Posted by: @dant

@julianc 

Hi Julian

With this product, I assume it still only diverts the excess to the water tank. i.e. on a sunny day, the solar let's say would be providing the power for the dishwasher, and then any excess would be diverted to the hot water tank?

It wouldn't divert all the power to the hot water tank, bypassing powering the dishwasher, right?

Not sure about Julian's system, but our iBoost only sends excess electricity (what would have been exported) to the immersion heater in the hot water cylinder. Your appliances take priority. At this time of your year, with plenty of sun around, and the ASHP off, it works like a dream. Free hot water for 4-5 months - maybe less this year because May was such a washout. We also crank our immersion up to 60C, so that we can mix down with cold water, thus having loads of hot water for the evenings. 

@editor thanks both

I am more inclined to get a diverter than continue exporting, we're only getting 3.5p per kWh back from the grid, yet spending 16.4p per kWh at home. If the solar can reduce some of that, I think it makes more sense for me to divert any excess to heat the water then send it to the grid. 

I've reached out to some installers.

@dan-t I think all diverters work in the same way. Sending “spare” PV to wherever you want. If you switch the kettle on, for a cup of tea, the diverter dynamically stops heating the hot water in my case, and uses the solar PV to heat the kettle. When the kettle switches off, it goes back to heating hot water. 
Some more sophisticated diverters you can set priorities like battery first, EV, hot water. 
But definitely get one - it is a no brainer decision if you have PV

@dant I fully agree - there's very little point exporting at the moment - the tariffs are just so low. You're better of utilising as much of the electricity as possible.

Here is an updated look at our 14kw Mitsibushi Ecodan ASHP performance. Not a great May 🤣 

Firstly @george great data. I do not have any like that available with my Daikin. Other than if I laboriously go press buttons and write stuff down. Errr no 😊

Secondly the split between heating and h/w is interesting. Despite May being a bit cool, I think I only ran the ASHP twice to heat h/w. The rest was by solar PV and Solic diverter.

My Daikin has used 247.08kWh since installation on 21st April. 1.13kWh on standby over the past day. Which is interesting. 5.61kWh / day since it was switched on. So you have used a lot more heating than me, ignoring the h/w. 

Maybe we need to normalise by dividing daily usage by m2 area of home. If so mine is 0.0275kWh/m2 per day 

Im waiting for my next Octopus bill to see the cost impact. All interesting stuff. Please keep posting everyone. 

Hi Dan,

Julian is perfectly correct in that diverters utilise the same principle, they measure the power flow and divert any excess.

For example, if your solar PV system was generating 1.3kW and your home was using say 300W, then 1kW would be being exported back to the grid. If you now switch on your kettle (3kW), then instead of exporting 1kW you would now be importing 2kW. When the kettle switches off it would revert back to exporting 1kW.

If you install a diverter unit, the 1kW that was being exported could be fed to an immersion heater or similar load up to 3kW. Although the immersion heater may be rated at 3kW, the diverter unit would limit the power being fed to 1kW and hence you would not be importing power from the grid. Of course it would take 3 times longer for the immersion heater to heat the water, since it is being fed with one third of its rated power.

I hope this makes sense.

I’d love to get my hot water costs down but sadly running the secondary return just kills the efficiency of the unvented cylinder and people aren’t happy to wait 20-30 seconds for hot water in our house.

I am looking into solar PV that is connected directly to a coil on the cylinder to heat the water as I think I’d only need a few panels to make it work. Lots of people seem to do this in the US whereas everyone in the UK seems to have solar PV for general household electricity use and a diverter for excess to be used on heating hot water/charging a car. 

Hi George,

I am not certain what you mean by 'running the secondary return'?

How are you heating your water at the moment? Are you using an immersion heater fed from the grid, or are you using your ASHP?

Do you know how much hot water is used?

To produce hot water using free 'green' energy there are various options.

You could install a solar thermal system, though you may require a hot water cylinder with both a primary and secondary heating coil, unless you already have one. Two or three solar thermal panels would probably be sufficient dependent upon how much hot water is required.

You could install a solar PV system and a diverter unit as described in previous messages.

Alternatively it should be feasible to install just solar PV panels connected directly to an immersion heater. An immersion heater is not bothered whether the electrical supply is Alternating Current (AC) or Direct Current (DC) and will work with either. Since DC is more dangerous than AC, any cabling would need to be adequately protected and fully labelled, and the two systems AC and DC would need to be completely isolated from each other. I can provide further details if you wish.

Hi George,

Having read some of your previous messages I think that I now understand your meaning of the secondary return, though you can correct me if I am wrong.

So from 5am to 11pm you are pumping water around the main hot water pipework so that it is fairly quickly available at the various take off points. Since you talk about pipework going under your driveway, is there just one building or two?

To reduce the need to be pumping the water round the system continuously you could try the following.

Install a second hot water cylinder, in a suitable location near to where the hot water is being used, in the area of the building furthest from the main hot water cylinder. It does no have to be as large as the main cylinder, maybe 200 litres would be adequate.

Have a thermostat fitted to this second hot water cylinder that switches on the pump, so that hot water is pumped from the main cylinder into this secondary cylinder. When the secondary cylinder is up to temperature the pump will be switched off. Whilst it may not be instantaneous, it should still be possible to have hot water available in much less than 30 to 60 seconds. The pump will therefore only operate when hot water is being used from the secondary cylinder or the water temperature falls due to heat loss. This should help reduce your energy consumption and hence cost.

You could further improve your carbon footprint by installing a solar PV system. I.T.S. Technologies are offering 6 panel kits online, ranging from £1200 to just over £1600.

@derek-m

Hello Derek, are you proposing one to install solar themselves? I would love solar but I felt it would be to expensive with the list of other demands, this price however looks good and I assume it’s a DIY kit, that scares me, big steep roof and heights!

Hi Phil3822,

I was mainly pointing out that the equipment is not that expensive. It may be possible to get a friendly local roofer and electrician to install a system rather than pay an arm and a leg for some company to supply a system.

When I had my solar PV system installed I had no choice other than to use a registered company, so as to be able to claim the Feed in Tariff. Someone can correct me if I am wrong, but I think that is no longer a requirement since the Feed in Tariff is no longer available for new installations.

Obviously most people would not be able to install a system themselves, but as the saying goes 'there is more than one way to skin a rabbit'.

The panels don't necessarily have to be on a roof, just look at a solar farm.

If more people started arranging their own installations, then it may encourage various companies to lower their prices. Obviously you would need to ensure that any requirements were met.