I use the myenergi Eddi and have it set to run the immersion up to 500w (used to be 1kw with the dragon). As soon as I have over 500w of excess solar (and the powerwall is full) the relay board triggers the ASHP to run on the smart grid mode and boosts the DHW to 50°c, it will then overheat the house up to 24/25°c before stopping.
I get that using a standard PV diverter without the extra bits above is pointless but even with the EDLA09DA3V3 last year it was nice to know I was running fully off of locally produced green energy and the buffering means it didn’t run at night at all.
Obviously need to see how that will work out on the new unit now we actually have weather compensation working and don’t have to live in a sauna.
It’s highly confusing to do this because it’s generally recognised that abbreviations DON’T take an ‘s’ to make the plural, and precisely for this reason; i.e. W is used irrespective of the number preceding it.
Incidentally, it’s always a capital ‘W’ because it’s a man’s name: James Watt. And likewise ‘K’ for degrees Kelvin (Lord Kelvin) which means the multiplier kilo must be a lower case ‘k’.
I was thinking about people who are trying to get to grips with the technology, who would be confused by what you wrote. Until the powers that be banned the moderators from correcting things like that, I’d have simply changed it. Now, the choice we’re obliged to make is either point it out or leave people to be confused or misled.
I have a question with regards to these new HG cylinders?
I have been considering purchasing either a 250l or 300l cylinder and noticed that there is a difference with regards to insulation on the 250 vs 300l (50mm vs 75mm) This is also references with regards to the difference in heat Loss over 24 hours. (2.15kwh vs 1.64kwh)
My questions:
We are a family of 4 and have 2 showers that use approx. 10 l/m. Our kids spend on average about 8 minutes in the shower but we don’t all have a shower every day and occasionally 2 visitors in the house. Now and then we could easily use 300l if 4 people have a shower especially if we only heat the cylinder to say 45-50 degrees most days and then do the odd legionella cycle.
What would be the best option be if we install a Vaillant AroTherm plus with sensoComfort controls?
Should I go with the 300l and heat it up and then use as much hot water as possible over a 48 hour period before reheating (if so can the Vaillant be setup to do this?)
Or should we go with the smaller tank (250l) and reheat it more regularly?
What makes the most sense financially when it comes to heating DHW cylinders and how big should we go???
Do you have cheap off peak electric and if so how many times a day. Octopus go is ~8p a night for 6 hours (but you need an EV) or Octopus Cosy is ~16p for two thee hour periods a day (so you have two chances to top up).
If you have access to a off peak electricity tariff (especially anything under 8p/kWh and your goal is only financial you may want to schedule a reheat to 50°c or higher and sacrifice a few points on the COP to make the biggest saving on ££
With COP you need to use as much hot water as possible before reheating to get the best results, Ours is currently set to heat to 45°c and then only reheat once it drops by 10°c (to 35°c). It will then re heat the tank regardless of the time of day and use either off peak from the mains or from our Battery.
If you all shower in the morning you may want to schedule a cycle to run at 5/6am to ensure you have a full tank, if you split between morning and evening then you may be able yo get away with reheating or schedule + reheat.
Your households usage patterns would determine what is best and for random events (visitors/ guests/ showering after gardening etc) you may need to boost or top up.
If you are after saving money (and have access to the downpipe or under the shower) then maybe you also want to look at WWHR so you are not just flushing the heat down the drain. WWHR preheats the incoming cold water to both the shower and the tank so that you use less hot water and a smaller tank can last longer.
For your example above 2 kids 8 minute shower 10l/m math says that is ~160l so if you then have two more people to shower you can either share the remainder of the tank (4.5mins each) or have a reheat kick in and have some more water (but not loads as the reheat will take time).
MCS will have their recommendations (4 bed house 250l etc.) but they are again recommendations and your usage pattern may dictate a more preferable size.
Personally, if you can fit a bigger tank, I would. I have 250 and wish I could have gone 300 with 2 adults and 2 kids.
That MCS guide doesn’t take into account how slow heat pumps are to recharge (compared to gas).
So the more usable you can get in one go the better for me.
This ‘mixing’ thread might be useful
And maybe my Mixergy performance thread.
Basically, emptying a tank and then reheating is better for performance.
as will lower target temp.
You can always top up when needed out of your normal day to day usage.
Please tell me if I’m talking nonsense but…
Are the two best options either to have a really big tank so you only have to heat it once a day or have a really small tank that reheats when temperature drops?
Obviously the big tank should be just larger than your normal high water use days and the small tank should be large enough to cover each use.
My reasoning is that we are stuck in the middle. We have to heat our tank twice a day (fine on Cosy) but sometimes we also trigger the reheat. Not good for trying to only heat when cold.
If we had a bigger tank then we could only do scheduled heats.
If we had a small tank there would be more reheats but they wouldn’t take long and most of the tank would be cold each times it heats.
The Best option in my opinion (although impractical) is to have a tank sized to meet your average daily usage and so that you are out of hot water in time for the 13:00 Cosy off-peak period each day, then use the heat pump during what would usually be the warmest part of the day to fully reheat the tank. This may be possible some days but even with a regimented routine it would not likely work out that perfectly (who wants the 28 - 22°c shower).
I know Daikin offer various options for the reheat including that you can set the reheat temperature and the hysteresis (drop before reheat kicks in) separate from the main scheduled temp. This way you could say heat up in the morning before showers to 48°c and if the temp drops below 40, have it top back up to 44/5, avoiding any potentially cold showers but not needing to fully reheat the tank so saving some money. I hope other manufacturers would have similar settings.
You also have the space aspect to consider. do you have the room for a bigger tank to easily fit.
If you do go for the smaller tank then you would also have the option to store the DHW at a slightly higher temperature if you found you were short or wanted more or you could again alter your routine so that you shower in the evening instead of the morning.
For some real world context we currently have a 4 bed house and 2 Adults, the 250l tank (recommended size with our Octopus install due to house size) is set to reheat only and only reheats once it reaches 36°c (back to 46°c). We run a legionella cycle once a week on a Tuesday morning and usually outside of that the tank will heat (due to reheat) every second day (unless I change the configuration as the DHW heats on system restart and certain config changes on Daikin trigger a restart). We have not yet had any cold showers or run out of water but your mileage may vary.
My strategy for 250l tank with a family of 4: Daily reheat at 1pm to 45° if temperature drops below 20° - some days will skip reheat if no one’s had a shower. Legionella run disabled.
I do have a Solar PV setup but no battery as we use 3 phase electricity and buying 3 battery inverters plus batteries are pretty expensive here… but something I do hope to do in the future when I replace my main SMA TriPower solar inverter for a hybrid inverter.
Based on this I guess it would be a very adhoc approach to try and optimise my evergy and cost usage.
As @myatix correctly said, the HG Series spec is standardised and fixed. We do however, offer a bespoke cylinder manufacturing service, within which most aspects of a design can be customised. As is often the case with bespoke manufacturing though, the extra costs for customisations are not proportional to the extra labour or materials - they also includes a premium which is based on the rarity of our ability (and willingness) to manufacture bespoke units. We do accept that people will often opt for a more cost-effective, off the shelf option wherever possible, but for those occasions where it isn’t, we’re here to offer an alternative solution.
If I can answer any questions regarding the HG Series or our bespoke service, please reply here, email me at [email protected], or call me on 01636 678437.
I’m totally confused by the pricing! There are three prices, HG Installer, Non-HG Installer, and retail.
If a Heat Geek installer was sourcing a 300A for me, what would I actually expect to pay for the cylinder? Without knowing this, it’s difficult to compare against other prices and make a decision! Does the installer charge me a mark up on the trade price? Sorry if I’m being a numptie, I don’t understand how the industry works
If the installer is a heat geek they would pay the first price, if not a heat geek the second and if you wanted to buy it directly the third.
There would be a delivery charge on top of this which seems to be £90.
Additionally the heat geek would likely charge some extra for the installation, handling and commissioning (as it is their business and the need to turn a profit).
Thanks, but that’s not really what I was asking. I (obviously) understand the HG installer would pay the HG price. And I also understand that I would have to pay for installation etc. I am trying to work out the cost to me just of the cylinder, if I use a HG installer. Otherwise it is impossible to make any sort of informed decision about whether these HG cylinders make economic sense. For instance, the online price for a 300L heat pump cylinder from major manufacturers is about £1300 inc VAT e.g. this Telford one. To work out whether the HG cylinder makes sense, I need to know how much I will be paying for it! By the way, the HG prices don’t include VAT, just in case anyone wasn’t sure. I checked with Newark.
For that you would need to talk with a heat geek locally who is able to install this for you.
While they may give you a price breakdown they may just say X price overall for an install and an extra y if you want the HG cylinder.
Unless your local heat geek happens to be in this forum I doubt you will get a definitive answer as most operate their own business their way and pricing will likely vary.
Thanks again. I can see that now. It has also occurred to me that an installer with HG certification might be able to charge a premium price for installation, which might negate any discount on the cylinder from the retail price. So what is the best way to try to assess whether these cylinders make sense? Is it best just to work from the retail price? That would mean £2400 for a 300l HG cylinder, delivered. Basically, £1100 more than a bog standard mass market heat pump cylinder. Also, is there any information yet on what sort of COP gain they might deliver. Hopefully, done in a scientific way!!
I have to agree with you that I think the Cylinder is very overpriced for what it is especially as there is so little data to justify the price and as you correctly stated the price is £1100 higher than other U.K. cylinders. Such as the Joule, Vaillant UniStor and numerous other manufacturers with otherwise sound reputations. However that said this is often the case with new innovations…
Adam from Heat Geek has his cylinder on Open Energy Monitors site showing the SCOP for a 6m2 coil cylinder which is similar but not exactly the same as the Newark HG300A. If you want a custom cylinder the same as Adam’s is going to cost you at least £2500 as it’s a “Custom Design Service“.
All installers decide themselves how much markup they put on materials so this will vary from installer to installer and it’s often not very transparent as previously mentioned by @KnightPhoenix.
I suggest you also read @Zarch blog on his general impression with regards to Adam’s Heat Geek cylinder. It’s a very in depth look into some interesting stats comparing his Mixergy Cylinder and Adam’s “Custom” Heat Geek cylinder.
I think what we will see is that a lot of manufacturers will start to increase the size of their coils as people understand that low temperatures require improved heat transfer. As far as I am aware this is the only cylinder at present with a 6m2 coil that runs in parallel, but I maybe wrong.
There are also some very interesting cheaper alternatives out their such as perhaps the Joule Premium Cyclone cylinders. Recently installed by the Urban Plumber which is also has stats on the open energy community. Check out his YouTube video here…
I hope this helps and remember to share any findings that you might have on your journey.
