kWp query

[Joeboy]

Pedant alert!!!

5.5kW so far today

That should be 5.5kWh so far today.

As I am sure you are aware kW is power or the rate that energy is flowing, kWh is the amount of energy that has flowed.

Usually it is obvious what is meant, but not always..

Sorry

Desp

[Joeboy]

Thanks guys, I get that at this time of year input will be reduced, and I was pleased with >11kW yesterday it's just that the max string capacity figure of 2.000kWp doesn't change, it seems to be a parameter that's been set at installation, as it's on a screen that shows the system details, not live or historical generation data. It may not matter and I'm being unnecessarily picky

I wouldn't worry about that figure as it will not affect the output from the system.

How are you getting on Iain in shoulder times? Our son is managing to live the gridfree lifestyle at our place. Washing machine, hot water, oven, beer cooling and video gaming on about 14kWh generation per day.

[Fintray]

How are you getting on Iain in shoulder times? Our son is managing to live the gridfree lifestyle at our place. Washing machine, hot water, oven, beer cooling and video gaming on about 14kWh generation per day.

Doing fine, over last 7 days PV has produced 175.2kWh (25kWh/day avg.) so no complaints! I'm impressed by the A2A heat pump really heats up the conservatory and the kitchen quickly.
Got to be doing some tree pruning to keep PV production at max

[Joeboy]

How are you getting on Iain in shoulder times? Our son is managing to live the gridfree lifestyle at our place. Washing machine, hot water, oven, beer cooling and video gaming on about 14kWh generation per day.

Doing fine, over last 7 days PV has produced 175.2kWh (25kWh/day avg.) so no complaints! I'm impressed by the A2A heat pump really heats up the conservatory and the kitchen quickly.
Got to be doing some tree pruning to keep PV production at max

That's great, long may it continue! I have some treetrimming to do myself. Is there a way to keep an eye on the CoP for the A2A as the year goes on? I am fascinated by the possibility of favourable ratios even up with us. Seems like magic to me!

[Stinsy]

That's great, long may it continue! I have some treetrimming to do myself. Is there a way to keep an eye on the CoP for the A2A as the year goes on? I am fascinated by the possibility of favourable ratios even up with us. Seems like magic to me!

I have a hypothesis about A2A HPs having a favourable CoP compared with A2W. Having a split system with the condenser inside the house is one part of it. Removing the temperature coefficients required to transfer the heat to water then to air is another part.

However, while we can measure the electricity consumed rather accurately, it is very difficult to measure heat output of an A2A accurately.

[JohnW]

Okay spread-tee, fair cop and thanks for pointing out my error, I'm off for a session of self flagellation.

[Fintray]

That's great, long may it continue! I have some treetrimming to do myself. Is there a way to keep an eye on the CoP for the A2A as the year goes on? I am fascinated by the possibility of favourable ratios even up with us. Seems like magic to me!

I have a hypothesis about A2A HPs having a favourable CoP compared with A2W. Having a split system with the condenser inside the house is one part of it. Removing the temperature coefficients required to transfer the heat to water then to air is another part.

However, while we can measure the electricity consumed rather accurately, it is very difficult to measure heat output of an A2A accurately.

Like Stinsy says it would be difficult to accurately measure the heat output v electrical input, at the moment not even the electrical input is being logged but that might change at some point.

[Oldgreybeard]

That's great, long may it continue! I have some treetrimming to do myself. Is there a way to keep an eye on the CoP for the A2A as the year goes on? I am fascinated by the possibility of favourable ratios even up with us. Seems like magic to me!

I have a hypothesis about A2A HPs having a favourable CoP compared with A2W. Having a split system with the condenser inside the house is one part of it. Removing the temperature coefficients required to transfer the heat to water then to air is another part.

However, while we can measure the electricity consumed rather accurately, it is very difficult to measure heat output of an A2A accurately.

Makes a great deal of sense. Looks as if the specific heat capacity of dry air is lower than that of humid air, so dry air will need less sensible heat to reach any given temperature. As it's sensible heat that we really pay for then it makes sense that dry air is going to cost less to heat to a given temperature than humid air. This may also help explain why heat recovery ventilation seems to have such a big impact on the sensible heat needed to keep a house warm. Heat recovery ventilation is very good, but it does tend to dry the air out. Not unusual for our house to be at an RH of around 35% in winter, slightly on the uncomfortable side in my view, and I have thought about adding an ultrasonic misting nozzle into the room fresh air ducting, but doing that would probably increase the heating bill.

[AE-NMidlands]

I thought low indoor RH was just a fact of life in winter (in a leaky or MVHR house) as outdoor air is cold with a very low actual moisture content, so the RH drops off dramatically when you increase the air temperature.
Not sure I would want to humidify indoors unless it was just by house plants transpiring...
A

[Oldgreybeard]

I thought low indoor RH was just a fact of life in winter (in a leaky or MVHR house) as outdoor air is cold with a very low actual moisture content, so the RH drops off dramatically when you increase the air temperature.
Not sure I would want to humidify indoors unless it was just by house plants transpiring...
A

Our last house (early 1990's brick and block) used to sit with the RH at between 45% and 65%, don't think I ever saw it drop below 45% in all the years we lived there. This house (with MVHR) regularly drops down to 30% to 35%, especially in winter. 30% is too low for our comfort, definitely starts to cause some irritation to my nose and throat. I believe that the core reason for this is just the effectiveness of the ventilation, in moving air outside that would otherwise contain moisture from breathing, cooking, showers etc very much more quickly than our old house.

We don't run our MVHR as "hard" as we're supposed to (according to building regs), but have it set to change the air in the house completely about once every two and a half hours. I've tweaked this a fair bit, through trial and error, primarily because the RH in winter was just too low with it set to the building regs ventilation rate. Others I know with MVHR have done the same, the general consensus seems to be that building regs require ventilation rates if MVHR is fitted that are significantly higher than optimum for either heat recovery or humidity control.

Although good ventilation is generally a good thing, too much ventilation, even with MVHR, can result in the air being too dry, IMHO. All I've read suggests that if the RH drops below about 40% then some people may find that uncomfortable. I believe that current guidance is that RH should be between 40% and 60% to be comfortable. Right now the air in our house is at 41%, and we've not yet had any heating on this year, neither has it been particularly cold. I expect the RH to drop below 40% over the next few weeks, as the weather cools, and it will probably be down around 30% by late December/January.