Immersion Heater - PV electricity

[echase]

In the summer you should really use the tier1 rates if you are able to turn the gas off completely. That said its still a rubbish return compared to a proper balanced system I am getting significant amounts of hot water on most days even in the winter and the system goes right down to 30W and no grid consumption.

What is a Tier 1 rate?

In Feb I turned my gas off when going away for a w/e. Forgot to turn it on again when I got back on Sunday and the water kept hot till next Friday even in a relatively unsunny week.

 

[pmcalli]

What is a Tier 1 rate?

In Feb I turned my gas off when going away for a w/e. Forgot to turn it on again when I got back on Sunday and the water kept hot till next Friday even in a relatively unsunny week.

Tier 1 is first 220 kwhr per month if you pay monthly. This incorporates the old standing charge. If you can turn off gas all together then you are saving this higher tariff not the lower tier 2

 

[JohnBoyZ]

Hi Guys
As I have a standard large vented hot water tank, and the excess pv provides loads of heat but it is all at the top 1/3 of the tank, so as suggested to me on this forum by JohnBoyZ. I have fitted a small pump eBay - The UK's Online Marketplace it was very cheap. I used a eBay - The UK's Online Marketplace non return valve to stop cold water being drawn up from the base when water is drawn off. I teed into the output at the top of the tank and teed into the inlet at the base. I have just used a timer so that it turns the tank over for 15 minutes 4 times a day, but I will be using two very small thermostats to automate it ( on order ), so that when the top of the tank is 65 c and the bottom is below 60 c it will activate the pump. The pump is very small and very low power, and I have just used an old 12 vdc plug in power supply. So today I now have a tank full from top to bottom with 65 C . Very pleased :- ) If any body wants a pictures or more info email me.

Hi Inie,
Sounds like its working well and good work sourcing such value components. Once you have the thermostats in place it might be be nice to somehow only run the stats/pump when PV is generating.

 

[TechyTim]

Only potential drawback is that as you draw off a lot of hot water, e.g. for a couple of baths, all the tank will revert to a mixed temperature, which could be less than 40 C, until it has time to heat up again. I worked at a British Gas research station in the '70s and thinking at that time was that stratification was acceptable, as it avoided the need for a fast recovery, and tank cold feeds were designed not to mix with the existing hot content.

 

[pmcalli]

Only potential drawback is that as you draw off a lot of hot water, e.g. for a couple of baths, all the tank will revert to a mixed temperature, which could be less than 40 C, until it has time to heat up again. I worked at a British Gas research station in the '70s and thinking at that time was that stratification was acceptable, as it avoided the need for a fast recovery, and tank cold feeds were designed not to mix with the existing hot content.

I am running similar system with an old ch pump and what you say doesn't happen the pump stops as soon as hot water at top of tank temp falls slightly so hot water remains at top of tank as cold is added to bottom same as normal hot water is only added to the bottom when the top is hot enough a check valve prevents the cold being added to the top.

 

[inie meanie]

Only potential drawback is that as you draw off a lot of hot water, e.g. for a couple of baths, all the tank will revert to a mixed temperature, which could be less than 40 C, until it has time to heat up again. I worked at a British Gas research station in the '70s and thinking at that time was that stratification was acceptable, as it avoided the need for a fast recovery, and tank cold feeds were designed not to mix with the existing hot content.

Hi
No it's not a problem as the design is, Thermostat at top is normally open at 65 deg C and thermostat at base is normally closed at 60 C so If above 65 at top and below 60 at base pump will run. As soon as either top is below 65 or above 60 at base the pump is deactivated. I know you have to have a hysteresis on the stats but you get the idea. My tank is nearly 6 feet tall so this has been a God send as I used to only have the top quarter heated properly. Any way I run two tanks in series so I heat both of them and have 400 ltrs of hot water All heated by spare PV. I think I'll have two baths tonight!

 

[inie meanie]

Hi Inie,
Sounds like its working well and good work sourcing such value components. Once you have the thermostats in place it might be be nice to somehow only run the stats/pump when PV is generating.

Yes I was thinking that I might just leave the timer on. But It could be automated from my circuit, I'll have a think about it. Timer works really well and is so simple.

 

[pmcalli]

Yes I was thinking that I might just leave the timer on. But It could be automated from my circuit, I'll have a think about it. Timer works really well and is so simple.

If you are using a sma inverter they have multifunctional relay that you can set via sunny explorer to activate on error or at a particular power level.

 

[pauldreed]

The sun's power is starting to pick up now
Got almost 12.5kWh's of solar power today (about the same as yesterday), and 4.75kWh's of it was diverted to water heating (5.4kWh's yesterday).
The Gas boiler hasn't fired up for water heating since Sunday, not bad as we were home both days, and used the oven, washer, dishwasher, TV etc as well.

Paul

 

[pmcalli]

The sun's power is starting to pick up now
Got almost 12.5kWh's of solar power today (about the same as yesterday), and 4.75kWh's of it was diverted to water heating (5.4kWh's yesterday).
The Gas boiler hasn't fired up for water heating since Sunday, not bad as we were home both days, and used the oven, washer, dishwasher, TV etc as well.

Paul

Sounds a bit low I got 20.8 today 7kwhr went into the tank haven't perfected the pump controls yet and made the mistake of using the shower outlet instead of the top outlet.

 

[pauldreed]

Sounds a bit low I got 20.8 today 7kwhr went into the tank haven't perfected the pump controls yet and made the mistake of using the shower outlet instead of the top outlet.

I'm probably north of you (Yorkshire), but in any event I got a full tank of hot water and ran the usual household stuff from a 3.3kW system so I'm well happy with what I got!!
How are you monitoring your data?

 

[echase]

Tried to run a EMI test on my system this morning but was thwarted by the immersion already being up to temperature by 9am. I have a Solartwin solar thermal system too which, whilst not very effective in winter, does provide this pumped mixing system with its 5watt DC pump as a by product of it's method of operation, so almost whole 210litres is still >59C at midnight. I have 5 temperature sensors on the cylinder left over from developing a solar thermal controller.

Was trying to work out if the SSR phase control action, which pumps a lot of EMI down the mains cable below the EMC band, as EMC filters are not designed to take it out, is interfering with Ethernet over powerline adapters. These work in the aprox 100-150kHz band. Anyone had any problems with theirs? Never noticed any problems with mine but they are set up so that I would hardly notice a 5-15mnute break in transmission. Some baby monitors use this transmission method too.

 

[pmcalli]

I'm probably north of you (Yorkshire), but in any event I got a full tank of hot water and ran the usual household stuff from a 3.3kW system so I'm well happy with what I got!!
How are you monitoring your data?

Mine is 4kw so a bit bigger and in Hampshire quite high up 680 ft yesterday was perfect conditions sunny and cold wind the wind makes about 10% difference due to the cooling effect. I have split meter tails and have installed an extra meter on the house only tail. This means I can accurately measure house consumption and hence export without having to install an export meter which contractually I have to report to my fit supplier. I use a data logger on my immersion controller and a web cam on the supply meter to collect data.

 

[pmcalli]

Tried to run a EMI test on my system this morning but was thwarted by the immersion already being up to temperature by 9am. I have a Solartwin solar thermal system too which, whilst not very effective in winter, does provide this pumped mixing system with its 5watt DC pump as a by product of it's method of operation, so almost whole 210litres is still >59C at midnight. I have 5 temperature sensors on the cylinder left over from developing a solar thermal controller.

Was trying to work out if the SSR phase control action, which pumps a lot of EMI down the mains cable below the EMC band, as EMC filters are not designed to take it out, is interfering with Ethernet over powerline adapters. These work in the aprox 100-150kHz band. Anyone had any problems with theirs? Never noticed any problems with mine but they are set up so that I would hardly notice a 5-15mnute break in transmission. Some baby monitors use this transmission method too.

The emc filters are only designed for ce conformance so I would expect to have problems that said I have had no problems with a100mb one haven't tried such a low frequency one. Am about to embark on preliminary ce testing for my immersion controller so will post the results when I have them.

 

[echase]

Mine has passed CE. It's not straightforward.