some warmth from it… is it a sign that it doesn’t get heated that often?

thansk

 

[dpmiller]

It only needs to be warmer than ambient, to heat the air above.

[JohnMo]

The floor is unlikely to be much warmer than the room, so will feel cool to touch.  If it was hot, your heat loss from the house would be higher.  Ours is also cold to touch, but house is warm.

 

We have a very similar house floor area, 192m2, but single storey, the ground floor area is 192m2, all vaulted ceilings and an outside surface area of 624m2, so twice as much area to leak heat.

 

If on the coldest day your thermostat is clicking off, you could be flowing at too higher temp, that means there are gains to be had by reducing flow temp, which will increase CoP and use less kWh.  Also review your domestic hot water flow temp and set point. Another thing to check especially if your flow temps are high or if you are close to capacity when in heating mode, do any immersions kick in, controlled by the heat pump?  Your heat pump could be asking for them to work as well as the heat pump.

[Moggaman]

[Moggaman]

[Moggaman]

[Moggaman]

1 minute ago, Moggaman said:

 Sorry for all the

photos. Might not express myself properly when describing so a picture paints etc…

thanks

 

[Iceverge]

 

 

Looked back through your posts and found this. 

 

Drawing it out I reckon the total outside surface is 429m2. A nice compact shape. 

 

Assuming an average envelope U value of 0.25w/m2k and an average night-time outside temperature of -5 deg your steady heat loss should be 429m2*0.25w/m2K *Delta T of 25deg  = 2681w. Plus MVHR @ 75% efficiency ventilation losses will be about 200w. 

 

Assuming your airtightness is as good as you say 3kw isn't far off the mark. 

 

From your first post here you used 20kWh in 9hrs so 2.2kw of power drawn by the heat pump. 

 

3/2.2 =  a COP of about 1/4  or 140% efficiency in heat pump salesman language.  

 

 

 

[Iceverge]

 

 

Looked back through your posts and found this. 

 

Drawing it out I reckon the total outside surface is 429m2. A nice compact shape. 

 

Assuming an average envelope U value of 0.25w/m2k and an average nighttime outside temperature of -5 deg your steady heat loss should be 429m2*0.25w/m2K *Delta T of 25deg  = 2681w. Plus MVHR @ 75% efficiency ventilation losses will be about 200w. 

 

Add some ventilation losses and 3kw isn't far off the mark. 

 

From your first post here you used 20kWh in 9hrs so 2.2kw of power drawn by the heat pump. 

 

3/2.2 =  a COP of about 1/4  or 140% efficiency in heat pump salesman language.  

 

 

 

[SteamyTea]

Just now, Iceverge said:

3/2.2 =  a COP of about 1/4 

1.4 to save any confusion