Hot Water Cylinder Questions

mmmmikey

pensionpawn wrote: »

Running it at a higher temperature isn't really an issue with heat losses as the energy to get it to 80c is free from the sun and would have been exported if not used.

Crystal ball gazing a bit here, but maybe something to consider......



At the moment, deemed payments make surplus solar power effectively free. However, it's quite possible that smart metering will lead to a situation where you are paid for actual export (because the smart meter can measure that). At this point, any surplus solar power diverted by your iBoost or whatever is no longer free in the sense that you are reducing your FIT payment by 5p or so per kWh for every kWh you use rather than export.



There are lots of arguments for and against smart meters and this is not the place for them, I just want to highlight that it's entirely possible that hot water system efficiency becomes more important. As things stand you can choose not to have a smart meter, but you might find in future that this limits your access to the best tarriffs. Also, it isn't a given that whoever makes your FIT payments won't insist on using export readings - who knows? I'm not looking to debate the rights and wrongs of this here, merely to point out that things may change.



Also, there is the environmental impact to consider, remembering that this is the Green and Ethical forum. If reducing your standing heat losses means you export more solar power (whether you benefit financially or not), then somebody somewhere can turn the dial down on a gas fired power station saving a little bit of carbon dioxide.

pensionpawn

mmmmikey wrote: »

Crystal ball gazing a bit here, but maybe something to consider......



At the moment, deemed payments make surplus solar power effectively free. However, it's quite possible that smart metering will lead to a situation where you are paid for actual export (because the smart meter can measure that). At this point, any surplus solar power diverted by your iBoost or whatever is no longer free in the sense that you are reducing your FIT payment by 5p or so per kWh for every kWh you use rather than export.



There are lots of arguments for and against smart meters and this is not the place for them, I just want to highlight that it's entirely possible that hot water system efficiency becomes more important. As things stand you can choose not to have a smart meter, but you might find in future that this limits your access to the best tarriffs. Also, it isn't a given that whoever makes your FIT payments won't insist on using export readings - who knows? I'm not looking to debate the rights and wrongs of this here, merely to point out that things may change.



Also, there is the environmental impact to consider, remembering that this is the Green and Ethical forum. If reducing your standing heat losses means you export more solar power (whether you benefit financially or not), then somebody somewhere can turn the dial down on a gas fired power station saving a little bit of carbon dioxide.

As I already have two monitoring systems, my inverter and and a stand alone system wild horses wouldn't bring me to install a smart meter. No need, concerns regarding IT security and yes I agree it opens the door wrt reneging on the export tariff. That said, I actually export around 48% of what I generate so the impact would be minimal at present however I do have plans to start making use of all that export in the next couple of years. Of course what would be fairer would be the introduction of net metering tariffs to replace the 'deemed' export tariff.

I'm not dismissive of good insulation for the hot water system and as my house is fairly new at 22 years old in that respect it is fairly good. However given the hidden runs of most hot water pipes after they leave the airing cupboard, in the winter months especially, there will be an unavoidable loss of energy in warming the pipes up first when running the hot water.

An alternative to a thermal store being an electrical one, which I will certainly install once cost effective, hopefully in a couple of years time.

I agree with all of your points as saving energy is good for the individual as well as the planet!

pile-o-stone

pensionpawn wrote: »

Indeed. See post #5.

Sorry, I missed that as I was skim reading the thread in the office.

EricMears

Coastalwatch wrote: »

Having experienced the limitations of shower systems accompanying indirect cylinders and pressure variations I'm thinking a direct unvented cylinder would be an improvement.

You can achieve all you want without needing to go down the unvented route (which necessitates ongoing bills for an annual 'service' !)

A 'Heatbank' would offer mains pressure DHW along with water storage as hot as you'd want but can be vented.
see https://www.heatweb.co.uk

michaels

EricMears wrote: »

You can achieve all you want without needing to go down the unvented route (which necessitates ongoing bills for an annual 'service' !)

A 'Heatbank' would offer mains pressure DHW along with water storage as hot as you'd want but can be vented.
see https://www.heatweb.co.uk

I had this in the past and it worked very well, not sure how long the heat exchangers last in hard water areas and of course no hot water during a power cut were potential downsides.

EricMears

michaels wrote: »

I had this in the past and it worked very well, not sure how long the heat exchangers last in hard water areas and of course no hot water during a power cut were potential downsides.

Mine is still working well after 19 years. Our water isn't 'hard' but since the fluid one side of heat exchanger should have various anti-corrosion additives and isn't 'used' (i.e. same water stays in tank for many years) that's not going to have any limescale build-up and the DHW side of heat exchanger shouldn't get hot enough to cause scaling.

pile-o-stone

EricMears wrote: »

You can achieve all you want without needing to go down the unvented route (which necessitates ongoing bills for an annual 'service' !)

A 'Heatbank' would offer mains pressure DHW along with water storage as hot as you'd want but can be vented.
see https://www.heatweb.co.uk

We have a heatbank and apart from the advantage of mains pressure hot water, it's also drinkable so no fear of legionella and nice warm water to brush those sensitive teeth.

It also helps the boiler to stay in the energy efficient condensing mode for longer as the return feed to the boiler can be set to a constant low temperature.

michaels wrote: »

I had this in the past and it worked very well, not sure how long the heat exchangers last in hard water areas and of course no hot water during a power cut were potential downsides.

This from a Thermal Store FAQ site:
"Q. Can the plate heat exchanger scale up?
A. It is possible but very uncommon. We are often asked by service engineers experienced with combi-boilers about this happening, as they also use a plate heat exchanger to heat water, which can scale up. The main difference between a thermal store and a combi-boiler is the output of the heat exchanger – typically 3 times larger on a Heat Bank. The much higher flow rates generated through the Heat Bank heat exchanger helps to clean it and prevent scale from depositing. It is very rare for performance to be adversely affected even in hard water areas.

However, in hard water areas, we advise choosing the option to factory fit an electronic water conditioner on the Heatbank™. This provides permanent and complete protection against limescale deposits with the heat exchanger. It also protects the rest of the property."

We had the electronic water conditioner fitted even though we are in a soft water area. It was only a few quid compared with the cost of the heatbank, so seemed a no brainer.

mmmmikey

Hi again, interesting timing re: discussion of thermal stores.



Was all set to order a repalcement cylinder, but then went up into my loft yesterday and realised that my cold water tank needs replacing as well, and there's a fair bit of pipework to tidy in the process. This prompted me to have another look at options, including this:



https://www.advanceappliances.co.uk/product/53-electric-thermal-store-hot-water-only/


When I compare the cost of this to the cost of replacing the cylinder and header tank there isn't much difference, because this would be so much easier to install. As well as being better insulated than the best direct vented cylinder I can find, it will provide mains pressure hot water and looks like it should be very low maintenance with no electric pumps, valves, controllers, etc. to fail (other than the immersion heaters of course). I personally wasn't too bothered about hot water pressure but I've been over ruled on that so this also saves the cost of a shower pump and installation.


Just about to order it, and looks easy enough to fit myself (saving even more), will let you know how I get on.



In the meantime, have hooked up additional energy monitors to my existing system so I can compare before and after costs, although this will be distorted by using more hot water for higher pressure showers.

michaels

Isn't there a pump in the tank to heat exchanger circulation?

michaels

pile-o-stone wrote: »

We have a heatbank and apart from the advantage of mains pressure hot water, it's also drinkable so no fear of legionella and nice warm water to brush those sensitive teeth.

It also helps the boiler to stay in the energy efficient condensing mode for longer as the return feed to the boiler can be set to a constant low temperature.

Unless you have the store at a decent temperature how are you able to top up/hot up a bath?