Circular reasoning (Rolfe's solar energy system)

[Rolfe]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.

EDDI works in two ways, one on a schedule so you can heat the water off peak and the second it diverts all export thats going to the grid into your immersion, it aims to keep your export at zero. If theres say 700w being exported it will feed that 700w into your immersion. As the Solar increases or decreases and / of house loads change, so does EDDI, it's a brilliant piece of kit. Set the schedule for peak and then forget it, it will do its stuff. If you need to boost the hot water for any reason, in the app you can set it to boost for 'x' hours etc.

Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

 

[Bam Bam]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

View attachment 26634

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.



Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

Yes I'm not sure how it works exactly but surely it must happen - if you had a smaller inverter than the panels could produce in full soon then it is "clipped off." Perhaps if the inverter cannot make a circuit then the electrons won't move in the panels?

I'd be curious to know what those levelled off amounts are between 1130 and 1630 - the yellow and orange. Are either of those 5kw or 3.68kw? That would indicate export-based clipping I think.

 

[Archev]

Yes, that's what my installer said to do. I thought he had left it switched on, but when I realised the water wasn't very hot this morning I checked and it had been sitting there switched off. So when I switched it on it had a bit of catching up to do.

I see it seems to be cutting in from time to time with a spike of usage. At least I assume that's what it is, there isn't anything else on that could do that. I was going to ask, should I switch it off once the sun has gone, because there really isn't any point in keeping on boosting the temperature unless there are free photons. But you have confirmed what my installer said. So it keeps the water scalding while there's free solar, and then what? How does it work when there isn't?

By all means keep the water in the cylinder very hot but have it at around 50 C at the kitchen and a max of 38 / 42 C at the taps on the wash hand basins and baths. Temperature blending valves can be fitted beneath / behind those taps to regulate the max temperatures at those taps. This leaves the storage cylinder at max temperature which makes the hot water “last“ longer and prevents bacteria build up.
I went to a tragic case of a wee laddie of three who had been scalded because the cylinder thermostat was set to max allowing nearly 80 C water to all taps in the house. That wee soul lost I think three fingers and suffered many skin grafts after trying to be helpful washing his own hands when everyone else was distracted.

 

[Rolfe]

Yes I'm not sure how it works exactly but surely it must happen - if you had a smaller inverter than the panels could produce in full soon then it is "clipped off." Perhaps if the inverter cannot make a circuit then the electrons won't move in the panels?

I'd be curious to know what those levelled off amounts are between 1130 and 1630 - the yellow and orange. Are either of those 5kw or 3.68kw? That would indicate export-based clipping I think.

It clips at 5.3 kw. The orange is just 5.3 minus the current house load, so the exported power.

 

[Archev]

By the way, I think you're dead right about the system limiting generation when the battery is full. The pattern of the top being sliced off the curve is very clear now, and as you say, it starts when the battery is full.

View attachment 26634

You can also see the peaks of the hot water. I think what I thought was a very high peak just before the dishwasher finished was actually a hot water boost coinciding with the dishwasher doing something.



Thanks. I'm not at the stage of messing with the settings as yet, baby steps. The installer did say something about this, but it's a lot to take in. Clearly I'm not going to need to boost the hot water for a while though! And I do have the option of asking the oil-fired central heating to do a hot water boost if I want. Although the installer said, now we're in the business of you not using any more oil until autumn.

I need to experiment, but it might be cheaper (or indeed even free) just to run an electric fan heater in the living room in the evening for a bit, if it gets chilly then, than to crank up the central heating boiler.

It's tea-time, and I'm tempted to put something on to cook, just to see how it works. Probably use a bit of battery. But it's too hot to eat a hot meal!

I’m loving these progress reports. Why not make a loaf or two of bread while you have a salad ??

 

[Bam Bam]

I’m loving these progress reports. Why not make a loaf or two of bread while you have a salad ??

Yeah I started using a bread machine we inherited much more when we had the solar installed!

The electricity expense of it had been putting me compared to store-bought. Once I got on the givenergy App I realised it wasn't drawing as much as I feared anyway.

 

[Archev]

Yeah I started using a bread machine we inherited much more when we had the solar installed!

The electricity expense of it had been putting me compared to store-bought. Once I got on the givenergy App I realised it wasn't drawing as much as I feared anyway.

Yeah I’m buying all the weird and wonderful flours and seeds etc for my loaf production.

 

[Rolfe]

By all means keep the water in the cylinder very hot but have it at around 50 C at the kitchen and a max of 38 / 42 C at the taps on the wash hand basins and baths. Temperature blending valves can be fitted beneath / behind those taps to regulate the max temperatures at those taps. This leaves the storage cylinder at max temperature which makes the hot water “last“ longer and prevents bacteria build up.
I went to a tragic case of a wee laddie of three who had been scalded because the cylinder thermostat was set to max allowing nearly 80 C water to all taps in the house. That wee soul lost I think three fingers and suffered many skin grafts after trying to be helpful washing his own hands when everyone else was distracted.

I didn't know that was possible. I've had this issue for a long time and a previous plumber was unable to solve. In fact I settled on timing the water heating so that it wasn't scalding at the times I wanted to use it. I was just thinking today, back to scalding water here, what do I do now.

Many of the sinks and wash hand basins in the house have mixer taps, but a couple don't, and it's still an issue with mixer taps anyway. So thanks for that.

What a tragedy for the wee boy.

Yeah I started using a bread machine we inherited much more when we had the solar installed!

The electricity expense of it had been putting me compared to store-bought. Once I got on the givenergy App I realised it wasn't drawing as much as I feared anyway.

I cooked. I wanted to see what happened if I did my usual thing with the oven and the hob and the electric kettle.

The earlier green load spikes are the immersion heater, and happily it doesn't go on doing it after the solar has faded away. The wider one must be oven and hob, and I think the electric kettle went on once at the beginning to boil water for the potatoes and vegetables, and once at the end to make tea. It's all just one spike though, not that impressive.

That brought the battery down to about 93% and although it tried to recharge there was bugger-all sunshine to spare by that time. The rest of it is just the house base load continuing, fridge and freezer and things on standby (and the cat's wee electric blanket which can't be 40 watts, I never bother to switch it off, he likes his warm bed when he comes in from the hunt).

Then at nine I put some lights on - having swapped out 440 watts of incandescent bulbs for new low energy ones. My installer said, if you prefer incandescent bulbs in these wall lamps why not just do it, you'll have plenty in the battery in the evening. But I'm thinking it will be different in winter when the battery is being charged up overnight, then the lights go on a lot earlier in the evening. I'm a reformed character, start as I mean to go on. And I put on the TV for a zoom call that lasted about two and a half hours.

But look at all that sunshine! Hell of a display for Day One of the system. I've learned so much! I don't think it's going to be so sunny tomorrow so we'll see how that goes.

 

[Archev]

I didn't know that was possible. I've had this issue for a long time and a previous plumber was unable to solve. In fact I settled on timing the water heating so that it wasn't scalding at the times I wanted to use it. I was just thinking today, back to scalding water here, what do I do now.

Many of the sinks and wash hand basins in the house have mixer taps, but a couple don't, and it's still an issue with mixer taps anyway. So thanks for that.

What a tragedy for the wee boy.

View attachment 26647View attachment 26647

 

[Rolfe]

Thanks, good to know.

I remember about 15 years ago a politician who was in a bit of trouble for excessive expenses claims for his second home declared that he needed to get a new boiler because his hot water was too hot!

 

[Archev]

Thanks, good to know.

I remember about 15 years ago a politician who was in a bit of trouble for excessive expenses claims for his second home declared that he needed to get a new boiler because his hot water was too hot!

I’ve tried simple X’s to help with their hot air

 

[decrep]

To me that solar drop off doesn't look natural, especially as it coincides with 100% battery and you don't notice any change in the sky.
I'm fairly sure there's something going on in the inverter that is limiting solar.
But I have no knowledge of your English system, so I have no idea what.

 

[johnb80]

I didn't know that was possible. I've had this issue for a long time and a previous plumber was unable to solve. In fact I settled on timing the water heating so that it wasn't scalding at the times I wanted to use it. I was just thinking today, back to scalding water here, what do I do now.

Many of the sinks and wash hand basins in the house have mixer taps, but a couple don't, and it's still an issue with mixer taps anyway. So thanks for that.

What a tragedy for the wee boy.

My system I run the water at 80 degC plus but have a temperature blending valve on the outlet from cylinder to reduce it down to 45 deg C. The plumbing is dead simple with the two pipes needed being at the cylinder already it was literally a T piece, the mixing valve and a bit copper piping, from memory all from Screwfix and was less than £80. Running the tank at higher temperature increase effectively the hot water storage capacity.

 

[Archev]

My system I run the water at 80 degC plus but have a temperature blending valve on the outlet from cylinder to reduce it down to 45 deg C. The plumbing is dead simple with the two pipes needed being at the cylinder already it was literally a T piece, the mixing valve and a bit copper piping, from memory all from Screwfix and was less than £80. Running the tank at higher temperature increase effectively the hot water storage capacity.

That is a compromise solution. Bear in mind that 45°C is on the hot side. Hand wash basins in hospitals, hotels etc are usually required to be set and signed for between 38 and 42 after installation / servicing ( sometimes even lower ). With thermostatic showers again the air requirement was usually for the 38°C to be maximum / or where the override button was set depending on the type of shower valve installed.
I did encounter a number of valves installed at, or sometimes directly on the cylinders but found in practice they needed more frequent servicing and actually had to replace a good few where internal springs, diaphragms, “O” rings etc. just couldn’t cope.

 

[Coulomb]

Bear in mind that 45°C is on the hot side.

Really? Blood temperature is 37°C, so that won't feel warm at all. 45°C is only 8° above that.

 

[Rolfe]

To me that solar drop off doesn't look natural, especially as it coincides with 100% battery and you don't notice any change in the sky.
I'm fairly sure there's something going on in the inverter that is limiting solar.
But I have no knowledge of your English system, so I have no idea what.

Not English. Just saying.

Really? Blood temperature is 37°C, so that won't feel warm at all. 45°C is only 8° above that.

Seriously, you'd be surprised. 37°C does feel warm and it ramps up quite quickly above that. Try some experiments.

 

[johnb80]

That is a compromise solution. Bear in mind that 45°C is on the hot side. Hand wash basins in hospitals, hotels etc are usually required to be set and signed for between 38 and 42 after installation / servicing ( sometimes even lower ). With thermostatic showers again the air requirement was usually for the 38°C to be maximum / or where the override button was set depending on the type of shower valve installed.
I did encounter a number of valves installed at, or sometimes directly on the cylinders but found in practice they needed more frequent servicing and actually had to replace a good few where internal springs, diaphragms, “O” rings etc. just couldn’t cope.

Why is it a compromise, it works well for me.

45 deg C isnt too hot, IMHO, a recent holiday in Corfu witnessed temperatures over that in the shade.

 

[Archev]

Really? Blood temperature is 37°C, so that won't feel warm at all. 45°C is only 8° above that.

Really ?, I mean really really ?
One or two of that master race, the Ladies might shower nearer that level but, really ? Sorry I’m a mere mortal

Why is it a compromise, it works well for me.

45 deg C isnt too hot, IMHO, a recent holiday in Corfu witnessed temperatures over that in the shade.

I meant the compromise was between the figures I quoted. A bit too warm to have left a wash basin and not quite hot enough for the kitchens in hospitals etc.

Seriously, you'd be surprised. 37°C does feel warm and it ramps up quite quickly above that. Try some experiments.

Or - don’t please - if my signature is anywhere near the certification documentation.

Why is it a compromise, it works well for me.

45 deg C isnt too hot, IMHO, a recent holiday in Corfu witnessed temperatures over that in the shade.

After crossing the Mojave desert I burned my bum on a stainless steel toilet pan in a toilet behind a gas station at an air temperature of around 43C on the car’s dashboard. A truly crap experience I assure you ( for a fair skinned Scottish posterior )

 

[johnb80]

I meant the compromise was between the figures I quoted. A bit too warm to have left a wash basin and not quite hot enough for the kitchens in hospitals etc.

Ah OK, understood.

After crossing the Mojave desert I burned my bum on a stainless steel toilet pan in a toilet behind a gas station at an air temperature of around 43C on the car’s dashboard. A truly crap experience I assure you ( for a fair skinned Scottish posterior )

Conjures up an image

 

[Rolfe]

Why is it a compromise, it works well for me.

45 deg C isnt too hot, IMHO, a recent holiday in Corfu witnessed temperatures over that in the shade.

Air temperature and water temperature are two entirely different animals. Particularly as regards to how quickly and directly that temperature is transferred to the body.