What energy rating is your HW cylinder?

[markocosic]

Why don't you get something that heats the water efficiently instead?

 

Rather than dumping your previous winter time PV into an immersion heated Sunamp for "100%" efficiency whey don't you feed it into a heat pump cylinder for 200-300% efficiency?

 

e.g.

 

https://www.electricpoint.com/dimplex-edel-hot-water-cylinder-heat-pump-200l-edl200uk-630rf.html

https://www.tesy.co.uk/heat-pump

 

Higher performance. Lower cost. Winner.

 

[Russdl]

Oo, this has kinda turned into a Sunamp thread! 
 

Ours sits there silently doing it stuff, not leaking heat etc. Heated by off peak electricity in the winter and PV in the summer (actually it’s heated by off peak all year round at the moment as it’s 5p a kW but I’m sure that’s going to change).
 

No gas/oil boiler or ASHP gubbins or any other shizzle to worry about.
 

It’s excellent. If it fails I would definitely buy another. 

[Spacey73]

Simple really, Sunamp goes where the boiler was in garage and the large immersion tank goes to scrapyard and bathroom gets extended into a wet room. I can charge Sunamp at 7.5p a kWh for 5 hrs on Octopus if I have to, but will most probably be fine using solar power to heat it during day even in winter. 
 

I hate that heating the water tank gets scuppered as soon as you use some of it as cold water is put back in to the mix reducing its temp plus the 2kwh at least a day loss.

 

I can always add more panels ground mounted (came up with a really good cheap fit mount that can be angled as well), for future proofing.

[markocosic]

Sounds like there's no reasoning with somebody who has decided to waste money doing things inefficiently.

 

Enjoy wasting electricity to produce hot water that could have been used to provide hot water and space heating.

[Spacey73]

That’s a really spiteful thing to say to someone you don’t know. Full of bile….cheers for that.

 

why would I buy a high temperature heat pump (yet another large thing hanging off the house looking not so awesome) which costs a lot of money compared to normal temp heat pumps…just to heat up the water tank efficiently…only for said water tank to inefficiently lose heat/kWh as they do and also mix in colder water as you use the hot water.

 

Really don’t get the snarky attitude, seems to be the way of things these days.

 

I have 3 acres of area to ground mount Solar so I would rather add cheap £1,200 per 5Kw modules and haven’t overkill on Solar to cover winter (with grid back up for emergencies) to cover slack in winter output.

 

I just don’t want another heat pump hanging off what is a really nice country bungalow which has 2 already

[SteamyTea]

9 minutes ago, Spacey73 said:

have 3 acres of area to ground mount Solar so I would rather add cheap £1,200 per 5Kw modules and haven’t overkill on Solar to cover winter

Do you have planning permission for that size array?

9 minutes ago, Spacey73 said:

why would I buy a high temperature heat pump

Why indeed.

Most 'high temperature' HPs are not very efficient at the top end.

 

9 minutes ago, Spacey73 said:

That’s a really spiteful thing to say to someone you don’t know

It is because you have already made up your mind and have not listened to counter arguements and real world experience of the SA.

[joe90]

Well I am an ASHP with DHW at 48’ tank fan, it’s only 5kW and my tank does not loose any heat as it’s within the well insulated house, during the summer it slightly warms the airing cupboard. I have not yet found that hot water is cooled by drawing cold as the tank stratifies adequately. When I installed this lot Sunamps we’re very new and the original versions had problems (see Jeremy’s blog). I am sure they are better now with version 3 or 4 but it was a risk too far for me back then.

[markocosic]

If you'd actually clicked any of the links you'd have seen an "all in one box" designed for installing in a utility / garage / basement @Spacey73

 

Buy. Plug in. Finished. You don't even need to duct the vents if it's in a garage / basement; and it will even dehumidify the air as it makes hot water so that your tools / cars etc don't rust. Pretty. Freaking. Awesome.

 

You then spend the £2.5k that you've saved by buying this instead of a Sunamp on more PV in the field.

 

Or...if you would enjoy it more...buy yourself the shiny Sunamp that you want and enjoy wasting the PV that you could be using to heat your house or run your fridge instead. It's dumb but if the Sunamp is what makes you happy then do go buy one and I hope you enjoy looking at it and aren't too bothered by all the electricity it is wasting.

 

Secondhand Electric Agas are also cheap on eBay at the moment if you fancy wasting some more electricity. 😉 

 

 

 

[Tom]

I'm kinda with Spacey73 here, in that resistance heating seems just a whole lot more simple way of doing things - if the numbers stack up. Sure, 100% vs 300% efficiency for a heat pump can certainly sway the argument, but it would depend largely on how much PV you have that you could dump in to a store - whether thats a Sunamp or a UVC. We have a 12kW array and think that we would probably get away with resitance heating for hot water and our UFH (via a Willis or two) - but those all-in-one units you link to above Mark do look pretty neat. The heat pumps are only relatively small units buy the look of them (1300W for the Dimplex), so I wonder what the real-world cost of running one would be as I guess the immersion would have to take up the slack a lot of the time - and then of course you have the standby draw for the pump itself, servicing costs etc etc

[PeterW]

19 hours ago, Spacey73 said:

I hate that heating the water tank gets scuppered as soon as you use some of it as cold water is put back in to the mix reducing its temp plus the 2kwh at least a day loss

So a Sunamp acts in a similar manner and goes off a cliff.. so does a UVC but it’s got much more capacity…
 

 

[markocosic]

It's a glorified fridge @Tom

 

No servicing (above any other G3 cylinder) beyond occasionally clearing out the spiders.

 

No need for immersion either unless your usage pattern is ridiculous. There's a 270L version too but 200 should be plenty.

 

A 12 kW array will probably be flat out in winter just doing your household electrical load. (assuming you're battery shifting the night load) what is your projected generation vs usage for Dec/Jan?

 

Not much left for hot water and space heat. Say An A2A unit to get 300 kWh source heat out of generation 100 kWh. An A2W unit to get 300 kWh hot water out of generation 100 kWh. 100 kWh left over from that 12 kW array for the rest of your household load if you're lucky.

 

Throwing an additional 8 kW array at the problem would get you 200 kWh more that you could waste via immersion heat / willis heat. Cost more than £5k probably £8-10k. Add £2.5k more for the extra cost of a sunamp Vs the heat pump cylinder.

 

Or you don't waste the 200 kWh. Spend £2.5k less on the water heating and make that extra 8kW array 12 kW. Now 300 kWh leftover to roast turkey or sling in the EV.

 

I just can't see any scenario where spending MORE to achieve a WORSE result (Sunamp) makes any sense whatsoever. Unless you're just obsessed with having a Sunamp?

[Spacey73]

Hardly compact solution that cylinder is it?

 

Hot water heat pumps are also not that efficient for those high temps needed, very expensive also. Really don’t want a 3rd heat pump hanging off the house.

 

3kw is the charging rate of the Sunamp, with an already large solar array and 32kwh of house batteries (Tesla S already catered for with its own solar car port setup and buffer battery)….. I don’t see me having any issues putting a 10kwh charge into Sunamp.

 

largest system was £3.8k I think, plus £1,200 for an extra set of solar panels. I have 2 spare mppt connections on the 8kw off grid inverter.

 

I think the price is pretty reasonable, air to air system up and running and very efficient. Went to bed with 76% left in battery ….also 75 miles put into Tesla and only the standing charge to pay for electric.

 

Not sure why my setup is so stupid?

[Dave Jones]

On 28/07/2022 at 12:44, Marvin said:

Hi @Spacey73

 

Depends on what is driving your decision: Installation cost, space, running cost, demand......

 

Also depends on what your other sources of heat are....

 

It's the winter you want to be thinking about. Are you considering a 300ltr tank because of the amount of hot water you use or thinking of using it as a heat sump. Also in winter how much PV power are you expecting to have excess of to use heating the water? The conundrum here is you could end up with only enough PV power to have a huge tank of tepid water, and so end up using other power to bring it up to temperature  What is the average kWh you expect to produce on each day in January?  We have 5.12kW PV and we produced about 6kWh a day in January, HOWEVER, your amount would depend on the panel slope, the angle in relation to the sun's zenith, the shading by objects and the location and so on.

 

 

 

Hi @Adsibob

Here is my 205ltr tank:

 

PIR in room walls, supersoft around tank, 6mm ply on frame to encase the lot.

 

 

HOWEVER!

 

Any thermostat in the insulation will need to be digital.

 

If I have it right,  this type of immersion heater thermostat relies on a bimetallic switch which relies on a typical room temperature to work:

so incasing it in insulation means it will not work. (I'm sure someone will correct me if I'm wrong)

 

I have used one of these to switch a 20amp relay to turn on the hot water immersion:

 

Note the type of sensor:

 

As you can see only the sensor enters the insulated area:

 

 

Secondly I removed the immersion heater thermostat because that would be effected by the insulation similarly.

 

AND

 

All power cables in the insulation will need to be ducted.

 

Good luck.

 

M

 

not with a mixergy tank.

[ProDave]

On 21/09/2022 at 22:43, Russdl said:

It’s excellent. If it fails I would definitely buy another.

That's an interesting statement.

 

Something like that, if it failed, I would expect it to be repairable for a reasonable price.  e,g it is easy to change the immersion heater in a normal HW cylinder.

 

If it failed and was not repairable, that would be a big put off for me and I would be wanting to replace it with something else.

[Tom]

On 28/07/2022 at 12:44, Marvin said:

you could end up with only enough PV power to have a huge tank of tepid water

 

Pretty sure you can get UVCs with multiple heating elements at different levels to avoid this - correct me if I'm wrong though

[joe90]

11 hours ago, Spacey73 said:

Hot water heat pumps are also not that efficient for those high temps needed,

I and others here heat our DHW to 45-48’ with heat pump with a decent COP, why go any higher?

[Marvin]

18 minutes ago, Tom said:

 

Pretty sure you can get UVCs with multiple heating elements at different levels to avoid this - correct me if I'm wrong though

HI @Tom   I think your quite right, and my tank is only very hot at the top, but then I am using a top down immersion and/or the mid level water coil, however, the example I was thinking of was using PV generated power in the winter when there is little or less power. 

+1 with @joe90 above, we only set the tank on about 45°C when using the ASHP and only exceed this with excess PV power, which sometimes means if the next day there is little PV power we do not need to buy in power to heat the tank using the ASHP.

 

This works for us, but we have super lagged the tank....

[joe90]

5 minutes ago, Marvin said:

but then I am using a top down immersion

I have two immersions in my tank, when/if I fit PV I would feed excess into the lower one to heat a greater volume rather than hotter at the top!

[SteamyTea]

If people bothered to measure their DHW usage, all the guesswork and opinions would vanish.

Shame people don't do the simple things.

[JohnMo]

55 minutes ago, joe90 said:

I have two immersions in my tank, when/if I fit PV I would feed excess into the lower one to heat a greater volume rather than hotter at the top!

But you may want to switch that around in winter, when generation is low.

[markocosic]

11 hours ago, SteamyTea said:

If people bothered to measure their DHW usage, all the guesswork and opinions would vanish.

Shame people don't do the simple things.

 

This kind l kind of thing? 😉

 

https://www.linkedin.com/posts/markocosic_too-many-people-think-that-gas-boilers-cost-activity-6970379299598045184-i81G?utm_source=share&utm_medium=member_android

 

There are still two sets of three of those heat meters available for those interested in monitoring the actual performance of boilers or ashps feeding cylinders.

 

Viewing the summer daily gas use on octopus also works just fine. 

Boiler Cost.xlsx

[PeterW]

13 hours ago, Tom said:

 

Pretty sure you can get UVCs with multiple heating elements at different levels to avoid this - correct me if I'm wrong though

Telford will make you what you want - immersions, connections, pockets etc can all be at your spec. 

[SteamyTea]

7 hours ago, markocosic said:

This kind l kind of thing

Yes.

Thanks, makes interesting reading.

 

[Spacey73]

I guess for me it comes down to:

 

1: Buying a Heat pump to charge up the Sunamp. 
 

Pro’s: Possibly 3 times less kWh of electricity needed to charge it.

 

Cons: That would mean 3 Heat pumps on the side of a Bungalow instead of the 2 we have already. 
 

Very expensive to buy and have installed.

 

To reach temps needed to charge up Sunamp I have a feeling efficiency goes down a bit.

 

Something else to service.

 

or…….

 

Just adding some more Solar panels to the setup.

 

Conclusion: My circumstance is probably very different to 90% of people installing Sunamp’s in that I have the space to install a lot of solar panels….and the spare inverter mppt inputs already installed to not add anymore cost other than buying say 12 x 390w panels at £160 each.

 

I’m pretty sure a 5Kw solar setup dedicated solely for charging up the Sunamp would cover just about all it’s charging needs, and for those days it doesn’t there is always the house/grid (which is already alll powered by a large solar installation and 2 x 48v 320ah Lifepo4 batteries.

 

Installation is free as I will do it, Solar panels are way cheaper than another heat pump plus no servicing. When you have enough space to add this solar array just for hot water then 1 to 1 efficiency still works out cheaper and less hassle.

 

Just because someone has a different idea or way of doing things isn’t a reason for some to get all uppity and grumpy old man syndrome just because I’m not conforming to their ideas they put forward.

 

Financially it makes sense for my situation and aesthetically (panels out of site on out building roofs and field) too.
 

Currently have Air Conditioning on holding a 1,900 square foot Bungalow at 22 deg C 24/7, cooking on large electric aga, tumble drying with heat pump dryer, washing electric, dishwasher, charging Zero Electric ride on mower (1.5kwh battery) 4 charges to do field and lawn….. and lots of lights appliances etc ……… and still end day with over 60% battery and wake up to over 30% battery. This is with a family of 4.

 

Sure it will get harder as Sun goes down, but my last house managed it and also running a bitcoin farm off Solar.

I do not want Oil or gas on the property and I also do not want to be at the mercy of whichever idiots are in charge of the country deciding when I can use my appliances or and silly carbon credit restrictions that are very possibly coming down the line.

 

 

 

Edited September 25, 2022 by Spacey73

[Nickfromwales]

Do you have planning permission for the >9m2 ground mounted array?

Do you have a hybrid inverter / DNO permission to add to the PV system?