Mini Store - Heat Geek / Newark Cylinders for ASHP

[Nick Laslett]

New mini store water tank from Newark Cylinders designed with Heat Geek. Specifically for ASHP, with 40° water temp requirement. Not an unvented Cylinder apparently. 
 

How it works video will be up tomorrow. 
 

 

Edited June 15 by Nick Laslett

[JohnMo]

There is a how it works video in 18 hrs or something.

 

It shows a cross section of the mini store and it's lots of coil inside. I am wondering if its more like a harlequin cylinder.

[dpmiller]

It's a small unvented cylinder with a massive (4 to 6m2) coil and stores just enough hot water to last until the ASHP cuts in and ramps up...

 

https://newarkcylinders.co.uk/wp-content/uploads/2024/04/HG-Series-Specification-Installation-Booklet-V2.0-Feb-2024.pdf

 

it's all then down to the configuration of the heat pump, getting the best deltaT and control hysteresis. Just as I have found, using a thermal store for the same application (but bigger...)

 

 

[dpmiller]

3 minutes ago, dpmiller said:

It's a small unvented cylinder with a massive (4 to 6m2) coil and stores just enough hot water to last until the ASHP cuts in and ramps up...

 

https://newarkcylinders.co.uk/wp-content/uploads/2024/04/HG-Series-Specification-Installation-Booklet-V2.0-Feb-2024.pdf

 

it's all then down to the configuration of the heat pump, getting the best deltaT and control hysteresis. Just as I have found, using a thermal store for the same application (but bigger...)

 

 

edit: I know that's for bigger cyls but the principle appears identical from what I can see?

[PhilT]

For low temp systems surely it must be possible to achieve a similar efficiency gain simply by allowing house heating and dhw flows to run simultaneously. So for my radiator setup the flow is typically 35 to 40. My dhw set temp is 40. My dhw tank would effectively be just another radiator. Timed dedicated dhw cycles could be added/configured to top up as necessary 

[JamesPa]

6 hours ago, dpmiller said:

edit: I know that's for bigger cyls but the principle appears identical from what I can see?

From the table 3mins into the video linked to, it seems to be an 80l cylinder with a very large coil (or a PHE?) with all of the PRV, expansion vessel etc inside the casing, designed to fit in an under-worktop kitchen cabinet.  I cant see anything to suggest that it does any 'real time' heating but of course it may; the gubbins for that (basically a PHE) may also be inside the casing.  Its unclear from the video whether it is un-vented or vented.  The table claims 14-34 mins DHW at 40C/10l/min, which in any sane world is enough, but of course wont satisfy some of the more extravagant demands that the MCS bods typically assume (which IMHO should be classed as a wholly unnecessary indulgence in a world which is heading for being turned upside down by climate change.  

 

It will be good when we have the full specs to understand what combination of compromises they have chosen/technology they have deployed, but it feels to me like it fills a gap in the market.  Its notable that they are, in the video, positively encouraging other manufacturers to copying.  Presumably they couldnt find anything that could be patented and/or decided it wasnt worth the bother and/or decided that sales would be maximised by gaining market acceptance, easier if there are multiple sources..

[JamesPa]

14 minutes ago, PhilT said:

For low temp systems surely it must be possible to achieve a similar efficiency gain simply by allowing house heating and dhw flows to run simultaneously. So for my radiator setup the flow is typically 35 to 40. My dhw set temp is 40. My dhw tank would effectively be just another radiator. Timed dedicated dhw cycles could be added/configured to top up as necessary 

I think that is essentially how Heat Geek achieve the high SCOP claimed for their 'super cylinder.  By having a very large coil the temp difference between the flow temp and the DHW can be smaller, meaning greater Heat Pump efficiency.

[JohnMo]

6 minutes ago, PhilT said:

For low temp systems surely it must be possible to achieve a similar efficiency gain simply by allowing house heating and dhw flows to run simultaneously. So for my radiator setup the flow is typically 35 to 40. My dhw set temp is 40. My dhw tank would effectively be just another radiator. Timed dedicated dhw cycles could be added/configured to top up as necessary 

I noticed a while ago in my ASHP instructions, there are settings for that type of operation. " In Heating, ASHP always turned towards DHW"

 

10.2.2 HEATING MODE ON DHW STORAGE TANK

If the parameter H130=1, the ASHP exploits the DHW storage tank even for central heating. In these conditions, the outlet of the DHW valve is also enabled during operation in heating mode and not only in sanitary mode. The valve is deactivated during defrosting and in cooling mode.

 

Think you would have to alter the plumbing to allow it to work. A a 3 port valve directs towards CH or cylinder not both.

[JamesPa]

Interestingly the pictures of the HG mini store at 4:20 in the video dont show any port for a (pressure relief) vent.  That suggests that its either vented (perhaps like Harlequin as @JohnMo suggests, or they have designed in a way to meet the building regs without a pressure relief vent and are prepared to warranty it, or of course its an artists impression (is the cylinder really purple?) omitting some detail.  I guess we will find out in a couple of days. 

 

I cant see how a vented solution, unless its a thermal store with the attendant limitations, would be a replacement for a combi though, since the downstream pipework and fittings will be designed for mains pressure hot water.   Unless of course there is also a water pump inside!   Since combis seem to make quite a racket when heating DHW, the noise from a water pump would probably be considered acceptable. 

Edited June 15 by JamesPa

[JamesPa]

27 minutes ago, JohnMo said:

I noticed a while ago in my ASHP instructions, there are settings for that type of operation. " In Heating, ASHP always turned towards DHW"

 

10.2.2 HEATING MODE ON DHW STORAGE TANK

If the parameter H130=1, the ASHP exploits the DHW storage tank even for central heating. In these conditions, the outlet of the DHW valve is also enabled during operation in heating mode and not only in sanitary mode. The valve is deactivated during defrosting and in cooling mode.

 

Think you would have to alter the plumbing to allow it to work. A a 3 port valve directs towards CH or cylinder not both.

Two two port valves instead of a three port would surely solve this and allow you to choose either or both at will. 

 

I do wonder if minimising the required temp difference between flow and DHW temp (with a big coil or PHE) opens up some interesting configurations that may well have applications in some circumstances.    WC would seem to be the issue, but perhaps just viewing the 'dhw cylinder' as a large energy store which can be deployed flexibly between DHW and space heating, and playing with flow temperatures as necessary to achieve what is needed at any point in time, has applications.

Edited June 15 by JamesPa

[JohnMo]

2 minutes ago, JamesPa said:

Two two port valves instead of a three port would surely solve this

Good point.

 

4 minutes ago, JamesPa said:

do wonder if minimising the required temp difference between flow and DHW temp (with a big coil or PHE

I have seen schemes where DHW is delivered via a PHE, such as a thermal store. The HG solution is really just adding a buffer to the system to allow the ASHP to ramp up. Mine would take a good 5 to 10 minutes. So it could be a coil in a coil HE within a buffer tank. The outer coil is in the buffer water the inner coil in the ASHP flow path. So are they just treating the store as a buffer from a plumbing perspective.

[Nick Laslett]

In the comments Adam is asked if it is vented or unvented and where the expansion vessel goes. He replied,

 

Quote

Neither! Watch our deep technical dive for more info soon!

 

[JohnMo]

7 minutes ago, Nick Laslett said:

In the comments Adam is asked if it is vented or unvented and where the expansion vessel goes. He replied,

 

 

Must be being treated as heating system volume, so must be full of central heating water, so the volume of main fed water is limited, contained in a coil or PHE as with a thermal store.

[JohnMo]

1 hour ago, Nick Laslett said:

In the comments Adam is asked if it is vented or unvented and where the expansion vessel goes. He replied,

 

 

 

A similar concept been about for years (since 2018 ish) - funny it for a gas combi boiler. Just swop the combi boiler for a heat pump with a bigger coil and delete the blending valve and go direct to taps (not to the combi). Same 4 connection.

 

Neither a vented or invented DHW cylinder, just allows for additional volume with an additional or increased heating expansion vessel

 

[ProDave]

10 hours ago, dpmiller said:

It's a small unvented cylinder with a massive (4 to 6m2) coil and stores just enough hot water to last until the ASHP cuts in and ramps up...

 

https://newarkcylinders.co.uk/wp-content/uploads/2024/04/HG-Series-Specification-Installation-Booklet-V2.0-Feb-2024.pdf

 

it's all then down to the configuration of the heat pump, getting the best deltaT and control hysteresis. Just as I have found, using a thermal store for the same application (but bigger...)

 

 

So in my case once the small cylinder has exhausted it would just supply hot water being heated by a 5kW heater.  Well I find a 7.5kW shower pathetic, a 5kW one would be a dribble.

 

So only begins to be viable with a 12kW or more ASHP?

[JamesPa]

52 minutes ago, ProDave said:

So in my case once the small cylinder has exhausted it would just supply hot water being heated by a 5kW heater.  Well I find a 7.5kW shower pathetic, a 5kW one would be a dribble.

 

So only begins to be viable with a 12kW or more ASHP?

Plenty of 6-9kW electric showers around, similar to a more typical 8kW heat pump.  I don't think hg are aiming this at large, highly insulated new builds where space for a large cylinder isn't a problem.  Also will the cylinder run out in the time taken for a shower, their video suggests not (based on 10l/s delivery rate).  Certainly if the 'requirement' is a 20 mins shower at 20l/s then nothing short of a vast storage vessel will do, but in reality 2-5 mins at 10l/s or less is easily sufficient to do the job.

 

If we are to fix climate change then we will need to adapt and, dare I say it, make  sacrifices.  Also we need a wide variety of solutions to fit the vast variety of circumstances not the one rule fits all that MCS seems to like.

 

 

Edited June 15 by JamesPa

[JohnMo]

Just watched the follow up video. Looks good, seems to work well. It is as shown in my post above. The heat pump heats the store directly and DHW is taken via a coil. The blending valve would be installed if you store water above 60 degs.

[HughF]

Yep, just watched the video. Standard thermal store with a coil for dhw. 
 

Could do the same with a small direct cylinder, a phe, flow switch and shunt pump.

[JamesPa]

The second video explaining it is now out and, as I am neither a father myself nor have a father who is still alive (its Fathers day!) I have the time to watch it. 

 

Its quite simply a small thermal store (filled with 'central heating' water but most likely at an elevated flow temperature as is normal for DHW) with a very large coil for the exchange of energy to the DHW, thus minimising the approach temperature.  That's it.  The only other 'clever' trick (if you consider it clever) is to arrange the settings on the heat pump to switch to DHW mode as soon as the store temperature drops by only (say) 3C, thus prolonging the 'life' of the store beyond that which you would calculate by assuming no heating whilst demand is present.

 

On the video it was demonstrated with a 7kW Vaillant at OAT 7C.

 

Nothing revolutionary so far as I can see except that it deploys pragmatism (ie it doesn't provide for all possible extremes of demands, just a reasonable demand), a feature that seems to be largely absent from the thought process in much of this area.

 

Will the industry 'buy' it.  Personally I fear not, because (I fear) there may be a preference to avoid altogether jobs where the customer may have to make a compromise (like waiting 15-20 mins between showers) and because (I fear) customers are now so used to getting everything they want that nothing less will do.  That said, there are now lots of 'heat geeks' out there who will presumably be more easily convinced.

 

Personally I'm very tempted, if only to avoid G3, but then I don't need (or even want) a 20 min shower at 20l/s and nor do I have over-indulged teenage children who are terribly concerned about climate change but haven't yet realised (or been told) that mitigating it may involve some lifestyle changes.

 

 

Edited June 16 by JamesPa

[HughF]

I’d have gone for one if it was available when I did my conversion…. Be nice to have something in the cylinder cupboard that was the same size as the vented that came out.

[Beelbeebub]

Just had a look, it appears as @JamesPa says to be a small thermal store with a big DHW coil.

 

I'm guessing they are relying on the "it's a HP so can't boil" approach to avoid the G3 regs.

 

The big issue I can see, is that it relies on the HP filling the store as you draw down to extend the volume of water you can draw before running cold.  This might be drastically curtailed when you start hitting defrost conditions.

[JohnMo]

10 minutes ago, Beelbeebub said:

I'm guessing they are relying on the "it's a HP so can't boil" approach to avoid the G3 regs

No stored volume of domestic water is below the need for G3. It's a buffer cylinder really with a DHW coil, not really a thermal store. Exactly as I listed in the image above.

 

Defrosts could be a issue, but my heat pump specifically doesn't defrost, during DHW - it's not allowed by the manufacturer control logic.

[JamesPa]

11 minutes ago, JohnMo said:

my heat pump specifically doesn't defrost, during DHW - it's not allowed by the manufacturer control logic.

As a matter of interest, how does that work out during an extended recovery in cold weather?

[JohnMo]

7 minutes ago, JamesPa said:

As a matter of interest, how does that work out during an extended recovery in cold weather?

Seemed to do fine, didn't seem to have any shortage of hot water. Hot water heater takes about 40 mins at the end of it the condenser is frosty.

[JamesPa]

27 minutes ago, JohnMo said:

41 minutes ago, Beelbeebub said:

I'm guessing they are relying on the "it's a HP so can't boil" approach to avoid the G3 regs

No stored volume of domestic water is below the need for G3. It's a buffer cylinder really with a DHW coil, not really a thermal store. Exactly as I listed in the image above.

With the immersion heater option it definitely could boil.  As @JohnMo says stored domestic dhw below G3, presumably it relies on the system prv and expansion vessel to deal with that (so the latter may need up sizing, as indeed it might with a buffer that has an immersion included as a 'backup'.)

 

I agree with @JohnMothat the tank itself (but not how it is plumbed) is better described as a buffer with a dhw coil.  I'm not sure I'd want to call it a buffer though, that has too many connotations in a heat pump context.

 

 

Edited June 16 by JamesPa