Sunamp container bulging

[Nickfromwales]

They're looking at a model that is good for mass housing / high volume sales. Folk like us are the niche im afraid.

[Jeremy Harris]

13 minutes ago, Nickfromwales said:

They're looking at a model that is good for mass housing / high volume sales. Folk like us are the niche im afraid.

 

I can understand that philosophy, but it seems at odds with the wide range of different models that are available.  If looking to take on, say, thermal stores, head-to-head, then they only really need to make one model, in varying sizes, that compares favourably in most respects to a thermal store.

 

The problem I have is that Sunamp started out by making a product that was specifically targeted at storing excess PV generated energy as heat.  That's what I bought into with the Sunamp PV and that's what I thought I was buying into with the Sunamp UniQ eHW.  In practice we've run out of hot water one morning (cold showers - not pleasant) since fitting the UniQ, something that never happened with the smaller, but much better suited to the task, Sunamp PV. 

 

To be fair, it seems that the controller for our unit was supplied set to not accept a charge until it was 90% depleted, which I've been told is a non-standard setting.  Now controllers are shipped  with all options set to "OFF", which defaults to no charge accepted until 50% discharged.  It was easy enough to change the setting, but even so we are still getting very poor excess PV generation utilisation.

 

This afternoon we were exporting around 3 kW for a couple of hours or so, I know full well that the Sunamp hasn't accepted any charge since two showers were taken this morning, so we've just wasted a load of energy that could have topped the Sunamp up to full capacity, ready for tomorrow morning.  Instead, the chances are that it will drop below 50% overnight and so end up getting boost charged off the grid in the early hours, which is really, really annoying.

[Eileen]

I think we (our project) are on the cusp of that. We were the ones who found Sunamp and understood the products enough to mandate them to our M&E people and installers (yes, we are in the luxury position to pay people to do it all!). However, they did not know the products and were not motivated like us to use them, but would be perfectly competent to install them given good manuals, etc. The other key service they needed was technical support - that is, dedicated person/s who could talk at implementation level to the people who are actually installing it. We started and grew a software company and dedicated technical support was a function we had from day 1.

 

[Russdl]

5 hours ago, JSHarris said:

Right now I'd recommend that no one fit a Sunamp if they intend to charge it primarily from excess PV generation.

 

A string of expletives spring to mind.

[Barney12]

6 hours ago, JSHarris said:

To be fair, it seems that the controller for our unit was supplied set to not accept a charge until it was 90% depleted, which I've been told is a non-standard setting.

 

Well that in itself is interesting as I have an email from Sunamp which clearly states the exact opposite!! 

[Onoff]

7 hours ago, JSHarris said:

 

I can understand that philosophy, but it seems at odds with the wide range of different models that are available.  If looking to take on, say, thermal stores, head-to-head, then they only really need to make one model, in varying sizes, that compares favourably in most respects to a thermal store.

 

The problem I have is that Sunamp started out by making a product that was specifically targeted at storing excess PV generated energy as heat.  That's what I bought into with the Sunamp PV and that's what I thought I was buying into with the Sunamp UniQ eHW.  In practice we've run out of hot water one morning (cold showers - not pleasant) since fitting the UniQ, something that never happened with the smaller, but much better suited to the task, Sunamp PV. 

 

To be fair, it seems that the controller for our unit was supplied set to not accept a charge until it was 90% depleted, which I've been told is a non-standard setting.  Now controllers are shipped  with all options set to "OFF", which defaults to no charge accepted until 50% discharged.  It was easy enough to change the setting, but even so we are still getting very poor excess PV generation utilisation.

 

This afternoon we were exporting around 3 kW for a couple of hours or so, I know full well that the Sunamp hasn't accepted any charge since two showers were taken this morning, so we've just wasted a load of energy that could have topped the Sunamp up to full capacity, ready for tomorrow morning.  Instead, the chances are that it will drop below 50% overnight and so end up getting boost charged off the grid in the early hours, which is really, really annoying.

 

I'm a bit lost here. Isn't the underlying tech and indeed the PCM material in your old Sunamp PV and new UniW eHW the same?

 

Therefore it's just a changeable controls setting issue?

 

Why are you "getting very poor excess PV generation utilisation" if you've changed the setting?

[PeterW]

7 hours ago, Onoff said:

 

I'm a bit lost here. Isn't the underlying tech and indeed the PCM material in your old Sunamp PV and new UniW eHW the same?

 

Therefore it's just a changeable controls setting issue?

 

Why are you "getting very poor excess PV generation utilisation" if you've changed the setting?

 

The old controller didn’t have a limit before excess  PV was utilised so if then Sunamp was 10% discharged and there was PV available it would use it until it reached 100%. Now the controller checks and won’t allow and input power until 50% discharged or 90% discharged depending on a setting in the control box. 

 

This means if it gets to the end of the PV day and is 45% discharged you need to use grid power to top it up - at 3-4 times the cost of the PV you’ve exported ..!

[Nickfromwales]

I’ll get some specific feedback on this.

[Jeremy Harris]

Spot on, @PeterW.

 

The old Sunamp PV controlled pretty much everything from the temperature sensed at various points in the pumped water charge circuit.  When excess PV was available, the pump would turn on, circulating water through the cell charging loop, which contained an inline water heater and a flow sensor, as well as temperature sensors either side of the cells heat exchangers.  If the temperature coming out of the cells heat exchangers indicated that the PCM was charged, then the unit would shut down with the status SoC LED on the side telling you that the unit was fully charged.  If you drew off some hot water, so lowering the temperature of the cell, then if excess PV power was available the unit would start charging again as soon as the water draw down had stopped (it couldn't simultaneously charge and discharge, because of the way the internal hydraulic circuit was arranged).

 

The electrically heated UniQ models are fundamentally different, in that the heating element is in the PCM at the base of the unit.  This means that another means has to be used to sense whether the cell is charged, and to what level.  This is done via three thermistors that sit in a vertical tube within the cell, one near the base, one in the middle and one near the top.  From what I can gather, this only gives a very approximate indication of the state of charge, both because three sensors in the middle of the cell is a bit coarse, in terms of sensing the whole cell PCM temperature, and because convection heating within the PCM is somewhat slower and probably a bit patchy, due to the mix of solid and liquid phase areas within it.

 

I'm tempted to try and run a string of sensors down the cell to measure how the PCM temperature changes as the cell charges, logging the data to try and map the pattern of temperature change during charge and discharge.  I have a feeling that by using this data I could come up with a more intelligent controller that allows the cell to accept excess PV charge before it has discharged to 50%.  The key to this may well be modulating the charge power carefully, to keep the PCM temperature within limits everywhere in the cell.  This isn't at all hard to do if the function of the control box and the PV diverter is combined into a single unit.  It would also give an approximate SoC indicator, based on the results of mapping the temperatures within the cell and the energy going in.  It would be nice to also measure energy going out, but that would mean adding a flow sensor, along with additional temperature sensors either side of the unit.

 

One neat thing about combining the functionality of the PV diverter with the Sunamp controller is that everything can be solid state controlled, so no more big contactor clunking away.  It would be easy to build in a boost function, too, just needs a RTC plus a small bit of additional code.  The boost functionality could also include the cold start process, where the heating element is pulsed on and off so as not to locally overheat the PCM.  I believe this could be done more effectively by modulating power to the heater, rather than just turning it on and off, and it should be straightforward to work out the required modulation from the existing on/off mean power.

[Russdl]

10 minutes ago, Nickfromwales said:

I’ll get some specific feedback on this.

 

I look forward to that. This change seems to have thrown my plans into disarray and I'm now wondering what is going to be the best way forward.

 

 

[Nickfromwales]

Just now, Russdl said:

 

I look forward to that. This change seems to have thrown my plans into disarray and I'm now wondering what is going to be the best way forward.

 

 

Wood burning stove, and live in the woods probably.  

[joe90]

@JSHarris, now that you have finished your house and you are bored ?, perhaps as an experienced user of the sunamp and technical wiz perhaps they would like to employ you as a consultant?. ( only half joking, not saying which half tho!!!!!).

[ProDave]

8 hours ago, Onoff said:

 

I'm a bit lost here. Isn't the underlying tech and indeed the PCM material in your old Sunamp PV and new UniW eHW the same?

 

Therefore it's just a changeable controls setting issue?

 

Why are you "getting very poor excess PV generation utilisation" if you've changed the setting?

Someone correct me if I am wrong but this is the impression I have got from the discussion.

 

The original Sun Amp PV had it's immersion heater in water and a pump to take the heated water in to heat the pcm.

 

The new Uniq has the immersion heater directly in the pcm material.  I presume that is to make it more efficient, but by doing so it seems to have placed this rather restrictive limit on when and how much charge the immersion heater can accept.

 

It would seem an "improvement" is not always so.

[Onoff]

1 hour ago, PeterW said:

 

The old controller didn’t have a limit before excess  PV was utilised so if then Sunamp was 10% discharged and there was PV available it would use it until it reached 100%. Now the controller checks and won’t allow and input power until 50% discharged or 90% discharged depending on a setting in the control box. 

 

This means if it gets to the end of the PV day and is 45% discharged you need to use grid power to top it up - at 3-4 times the cost of the PV you’ve exported ..!

 

If that's the case it's crap, a serious oversight by Sunamp and a serious step backwards for the product as a whole. People expect to be able to store every drop of excess PV they can. I really wonder if they've been "got at". Think of the money the British public pump into goods and services that tick an eco box but aren't really as good as they could be; double glazing when triple should be standard, the fitting of either and poor install methods by Part N approved contractors. New housing stock. With all of this the net result is energy loss and more £££ in the coffers of UK plc. Sorry, rant over, I can hear the black SUVs pulling up outside and choppers overhead.

 

My mate has just specified one on his new build  (though he has no PV just an ASHP). I'll be talking to him tomorrow. Another one was toying with it to store his excess PV. Let's face it their service is crap anyway. Same mate saw them at Build It and his enquiry died a death.

 

Sounds like, PV utilisation wise that you were in a better position with the old Sunamp PV. I believe Sunamp took yours back for a strip down and look see how it has performed. Can I ask though whether there was fundamentally anything wrong with it? 

 

Is it that with the UniQ there are less sensors hence less complexity but they are limiting the number of recharge cycles deliberately to prevent early failure?

[Nickfromwales]

17 minutes ago, joe90 said:

@JSHarris, now that you have finished your house and you are bored ?, perhaps as an experienced user of the sunamp and technical wiz perhaps they would like to employ you as a consultant?. ( only half joking, not saying which half tho!!!!!).

I was actually thinking the same thing last night tbh. They need someone who is both a consumer, an installer,  AND is someone they don't directly employ ( so can tell them "how it is" without the fear of getting sacked ). The problem with most good staff is they don't want to rock the boat, not a problem for me as I told my old employer to take his neanderthal way of doing things and to shove it right up his arsehole ( as I was the one taking the flack all the time ). He was stuck in his ways and couldn't be told.    

[Jeremy Harris]

10 hours ago, Barney12 said:

 

Well that in itself is interesting as I have an email from Sunamp which clearly states the exact opposite!! 

 

When I noticed that our Sunamp wasn't accepting a charge, despite us having run a couple of showers that morning, I took the lid off the controller and checked the settings (hold down SW1 and read the settings on the four LEDs on the board).  As supplied, my controller was showing LEDs D4, D3, and D2 OFF and LED D1 ON.  According to the manual, this means the unit is setup as:

 

Option 4 - Not used - OFF

Option 3 - Heat pump (65 deg C flow) - OFF

Option 2 - PV input possible - OFF (this seems weird to me)

Option 1 - Charging demand level - ON

 

 

There are another set of options that these status LEDs can display, which sets the type of unit that the controller board is operating.  These are shown by holding down SW2, with the LEDs then giving this information:

 

LED D4 on = Not used

LED D3 on = UniQ_SBC_03

LED D2 on = UniQ_SBC_02

LED D1 on = UniQ_SBC_01

 

My unit is labelled as being a UniQ_SBC_01_PV, and shows in the above check as a UniQ_SBC_01

 

Charging demand level, Option 1 in the first set of checks above, is further defined in the manual as:

 

Controller type: UniQ_SBC_01 (Electric storage water heater)

• Heating from bottom to top
• Cooling from top to bottom
• Option 1 on: demand signal generated when battery is approx. 90% depleted
• Option 1 off: demand signal generated when battery is approx. 50% depleted

I sought clarification on the settings, specifically whether Option 1 = ON meant 90% depleted or 90% remaining, as if it really meant 90% depleted then that would explain why we'd run out of hot water one morning and also why the unit wasn't accepting any charge when we were exporting and had just run two showers.

 

I got a quick response from Sunamp, which said this:

 

Quote

As standard the units are shipped with all options off so the cell will start to recharge once a 1/3 or 1/2 has been used (the cell is roughly 50% depleted).

 

 

If you switch this option on (by holding down SW1 until the LED is on) the unit will “deep discharge” (down to just 10% energy left, or 90% depleted) so will have used the majority of the stored energy before the Qontroller triggers a recharge. This allows better utilisation of the store under the conditions that you have described.

 

 

Most of our customers obviously just want to keep it topped up the majority of the time, so with this option off it will recharge more often.

 

So, the first point is that my unit was not shipped with all options OFF, but was shipped with Option 1 ON, so the cell was being allowed to deplete to only 10% charge remaining before it would accept a charge.  This explains why we ran out of hot water one morning this week and had to endure cold showers.

 

The second point is that even after I changed the setting on my unit to turn Option 1 OFF (as, apparently, it should have been in the first place) it still won't start to accept a charge until it has discharged by ~50%.

 

The final sentence of that email doesn't make sense, as if the unit won't accept a charge until it's ~50% depleted then you cannot keep it topped up.  I proved this yesterday.  We ran two showers first thing in the morning, and then we had a period of bright sunshine when we were exporting ~3kW for a couple of hours or so.  The Sunamp refused to accept any charge at all during this period, despite the fact that I know for sure we pulled about 4 kWh out of it with the morning showers.  It would have been nice to have the Sunamp topped up with the excess PV generation, but instead it didn't top up until 3 am when our boost timer came on, so we paid for ~5 kWh of grid electricity to top the thing up, when we could have topped it up for nothing from yesterday's excess PV generation.  I'm bloody angry about this, especially as the old Sunamp PV would not have behaved like this at all.  I really wish that I'd just opted to keep the Sunamp PV and add a couple of extra cells to it, as that would have been a far better solution.

 

1 hour ago, joe90 said:

@JSHarris, now that you have finished your house and you are bored ?, perhaps as an experienced user of the sunamp and technical wiz perhaps they would like to employ you as a consultant?. ( only half joking, not saying which half tho!!!!!).

 

Right now I'd happily look at developing an open source controller for these units.  Not sure I'd want to work as a consultant (I already have one job like that) but I'm sorely tempted to have a go at modelling the behaviour of the PCM cell and coming up with a control system that allows it to be kept topped up whenever there is excess PV generation available.  I have to say that I'd be very tempted to just use the low power heat exchanger (there are two inside the cell, currently connected in parallel) with a cell charging system like the Sunamp PV.  Perhaps a Willis heater, pump, and temperature sensors, so that the charging loop could run at a carefully controlled temperature to keep the cell topped up all the time.

[ProDave]

22 hours ago, JSHarris said:

It turns out that this doesn't work at all, and we've already run out of hot water once, before I altered the boost charge timings.  Seeing the unit yesterday morning just sitting there, having just delivered around 4 kWh of hot water, yet not accepting any charge at all from the loads of excess PV we were generating, was bloody annoying to put it mildly.  It's meant we're using significantly more grid power, and wasting a significant amount of PV generation that we should be able to store in the Sunamp.

My SWMBO has a set of fine words to describe something like that. She would be telling me what a POS it was and how it was unfit for purpose and wanted it replaced with something "that works"

[Nickfromwales]

4 minutes ago, Onoff said:

Is it that with the UniQ there are less sensors hence less complexity but they are limiting the number of recharge cycles deliberately to prevent early failure?

Early failure is not a problem, these things will attend your funeral ( on a good day ).

 

@JSHarris

Its my assumption that SA hasn't cracked the stop-start of the 'freezing' of the PCM, more that it is so well insulated it just shoots its bolt ( sorry ) and the heat energy sits there waiting to be utilised. The get out of jail card is that these are aimed at the domestic sector, in the UniQ form, and therefore are assumed to be getting recharged every 24hr period, hence they can get away with not stopping the phase change. 

Would you concur? 

[Jeremy Harris]

4 minutes ago, Onoff said:

 

If that's the case it's crap, a serious oversight by Sunamp and a serious step backwards for the product as a whole. People expect to be able to store every drop of excess PV they can. I really wonder if they've been "got at". Think of the money the British public pump into goods and services that tick an eco box but aren't really as good as they could be; double glazing when triple should be standard, the fitting of either and poor install methods by Part N approved contractors. New housing stock. With all of this the net result is energy loss and more £££ in the coffers of UK plc. Sorry, rant over, I can hear the black SUVs pulling up outside and choppers overhead.

 

My mate has just specified one on his new build  (though he has no PV just an ASHP). I'll be talking to him tomorrow. Another one was toying with it to store his excess PV. Let's face it their service is crap anyway. Same mate saw them at Build It and his enquiry died a death.

 

Sounds like, PV utilisation wise that you were in a better position with the old Sunamp PV. I believe Sunamp took yours back for a strip down and look see how it has performed. Can I ask though whether there was fundamentally anything wrong with it? 

 

Is it that with the UniQ there are less sensors hence less complexity but they are limiting the number of recharge cycles deliberately to prevent early failure?

 

 

I have to agree with you 100%.

 

Yes, our old Sunamp PV went back to be stripped and inspected, and no, there wasn't anything really wrong with it.  It could usefully have had the software changed to increase the pump over-run time, something that was done on later Sunamp PVs, to prevent occasional over-temperature trips on the water heater tube, from heat soak after turn off, but that's all.  All I really wanted was more storage capacity, to make better use of excess PV generation.

 

 

7 minutes ago, Nickfromwales said:

I was actually thinking the same thing last night tbh. They need someone who is both a consumer, an installer,  AND is someone they don't directly employ ( so can tell them "how it is" without the fear of getting sacked ). The problem with most good staff is they don't want to rock the boat, not a problem for me as I told my old employer to take his neanderthal way of doing things and to shove it right up his arsehole ( as I was the one taking the flack all the time ). He was stuck in his ways and couldn't be told.    

 

I'd happily give direct feedback and am quite prepared to do some detailed measurement and data logging to determine what the unit is actually doing, with a view to trying to work out how to come up with a more intelligent control system.  I'm sure the key is understanding heat transfer within the PCM, and making absolutely certain that the PCM cannot locally over heat.  I very strongly suspect that the current set up has been designed to protect the PCM whilst allowing the cheaper and simpler direct heating system from the embedded element.  One major advantage of the old Sunamp PV charging system was that it could never overheat the PCM locally, as the flow temperature in the charging circuit was restricted to around 65 deg C, IIRC.

[Barney12]

1 minute ago, JSHarris said:

All I really wanted was more storage capacity, to make better use of excess PV generation.

 

Ouch!  

[Jeremy Harris]

1 minute ago, Nickfromwales said:

 

@JSHarris

Its my assumption that SA hasn't cracked the stop-start of the 'freezing' of the PCM, more that it is so well insulated it just shoots its bolt ( sorry ) and the heat energy sits there waiting to be utilised. The get out of jail card is that these are aimed at the domestic sector, in the UniQ form, and therefore are assumed to be getting recharged every 24hr period, hence they can get away with not stopping the phase change. 

Would you concur? 

 

Not sure, TBH.  I suspect the controller is playing safe to prevent any possible local overheating of the PCM, and one way of doing that is to prevent it from accepting a charge when it's partially discharged, as heat transfer internally may be a bit of an unknown.  I suspect that convection is pretty slow within the PCM, and that it may be impeded by there being lumps of solid PCM randomly "floating around" within the liquid PCM.  My guess is that letting the unit sit partially charged and not accepting a charge is simple a way to get around this problem, albeit at the loss of a lot of functionality in terms of optimising energy storage from excess PV generation.

 

2 minutes ago, Barney12 said:

 

Ouch!  

 

Yes, "ouch" indeed, especially given the effort it took to move the 150kg of Sunamp UniQ upstairs - that took me a whole day...

[Guest Alphonsox]

There seems to have been a step up in efficiency between the SAPV and the UniQ units. The original versions had a ErP rating of "C" while the latter get a "A+" with very similar heat loss rates (@0.7KWh/24h). I assume the efficiency gain is a function of the new charging mechanism.

[Nickfromwales]

14 minutes ago, JSHarris said:

when it's partially discharged

My previous point. What if it isn't ever partially discharged? What if it just nucleates and turns into one hot frozen lump as quickly as you see the little demo sachets change? I genuinely cannot see how that reversal could be stopped, or even slowed, but I am just a lowly plumber from Swansea and the only white coat I've ever worn did up at the back  

 

4 minutes ago, Alphonsox said:

There seems to have been a step up in efficiency between the SAPV and the UniQ units. The original versions had a ErP rating of "C" while the latter get a "A+" with very similar heat loss rates (@0.7KWh/24h). I assume the efficiency gain is a function of the new charging mechanism.

Its also got to be the fact that theres no network of pumps, pipework and what-not acting as mini radiators with the UniQ vs the tin of spaghetti thats in the upper section of the SAPV. 

 

@Alphonsox I lost about 15 mins yesterday watching your avatar. Bills in the post mate !

[Jeremy Harris]

18 minutes ago, Alphonsox said:

There seems to have been a step up in efficiency between the SAPV and the UniQ units. The original versions had a ErP rating of "C" while the latter get a "A+" with very similar heat loss rates (@0.7KWh/24h). I assume the efficiency gain is a function of the new charging mechanism.

 

I think there is more to it than this.  Back when we were talking with Sunamp about the Sunamp PV, one issue they had was with the way the product was being assessed for the energy rating.  It didn't fit any standard category, so had been tested as an electric water heater, IIRC.  As such it had quite a poor score.  I believe that some work was done to allow a more accurate assessment of the product range in the light of it's unique features, and that probably explains the difference in the rating.  The Sunamp PV was no less efficient as far as I can tell, as it never got warm on the outside, much like the UniQ, so wasn't wasting much energy.

 

16 minutes ago, Nickfromwales said:

My previous point. What if it isn't ever partially discharged? What if it just nucleates and turns into one hot frozen lump as quickly as you see the little demo sachets change? I genuinely cannot see how that reversal could be stopped, or even slowed, but I am just a lowly plumber from Swansea and the only white coat I've ever worn did up at the back  

 

The key is either monitoring temperature throughout the cell, or just heating the cell to a few degrees above the phase transition temperature.  If all the PCM in the cell is above 58 deg C it will always be liquid, and this was, I believe, the way that the Sunamp PV control system worked.  It just chucked water at ~65 deg C through the heat exchanger until the output from that heat exchanger showed that the PCM was above transition temperature, at which point it stopped accepting charge.  This worked well, as it is easy to just control the temperature of the charging loop, to be absolutely certain that the PCM can never locally overheat.

 

I'm coming around to the view that a Willis heater, pump and temperature sensors, connected up to the low capacity heat exchanger, could turn a UniQ into a SAPV, in effect, and allow a much wider charge acceptance range.  The key is that this would never allow the PCM to exceed the temperature in the charging circuit, which would be very easy to regulate to a safe temperature.  Another advantage is that the cell could be charged and discharged at the same time with such a set up. 

[dpmiller]

I might've asked this before but what *is* the "breakdown" temp, where the goo starts to cook? Surely a hard limit on the immersion element temperature would be all that is required to safeguard it.

We see similar strategies in Autoclaves for redundant boil dry and overheat protection; some have a capillary stat clamped onto the element, others ( in an external boiler) have a PT100 in contact with the element, going to a spare way on the microcontroller.