Sunamp heat battery

[Jeremy Harris]

1 minute ago, PeterW said:

 

Its a negligible improvement as CoP isn’t linear. 

 

 

The small Samsung’s have a max flow of only 14 l/min and that’s not going to be enough for this sort of scenario. 

 

Given a low heat requirement, ASHP is overkill anyway and a Willis Heater would work. Capex of £50 vs £2300 for the smallest Samsung means even with a CoP of 4-5 your payback is decades. 

 

 

Exactly.

 

The only advantage of a heat pump is it's ability to cool, and we find that extremely beneficial (like right now when the house is at 21.5 and it's approaching 30 deg C outside).

[ProDave]

18 minutes ago, pdf27 said:

http://heatpumps.co.uk/2014/03/06/getting-the-best-from-underfloor-heating/ is worth a read - it's clear that provided the heat pump will regulate low enough then blending valves make things worse rather than better.

Interesting read, and of course common sense. But when you start looking at a graph suggesting that because I have set my UFH pipes at 200mm spacing, I will need to run water around them at about 40 degrees, you realise that article is not "fine tuned"  for a low energy house.

[pdf27]

9 minutes ago, JSHarris said:

 

 

All I'm saying is that it very definitely doesn't work for our 130m² house.  Turn the buffer off and the heat pump short cycles.  Turn the buffer on and it works perfectly.  Our heat pump will modulate down to about 1 kW to 1.5 kW minimum output, and that is just way more heat than the slab can absorb at the set UFH flow temperature.  If I turn the UFH flow temperature up, to increase the heat flow rate, then we get a massive room temperature over-shoot.

 

Turning the heat pump flow temperature down makes the problem massively worse, as the pump just shuts down within a couple of minutes of starting up, then stays shut down for around 20 mins.

 

Theory is great, but I've found that practical experience and experiment is a hell of a lot more accurate.

Except in this case the theory matches what you've found, and explains why you need a buffer and Jack doesn't. Because you have a circulating pump on your manifold set to a higher flow rate than the heat pump, you will start to see a small increase in the return water temperature on the UFH circuit (and thus the return temperature to the heat pump) very rapidly. The heat pump will have a minimum dT it can run at - turning down the heat pump flow temperature will cause this to be hit earlier leading to far worse short cycling, while turning the UFH flow temperature up while maintaining the circulator flow rate will both increase the return temperature to the heat pump (not helping at all) and increase the slab temperature leading to major temperature overshoots and comfort issues. Essentially the effective volume of water in your system is between the heat pump and manifold, which is why you need a buffer tank - the effect of the slab is very minimal.

In Jack's case, the heat pump is connected directly to the UFH circuit without a circulating pump. Water is circulated at a low temperature eliminating the overshoot issue, and the low flow rate of the circulating pump compared to the volume of water in the pipes means that the time constant before the return water can possibly warm up is 2-3 times longer. This means that the slab actually has an impact on the system, and eliminates the short cycling problem - which as I understand it is his experience.

 

8 minutes ago, PeterW said:

 

Its a negligible improvement as CoP isn’t linear. 

 

 

The small Samsung’s have a max flow of only 14 l/min and that’s not going to be enough for this sort of scenario. 

 

Given a low heat requirement, ASHP is overkill anyway and a Willis Heater would work. Capex of £50 vs £2300 for the smallest Samsung means even with a CoP of 4-5 your payback is decades. 

From Samsung data at 7°C air temperature - W30 has a COP of 5.59, W35 has a COP of 4.72 and W40 has a COP of 4.01. I don't have any W25 data, but that looks a pretty significant improvement to me. The improvement seems to hold good across the air temperature range, and as Jeremy has noted reducing the water temperature has a major impact on defrosting problems.

 

I agree that for a low energy consumption house a Willis heater or similar (air heater in the MVHR?) would work just fine and provide a very cheap solution. I'm less convinced it's an optimised solution however - in most cases it will be cheaper to meet say a given energy budget by using a heat pump and insulating to building regulations standard than by superinsulating and using resistance heat. It only really makes sense to go down that route as either a low capital cost route with an upgrade path, or if you have very specific comfort requirements - in which case the cooling capacity of an ASHP starts to become very attractive.

[jack]

1 minute ago, pdf27 said:

In Jack's case, the heat pump is connected directly to the UFH circuit without a circulating pump. Water is circulated at a low temperature eliminating the overshoot issue, and the low flow rate of the circulating pump compared to the volume of water in the pipes means that the time constant before the return water can possibly warm up is 2-3 times longer. This means that the slab actually has an impact on the system, and eliminates the short cycling problem - which as I understand it is his experience.

 

Actually, we do have a circulating pump on our UFH manifold (I assume this is the one you're talking about?)

 

This setup works fine to keep the house comfortable over winter, but I'm not convinced that the current setup is optimal. I have no idea, for example, how often or for how long the ASHP comes on for. I plan to look at it before winter later this year.

[Nickfromwales]

1 hour ago, pdf27 said:

I would also take issue with the idea that heating is mostly required at night in a well-insulated house - you're normally in bed and would want a slightly lower temperature for comfort. With a well insulated & high decrement delay house the time constant for it to cool down is very long, so with no heating on overnight the temperature drop is likely only to be a degree or so, making the value of shifting space heat from day to night pretty minimal. Where you do need to shift heat is from summer to winter, which unless you go for the container sized storage units isn't happening with a Sunamp and there is significant value in increasing the COP since there won't be much surplus PV available after plug loads are taken care of.

Comfort is an individuals perception of, so I work on generalisation when commenting here, or specifics if I'm designing for someone  .

 

Modelling heat migration through the upper floors where bedrooms typically reside shows that with MVHR, but without local auxiliary heating in those rooms, temp drops of the rooms ( as opposed to the buildings fabric as a whole ) are notable. That is the reason people want UTH or towel warmers in bathrooms, as they want that additional comfort heat introduction albeit not lots, but some at least. 

In one example I'm consulting for someone who is having a Beatie PH built. The selected MVHR supplier has stated that 2 of the 4 bedrooms will never achieve the target temp of 20.5, and therefore require auxiliary heating.  

Accepting that daytime solar gain may well give a little uplift, it's safe to say the nighttime will have a deficit which needs consideration for anyone who wishes to raise individual rooms temps rather than the overall temp as dictated by the downstairs room stat. 

Some people boil, and some freeze. 

 

My comment about heat / night etc should have been more specific but when the sun goes down the solar gain through glazing goes with it. Also, if reinforcement IS ever required them to not have stored solar energy in the daytime to provide it, by whatever means, is not a very good idea. 

That brings us back to chooses of how to store it. Clearly the SA unit withit lower losses and dramatically smaller physical size per kW ( a factor of >3 iirc ) equivalent is a serious contender. 

When the suns are done, unless it's a large dwelling with very high demand DHW, an all electric solution is IMO preferable to a HP. 

Whether its a la @TerryE ( Willis heaters on E10 and no PV ) or the likes of @Barney12 & @vivienz eg ( plenty of PV and no desire to have a HP, instead favouring just pressing a button and getting on with their lives ) then SA becomes the winner by far. 

The more complex you make things the more you become a slave to it so at some stage you remove the sieving of the pennies and choose what suits your lifestyle. The house should work for you, not vice versa. 

PCM58 is bench tested with staggeringly good statistics. @AndyT may well garnish this thread with the current stats, so if your middle-aged it's likely the still working SA will attend your funeral. Your ASHP will have been long buried and have cost you a good few quid in the process with its purchase, maintenance, and antifreeze changes. 

Even if it cost slightly more to run than PV > ASHP, I'd still go for the all electric option as it's just so simplistic, and has the least amount of impact on the dwelling. Not buying the HP, insulated pipework, controls and looking after it buys a lot of E10 electricity. 

 

The PCM34 is nearly twice the price of the PCM58 so systems with an ASHP will either need to employ a HT ASHP or a hybrid ( LPG / gas fortified ) ASHP. Further argument to fit a cylinder if your short of capital but not that much of an argument if your stating at the property long-term which is where longevity and low / zero maintenance costs become paramount. 

[Nickfromwales]

1 hour ago, jack said:

 

Actually, we do have a circulating pump on our UFH manifold (I assume this is the one you're talking about?)

 

This setup works fine to keep the house comfortable over winter, but I'm not convinced that the current setup is optimal. I have no idea, for example, how often or for how long the ASHP comes on for. I plan to look at it before winter later this year.

Yes, as you cannot have an UFH manifold without a pump or blending valve. To FO so would be unsafe and unwise asvyou have no way of mitigating against the hysteresis of the HP output and more importantly no protection against the stat failing and driving high temp water through the loops. 

[Jeremy Harris]

3 hours ago, pdf27 said:

Except in this case the theory matches what you've found, and explains why you need a buffer and Jack doesn't. Because you have a circulating pump on your manifold set to a higher flow rate than the heat pump, you will start to see a small increase in the return water temperature on the UFH circuit (and thus the return temperature to the heat pump) very rapidly. The heat pump will have a minimum dT it can run at - turning down the heat pump flow temperature will cause this to be hit earlier leading to far worse short cycling, while turning the UFH flow temperature up while maintaining the circulator flow rate will both increase the return temperature to the heat pump (not helping at all) and increase the slab temperature leading to major temperature overshoots and comfort issues. Essentially the effective volume of water in your system is between the heat pump and manifold, which is why you need a buffer tank - the effect of the slab is very minimal.

In Jack's case, the heat pump is connected directly to the UFH circuit without a circulating pump. Water is circulated at a low temperature eliminating the overshoot issue, and the low flow rate of the circulating pump compared to the volume of water in the pipes means that the time constant before the return water can possibly warm up is 2-3 times longer. This means that the slab actually has an impact on the system, and eliminates the short cycling problem - which as I understand it is his experience.

 

From Samsung data at 7°C air temperature - W30 has a COP of 5.59, W35 has a COP of 4.72 and W40 has a COP of 4.01. I don't have any W25 data, but that looks a pretty significant improvement to me. The improvement seems to hold good across the air temperature range, and as Jeremy has noted reducing the water temperature has a major impact on defrosting problems.

 

I agree that for a low energy consumption house a Willis heater or similar (air heater in the MVHR?) would work just fine and provide a very cheap solution. I'm less convinced it's an optimised solution however - in most cases it will be cheaper to meet say a given energy budget by using a heat pump and insulating to building regulations standard than by superinsulating and using resistance heat. It only really makes sense to go down that route as either a low capital cost route with an upgrade path, or if you have very specific comfort requirements - in which case the cooling capacity of an ASHP starts to become very attractive.

 

 

Not true, I'm afraid.  The UFH flow rate in heating mode (not in cooling mode) is way lower than that from the ASHP pump, well under half the ASHP flow rate.  If the ASHP flow rate is turned down then there isn't enough flow to keep the unit running and it trips on a low flow condition.  Having the buffer allows the full flow from the ASHP to be absorbed, without the restriction of the UFH, and also allows the flow temperature to be higher, keeping the heat pump operating in it's most optimal range most of the time. 

 

There will be differences between different models of heat pump, but trying to extrapolate from the dry air test data isn't easy, as RH has a big impact on COP, for two main reasons.  Firstly, humidity has a significant impact on air heat capacity, so more humid air has a higher heat capacity for a given temperature than dry air.  Secondly, humidity has a massive impact on defrost cycling when the air temperature gets down to around 4 deg C or so.  Cold, dry air is fine, cool moist air is a PITA as far as frost build up goes, and none of the data given from the standard tests includes defrosting impact.

 

I modelled our house to death before we built it, and was convinced I understood how it would behave thermally.  I freely admit that I got a heck of a lot wrong, both because I didn't recognise the impact of some local conditions, I didn't understand the nuances around the way heat pumps really work (as distinct from the semi-pretend data the manufacturers supply) and I couldn't easily model the heat transfer function from the UFH flow to the slab surface.  All these had a major impact on how our heating/cooling system really operated.  As proof of that it's now working well, but on about the fifth or sixth iteration of the temperature control system.

 

As an aside, and just for completeness, a buffer isn't needed in cooling mode, as the ASHP doesn't going into short cycling mode when it's cooling, it just runs as cool as it can, within limits.  As there cannot be any defrost risk in cooling mode, the unit will just happily run at it's lowest modulated power with only the UFH supplying heat to the heat pump.  The heat flow rate from the slab to the UFH is a great deal higher in cooling mode, because of the very much higher Δt, and that's more than enough to make up for the lack of the buffer.

[Barney12]

9 hours ago, Nickfromwales said:

PCM58 is bench tested with staggeringly good statistics. @AndyT may well garnish this thread with the current stats, so if your middle-aged it's likely the still working SA will attend your funeral.

 

I resemble that remark  

On the up side it may be the one thing that’s heavier than my corpse  

[Stones]

As those who have read my blog know, I have an 8.5kW Mitsubishi Ecodan and 300 litre preplumb cylinder with UFH, 155m2 slab, no buffer, no PV.  I will in the next few weeks be posting on my blog in respect of how the DHW and heating have performed over the course of 12 months.

 

DHW over the course of the year, COP of 2.3, a bit higher in summer, lower in winter. Heating COP of 3.5

 

No short cycling on the heat pump.

 

Plenty of DHW capacity and fast recovery - despite continuous drawing off of DHW we have not experienced DHW running out or going cool.

 

I did a cost comparison before deciding on the ASHP set up, including Sunamp and PV, but ASHP came out on top taking into account capital, running, service and replacement costs into account.  I'll go into more detail in due course, but thought it worthwhile highlighting that an ASHP is a good solution and works well for us.

 

 

[Alexphd1]

On 08/07/2018 at 08:41, pdf27 said:

When they eventually commercialise the PCM43 material, I suspect all this will change. 43°C is hot enough for just about all DHW applications and eliminates the need for a TMV to deal with scalding, while the minimum charging temperature will be ~50°C which is comfortable for a heat pump.

 

Is their a PCM43 sunamp on the cards?

 

Has anybody a update price list for sunamp?

Edited July 28, 2018 by Alexphd1

[le-cerveau]

11 hours ago, Alexphd1 said:

Is their a PCM43 sunamp on the cards?

I think you will find it is PCM34 not 43.  I have a couple of pre UniQ cells attached to my ASHP.  The cells require water at least 5C above the temperature to work currectly and they are set to 45C (factory default).  This is the same for the UniQ PCM34 cells.

[pdf27]

3 hours ago, le-cerveau said:

I think you will find it is PCM34 not 43.  I have a couple of pre UniQ cells attached to my ASHP.  The cells require water at least 5C above the temperature to work currectly and they are set to 45C (factory default).  This is the same for the UniQ PCM34 cells.

If you look at their promotional material they say that a number of different PCM operating temperatures are possible, with PCM34 and 58 currently being the focus. PCM43 is particularly interesting to me because it looks like it might be in the sweet spot for providing DHW from a heat pump - the output temperature should match nicely to the temperature downstream of a scald protection TMV, while the charging temperature should be within the temperature output capability of most heat pumps.

 

 

I have a suspicion that they may be aiming it at the UniQ rHW device (integrated into a heat pump, with the refrigerant circuit being used directly to charge it). Unfortunately that will be an OEM-only option, and nothing has yet been released about when or if this will become available.

[volcane]

I'm planning to install a Sunamp UniQ unit, I thought this time last year that I would need to have the heating and hot water sorted within weeks. A year later it could still be many weeks away?

 

I'm trying to grasp at positives and one is the advance of the Sunamp units available.

 

I need to be able to supply 5 bathrooms (5 showers, 1 bath) with a request to never run out of hot water! and also underfloor heating. We should have a near passive house (at least that was the plan but we have no real idea of what we have or what we will end up with, just over 400 sqm, 5 beds).

 

I think the ability to cool could be extremely useful.

I would like to fit PV (but no 'grants') so may wait to fit later? and have all cabling in place to make later fitting simple. (large unshaded South facing roof)

 

 

Sunamp have proposed a UniQ Dual (26 kWh) paired with a 11 kW Daikin split ASHP, with Economy 7.

 

But;

this system has no ability to cool which takes away some of the benefits of the ASHP (and then makes me think could I go Electric +PV only and save on the ASHP cost)

 

@Nickfromwales do you know much about this proposed system?

 

Is there a way to bypass the Sunamp and have a totally separate circuit to the ASHP specifically to allow cooling.

 

This is for life, I've run out of board and there are no more moves left! so any system should be looked at with this in mind. I don't want to over complicate things as that is another requirement from my partner who will have to be able to manage when I can't.

 

thanks for all opinions/advice

 

[le-cerveau]

21 minutes ago, volcane said:

Is there a way to bypass the Sunamp and have a totally separate circuit to the ASHP specifically to allow cooling.

 

Yes,

 

that is what I have done, though mine are pre UniQ units.

I have a Panasonic 9kW Split.

 

[Nickfromwales]

29 minutes ago, volcane said:

@Nickfromwales do you know much about this proposed system?

Just a bit   

 

Ok, cooling first. You either go mono block ASHP and reverse it a-la @JSHarris, or you go for air-con. Simples ( ish ).

For one current client we are working with an ASHP + Sunamp solution so they have the ability to cool the ground floor slab. They will also be able to cool individual rooms via fan-coil units wet fed by the ASHP ( with the same cooled water that will circulate the slab in 'cooling mode' ). Pointless fitting air con in a house that'll have an ASHP imo, unless theres no UFH loops of course. I may look at taking chilled water to the MVHR inlet and send that through a duct heater ( cooler ) for maximum cooling effect. 

 

As its a bigger than average home the ASHP remains, but it would still have been possible to do away with it TBH if cooling wasn't part of the remit. Having a 'non-optimum' PV array there also reinforced using the ASHP for the primary heat energy source, basically for charging the PCM34's as quickly and cheaply as possible leaving the remainder of PV and grid ( economy ) to top up the PCM58's ( DHW ).

 

2 hours ago, volcane said:

I'm trying to grasp at positives and one is the advance of the Sunamp units available.

Well that is a positive as they've come on leaps and bounds. Now very simple units with nowt to go wrong other than a failed immersion which is now a 5 min job to replace.

 

2 hours ago, volcane said:

We should have a near passive house (at least that was the plan but we have no real idea of what we have or what we will end up with, just over 400 sqm, 5 beds).

 

2 hours ago, volcane said:

Sunamp have proposed a UniQ Dual (26 kWh) paired with a 11 kW Daikin split ASHP, with Economy 7.

Which exact (e)Dual units? PCM34 or PCM58 or mix of the two?

With an ASHP I assume they're suggesting 2 units to get to the 26kW, ( 2x 'size12' units which will store an average of 26kW actual useful heat energy at peak charge state ), which would give you a decent chunk of cold mains uplift ( to 30oC ) and then into the PCM58 for DHW, which will then have extended capacity due to reduced duty.

 

2 hours ago, volcane said:

I need to be able to supply 5 bathrooms (5 showers, 1 bath) with a request to never run out of hot water!

And heres the 'gotcha'.

Does that mean 5 staggered showers, or 2 - 3 running simultaneously / 1-2 showers plus a bath filling etc? A huge question but needs answering before even getting within a mile of choosing an end solution. 

You have to remember that a SA is an instantaneous water heater, just like a combi boiler, so the faster the water flows through it the cooler the flow can become. An UVC for eg will give you full wallop and empty all of its guts out in a very short space of time, AT FULL STORED TEMP, but will then just go stone cold and then need time to recharge before doing the same again. So, for the aforementioned clients SA spec; there will be a pair of smaller PCM58's ( 2x 'size 6' units to get near the required 12-14kWh required for DHW ) specifically being done to get the 2 pairs of DHW heat exchangers inline with the DHW max flow rate requirements.

 

So ( rough figures for eg ) 1x 30 l/p/m flow rate through one SA unit = 60 l/p/m through two units in parallel. More if preheated. That incurs additional capital expenditure so the pros and cons need weighing up.  You do not get higher flow rates with bigger unit sizes as they all share the same H-Ex afaik. I'm still getting info through on these so I can update as I go along. 

 

A single SA H-Ex will happily run 2 high-flow showers or 3 average showers simultaneously but thats about it. After that you'll need to look at pre-heat. That would then allow you to use a 4th shower alongside the other three. From there you'd then be looking at multiples of SA units to get the flow rates up higher and then onto additional preheat to go crazy. Yes it makes my head hurt too!

With an ASHP + PH you'll need to go to a DHW priority setup which allows the ASHP to fully recharge the 34's before allowing space heating to continue to draw heat, that way the DHW system will be fortified for pre-heat by the HP, and the DHW can either be maintained by PV, or if the 58's call for help, grid electricity too. That arrangement lends itself to the space heating depleting all of the stored PV before the ASHP has to kick back in again. Hopefully with a correctly sized setup that would be for a good few months of the year. 

For absolute peak usage, the ASHP AND grid electricity ( via the immersions ) can all join force, for what we refer to as "boost".

 

Space heating is, by contrast, a doddle. One PCM34 will act as a buffer, an option if you only actually want to dump excess PV into space heating. You could just have a cheaper 'eHeat' unit then, ( ASHP on one H-Ex and the space heating on the second H-Ex ) but the eHeat cannot carry potable water for DHW as its not WRAS approved. You can only use an 'eDual' for DHW / DHW uplift as that can carry potable water, but the 'eHeat' isn't WRAS approved so is only good for heating grade water.

The eDual is the highest SAP scoring unit too.

 

Design is the key tbh and treble-thinking your requirements is paramount before moving forward. It can be as easy or as complex as your situation commands !

 

Hope that is of SOME help to you. 

[le-cerveau]

My system is based on the old cells, UniQ equivalent would be 4 x UniQ HW6 (2 with PCM58 and 2 with PCM34).

They are wired in Parallel to give higher flow (ie 2 x PCM34 in parallel, followed by 2 x PCM58 in parallel) so parallel (same PCM) and series (PCM34-58).

The ASHP heats the PCM34's (low pressure circuit) and the UFH takes heat from the same.

The PCM58's are heated by a boiler (may change in due course) (low pressure circuit).

DHW is parallel into High pressure circuit (PCM 34) followed by (series) parallel into the 2xPCM58 high pressure circuit.  There is a tap off at the interface for the DHW mixing valve to mix the Hot from the PCM58 with warm from PCM34 to give distribution water temperature, also the circulation system returns to this point.

We have 5 showers and 2 baths.  Though the showers are Hansgrohe ecoflow (9 l/m), we have a Rainmaker Select 460 2 jet with a hand shower and a highflow valve so I can select 2x overhead jets and the hand shower all at 9 l/m each = 27 l/m and the system easily copes (though officially it is a 9 l/m shower).

 

Our house is just over 400m² and PH standard (not certified).

 

As @Nickfromwales say DHW is the key, heating an aside and just taken from the preheat system.  My cooling does work and has been kicking in, though it takes all day for the house to heat up and it is in the evening when cooking that the greatest effect is, cooling then starts to kick in, as night comes in and the outside temp drops the MVHR goes into bypass and helps cool the house down so by morning it was back to normal.  I had the cooling set not to come on until above 24 and it would only kick in in the evening when we were all home and cooking.  By morning the house would have cooled back to 23ish, mostly based on MVHR bypass as the cooling will shut down below 24 (as currently set).

[Nickfromwales]

1 hour ago, le-cerveau said:

(though officially it is a 9 l/m shower).

What they don't know eh?