What heating appliances will still work with a restricted current?

Kernel_Sanders

I'm having solar panels fitted, which will be producing over 3 Kw in the summer. This month, however, they will only be producing a tenth of this, so not enough to power even a 400w heater, let alone anything else. I want to temporarily cut the incoming supply from the mains so I'm not using expensive daytime power @18p/Kw (I'm on Economy7). I'm presuming that heaters with thermostats will not work at all as they seem to demand a certain current or nothing at all. But what about the type that draw a constant current and don't have thermostats? Will they still work, abeit with a dimmer glow?
I realise that current to the fridge-freezer and all lesser demanding appliances will be cut, but that is fine when all I need is some free heat whilst using my laptop.

John_Gray

Does the solar panel's inverter always produce 230V AC? Or does it reduce the voltage when there's less sunlight?

S0litaire

Grab an energy meter and see what you use on average during the day.

I'm living alone and my usage is around 4-6Kwh per day. (2Kwh is used during the day. i'm a night owl! lol)
meter currently reads 179w with fridge, freezer TV, FreeSat Box and laptop plus 2 DECT phones on charge and my ADSL router.

The solar panels should feed direct into your mains supply and it's set to use that first before taping into the grid. so for example, to power your 400w heater for 10 hours would cost 18p (300w free from solar and 100w @ 18p per 1000w from the mains)


First check to see if you can get on another tariff or invest in some thermal undies ^_~ lol

As for thermostats and all those LED's, they would be lucky to draw 2w combined and it depends on the type of heating system you have. My Gas combi-boiler uses around 30w to power the water pump to the radiators.

S0litaire

John_Gray wrote: »

Does the solar panel's inverter always produce 230V AC? Or does it reduce the voltage when there's less sunlight?

It's constant.

IIRC:
Each cell produces around 1.5v and their is between 150-170 cells per panel to provide around 230v

Think it's just the wattage that varies with the sunlight.

Kernel_Sanders

John_Gray wrote: »

Does the solar panel's inverter always produce 230V AC? Or does it reduce the voltage when there's less sunlight?

Whatever the panel is producing (DC), the inverter always converts it to 230v AC. (even though it is 'transformerless'!)

Dave_C_2

You have this totally wrong.

If the appliance is switched on it will draw current.

If it has a thermostat all that means is that it will draw current until the thermostat temperature is reached then it will switch off and cool for a few minutes. Then the thermostat will have cooled enough to switch on again and so on...

Of course too many appliances trying to draw current at the same time will either pop a fuse or reduce the voltage to an unusable level.

Think about it, if the sun isn't hot enough to heat your house by itself then it certainly isn't hot enough to heat your house with a few solar panels on the roof! You need the extra heat from somewhere! Hence economy 7

The whole point of economy 7 is that you use the cheap night-time electricity to heat up storage radiators (and your hot water) overnight During the day you use daytime electricity to power the fans in the storage radiators to blow warm air from the storage radiators round the house. The electricty used to power the fan is small compared to that used to heat up the radiators.

Dave

HappyMJ

Kernel_Sanders wrote: »

I'm having solar panels fitted, which will be producing over 3 Kw in the summer. This month, however, they will only be producing a tenth of this, so not enough to power even a 400w heater, let alone anything else. I want to temporarily cut the incoming supply from the mains so I'm not using expensive daytime power @18p/Kw (I'm on Economy7). I'm presuming that heaters with thermostats will not work at all as they seem to demand a certain current or nothing at all. But what about the type that draw a constant current and don't have thermostats? Will they still work, abeit with a dimmer glow?
I realise that current to the fridge-freezer and all lesser demanding appliances will be cut, but that is fine when all I need is some free heat whilst using my laptop.

Can your system do that?

When the external power supply to the property is cut then the panels stop generating. They need a line voltage.

fwor

I know I'm going to demonstrate my lack of understanding of this subject, but...

Doesn't this defeat one of the main gains of the solar FIT? The fact that you get paid for whatever power you generate - even if you use it all yourself?

Do you know for sure that you're going to get paid the FIT even when you disconnect from the grid? I confess I don't know, but I suspect that you won't - in which case your scheme will simply mean you can only use the power, rather than use it and get paid for it.

Kernel_Sanders

Dave_C wrote: »

Of course too many appliances trying to draw current at the same time will either pop a fuse or reduce the voltage to an unusable level.

Think about it, if the sun isn't hot enough to heat your house by itself then it certainly isn't hot enough to heat your house with a few solar panels on the roof! You need the extra heat from somewhere! Hence economy 7

The whole point of economy 7 is that you use the cheap night-time electricity to heat up storage radiators (and your hot water) overnight During the day you use daytime electricity to power the fans in the storage radiators to blow warm air from the storage radiators round the house. The electricty used to power the fan is small compared to that used to heat up the radiators.

Fuses blow through too much current, not too little.

Solar panels that produce electricity are photovoltaic, which means they work from light, not heat. In any case, I don't see where I am claiming that they will heat the whole house.

You seem to be attaching a degree of importance to the fact that I am on Economy7. This is completely irrelevant, and I don't have storage heaters. I only mentioned it to explain why my daytime rate wa so high!

penrhyn

Your inverter will only work when its connected to the incoming mains, in the event of a mains failure it will shut down. Its designed this way to protect itself.

Kernel_Sanders

fwor wrote: »

I know I'm going to demonstrate my lack of understanding of this subject, but...

Doesn't this defeat one of the main gains of the solar FIT? The fact that you get paid for whatever power you generate - even if you use it all yourself?

Do you know for sure that you're going to get paid the FIT even when you disconnect from the grid? I confess I don't know, but I suspect that you won't - in which case your scheme will simply mean you can only use the power, rather than use it and get paid for it.

This is a question I was only going to put to my supplier when I have ascertained that the heaters will still function. I was going to suggest an arrangement where a switch diverts current into a bypass and through a diode, so that any unused power (and data?) can still reach the National Grid. Domestic PV systems have a separate meter to measure the total Kwhs produced, and I am hoping this will only be monitred quarterly, so that all the accumulated generation is recorded.