What ho one and all,

Chatting with a friend who is upgrading his house and having installed a Mixergy thermal store tank, is most impressed with it.

Out of interest, I have been searching the internet and do not understand all the hoola. It says that only the hot water needed is heated which I assume means that only the top of the tank is hot. What happens if one wants a bath? Does the hot water run out?

I assume the Mixergy runs via a heat exchanger but I as a point of interest, I cannot find any mention of one.

When I was building, I did investigate a thermal store but for various reasons, did not install one. I was taken with the European models that had around 100mm of insulation. The Mixergy has the standard UK insulation of around 50-60mm; is that really sufficient to reduce heat loss?

Don't know what I a missing but what benefits does app control and an Ethernet connection offer? Frankly, the last thing I want in my life is a hot water tank that is controlled from my phone, but mine not to reason why.

Posted By: revorWould not suit me as I have an aversion to using electricity to heat up water but horses for courses.
I am more than happy with my Gledhill solar thermal store just wish there was a bit more insulation on it.

I'm looking at an in-line instant water heater to boost the temperature of the water in my TS. It will take warmed water and simply boost it to the required temperature.

I'm reasonably sure the small amount of energy required to do the 'boost' will be outweighed by

1. The need to heat the tank to a higher temperature i.e. I can run the boiler more efficiently.
2. The static losses from the tank sitting with over hot water in it.
3. no overshoot (i.e. the boiler still heating when the showering has finished).

I have recently been trying to reduce the temperature in the tank (for the above reasons) by reducing the max boiler temp, but as my new 'modern' boiler takes an age to get up to the point of delivering hot water to the tank (by design, more efficient I'm told), we currently need to plan the showers about 20 mins in advance.

I'm hoping the booster will alleviate that problem, be more flexible and ultimately be no more expensive to run.

I'm afraid I don't know anything about Mixergy tanks but for those commenting on lack of insulation on thermal stores, I have been looking into this and both McDonald and Newark will supply 100mm insulation on their tanks.

Posted By: tonyWhere are the heat losses going?

In my situation the heat will go into the room the tank is situated which is a plant/utility room. That has UFH with its own thermostat so any heat loss self compensates. In summer it is not an issue as almost without exception all the hot water is solar thermal production. I did my own plumbing and I got a local heating engineer to quote to fit a boiler and connect the gas. He said I could get my own boiler install it and he would connect up the gas (LPG) He noticed that I had fitted a London loop on the cold feed to the ST (stops hot water going up cold feed) and asked what it was. I told him and then said I would do similar with the return from the tank to the boiler to prevent gravitational circulation to the boiler when boiler not in use. He said it was not necessary as there was too much friction in modern boilers to allow that to happen. Bowing to his 40 years experience I left it out. Guess what, I was right, before I was connected to gas the solar thermal heat was going around the boiler and making it a "radiator". Later on had to fit a gravitation spring assisted non retrun valve.

Posted By: WillInAberdeen
I've built a PIR box around our last couple of tanks, but the modern style of mounting all the plumbing/valves/pumps directly onto the tank, makes that awkward to fit.

+1 same here. I used rockwool stuffed refuse bags held in place with netting to cover the on-tank plumbing.

Just searching (out of interest) for European thermal stores and found this web site. Albeit rather old (dated 2008) the same principle presumably still apply in 2023.

https://www.pmmag.com/articles/91937-thermal-accumulators

And quoted from the site:

Superinsulation
At trade shows like Mostra or ISH, it’s quickly evident that European manufacturers take their insulation seriously. Seldom will you see uninsulated pipe, even in situations where the pipe passes through heated space. Ditto for tank insulation. Most thermal accumulator tanks have at least 3 inches of foam insulation surrounding the entire water vessel. Some use rigid urethane foam. Others use a flexible foam wrap that’s installed on site. This allows the tank shell to fit through narrower doorways. Once set in place, the insulation wraps around the tank, and closes up with a heavy-duty zipper.
One manufacturer lists the thermal loss of its thermal accumulator at 0.1 degree Kelvin/hr. This converts to 0.18 degree F per hour. It states that a thermal accumulator initially heated to 95 degrees C (203 degrees F), remaining in standby mode, will still be at 70 degrees C (158 degrees F) eight days later. Compare this to some North American tanks that proudly promote losses of only 0.5 to 1 degree F per hour.
The way I see it, if you’re going to build a high-quality device to accept and deliver heat precisely when and were it’s needed, why not build it like a big Thermos bottle? You wouldn’t be pleased with an electrical battery that self-discharges in a few hours, why accept such performance from a “thermal battery?”

Currently looking at this heater.

https://www.stiebel-eltron.co.uk/en/products-solutions/Hotwater/instantaneous_waterheater/compact_instantaneouswaterheater/dce-x-premium/dce-x-10-12-premium.html

Tech services were really helpful. Suggested that instead of putting it inline, just put it on a divert loop with the demand valve on the outlet side. They also said it would modulate right down.

I'm pretty certain that heating the water to a lower value (gas boiler) and using this to provide short boost will be ultimately more efficient in overall energy use, mean I do not have to pre-plan showers, and be fully ready for the HP (in 10 years when the new boiler packs in).

I have an Akvaterm tank that does stratify. The disadvantage is that the boiler currently only heats the very top (I was going to fit Solar Thermal but that never happened) so the volume of water available for DHW is relatively small so it has to be hotter.

https://www.stovesonline.co.uk/wood_burning_stoves/Akvaterm-Solar-Thermal-Stores.html

I plan to get the plumber in this year to flush through the system and rework a load of the pipework so it can be properly insulated, add in the instant heater, plumb it into the bottom of the tank (for the boiler return) and improve some other bits.

The fitting of pipes so you cannot get a really good layer of insulation really bugs my happiness! I wouldn't let it happen again!

Posted By: djhThat seems to be about tanks rather than a heater?

Yes, wrong link posted, corrected above.

Posted By: djhI take the view that for the majority of the year the tank is heated by PV

Which is fine if you have PV!

As I wanted to respond in the context of stratifying tanks in general - I have replied on the 'Stratified Hot Water Tanks' thread: rather than this one titled 'Mixergy', as they are just one supplier, and an unhelpfully proprietary one at that.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16032&page=1#Comment_299675

While I was only have an academic interest in this tank because I try to keep up to speed with these things, it is interesting that you found them 'unhelpful.'

I feel their web site is also unhelpful, just telling me how great the product is. Will be interesting to learn from my freind (more of an acquaintance really) how he finds his tank after he has settled in with it.