domestic hot water tank advice needed!

[finyuk2005]

So the folks' 1000 liter hot water tank has started leaking after just 8 years, he found it has rusted through.
It was about £1500 back then, likely a lot more now!

But we are hoping to have excess power from a 26kw solar array and a 6kw wind turbine fairly soon, and would like to find a way to put that into the hot water.
I wondered about doing a ground source heat pump set up, as we have plenty of field space available right next to the house we could burry pipes in.

Anyone know the best way of adding that into the system?
I wondered about using a smaller seperate hot water cylinder to pre-heat the incoming water before it gets to the pellet burner?
Or does an all in one system exist for such a task?

The other option would be to just use electric immersions, possibly even a 3 phase one as I have 30kw genny I would like to give a decent workout to every so often.
Also the Victron 48v inverter system is able to control contactors to switch the immersion heaters on and off depending on battery voltage and wind/solar input.

Any advice is greatfully recieved!
It wont be cheap, and even dad is agreeing with me that stainless would be a better option this time, as 8 years seems a pretty poor lifespan for such an investement!

cheers

 

[James1979]

I’ve got an IBC you can buy

 

[Fraserb]

I’ve got an IBC you can buy

I've got about 40 he can buy.

 

[armalites]

It's pretty common with solar thermal when adding to an existing system to just put a solar heated tank feeding the existing hot water tank so the cold goes to the solar coil tank and the outlet from there feeds the inlet of the original tank

1000L is a really big hot water tank, I've got two solar themal arrays which have not been comissioned yet and I'm looking at a 300L tank.

 

[finyuk2005]

I've got about 40 he can buy.

Ha ha we dont have quite that many, but still have some, propionic acid smells great!

 

[finyuk2005]

It's pretty common with solar thermal when adding to an existing system to just put a solar heated tank feeding the existing hot water tank so the cold goes to the solar coil tank and the outlet from there feeds the inlet of the original tank

1000L is a really big hot water tank, I've got two solar themal arrays which have not been comissioned yet and I'm looking at a 300L tank.

That was kinda my thinking indeed,
Yes its a pretty huge tank, its part of a fairly large pellet burner system

 

[James1979]

I've got about 40 he can buy.

I actually put that comment to take the p155 but you do get stainless IBCs. Even new would they be cheaper / better / whatever than a tank

Must be the week of it @finyuk2005 - mine burst Sunday morning. That was my afternoon off this week

 

[finyuk2005]

I actually put that comment to take the p155 but you do get stainless IBCs. Even new would they be cheaper / better / whatever than a tank

Must be the week of it @finyuk2005 - mine burst Sunday morning. That was my afternoon off this week

Just wrap one in plenty of insulation!! the big valve on the bottom would be handy for draining it when i decide to drill through a pipe again!


Ah man, thats fun!! cant really blame the cold weather either!!

 

[gaz1]

you have other options instead

heating my indoor pool with solar

I have discussed installing the six flat plate solar hot water panels in the past but never quite get around to it, had them (new) for years, now thinking of a far easier way than a sealed system with heat exchanger extra pump, control systemand expansion vessel etc. How about connecting them...

www.mig-welding.co.uk

 

[Gareth J]

For context, we have 6kw of solar, 2.5kw of wind, with excess feeding a 400l hot water tank that does hot water and some heating.

It's done with relatively cheap "diverter" gadgets. Immersun, iboost, solic200. That sort of thing.

Because your folks have so much generation to play with, it may make the costings of a heat pump less straightforward. I.e, if the times when you're generation little to no excess electric, and therefore the CoP bonus of a heat pump are less valuable, especially if the expected backup is going to be a pellet burner anyway.

So, if on 3 phase? I'd be tempted to put in X3 immersions in the new tank, one per phase and use X3 diverter gadgets and see how they go. That will cope with full turbine output and, honestly, a very decent amount of solar.

Then, make sure there are tank connections or a built in coil as appropriate for a heat pump on the new tank and see how you get on without for a bit. Depends on their demand as well as supply. They might live in a castle!

There are relatively simple ways to get more than 3kw per phase if you'd like to. But it gets a bit more expensive/complicated.

I would also consider including a smaller, separate, DHW tank, that's heated as a priority to a higher temperature. Again, a bit more complicated, but still relatively cheap.

Then, if you're getting into cascading loads for the diverter gadgets to feed into, I'd consider adding 3x (again, presuming 3phase) night storage heaters that accept load if the DHW tank is full, and the 1000l tank is full. Though, that's probably diminishing returns.

Seems odd that the big tank rotted so quickly.

 

[finyuk2005]

For context, we have 6kw of solar, 2.5kw of wind, with excess feeding a 400l hot water tank that does hot water and some heating.

It's done with relatively cheap "diverter" gadgets. Immersun, iboost, solic200. That sort of thing.

Because your folks have so much generation to play with, it may make the costings of a heat pump less straightforward. I.e, if the times when you're generation little to no excess electric, and therefore the CoP bonus of a heat pump are less valuable, especially if the expected backup is going to be a pellet burner anyway.

So, if on 3 phase? I'd be tempted to put in X3 immersions in the new tank, one per phase and use X3 diverter gadgets and see how they go. That will cope with full turbine output and, honestly, a very decent amount of solar.

Then, make sure there are tank connections or a built in coil as appropriate for a heat pump on the new tank and see how you get on without for a bit. Depends on their demand as well as supply. They might live in a castle!

There are relatively simple ways to get more than 3kw per phase if you'd like to. But it gets a bit more expensive/complicated.

I would also consider including a smaller, separate, DHW tank, that's heated as a priority to a higher temperature. Again, a bit more complicated, but still relatively cheap.

Then, if you're getting into cascading loads for the diverter gadgets to feed into, I'd consider adding 3x (again, presuming 3phase) night storage heaters that accept load if the DHW tank is full, and the 1000l tank is full. Though, that's probably diminishing returns.

Seems odd that the big tank rotted so quickly.

some great ideas thanks!
i had thought about 3 immersion units as well, I also have 3 x 2.5kw 48v chargers to use one on each phase,
The house has a normal sized hot water tank as well, with an immersion fitted, I could have that be heated first.

I dont think we will ever have too, too much spare power, its a pretty big house, and over winter can use as much as 80kw/h per day!!

Yeah i was surprised the tank has only lasted 8 years, seems very poor to me,
Its possibly been a small leak from somewhere and that has soaked the insulation at the bottom.
I didnt even know they bothered making them out of mild steel, just seems daft to me!

 

[finyuk2005]

A friend of mine whos family used to be a dairy farm where planning to re-use two of the old stainless milk tanks, i think they where a few thousand gallons each, insulate the hell out of them and heat them with a gassification boiler of some kind,
That was a while ago, i must go by and see if they finished that project!

 

[Gareth J]

some great ideas thanks!
i had thought about 3 immersion units as well, I also have 3 x 2.5kw 48v chargers to use one on each phase,
The house has a normal sized hot water tank as well, with an immersion fitted, I could have that be heated first.

I dont think we will ever have too, too much spare power, its a pretty big house, and over winter can use as much as 80kw/h per day!!

Yeah i was surprised the tank has only lasted 8 years, seems very poor to me,
Its possibly been a small leak from somewhere and that has soaked the insulation at the bottom.
I didnt even know they bothered making them out of mild steel, just seems daft to me!

You will definitely have too, too much in the summer! With no heating demand there's always more than needed with solar. Especially that much.

Batteries are a whole different world and not something I have any experience with. However, if it's obvious that, if you can store energy for later use as 240v AC, that's a lot more valuable than storing it as dumb heat.

Which 5kW wind turbine are they getting, if you don't mind me asking and how have they managed to get planning?

 

[finyuk2005]

You will definitely have too, too much in the summer! With no heating demand there's always more than needed with solar. Especially that much.

Batteries are a whole different world and not something I have any experience with. However, if it's obvious that, if you can store energy for later use as 240v AC, that's a lot more valuable than storing it as dumb heat.

Which 5kW wind turbine are they getting, if you don't mind me asking and how have they managed to get planning?

Its a second hand Eoltec turbine we got at a pretty good price, they are fairly simple machines, designed in Orkney to withstand a lot of wind!
As for planning, its still ongoing, but should be through next month,
Had one objection from somebody 8 miles away that spends his life searching the planning website for the word windturbine and copy and pastes an objection letter....

 

[gaz1]

its a pretty big house, and over winter can use as much as 80kw/h per day

what size place are you running at that rate ?

i note that you have a pellet burner for winter reference

you also state you have the fields as well so that means you have space

now heat can be stored from summer into winter use but still needs a top up of heat

 

[gaz1]

As im a plumber i can make a tank easily enough wether i use copper or stainless steel steel is just as good

the issue starts with the coating that they need

whilst 316 stainless steel will last you need to consider its maintenance more so with limescale areas

when taking these cylinders out they have been so full with mud/grime in the bottom of the tank its interesting

dosnt matter what the companys says with its 20-30 lifetime guarantee its really worth nothing as there is always a get out clause not to replace them maintenance been the main one

 

[finyuk2005]

As im a plumber i can make a tank easily enough wether i use copper or stainless steel steel is just as good

the issue starts with the coating that they need

whilst 316 stainless steel will last you need to consider its maintenance more so with limescale areas

when taking these cylinders out they have been so full with mud/grime in the bottom of the tank its interesting

dosnt matter what the companys says with its 20-30 lifetime guarantee its really worth nothing as there is always a get out clause not to replace them maintenance been the main one

thats interesting, we do have pretty hard water, an electric kettle never used to last much more than a year or two, but as we have a steam oven that needs descaled regularly dad chucks the solution in the kettle after, so they last a bit longer!

Dad is going to get a price from a company in Fife that would do a replacement in copper, I dread to think what price that would be!

He is going to have a closer look at the old one with the plumber and see if it would be possible for me to repair it when im back home in a few weeks

 

[James1979]

If you can’t weld it but it’ll bond then I’ve a tub of hysol here which would do it. Let me know.

 

[finyuk2005]

My first, initial and obvious thought was: No sacrificial anode protection fitted at installation?

its possible, it was fitted by a bit of a cowboy outfit at the time, ended up with a pretty big insurance job as a fitting wasnt tightened properly up in the attics, 3 stories up!

 

[Gareth J]

thats interesting, we do have pretty hard water, an electric kettle never used to last much more than a year or two, but as we have a steam oven that needs descaled regularly dad chucks the solution in the kettle after, so they last a bit longer!

Dad is going to get a price from a company in Fife that would do a replacement in copper, I dread to think what price that would be!

He is going to have a closer look at the old one with the plumber and see if it would be possible for me to repair it when im back home in a few weeks

McDonald? I've one of theirs. Am hoping it will be reliable. Might be worth getting a quote for two off the shelf 500l ones. Probably more expensive but you never know.

If you want to divert more than 3kw per phase, you can. Some brands of diverter will, intelligently, run two diverters in tandem, that will run two immersions simultaneously. And I've also seen a specialist 6kw diverter made by "MK2 PV router", which you could tie together with a 6kw immersion. 6kW per phase.... that's a LOT, for a domestic property. Any chance of reducing the heat load?

Limescale shouldn't be relevant here. Gaz's videos are showing DHW water heaters, so there's a constant drain off and topping up with drinking water. Your thermal store should be the same old water in it all the time. With whatever inhibitors and softeners required. Getting heat from the store into DHW though, will inevitably involve a heat exchanger which, because it's got tap water flowing through, will be prone to corrosion or scale.