Nibe Fighter 360p ashp costing me loads to run

richardc1983

The reason these units work in colder countries is because they have compressors and components capable of working down to the low temps where the nibe is so poor quality it struggles below about 8c! It was never designed properly.

Cardew

jasonoldy69 wrote: »

Thanks for pointing that out. I was aware of the two tiers, but I thought it wouldn't be good idea to ignore the higher tier. It would take a good ~40 days, each quarter (our tier 1 is per quarter), to eat through 900kw.

I think you will find it is 900kWh tier 1 units per year(some companies are less) so approx 2.5kWh per day.

Your 'day to day' electricity consumption - fridges, lights, appliances, TV etc - will use far more than that - so you can use tier 2 prices for all heating calculations.

grahamc2003

richardc1983 wrote: »

The reason these units work in colder countries is because they have compressors and components capable of working down to the low temps where the nibe is so poor quality it struggles below about 8c! It was never designed properly.

But iirc, NIBE is a Swedish company.

Are you saying that NIBE Fighter systems simply don't work at all, due to poor or badly designed components?

They are a conglomerate with pretty much worldwide operations. I'm not sure that could be the case if all users experienced the same as the posters here.

As I tried to explain above, exhaust HPs may not work well with exhaust air at 8C, because the design will be most efficient at expected temperatures, which is probably 20c.

Or do you mean they don't work at an ambient 8C? Which doesn't at all explaoin how they appear to work in countires with much colder temperatures (much of the time sub zero, and frequently much colder than that).

richardc1983

grahamc2003 wrote: »

But iirc, NIBE is a Swedish company.

Are you saying that NIBE Fighter systems simply don't work at all, due to poor or badly designed components?

They are a conglomerate with pretty much worldwide operations. I'm not sure that could be the case if all users experienced the same as the posters here.

As I tried to explain above, exhaust HPs may not work well with exhaust air at 8C, because the design will be most efficient at expected temperatures, which is probably 20c.

Or do you mean they don't work at an ambient 8C? Which doesn't at all explaoin how they appear to work in countires with much colder temperatures (much of the time sub zero, and frequently much colder than that).

I am saying that the NIBE 360 featured in this long standing topic is not upto the job in the UK climate. It has not been designed taking into account our temps in the uk. It would be better off used somewhere like spain. Most heat pumps work down to -10C-15C in places like scandinavia and germany -20C. The Nibe starts to use electrical heat when temps drop below 8C and it just cannot keep up. Here today in Leeds it is 5C so the system is useless. As I have said before the idea of using exhaust heat is a great idea. However the system also has to cope with the make up air that it is dragging into the property through the vents. This air is not pre heated so is introduced cold/very cold into the property making it even harder to heat. If you look at the nibe brochures the next models up actually pre heat the make up air rather than bring it in through the vents. Using the exhaust heat to reheat the fresh air being brought in... this is how true heat recovery works. They seem to have overloooked it on this model as well as it performing very badly. Air to air heat pumps use external air this thing is using internal air so even if the air was at 15C it has a big advantage over units that are working outside. The nibe is just not upto the job and this has been stated many times before.

richardc1983

Not sure why it put it in one long paragraph either.

The nibe is trying to do something it cant, create heat from the same internal air but its ineffecient because as the main heat source you are bringing cold air in to replace the air you are extracting out of the property. THe problem is it is so reliant on ventilation to create the heat source. Most buildings with heat recovery ventilation have a main heating plant be it an air source heat pump they dont rely on ventilation alone to heat the property. However what if there is no one in the property creating heat. Where is that heat coming from then because what you are doing is just removing heat from the internal space and putting it back into the water circuit but then you are introducing cold fresh air from outside that is untreated. Its the same as leaving the window open. It is the design of this particular model that lets it down. If it was a true heat recovery system it would be able to recover heat from the exhaust air and then preheat the make up air.

Page 6 of 32 shows the two different set ups with the 360/370 system layout and then below how it really should operate. !!! you can see the F470 does not have the outside vents as it brings warm clean pre heated air into the property directly from the pump. http://www.nibe.co.uk/upload/nibe_co_uk/documents/NIBE%20Exhaust%20Air%20Brochure.pdf

http://www.nibe.eu/Domestic-heatingcooling/Exhaust-air-heat-pumps/Product-range/NIBE-F750/ - Uses outside and internal air and is inverter controlled says down to -15C

http://www.nibe.eu/Domestic-heatingcooling/Exhaust-air-heat-pumps/Product-range/FIGHTER-640P/ Also utilises outside air as well as the internal air and says down to -5C.

The 360p is just a basic cheapo unit that is not upto the job, you may as well ahve installed something from ebay!

grahamc2003

The nibe is trying to do something it cant, create heat from the same internal space. THe problem is it is so reliant on ventilation to create the heat source. However what if there is no one in the property creating heat. Where is that heat coming from then because what you are doing is just removing heat from the internal space and putting it back into the water circuit but then you are introducing cold fresh air from outside that is untreated

I think this is where some confusion lies - i.e. you think the system can't work because it is taking the heat out of the house which it is heating.

The heat source isn't just the heat from the house - heat is also extracted from the ambient air which passes through the house. It's easy to see how this is possible - air enters at say 10C, gains heat from the radiaters/ufh etc, then enters the heat exchanger of the exhaust HP. If it exits the heat exchanger below ambient (which in this case is 10C), then not only has all the heat from the house been extracted, but further heat from (what was) the outside air has.

The diagram you referenced doesn't show the situation very well - implying the air leaves the heat exchanger at 0C (which in itself is fine if the ambient is 10C). But if the ambient is -5C say (the lower spec of wher this particulatr HP is supposed to work), then the air exiting the HP has to be less than -5C. (Other have posted the air leaving heat exchanges can do so at -60C).

For steady state running, all you have to do to maintain say a 20C house temperature is to maintain a differential between the ambient and the expelled air temperature sufficient to replace the heat loss through walls and window etc - the heat loss from the house through the exhaust air is captured in the cooling from the room temperature down to ambient (i.e. if the exhaust air is 20, and ambient is 5C, then the extraction from 20C to 5C will be enough to heat the incoming ambient air in the house to 20C).

The theory is pretty sound (as you would expect since plenty of these systems appear to work well).

richardc1983

grahamc2003 wrote: »

I think this is where some confusion lies - i.e. you think the system can't work because it is taking the heat out of the house which it is heating.

The heat source isn't just the heat from the house - heat is also extracted from the ambient air which passes through the house. It's easy to see how this is possible - air enters at say 10C, gains heat from the radiaters/ufh etc, then enters the heat exchanger of the exhaust HP. If it exits the heat exchanger below ambient (which in this case is 10C), then not only has all the heat from the house been extracted, but further heat from (what was) the outside air has.

The diagram you referenced doesn't show the situation very well - implying the air leaves the heat exchanger at 0C (which in itself is fine if the ambient is 10C). But if the ambient is -5C say (the lower spec of wher this particulatr HP is supposed to work), then the air exiting the HP has to be less than -5C. (Other have posted the air leaving heat exchanges can do so at -60C).

For steady state running, all you have to do to maintain say a 20C house temperature is to maintain a differential between the ambient and the expelled air temperature sufficient to replace the heat loss through walls and window etc - the heat loss from the house through the exhaust air is captured in the cooling from the room temperature down to ambient (i.e. if the exhaust air is 20, and ambient is 5C, then the extraction from 20C to 5C will be enough to heat the incoming ambient air in the house to 20C).

The theory is pretty sound (as you would expect since plenty of these systems appear to work well).

You are missing my point my point is that the 360 has cold air flooding into the house from the vents, would you want windows open in winter this will make the house feel colder. It should pre heat this air as the other models do. Have you noticed the 360 is no longer on their website!

grahamc2003

richardc1983 wrote: »

You are missing my point my point is that the 360 has cold air flooding into the house from the vents, would you want windows open in winter this will make the house feel colder. !

I haven't missed that point at all.

I've specifially and at length in detail posted how the air entering the house is heated. I'll try it again.

Assume

ambient = 5C
house temp = 20C
air leaving heat exchanger = 0C

Then, the heat extracted in colling the exhaust air from 20C to 0C can be proportioined as follows ...

- heat lost in coolling from 20C to 5C is used in heating the incoming air (or 'cold air flooding into the house through vents') from 5C to 20C

- heat lost in cooling from 5C to 0C is used to replace heat lost through walls, windows, floor and loft.

All I'm saying is that the theory is sound ... very sensible even, given the avoidance of icing.

richardc1983

grahamc2003 wrote: »

I haven't missed that point at all.

I've specifially and at length in detail posted how the air entering the house is heated. I'll try it again.

Assume

ambient = 5C
house temp = 20C
air leaving heat exchanger = 0C

Then, the heat extracted in colling the exhaust air from 20C to 0C can be proportioined as follows ...

- heat lost in coolling from 20C to 5C is used in heating the incoming air (or 'cold air flooding into the house through vents') from 5C to 20C

- heat lost in cooling from 5C to 0C is used to replace heat lost through walls, windows, floor and loft.

All I'm saying is that the theory is sound ... very sensible even, given the avoidance of icing.

But from a comfort perspective it should pre heat the incoming makeup that is how all the heat recovery systems work. Its backwards way and I would hate to be sat near those vents in the room when air at 0C or less is blowing in. So air at 0C when your sat in a room at 20C if you are lucky to get it that high is going to feel mighty cold. IN theory its a good idea but the reality is it just doesnt work and hasnt been designed properly.

grahamc2003

richardc1983 wrote: »

But from a comfort perspective it should pre heat the incoming makeup that is how all the heat recovery systems work. Its backwards way and I would hate to be sat near those vents in the room when air at 0C or less is blowing in. So air at 0C when your sat in a room at 20C if you are lucky to get it that high is going to feel mighty cold. IN theory its a good idea but the reality is it just doesnt work and hasnt been designed properly.

Regarding the airflow - people seem to have open fires, which entails bringing in loads of outside air into the house and then up the chimney. There are regs for where vents go to minimise cold draughts, but most people with open fires don't even notice. Notice also the amount of heat lost from a room with an open fire is probably significantly more than exhausted with an exhaust HP, and an open fire doesn't have much problem maintaining 20/21C (even though most of the heat generated goes straight up the chimney, along with gallons per second of warm room air.).

I don't think draughts are an issure here, judging by the more demanding situation with open fires.