Sunamp help in Kent

[Marco Van Bowden]

Hi,

Looking at a Sunamp and not really getting anywhere fast ?

 

Hoping to tap into people's knowledge please!??

 

I have a 3 bed semi that is effectively morphing to six bed 3.5 bathroom home.  I want a Sunamp, after having seem them via fully charged years ago.  The corgi registered plumber (via the builder) is a nice enough chap, but not really interested in reading page after page of manuals about a product he has never heard of vs putting in a megaflo that's he's done hundreds of.  

 

The plan is to use the existing 24kw combi to charge the Sunamp, and have the Sunamp do the hot water for the house.  The combi itself (as I'm on mains gas) doing the heating.

 

Plumber wants to know how to plumb things in. Which seems pretty reasonable to me!  Sunamp seems to want to sell me a solution, whereas, I just need a product, if that makes sense?

 

Anyway, what does your respective collective knowledge say?  And is there a way to private message people on here??  As I see a few threads from 2017, 2018 and thought best to start a new vs trying to bring them back to life.  

 

Any all help welcome

[PeterW]

Welcome.. That may need more than one sunamp if you're after enough hot water to service 3 showers in a six bed house. This also assumes you have enough water pressure and flow rate to service that sort of arrangement.

 

Assuming you want 2 UniqHW12 then it is as simple as having a pair of zone valves and the correct settings in the controller which is effectively setting a few DIP switches. As per the manual this is the schematic for the one UniqHW, 2 is just do it in parallel.

 

 

Your only restriction may be the boiler will not provide enough heat as you cannot use the hot water circuit, you will be using the heating circuit to supply heat to the sunamps and it will be close as to whether it can give you the flow - and the heating to the house - from an old 24kw combi. If you're doing this as big extension etc, and are prepared to pay north of £4,500 for the sunamps, why not upgrade to a system boiler for an extra £12-1500..??

 

 

 

 

[Marco Van Bowden]

Hi Peter, 

I've not quite read the 16 pages from February 2019, but ya name rings a bell ?

 

OK.  I've had a smart meter fitted (via Thames water) just under a year ago, that has pretty much told me I've only nudged 1,000 liters of water in a given year a handful of times.  Thus.  Do I really need two 12's?  Yeah, the house is bigger, but the number of occupants hasn't changed.  In the new layout we will have one bath and two showers, and I was of the understanding that the HPC on the SA 12 was good for 25L/min, or am I just being naive?  

 

Pre building work, we had a shower over the bath in the bathroom.  

 

Again, if I'm being naive here, fine... Tell me, but I thought the 12 was good for 370 litres of hot water, so I was going to go with 350 and thought... Sounds fine to me.  That's comfortably a third of what we use as a family.  When we go to bed, the heating switches off and the boiler effectively charges the Sunamp ready for the next day.

 

Unless!

 

Octopus tells me the grid is giving away free electricity again, and I'll charge the Sunamp from electric instead.   Or will I?  More reading to be done... ?

[PeterW]

2 minutes ago, Marco Van Bowden said:

Octopus tells me the grid is giving away free electricity again, and I'll charge the Sunamp from electric instead.   Or will I?  More reading to be done... ?

 

Not with a Uniq12HW, you would need a Uniq12HW+i to use the electric heater, and then I'm not 100% sure how you can override it to call for electric heating not gas.

 

A 12kw has a theoretical supply of 370 litres at 40c. The downside is a lot of new showers expect the water at a minimum 45c so you're borderline getting 280 litres out of it. Could use 2 9's but it is the control that will be the hardest.

 

Other than the gadget factor, any reason for not going with a 400 litre UVC..?

[Marco Van Bowden]

7 hours ago, PeterW said:

Other than the gadget factor, any reason for not going with a 400 litre UVC..?

 

Maintenance, or the lack there of.   Sure, the 400 litre tank will be half (a third?) The cost of a SA 12 upfront, but the UVC needs love.  As I understand things, the SA (charged via my 24kw combi remember) doesn't.  What is the marketing blurb?  10k, 40k, 82k cycles and zero degradation?  It's hard to argue with those numbers.

 

Past that, if the charge/discharge is something I need to be aware of, let the education begin!  

 

Ergo, let's take ya 280 liters.  When does the SA say to the boiler.  Eh! Bitta hot water please boss?  Meaning... 280 divided by 25 (for the max flow rate on a 12) will yield ~11 minutes of hot water.  Seems fine to me. 

 

But! 

 

And this is just a guess, Barney could quite easy give situations where there is a need for back to back bath/showers/hot feed dishwasher/hot feed washing machine/etc, etc, etc that means the PCM in the SA can of course be effectively trickle charger via the combi, and drawn off at mains water pressure/considerably faster.  But!  How does this work in the real world?  Nick perhaps??

[A_L]

@Marco Van Bowden, to either UVC or Sunamp why not fit waste water heat recovery (WWHR) and effectively half heat usage for showers? e.g.

 

https://www.heatraesadia.com/products/renewables/waste-water-heat-recovery

 

https://recoupwwhrs.co.uk/?gclid=Cj0KCQjw0Mb3BRCaARIsAPSNGpV3WsbaECDhy1CMA5wGDyN4nZj39Wa9nPqndlyVVdBFcZVs1QOa2nMaAq43EALw_wcB

 

others are available

 

 

[PeterW]

2 hours ago, Marco Van Bowden said:

Ergo, let's take ya 280 liters.  When does the SA say to the boiler.  Eh! Bitta hot water please boss?  Meaning... 280 divided by 25 (for the max flow rate on a 12) will yield ~11 minutes of hot water.  Seems fine to me. 

 

So what happens after the 11 minute shower in this case..? You have no hot water.

 

The Sunamp either calls for heat at 50% or 90% depleted. Once you have the boiler running then you will be getting a request to the boiler to reheat the sunamp. Now you have a priority issue, so if the hot water is taking priority (W-Plan) then your heating will take a hit if it is running. If you have S-Plan then potentially you have a reheat but at a much lower rate and you are potentially out of water again.

 

In terms of pure cost, 400 litre UVC is change of £1,000 and is about £80-100 to service annually. If you have a gas boiler anyway, that reduces to about £40-50. 20 year lifecycle means you have a TCV of £2,000 and you have something any plumber can work on. Sunamp has a similar life, as your plumber is calling out too the skills for supporting these things are not the widest in the market. I know a few people have had to have the controllers replaced or components fail in the control system rather than the Sunamp itself. They had issues with the cases bowing in the early days and were changed under warranty,  but not sure if it fully fixed it.

 

Sunamp does have a place in low energy houses and also in ones with PV available etc, but in a standard build with a gas boiler the benefits do start to look less tangible

[ProDave]

If you think back to back showers / baths are going to give you a "ran out of hot water" issue (with any form of DHW storage) then consider what I have done, fit a modulating 10kW instant hot water heater on the output of the DHW tank

 

Most of the time the electric heater sits there doing nothing, but if the hot water starts to run out, the electric heater saves the day.

 

As you will see on that thread I am a bit unusual in heating water with an ASHP and only heating DHW to 48 degrees. the ASHP is only 5kW so the re heat time is a lot slower than a gas boiler so there is more scope for lots of showering before it has re heated.

 

[Nickfromwales]

1 hour ago, PeterW said:

Now you have a priority issue, so if the hot water is taking priority (W-Plan) then your heating will take a hit if it is running. If you have S-Plan then potentially you have a reheat but at a much lower rate and you are potentially out of water again.

The biggest issue is if you have radiators, as the SA will need the boiler flow set to at least 65 degrees ( arriving at the SA ) which means that the surface of the radiators will be at the same temp.

 

11 hours ago, PeterW said:

I'm not 100% sure how you can override it to call for electric heating not gas

Its a PITA. I've had to use contactors on the 20a supply into the SA controller ( outside of their equipment so as to not interfere with the warranty as SA don't like you going in there ) to arrest the flow of electricity, due to the single discipline ( rather shit ) controller. Idea being, the contactor flips from electricity in + zero call for heat to the W-plan / to call for heat to the W-plan + zero call for electricity. The former for standard 24 hour operation, where the SA heats up off Octopus between 12:00 and 04:00, and the latter is for 'duress heating' so the exception not the rule. That's how I would set it up for normal use, with a single 12HW+I. A simple timer / boost button changes the contactor state.

 

4 hours ago, Marco Van Bowden said:

How does this work in the real world?

Calculation.

Also if you re-use the combi, you should connect the nearest DHW tap to the hot outlet so it gets at least some exercise of the internal components. Combi's don't like to sit dormant. Also remember a 24kW combi prob won't give the full 24kW to space heating  The highest rating is reserved for solely for DHW production, and very high temp duties will see you operate outside of the ideal condensing range ( 30-50 for Vaillant iirc ) in a lot of cases. Check the MI's of your boiler and that will give you the true output to 'heating' which is what your SA will get.

Don't forget the magnetic filter if going for a SA as the HeatEx has very small bore internals vs an UVC.

 

 

[PeterW]

7 minutes ago, Nickfromwales said:

Also remember a 24kW combi prob won't give the full 24kW to space heating

 

This was my call out at the top - reckon on 9-12kw at best usually.

7 minutes ago, Nickfromwales said:

The biggest issue is if you have radiators, as the SA will need the boiler flow set to at least 65 degrees ( arriving at the SA ) which means that the surface of the radiators will be at the same temp.

 

TMV or could you end up with short cycling..?

[Nickfromwales]

1 hour ago, PeterW said:

This was my call out at the top - reckon on 9-12kw at best usually.

Not that bad, but still up to 20% less or worse. 
 

 

1 hour ago, PeterW said:

TMV or could you end up with short cycling..?

You’d need a second recirculating loop for the heating, hydraulically separated from the boiler pump loop, as you can’t pump through a TMV so you have to ‘pull’ through it. 

[Marco Van Bowden]

WOW!

 

You boys have been busy, I feel honoured!  Thanks lads ?

 

@Nick, on the assumption you know, when does the SA call for more heat?  Straight away, or as PeterW has suggested??  And with in that, if the LPC is being used to charge the SA (vs the +i) what is the charge time?  Conversely, what is the charge time via the +i?  For a SA 12??

 

@PeterW you make a good point, but as I've already said, we don't use a massive amount of water. In the last year we have never gone over 1,100 liters in a day, and only gone over 1,000 liters one a handful of occasions.  

 

I freely admit that the main draw card for me is "set and forgot" so if we say the SA is what, round numbers, £2,500 and a 300L megaflo is what...  £1,250 it's the maintenance thing.

 

I do like the scalability of the thing, so if (and I do honestly doubt this) I find I need more hot water, surely the SA is more scalable, yes?

 

Oh, and the combi is only being retained as it's done very little work, and well... When it dies perhaps it'll be upgraded, but until then... Why not use it??  ...and yeah, the combi will feed the kitchen sink.  

 

PS - House is a long way off passive, but it is over regs.  

 

 

Edited June 23, 2020 by newhome
Edited out quote as requested

[PeterW]

37 minutes ago, Marco Van Bowden said:

@Nick, on the assumption you know, when does the SA call for more heat?  Straight away, or as PeterW has suggested??

 

It is in the MIs that I linked, see the extract below from page 10 - you set it to call for heat at either 50% or 90%

 

[Nickfromwales]

4 hours ago, Marco Van Bowden said:

what is the charge time? 

From a boiler, it’s subject to / affected by the flow temp.
 

With the immersion it’s roughly a kW in per hour so via the ~3kW immersion heater a 12 should reheat from zilch in a bit over 4 hours, in practice I think it’s a bit quicker, but then it does hold around 14kWh of heat energy when heated by a premium heat input. Well matched to be sucked dry by the evening bathing and reheated at midnight on Octopus, or other cheap tariff. If you have any PV then that reliance on the full recharge should reduce in the summer.

[Marco Van Bowden]

Peter & Nick - Thanks!  Anyone else, chip in as necessary.  I'm skipping over the waste water recovery stuff, as core theme here is Sunamp vs Megaflo or UVC and Peter has made some valid points.  Oh, and Dave... I'll read it and come back to ya.  Cheers!

 

So... Calculations.  Fag packets ready guys? ?

So let's say a 12 holds 12kw (yes, I read above Nick, please let this slide for now) and the combi kicks out 24 on the CH circuit.  We could round down to 20 kw for age/degradation or 15, or hell 12 and be done.  So... Is it reasonable to assume that the combi can kick out enough heat to melt the PCM (I assume yes, this is north of 65 degrees isn't it?) So the combi would effectively charge the SA in no more than an hour.  Probably a little less.  Fair/reasonable?

 

So, if the SA only asks for charge at 50% and we went with 280 litres.  140 would be left.  140/25 is five minutes, flat out.  

 

https://www.showerheadhosesmixers.co.uk/getting-a-good-shower-the-wright-way/#:~:text=A typical UK power shower,to 10 litres a minute.

 

This link tells me, that'll allow both showers to be run simultaneously.  At 10L per minute, each.  So seven minutes vs the five above.  Let's also tick off that the combi is charging the SA at the same time.  So is it fair to say both showers could be run, simultaneously, even with the SA at half full, for ten minutes?  Now, two things jump out at me.  Chances of both showers going at the same time, low.  Chances of that happening when the SA is at 51% charge, even lower.  And should it happen, the worst thing is... You've had 10mins in shower, stop wasting water!

 

Fair/reasonable?

 

So, how does this differ to a 300L UVC at £1,250 or a £2k 400L unit?  I assume they would have a sensor in them, so once say 100L had been drawn down, the cylinder would ask for more hot water (via the heat source, so in my case, the combi) to replenish itself, depending on how things are set-up.  Combi fires up and supplies hot water.  I'm guessing it's only possible to set the SA at 90% or 50% (Thanks Peter) whereas the UVC is either "always" holding 300 or 400L of hot water, by simply asking for it straight away, or the threshold is something that can be set to suit the individual requirement of the user, right?

 

Last question, if a +I unit was purchased vs a non +I unit, all I would gain, is the ability to charge the unit overnight via the 5p per KW deal from our friends at Octopus energy, correct?  Oh... That, and should combi die, which let's face it, it will at some point, I could still enjoy hot water.

 

 

 

 

 

 

[PeterW]

11 minutes ago, Marco Van Bowden said:

so, how does this differ to a 300L UVC at £1,250 or a £2k 400L unit?

 

Is that the plumber installed price..??? 400litre Telford UVC for £1,000 - here

 

That's a tank that if you wanted to, you could boost to 85c using your 0p/Kw Octopus deal and hold even more than 2 Sunamps that can only really do the 40c otherwise they deplete too quickly.

 

Yes the combi will pick up the Sunamp and give it 12-15kw or whatever, but I am struggling to see the benefit over a decent size UVC. And if the combi dies, you still need a new boiler for the central heating.

[Marco Van Bowden]

21 hours ago, PeterW said:

and if the combi dies, you still need a new boiler for the central heating.

 

Going to need that regardless of UVC, Sunamp, or... Curve ball.  A Mixergy.  So can't see the relevance of this last bit to be honest.

 

Also, what do want 85c water for? ?

 

Don't get me wrong, the feedback has made me stop and think perhaps I should "look again" but I do like the scalability of the Sunamp and it's set and forget characteristics.

 

Right, let's read what Dave has done...

[PeterW]

1 minute ago, Marco Van Bowden said:

Also, what do want 85c water for? ?

You don’t ... you blend it down to 45c anyway but storing it at 85c means you have substantially more “capacity” than the same tank at 55c. 

[Nickfromwales]

3 minutes ago, Marco Van Bowden said:

Right, let's read what Dave has done...

Dave stores at a very low temp, so has limited DHW capacity because of that. Hence the need for a post-heater. Factor the cost of buying and installing one of those, then the cost of using it at indiscriminate times, eg not always at cheap rate, and then the fact it only has a 15mm inlet, and it's not how I'd ever design a system TBH. The elevated heat thresholds @PeterWmentions expand the energy capacity of the sme sized tank significantly, so will give more DHW during times where the PV is in abundance or when you've 'duress boosted' via the immersion(s). 

UVC's are given a stated capacity by the manufacturers. If you ring them and say you only intend to heat to sub 48 degrees, they will state that the capacity for DHW will be reduced accordingly.

 

[Marco Van Bowden]

I'm not convinced I need any more than a 12, so 370 or 380L at 40c anyway.  I could be wrong, but I think someone said a SA 12 was only good for 280L at 45c.  That still seems like ample for what I need, but hey... Good to know I guess.  Tar

[Marco Van Bowden]

2 minutes ago, Nickfromwales said:

...will give more DHW during times where the PV is in abundance

 

I'm not going to be running any PV

[Marco Van Bowden]

On 23/06/2020 at 10:47, ProDave said:

 

 

Most of the time the electric heater sits there doing nothing, but if the hot water starts to run out, the electric heater saves the day.

 

 

?

 

Interesting, but ultimately... Nah. Not for me.

[joe90]

54 minutes ago, Nickfromwales said:

Dave stores at a very low temp, so has limited DHW capacity because of that. Hence the need for a post-heater. Factor the cost of buying and installing one of those, then the cost of using it at indiscriminate times, eg not always at cheap rate, and then the fact it only has a 15mm inlet,

I also store at a low temp with a 360litre DHW tank heated by a 4kW ASHP. I did buy an Eltron heater as a back up but never fitted it (still in the loft I think). During my build the Sunamp was very new and I wanted something I understood ( I am a Luddite) and some were having problems at that time setting the Sunamps up. There are only two of us here but even with a house full of visitors we have never run out of hot water. We don’t have PV or gas

 

someone on this forum plumbed an Eltron into his hot water system and did not find the flow rate through the 15mm connection a problem.

[Nickfromwales]

2 minutes ago, joe90 said:

someone on this forum plumbed an Eltron into his hot water system and did not find the flow rate through the 15mm connection a problem.

Agreed, but the OP mentions high'er' DHW so am addressing the answers as per the OP's needs. UVC's and SA's both have 22mm inlets / outlets, so putting a 15mm 'restriction' inline is converse to my thinking.