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Sunamp - new label showing only C rated energy efficiency

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5 minutes ago, JSHarris said:

My feeling at the moment is that the simple temperature measurement system, combined with a bit of logic that just does something like "IF contactor has been off for > x hours THEN turn contactor ON", with the existing "PCM fully charged" logic over-riding that to turn the contactor off, as it does now, would work well enough for pretty much any use case I can think of. 

 

I don't think there's much controversy with respect to PV diversion: if there is spare PV power available and the store is not full then you should divert to the store. The only complication is if there are multiple stores, e.g., Sunamp + some sort of battery either in an EV or hanging on the house wall, when there might be a decision to be made as to which gets priority at any time.

 

The question then is if there is another heat source, an oil or gas boiler or mains electricity: when should it be used and to what SoC should it aim to bring the store? E.g., it would be sad to charge the store fully on overnight electricity then only a few litres of DHW be drawn for washing in the morning followed by a bright sunny day with PV going to “waste” into the grid. This depends so much on the other system components (e.g., whether the other heat source's cost is time dependent, whether as @Nickfromwales says there's a combi downstream of the Sunamp in which case you'd be more willing to “risk” a low SoC to leave room for PV) and lifestyle (do you shower in the evening or morning, does the household use more or less the full capacity in a day or just a fraction).

 

I think the most general solution is to have a target SoC for different times of the day (e.g., 70% at 06:00, 30% at 18:00 or whatever), leave the PV to do the best it can then boost as required to meet those targets.

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But the bone of contention is still not having an accurate ( actually ANY ) SoC indicator.

How do you know how long to boost for? How long do you leave the SA deenergised for before boosting, without running out of hot water? Simple answer is trial and error I suppose, but then there is the question of sizing...…...

Paracetamol, anybody?

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48 minutes ago, Nickfromwales said:

But the bone of contention is still not having an accurate ( actually ANY ) SoC indicator.

How do you know how long to boost for? How long do you leave the SA deenergised for before boosting, without running out of hot water? Simple answer is trial and error I suppose, but then there is the question of sizing...…...

Paracetamol, anybody?

 

The interesting thing was that the Sunamp PV didn't appear to have this problem.  It would just heat the charge circuit (a closed water loop) up to the target temperature whenever it detected that there was a supply, whether continuous, pulsed, phase angle controlled, or whatever, available.  The water charge loop was both physically small and low in volume, so the heat losses from it were small.  

 

In many respects I prefer the way the Sunamp PV charge circuit worked.  Not only did it reliably keep the PCM charged when power was available, but it also had other advantages.  It was inherently safe, in terms of not allowing the PCM to overheat, plus all the working components could be replaced easily, as they were fairly standard parts and were easy to access.  If the heating element failed, for example, then it was perhaps an hours work at most to replace it.  The same goes for the charge circuit circulating pump, or the flow or temperature sensors - all could be pretty easily serviced/replaced.

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Agreed. They seem to have added more problems, by involving the inbuilt immersion heater, that didn't previously exist. Was the SAPV A rated? I cannot recall.

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16 minutes ago, Nickfromwales said:

Was the SAPV A rated? I cannot recall.

 

No, IIRC it was also C rated, for the same reason as the current electrically heated versions are C rated.  The heat losses from the Sunamp PV were a little higher, in proportion to the stored energy, around 600 Wh/24 hours for a nominal capacity of around 4.5 kWh.  The difference in heat losses is probably partly down to the smaller size of the Sunamp PV and partly down to the small additional loss from the charge circuit plumbing in the top of the unit.

 

I'm still toying with the idea of making a well insulated electrically powered hot water charging unit for a Sunamp UniQ.  I think that it could be a bit simpler than the system used in the Sunamp PV, as a Willis heater would be the obvious off-the-shelf heating unit, and that has a greater volume than the tiny heater that was in the top of the Sunamp PV.  The advantage of that is that I think that good enough charging temperature control could be achieved just by turning the pump on and off (rather than using a variable speed pump).  Monitoring the return temperature should give a reliable indication as to when the PCM cell is charged, as when that rises above about 60 deg C or so then it's a reasonable bet that the PCM is close to being fully charged.  Also dead easy to build in two fail safes that are outwith the main control system, using the Willis immersion thermostat to turn off power to the element at around 75 deg C and using the cut-out in the immersion as the final backstop over-heat prevention measure.

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2 hours ago, Nickfromwales said:

But the bone of contention is still not having an accurate ( actually ANY ) SoC indicator.

 

Yes. I guess we're looking into how you'd use a hypothetical SoC indication to motivate asking for one.

 

1 hour ago, JSHarris said:

Monitoring the return temperature should give a reliable indication as to when the PCM cell is charged,

 

But sometimes you don't want to charge the PCM cell fully. E.g., you're charging from peak rate electricity in the early evening and only want to put in what will be needed until cheap rate electricity arrives at midnight. Or you're charging in the early morning and want to put in enough for a couple of start-of-day  showers but leave as much room for charging from PV as possible. Households differ.

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9 minutes ago, Ed Davies said:

But sometimes you don't want to charge the PCM cell fully. E.g., you're charging from peak rate electricity in the early evening and only want to put in what will be needed until cheap rate electricity arrives at midnight. Or you're charging in the early morning and want to put in enough for a couple of start-of-day  showers but leave as much room for charging from PV as possible. Households differ.

 

I think that you could still use the same method to partially charge the PCM to a particular SoC, within a reasonable error margin, just by determining the difference between energy out, plus losses, and energy in.  I use something similar to partially charge my motorcycle battery pack and yet still have the "fuel gauge" give a reasonably OK SoC indication.  In that case, the BMS measures the charge energy, subtracts a notional charge inefficiency % and then using that, together with the known SoC from before charging started, displays the resulting SoC. 

 

It wouldn't be hard to adapt the same basic process for charging the PCM cell up to an approximate SoC, I think, as measuring the electrical input energy is pretty easy and with a flow meter and two temperature sensors it should be straightforward to measure the output energy.  Losses over time would have to be taken into account, but they are small, so a simple linear approximation over time would probably be good enough, depends on how accurately you want to charge to a specified SoC.  Getting to within 10% is probably realistic, and given the likely variability around any predicted energy requirement this may be good enough..

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1 hour ago, JSHarris said:

I think that you could still use the same method to partially charge the PCM to a particular SoC,

 

Ah, OK. I was reading your Willis heater thoughts as a substitute for knowing the SoC well, rather than an addition to it.

 

A slightly scary aside, but airliner fuel tank gauges also work this way. They, of course, have sensors in the tank to measure the quantity of fuel present but they're not very accurate so the quantities displayed to the crew come from counting the fuel put in (off those sheets of paper on the clipboard the dispatcher brings on board after you've just finished boarding) and fuel out via flow meters in the fuel lines to the engines. The tank gauging is just used to adjust the running total so it doesn't get totally out of wack due to cumulative errors.

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I got a further response today to my Facebook post from Andrew Bissell the CEO.

"No they can be set to recharge when nearly full or nearly empty. Settings are in the manual if you have bought the product."

Seems differ from @JSHarris experience.

Confusion reigns.

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15 minutes ago, vfrdave said:

“No they can be set to recharge when nearly full or nearly empty. Settings are in the manual if you have bought the product."

 

Well that’s not what it even says in the manual according to @JSHarris  Figures of 50% and 90% are quoted are they not?  50% isn’t ‘nearly full’ in my world. So is the manual wrong? 

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@newhome I have just replied sending him this exert from the manual:-

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

 

Not much ambiguity in the above.

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No, it's definitely around 50%, for sure, as I've tested this many times now.  Our usage pattern means that we draw around 3 kWh to 4 kWh from the Sunamp very soon after the early morning boost, when it is fully charged.  I then expect it to be ready to accept charge from excess PV generation during the day, but 9 times out of 10 it won't be, as it doesn't think it's discharged to 50% (and to be fair, it almost certainly isn't).  If I power the controller off and then on again immediately after the last morning shower it always, without fail, switches on and starts to accept charge from the PV when it becomes available.

 

If I don't switch the power off and then on again the Sunamp will go the whole day without using any of our PV generated energy at all, which rather defeats the main reason I have the thing.  What's worse, is that if I don't do this reset procedure, then there is a good chance that the Sunamp controller still won't enable any charge for the next early morning boost period.  We've run out of hot water because of this, because although it may start to deliver hot water for the first shower the next morning, if that's longer than normal then the second shower will run cold (we've had this happen).

 

Resetting the controller by turning the power off and then on again always works, and for as long as I remember to do this every morning the Sunamp works extremely well indeed.  Today is a good example.  At around 07:30 I did the reset procedure and by around 11:30 this morning the Sunamp was fully charged from excess PV generation (my car is currently charging at around 3.5 kW from excess PV right now, too - it's a nice, cold, clear day here).  Had I not reset the Sunamp this morning then it would be sat there doing sod all, and we'd either have had to pay to charge up from the grid in the early hours tomorrow or we may well have ended up with a cold second shower tomorrow.

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3 minutes ago, JSHarris said:

No, it's definitely around 50%, for sure, as I've tested this many times now. 

 

Sounds like @vfrdave got the brush off from the CEO then. That's pretty disappointing. And they should just make the manual available on the web like 99% of suppliers these days. 

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5 minutes ago, JSHarris said:

Here's the latest manual I have (may be out of date now, but I'm not aware of a newer version):

 

UniQ manual 180719.pdf

 

Now that’s odd as if you look at the settings for the thermal store with heater, UniQ_SBC_02, it states it has a PV diverter option to take any charge when available ..!

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22 minutes ago, PeterW said:

 

Now that’s odd as if you look at the settings for the thermal store with heater, UniQ_SBC_02, it states it has a PV diverter option to take any charge when available ..!

 

It's more than odd, because whilst up at the NSBRC at Swindon on Friday I was talking to someone who has an older prototype, or pre-production, control box on their Uniq and that has far more functionality, and doesn't have any of the daft "wait until ~50% discharged before accepting any charge" nonsense.  He was telling me that his controller enables charging as soon as there is any spare capacity to accept any charge, which is exactly how the old Sunamp PV used to work. 

 

In many ways, the Sunamp PV charging system was superior, as it would always try to maintain the heat battery at ~65 deg C if there was any power available to do so.  This was pretty much ideal in terms of being able to utilise any available excess PV generation, and also made sure that the unit was always charged up to the maximum possible whenever it needed to be.

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@JSHarris, would it be possible to run your system as an SBC_02 just ignoring the boiler input? Like the boiler was broken or something.

 

The discharge direction is the opposite but would this matter? How does that work anyway? Pipes plumbed the other way?

Edited by Ed Davies

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11 minutes ago, Ed Davies said:

@JSHarris, would it be possible to run your system as an SBC_02 just ignoring the boiler input? Like the boiler was broken or something.

 

The discharge direction is the opposite but would this matter? How does it would, anyway? Pipes plumbed the other way?

 

 

Unfortunately the SBC_02 control box is physically different to the SBC_01 control box internally, from what I've seen.  The SBC_02 is only capable of switching a low powered electric heating element, I believe, as the Sunamp that it is designed to operate cannot be used with a PV array of greater than 2.5 kWp, according to the manual.  I seem to remember reading somewhere that the heating element in these units is 1.5 kW, rather than the 3 kW that's in ours, but I could be mistaken.

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1 hour ago, JSHarris said:

 

 

Unfortunately the SBC_02 control box is physically different to the SBC_01 control box internally, from what I've seen.  The SBC_02 is only capable of switching a low powered electric heating element, I believe, as the Sunamp that it is designed to operate cannot be used with a PV array of greater than 2.5 kWp, according to the manual.  I seem to remember reading somewhere that the heating element in these units is 1.5 kW, rather than the 3 kW that's in ours, but I could be mistaken.

I don't see why that should not be capable of being used with any size PV array.  Sure it won't use up as much excess due to a lower power heating element, but it would surely still work.

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2 hours ago, JSHarris said:

Here's the latest manual I have (may be out of date now, but I'm not aware of a newer version):

 

UniQ manual 180719.pdf

 

Yours @JSHarris is an SBC_01? So it's wired as figure 6.1 in that manual? But your high current supply comes via your diverter so is off when the sun doesn't shine so where does the supply for the controller come from at night?

 

From my hazy recollection of previous conversations here and application of a bit of logic I think your wiring is actually more like that in figure 6.3 (for the SBC_02) but maybe not having the 3A relay. In particular, the controller supply I think comes in separately from the heater supply.

 

I think the low power restriction for the SBC_02 configuration applies to the HW+iPV (not the HW+i) where the immersion is driven directly from the PV (not via the AC wiring at all). Obviously a lot of checking would be needed first but I think your system could be switched to an HW+i setup with only button pushes, no rewiring.

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33 minutes ago, ProDave said:

I don't see why that should not be capable of being used with any size PV array.  Sure it won't use up as much excess due to a lower power heating element, but it would surely still work.

 

 

I agree, but the spec and manual stipulate that it shouldn't be used with a PV installation that's over 2.5 kWp.  I've no idea why, as if these units are fitted with lower power electric heating elements (which I think they are), then it shouldn't matter at all how large the PV array is.  TBH, I'm inclined to think it may well be a cock-up or misunderstanding by Sunamp, as I can't understand the logic behind it.

 

22 minutes ago, Ed Davies said:

 

Yours @JSHarris is an SBC_01? So it's wired as figure 6.1 in that manual? But your high current supply comes via your diverter so is off when the sun doesn't shine so where does the supply for the controller come from at night?

 

From my hazy recollection of previous conversations here and application of a bit of logic I think your wiring is actually more like that in figure 6.3 (for the SBC_02) but maybe not having the 3A relay. In particular, the controller supply I think comes in separately from the heater supply.

 

I think the low power restriction for the SBC_02 configuration applies to the HW+iPV (not the HW+i) where the immersion is driven directly from the PV (not via the AC wiring at all). Obviously a lot of checking would be needed first but I think your system could be switched to an HW+i setup with only button pushes, no rewiring.

 

Yes, ours is an SBC_01_PV, and I have a time switch in series with a 20 A boost on/off switch that bypasses the excess PV generation diverter, so that I can switch in a timed 2 hour early morning boost if the Sunamp will accept a charge.  The logic is this:

 

  • If Sunamp is fully charged from PV during the day, then the contactor will be open, so the timed boost has no effect.

 

  • If Sunamp isn't fully charged from PV during the day, then the contactor will be closed, so the timed boost charges the Sunamp at a ~3kW for up to 2 hours (enough for two morning showers, with ~50% extra, just to be sure).

 

I'll have a closer look and see if the SBC_01_PV control box we have (not sure what the _PV suffix indicates) can be set up as an HW+i, and whether or not that significantly changes the charge acceptance threshold.  The specification seems a bit vague on this, as whilst the text for the SBC_02 indicates that it can be set to  "Option 2 on: electrical input is from solar PV diverter. High current relay will be activated to allow input whenever possible." the temperature control set points in Table 3 don't seem to indicate much, if any, real difference.  Also, the text for the SBC_02 still mentions that the charge acceptance points that can be selected are either 90% discharged or 50% discharged, the same as for the SBC_01.  I'd be interested to understand what the difference is between the SBC_01 and the SBC_01_PV is, too, as our box is clearly labelled as an SBC_01_PV for some reason.

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I’ve just caught up again with this thread. Doesn’t seem like we’ve made much progress. What happened to the promised ‘New Year Update’ solving the issues. 

 

I cant even get them to respond to my requests to fix YET ANOTHER faulty unit.

 

Buyer beware is frankly my best advice at this stage. 

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Bloody hell, that's more than bad luck.  What's wrong with this one?

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14 minutes ago, Barney12 said:

I cant even get them to respond to my requests to fix YET ANOTHER faulty unit.

 

Call them out on Twitter and keep doing so until they address the issue. At least they appear to respond on there. 

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My understanding is that they are working hard to right previous "wrongs".

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