Sunamp container bulging

[Ed Davies]

59 minutes ago, JSHarris said:

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.

 

This is more or less what I have in mind though with additional sources and sinks for the heat. Would that ever have problems with starting from cold, like the electric element does? I.e., would you have to keep the flow rate down when there's solid PCM round the pipes or would it be sufficient to simply keep the flow temperature not above 70 or 75 °C or whatever the limit is? I assume that'd be safe but it'd be nice to be sure.

[Jeremy Harris]

2 hours ago, dpmiller said:

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.

 

I'm not sure, but would guess that it's probably over 100 deg C, so just limiting the element temperature to something like 70 or 80 deg C may well work OK.  I'm not sure how easy it is to monitor the element temperature, though.  It's not removable and I've not looked in the base of the unit to see if there's a thermostat or over-temperature sensor pocket adjacent to the element.  I do know that there are no sensor cables running from the heater to the control box.

 

@Nickfromwales may have looked at the area around where the element is installed into the base of the cell and be able to shed some light as to whether it would be possible to sense the element temperature directly.

 

Alternatively, it wouldn't be hard to sense the element temperature indirectly, from measuring the change of resistance of the element itself.  Easy enough to do by just adding voltage and current sensing to the element power cable.  The element is bound to have a positive temperature coefficient, with the resistance increasing with temperature.

[Onoff]

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!!!!!).

 

Why would Sunamp employ (& pay) him? They've only got to read this and the other threads and glean loads of free R&D.

 

The thing is that, imho, despite the evidence of what works and maximises storage which the majority on here want they've come up with a mass market product with safeguards at the expense of efficiency.

 

They should at least give Jeremy his old unit back, gratis. This new one is costing him money.

[scottishjohn]

On 01/12/2018 at 10:53, JSHarris said:

 

It's a major cause for concern, and one I only discovered by accident, although I would have discovered it from the two energy meters I installed last Monday within a week or two.

 

Having the unit sitting nearly half discharged and yet unwilling to accept any excess PV charge is a major flaw, in fact so major that it needs immediate rectification, in my view.  We deliberately opted to "upgrade" to a Sunamp unit with more than double the capacity so that we could better make use of the occasions in winter when excess PV generation is sporadic.  I had thought that we'd be able to keep the Sunamp topped up, so that during days with no excess PV generation we'd be able to use some of the stored heat in our larger than needed Sunamp. 

 

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.

its looks pretty certain that you have found the reason for panels bulging --pcm stuff is getting over hot and expanding more than designed too.

 

[Jeremy Harris]

8 minutes ago, Ed Davies said:

 

This is more or less what I have in mind though with additional sources and sinks for the heat. Would that ever have problems with starting from cold, like the electric element does? I.e., would you have to keep the flow rate down when there's solid PCM round the pipes or would it be sufficient to simply keep the flow temperature not above 70 or 75 °C or whatever the limit is? I assume that'd be safe but it'd be nice to be sure.

 

The Sunamp PV didn't have any special startup sequence as far as I could tell.  It had a pretty simple control system that just maintained the flow temperature into the heat exchanger when charging at around 65 deg C or so (may have been a bit higher).  Because it used a relay to turn the heater on and off, it modulated the temperature by using a variable speed pump, together with an ultrasonic flow sensor.  This meant that it could deal with a variable power level to the heater, as happens when using a PV diverter, by just varying the pump speed to maintain the set temperature.

 

Despite the complexity of this charging system, part of which was a consequence of the unit using the same heat exchanger for both charging and discharging, with a cunning arrangement of non-return valves to keep the charging loop separate, it did work very well indeed. 

[Jeremy Harris]

7 minutes ago, scottishjohn said:

its looks pretty certain that you have found the reason for panels bulging --pcm stuff is getting over hot and expanding more than designed too.

 

 

 

No, that's definitely not the case at all.  The bulging is just down to everything being packed in too tightly and the case not being sufficiently rigid, that's all.  The insulation at the top is closed cell neoprene, and it's too thick for the space available.  This makes it push the top of the case upwards.  The sides of the case aren't stiff enough either, and with the increased size and weight of the big PCM cell (which is slightly flexible) the case isn't stiff enough to resist the effect of the weight inside.  The slight side bulging and the much greater lid bulging (with the old design of lid) was apparent on our brand new unit that hadn't been powered up, so definitely nothing to do with temperature at all. 

[scottishjohn]

1 hour ago, JSHarris said:

 

 

No, that's definitely not the case at all.  The bulging is just down to everything being packed in too tightly and the case not being sufficiently rigid, that's all.  The insulation at the top is closed cell neoprene, and it's too thick for the space available.  This makes it push the top of the case upwards.  The sides of the case aren't stiff enough either, and with the increased size and weight of the big PCM cell (which is slightly flexible) the case isn't stiff enough to resist the effect of the weight inside.  The slight side bulging and the much greater lid bulging (with the old design of lid) was apparent on our brand new unit that hadn't been powered up, so definitely nothing to do with temperature at all. 

so just another quality british made product then.

like i said last  week "bean counters " trying to cut corners

[Nickfromwales]

SA are looking at thickening the case sides and embossing them to gain rigidity.

[Jeremy Harris]

42 minutes ago, Nickfromwales said:

SA are looking at thickening the case sides and embossing them to gain rigidity.

 

Sounds like a good move, although the slight side bulging isn't really that much of an issue, IMHO.  The main issue seems to be the excessive thickness of closed cell neoprene above the cell.  I'm convinced that replacing the top sheet of neoprene with a rigid insulation sheet, bonded to the underside of the new lid design, would fix that problem easily, although I've found that careful trimming of the middle neoprene sheet, to allow room for it to expand out when compressed, seems to sort of work OK. 

[Onoff]

Fixing the bulging issue is a bit of a moot point if the underlying efficiency is down on the new systems.

[Jeremy Harris]

13 minutes ago, Onoff said:

Fixing the bulging issue is a bit of a moot point if the underlying efficiency is down on the new systems.

 

It is indeed.  The bulging is only a cosmetic issue, and has no impact on performance as far as I can tell, but the inability to accept a charge when partly discharged is a significant issue, one that has a big impact on performance, to the extent where we ran out of hot water one morning because of it.   This was crazy, as it never happened with the old Sunamp PV, and yet the Sunamp PV only had half the storage capacity.

[ProDave]

2 hours ago, Onoff said:

The thing is that, imho, despite the evidence of what works and maximises storage which the majority on here want they've come up with a mass market product with safeguards at the expense of efficiency.

 

Except if under certain circumstances it can only actually store 50% of it's capacity, and you run out of hot water as a result while SWMBO is in the shower with her hair full of shampoo,  the "useless POS" might not last much longer in that house.

[Stones]

So, having developed what they thought was a viable product with the SunampPV (intended IIRC as a means for those with gas boilers to benefit from diverted PV generation - I think they had identified a reasonable sized social housing market for this) and thanks in part to this forum, they realised there were other applications and that larger capacity units with low / negligible heat loss was potentially quite a lucrative market (especially if they could sell to big developers who need to get an easy extra SAP point).  They develop their range, simplify the internal workings presumably to make it quicker, cheaper and easier to manufacture, but in doing so, took away one of the big positive features of the original product, i.e. ability to charge the unit whatever the state of depletion.  Combined with the bulging lid, which doesn't look at all good, does seem to indicate it being a case of trying to push forward too quickly and perhaps taking eyes off the ball.  Hopefully with the feedback they are getting will turn things around.

[joe90]

2 hours ago, scottishjohn said:

so just another quality british made product then.

like i said last  week "bean counters " trying to cut corners

 

At least they are making an effort to bring something to market that’s made in this country, from what I have read they are very good at replacing anything that’s wrong (lids) and hopefully with feed back will update their units and remove the gremlins.

[newhome]

11 minutes ago, joe90 said:

At least they are making an effort to bring something to market that’s made in this country

 

Until it goes mass market probably ... 

 

[scottishjohn]

31 minutes ago, joe90 said:

 

At least they are making an effort to bring something to market that’s made in this country, from what I have read they are very good at replacing anything that’s wrong (lids) and hopefully with feed back will update their units and remove the gremlins.

I hope you are right.

but they need to be made aware in no uncertain terms that these sort of problems will not be tolerated,

the idea that a bit of case deformation is ok  and people need to live with it is just nonsense.

my architect friend who is refurbishing  a castle with its own hydro  scheme   , and when i linked him to the sunamp  site was very keen ,as he would need 10+ units --he will not be very keen when I forward these forum postings on to him

[Onoff]

I'm a little concerned that their new stronger lid will contain the expansion and it f**k something inside. I can see people fitting the new lids but not trimming the insulation to give clearance unless there's clear instruction to do so.

 

With all the flak over this on here and people rapidly having serious thoughts about jumping on board the Sunamp train I'm amazed they've not posted up themselves. Where's the new @AndyT?

[Jeremy Harris]

15 minutes ago, Onoff said:

I'm a little concerned that their new stronger lid will contain the expansion and it f**k something inside. I can see people fitting the new lids but not trimming the insulation to give clearance unless there's clear instruction to do so.

 

With all the flak over this on here and people rapidly having serious thoughts about jumping on board the Sunamp train I'm amazed they've not posted up themselves. Where's the new @AndyT?

 

I tend to agree, as even the new lid bends upwards unless the insulation is trimmed.  I'm certain that just substituting a bit of rigid insulation about 25mm thick, as a replacement for the top layer of closed cell neoprene, would completely cure the lid bulge problem, and remove the stress from the compressed foam (not that there's anything under it that would be harmed by this).

 

This is what the unit looks like in the top, with the middle and top layers of neoprene foam removed.  This was just as I'd unpacked it ready for installation, and the middle foam layer had four punched holes where the elbows stick up.  However, you can clearly see that even with no pipes running out the foam was over-compressed, and has left witness marks where the coiled cables were stowed:

 

[scottishjohn]

4 hours ago, JSHarris said:

 

 

No, that's definitely not the case at all.  The bulging is just down to everything being packed in too tightly and the case not being sufficiently rigid, that's all.  The insulation at the top is closed cell neoprene, and it's too thick for the space available.  This makes it push the top of the case upwards.  The sides of the case aren't stiff enough either, and with the increased size and weight of the big PCM cell (which is slightly flexible) the case isn't stiff enough to resist the effect of the weight inside.  The slight side bulging and the much greater lid bulging (with the old design of lid) was apparent on our brand new unit that hadn't been powered up, so definitely nothing to do with temperature at all. 

I understand what you say --but that is even worse really  in some ways-

it means no one of technical knowledge oversaw the drawings for final production line build spec. and you say the new one is still over packed,as you show by pointing out the witness marks of wiring -so who is listening at sunamp?

 

 

[Jeremy Harris]

I've no idea at all as to how the overly-thick insulation ever got signed off for production.  The people in the manufacturing plant, packing the units for shipment and fitting the lids, must have seen the problem, as it's unmissable. 

 

 

[jack]

The problem I have with all this is that the design flaw is a lack of space, but the solution seems to be reinforcing the casing in various ways. To me, that doesn't address the actual problem, even if it stops the bending.

[Russdl]

44 minutes ago, Onoff said:

people rapidly having serious thoughts about jumping on board the Sunamp train

 

I'm still smitten (planning to be a future user) but this information, coupled with my mud bath plot, is piling on the pressure. I sincerely hope they take a step back, take note of these criticisms and continue to produce a World leading innovative product that I'd be delighted to use.

 

[joe90]

All new stuff has teething problems, it’s just wether they listen and resolve the issues that I would be worried about. Personally I don’t like buying newly invented stuff, I like to wait till the wrinkles are ironed out (and the likes of @JSHarris and @Nickfromwales and others on this forum will help them achieve that I am sure.)

[Jeremy Harris]

2 hours ago, jack said:

The problem I have with all this is that the design flaw is a lack of space, but the solution seems to be reinforcing the casing in various ways. To me, that doesn't address the actual problem, even if it stops the bending.

 

There are two separate and unrelated issues around bulging cases.

 

The most obvious and noticeable is the design flaw with the insulation at the top of the unit, which is too thick/too resilient to fit in the space available and pushes the lid upwards.

 

The second isn't related to space, it is down to the flexibility of the case itself.  The heat cell looks a bit like a plastic jerry can, and like a plastic jerry can it tends to bulge outwards when full, unless it is properly restrained.  The Sunamp PV had cells with a similar construction, but also had an extremely rigid, bolted together, heavy duty alloy case.  The Sunamp PV case was much more rigid than that of the Sunamp UniQ range, as its bolt-together design meant that there were flanges that stiffened it up a great deal.  I commented on how robust the case was when our Sunamp PV was delivered:  http://www.mayfly.eu/2015/10/part-forty-getting-into-hot-water-episode-two/

 

The Sunamp UniQ range have a single piece alloy case that is a lot less rigid than the Sunamp PV, and as a consequence it isn't stiff enough to stop the heat cell from bulging.  Stiffening the case, as @Nickfromwales has mentioned, will fix this, i'm sure.

[Ed Davies]

7 hours ago, dpmiller said:

I might've asked this before but what *is* the "breakdown" temp, where the goo starts to cook?

 

According to the Sunamp manual the maximum constant heat source flow temperature is 85 °C. Linked from le-cervaux's post . Table 4.2a.

 

Strangely, their section of solar thermal doesn't mention limiting to this.