Sunamp PV - Heating Element

[Adrian Walker]

2 hours ago, TerryE said:

@MikeSharp01 that's why I like 2 off units.  The PV units are quite compact (D x W x U): 530 x 300 x 740 mm so two side-by-side are a small footprint and one does use a day's HW so long as we don't want a big bath.   They weigh 80 kg, so you really need a hoist and trolley to be one-man manoeuvrable.  The Uniq series have a bigger footprint  (W x D): 365 x 575 with height depending on capacity, so if we did decide to replace the PVs, I'd probably go for the 210e model (which is 870mm high), but I am loathed to replace the PVs after only 6 years use.

 

And it the circuit board that is the Achilles' heel, and I really can't see what the issue is with redoing it. 

I totally agree, the physics is good, the electronics is poor. 

[Nick Laslett]

Looks like Sunamp have a new iteration the Thermino ePlus and xPlus, coupled with a new “Optimino controller, which allows the heat battery to work with different energy sources by using a compatible Optimino key.”

 

Specs look the same, hopefully this is a simplification of the range, as the naming conventions were a bit messy. 
 

No new manual available yet. Maybe the electronics have improved with this update?

[TerryE]

@Nickfromwales, I have just done a 101 cockup.  😪  The heater thermo hat tripped, so I took one side off to get at the heater and reset the trip.  I then did a quick trial heat to see if everything was hunky-dorey.  What I didn't do was to put the side back on first.  Unfortunately the cells keep their shape because they are retained by the steel outer container, and with one side missing they started to slump slightly. By the time that I noticed the two cells had belled about 5mm -- not enough to cause permanent damage, but enough to pop the unsupported vacuum panel off and to stop me reassembling the unit.  I am an idiot.

 

So I now have a catch-22: the cells are still integral, but have sagged slightly, and I need to get them back to their constrained cuboid shape in order for me to be able to reassemble the unit.  To do this i need to bring enough of the PCM salt past its phase change (at least 50%) of the contents into the liquid phase with the cell is a correctly sized box formwork for it to reset into correct shape.  This is all entirely doable but just a total PITA to do.  The unit is currently on a shelf ~1m off the desk and with each cell at ~40Kg weight, this is enough of a lifting hazard for an old fart like me to need a lifting aid(e.g. a pulley) but again thanks to my time in the Royal Engineers, this is something that I am familiar with.

 

I will try chatting to a SunAmp engineer, but I am not hopeful.  I suspect the answer will be: "sorry, but it's an out of warranty obsolete unit", with maybe an offer of a small discount on a replacement unit -- which would need me to replumb by HW runs and move my control panel 😞   So it's going to be a case of disconnecting and dismounting the SA (the front unit in the pic below, which as taken 6 years ago during commissioning), and then working on it in slow time.  I still need to diagnose the root cause for the thermo tripping in the first place and fix that before I can recommission the unit.

 

 

The moral of this story is that using a constrained space like this for services is a bit fraught with gotchas.  I would have been better having the heavy kit on the deck and moving the manifolds up to the top shelf to leave room for the heavies below -- but this would have required me to have left 2m tails on the UFH loops before the slab pour -- something that I didn't even consider at the time.   At least I have the isolation valves with compression fittings so breaking out the unit itself is straightforward.

Edited November 13, 2023 by TerryE

[ProDave]

That just strikes me of a lousy design.

[TerryE]

@ProDave Dave, it is 6 years too late to cry about that.  🤣  BTW, The two PCM cells in each unit are roughly the size and shape of a Jerrycan. 

 

The internal plumbing is a mix of end-feed, standard compression, Pegler Tectile and John Guest Push fit.  I can't understand the rationale here for this .

Edited November 13, 2023 by TerryE

[TerryE]

After some debate, Jan and I decided that we could press out the sag in the cells if I made a suitable jig, so I made up an H frame that is held against the side of the SunAmp by some tape strapping, and which could hold a pressing plate (a square of OSB3, and with two bars that allowed a set of folding wedges to apply the pressure. I then brought the SA to temperature and used the wedges to load up the pressing plate and push the cells back true. All that remains is to allow the cells to cool back to solid phase and then I can reassemble the SA. 

 

A bit Heath Robinson, but simple, very cheap and effective. Job done.  Here is a pic (note that the wedges are pretty much at the end of their travel as the cells are back in shape and position :

 

 

 

 

Edited November 17, 2023 by TerryE

[Adrian Walker]

1 hour ago, TerryE said:

After some debate, Jan and I decided that we could press out the sag in the cells if I made a suitable jig, so I made up an H frame that is held against the side of the SunAmp by some tape strapping, and which could hold a pressing plate (a square of OSB3, and with two bars that allowed a set of folding wedges to apply the pressure. I then brought the SA to temperature and used the wedges to load up the pressing plate and push the cells back true. All that remains is to allow the cells to cool back to solid phase and then I can reassemble the SA. 

 

A bit Heath Robinson, but simple, very cheap and effective. Job done.  Here is a pic (note that the wedges are pretty much at the end of their travel as the cells are back in shape and position :

 

 

 

 

 

Well done

[TerryE]

I ran the HW (a bath for visiting grandkids) to cold using this SunAmp for its salt to go through phase change to solid, and I then left it overnight to thoroughly cool, before disassembling / removing the OSB pressure plate and retaining frame.  The cells were now solid and nicely cuboid, so reassembly was now straightforward.  I will do my commissioning tests at midnight (when the Octopus price drops). 

 

I recall that some of our members have discussed issues with their UniQ series SunAmps having issues with sagging or split cells.  The lesson is quite clear: 

• Do not remove a side panel unless the unit is well below the phase change as the cells do not have internal bracing to retain their shape at operating temperature without the steel casing support in place.
   
• If you need to bring the SunAmp up to operating temperature with a side panel removed then you will need use some  bracing formwork to retain the cell side shape.

Edited November 19, 2023 by TerryE

[Russdl]

@TerryE I hope I never need it but many thanks for that insight. 👍

[Cooeyswell]

@TerryE Have you any further insights as to the cause of the heater thermo hat tripping ? I am getting this fault fairly frequently at the moment. I suspect there may be an issue with the pump - it seems a bit noisy but still operational.

 

FWIW - I recommend mounting a mains neon/LED across the immersion feed after the trip, It at least makes the failure visible without taking the unit apart.

[TerryE]

@Cooeyswell, do you use something like a Harvey water softener on your potable water supply?   If you don't on the HW, then pipe furring can become a real issue over time and cause TMVs etc. to fail as the fur builds up in such devices and pipework.  This is why the SunAmp people say that you should using a water softener for all potable water if you have anything but a very soft supply.  This is especially the case as heat cycling causes calcium salts to precipitate out on the surfaces inside the SA.   Unlike the classic CH pipework which runs that water in a closed cycle and you add scaling inhibitors to it, the SAs use open-cycle potable water so scaling will become a problem.  (Think of what happens inside a kettle, and hint: if you need to descale your kettle even once a year then your water is too hard and the Sunamp units will fail over time.) 

 

If your circulating pump is getting noisy, then you do have a furring problem.  If you are in this situation, then the unit might need a complete strip down and descale. However, note my above high-jinks: the SA unit needs to be cold before you attempt any panel removal for disassembly otherwise the cells will sag and bulge, and you won't be able to reassemble.

 

I suspect that this a 'once every X years' sort of service, where X depends on residual hardness.   (In my case I am at 6 years, and X is probably 5. 🤣)  This is all a pretty straightforward job, if you have any plumbing experience as the pipework has demountable joints at all the necessary places.  Just make sure you know how to demount standard compression, Pegler Tectile and John Guest Push-fit fittings before you begin.  (Watch a Youtube tutorial.)  Also take a load of photos during each stage of disassembly, so you can reverse it to reassemble.   One of my big bugbears with the SunAmp factory assembly is that they didn't use PTFE tape on the standard compression couplings so many of mine have wept over time until being sealed by the weap furring; these will all need clean-up before reassembly.  I guess that this is a job that I am going to have to schedule for next spring, if I want my SunAmps to last another 6 years.  In my case I have 2 units, so I can do one at a time without loss of hot water.  

 

My concern here is that the thermometer on the heat outflow is an analog one that is clipped to the output pipe:  any scaling in this pipe section will cause this thermo to start to read low so the SA control algorithm will tend to run hotter over time and eventually the independent safety cut-out (which trips at ~80°C) will start to trip.   I have now lagged around these thermometers, so hopefully they don't read low now.   In my case, I already have a load of DS18B20 digital thermometers wired into my CH system (which runs using Node-RED on an RPi).  So  it is relatively straightforward to tape another DS18B20 to the pipe coming out of the heater (next to the analog thermometer that the CS control uses and to gate the SunAmp demand on that, so that the SunAmp never overheats.

 

@Nickfromwales, you are probably the most experienced member with installing and using SA units.  Have you any comments or advice? 

 

[TerryE]

@Cooeyswell, BTW, this is easy to diagnose with the lid off if you have a multimeter with decent probes.  The cut-out has 240V live in & out push connector terminals on it. The resistance to ground should be around 18Ω (Ohm's law for a ~3kW heater at 240V) when measured at both sides.  If one side is open-circuit, then the thermal cut-out needs reset.  However, if this happens then you should really get to the root cause. 

 

PS. Turn off power to the unit before you start poking around if you don't want any flashes or jolting surprises. 

 

Edited November 21, 2023 by TerryE
Add PS

[TerryE]

And here is the Heating Curve for last night's heating cycle.  Note that the funny ripple is because I have 2 SunAmps, but I decided only to have one being reheated at any time (as the Willis is also typically running as well), so they alternate getting 15 mins each for 3 hours heating.  Note that we'd had a big bath last night so the SunAmps were pretty low on stored heat.  Also the SunAmp reached the cutoff  temperature at about 6 mins into the last 15 min cycle.

Edited November 21, 2023 by TerryE

[Cooeyswell]

@TerryE Many thanks for the detailed response(s).

My water here is extremely soft, with no furring in the kettle after 5 years of use. My assumption is that whatever is causing the thermal hat to trigger it is unlikely to be due to furring.

Unfortunately I have intimate knowledge of the Sunamp PV internals. Over the last two years I have replaced :-

- The thermal cutout (2021)

- The control board (2021)

- The immersion heater (2023)

Like you this is after approximately 6 years use.

 

The thermo trip fired again last night so I now have a completely cold unit after this mornings showers.

 

@Nickfromwales mentioned the Y-Strainer which I have not yet looked at. That's probably my next thing to try.

[Cooeyswell]

A quick update :-

The Y-Strainer was completely full of crud. It looks like stone flakes of some kind. At a guess I would suspect this was kicked up by the local water company doing repairs a few months ago but may have been building over the last 6 years. I'll closely monitor the thermal trip status for the next week or so before declaring success.

[TerryE]

31 minutes ago, Cooeyswell said:

The Y-Strainer was completely full of crud. It looks like stone flakes of some kind. At a guess I would suspect this was kicked up by the local water company doing repairs a few months ago but may have been building over the last 6 years.

 

That would both strain the pump and tend to cause the heater to trip. I already have a Y-strainer on my rising main to prevent this sort of crap getting into the house potable supply in the first place. (I have checked this once about a year after we moved in but it's probably due for a recheck).  I thought that these have been standard in new builds for years.  Didn't your plumber fit one?  I will check mine as part of the "5 year service" that I mentioned about, but you need to take the side panel off to get at it. (Loop back to previous caveats on doing this.)

 

[Cooeyswell]

17 minutes ago, TerryE said:

 

That would both strain the pump and tend to cause the heater to trip. I already have a Y-strainer on my rising main to prevent this sort of crap getting into the house potable supply in the first place. (I have checked this once about a year after we moved in but it's probably due for a recheck).  I thought that these have been standard in new builds for years.  Didn't your plumber fit one?  I will check mine as part of the "5 year service" that I mentioned about, but you need to take the side panel off to get at it. (Loop back to previous caveats on doing this.)

 

 

Funnily enough I had the same thought but I cant see one on the mains incomer unless it's combined the pressure reduction valve in some way. I may have to retrofit one.

[Russdl]

@Cooeyswell that 'Y' strainer you cleaned. Was that within the Sunamp unit? 

[TerryE]

2 minutes ago, Russdl said:

@Cooeyswell that 'Y' strainer you cleaned. Was that within the Sunamp unit? 

 

Yes, there is one inside the PV models on the recirculation path, but not in the UniQ ones AFAIK.

[Russdl]

Ah, thanks @TerryE, I didn’t think there was one inside my Sunamp.
 

I’m guessing there should be one on my incoming main though, I’d better go looking for it as my Sunamp has been issue free since the thermistor string was replaced and I’d like to keep it that way. 

[TerryE]

@Russdl, if you take the lid off, it is an inline Y intake filter located above the heater (on the opposite side to the entry ports). On mine, the maintenance access port face downwards so it isn't easy to maintain or to access and you need to remove the side panel to do so, so you need the unit cold first, ...

[Cooeyswell]

44 minutes ago, Russdl said:

@Cooeyswell that 'Y' strainer you cleaned. Was that within the Sunamp unit? 

Yes it was - a PITA to get at as Terry says, which is why I haven't looked at it until now.

[Russdl]

@TerryE mines a UniQ. I don’t recall seeing a ‘Y’ filter in there but the last time I looked I wasn’t looking for one. 

[TerryE]

If I remember what @Nickfromwales said, they've pared down the UniQ design. Instead of using a heating loop with pump and (external to cell) inline water heater to heat up the salt cells, the UniQ cells have an electric heater in-cell.  The upside of this is that the engineering is significantly simplified, but the downside is that if the heater fails then it might not be a simple field replaceable item.  Maybe a more knowledgeable UniQ owner can comment.

 

TBH, if my current PVs failed or became End-of-Life unrepairable then I would still have SunAmp at the top-of-list as a replacement supplier. 

[Russdl]

There’s certainly no pumps in the UniQ, I shall see if I can find evidence of a ‘Y’ strainer in the documentation or by lifting the lid.
 

(Message received loud and clear about removing any side panels whilst there is warmth in the unit).
 

8 minutes ago, TerryE said:

TBH, if my current PVs failed or became End-of-Life unrepairable then I would still have SunAmp at the top-of-list as a replacement supplier. 

Likewise. If my UniQ were to stop doing it’s thing I’d go for a Sunamp replacement as a first port of call.