Powering Sunamp

[Big Neil]

Evening All.

 

Does anyone charge their sunamp purely off the mains/pv/windmill etc, as opposed to also involving an ASHP? At the very least has anyone (i imagine Mr @JSHarris definitely has) done the calcs to show the cost of doing this both ways?

[Jeremy Harris]

Yes, that's how I run ours.

 

It's charged only by electricity, so can either charge from off-peak mains (mainly in winter) or from PV generation (pretty much 100% of our charge for the past few weeks has been from PV).

 

Since last mid-November last year to today, PV charging has used 370 kWh, mains charging (mainly off-peak) has used 341 kWh.  We seem to be averaging around 4.6 kWh/day for hot water use, with about 52% of it (so far) being "free" PV generation.  That ratio  will increase, as between now and the anniversary of me fitting the separate energy meters (mid-November this year) most of the charging will be from PV generation (I'm expecting at least 70% of our hot water to come from PV over the course of a year).

 

In terms of cost, then as mains charging is off-peak (currently 8.148p/kWh here) the daily average cost for hot water is about 27.8p.  I anticipate that the annual average daily cost for hot water will be lower than that figure suggests, probably around 15p/day, maybe less.

[Ed Davies]

@JSHarris, you prewarm the cold water going into the Sunamp with a UFH-temperature buffer, don't you? So the costs for doing direct heating for all your hot water heating would be a bit higher, wouldn't they?

 

If not then 4.6 kWh per day for two people is quite low. The usual rule of thumb is 3 kWh/person/day.

[Jeremy Harris]

1 minute ago, Ed Davies said:

@JSHarris, you prewarm the cold water going into the Sunamp with a UFH-temperature buffer, don't you? So the costs for doing direct heating for all your hot water heating would be a bit higher, wouldn't they?

 

If not then 4.6 kWh per day for two people is quite low. The usual rule of thumb is 3 kWh/person/day.

 

We pre-warm whenever the UFH is on, which isn't a lot of the time (not at all recently) so yes, the first shower of the day has the benefit, if the UFH has been on overnight, of around 1 to 1.5 kWh.  I'm not sure how many times the UFH had been on overnight during this time (need to pull the stick from the data logger and check at the end of the month) but at a guess I say there may have been another 100 kWh contributed by the ASHP, so the daily average would have been around 5.2 kWh, perhaps a little more, so a bit lower than the 3 kWh/person used for DHW estimating. 

 

The additional cost of the off-peak electricity for the ASHP pre-heat since mid-November 2018 may have been around £3 at the most, so not a lot.

[Ed Davies]

OK, that makes less difference than I thought. Still, the buffer tank will be at room temperature when the UFH is off so will still raise the incoming cold water from something like 8 °C  to around 19 °C.

[Big Neil]

As usual i probably should have been clearer, what i really meant was in a situation where the sunamp unit is both the soul source of hot water and also used for the UFH. All god things to know anyway, so thanks.

 I'm not sure I fllly understand the need for both sunamp and ASHp. I've read a number of the threads relating to both and it just confuses me a little at the moment. tank and ASHP i get. Sunamp by itself, I get. Sunamp and ASHP - can't quite understand

Edited April 17, 2019 by Big Neil

[Jeremy Harris]

My personal view is that the case for using a low temperature Sunamp as a UFH buffer, charged by an ASHP, is probably a bit marginal in many cases.  There are circumstances where it will work fine, and be a good solution, but I would guess that most people fitting an ASHP and UFH would be better off just running the UFH directly from the ASHP.

 

Using a high temperature Sunamp as a hot water heating system definitely has some useful advantages, with the heat losses being lower and the unit being physically smaller than an equivalent hot water tank.  Being a low water capacity thermal store also means that it doesn't require a Part G3 sign off on installation, or ongoing inspections, which is useful.

[scottishjohn]

9 hours ago, Big Neil said:

As usual i probably should have been clearer, what i really meant was in a situation where the sunamp unit is both the soul source of hot water and also used for the UFH. All god things to know anyway, so thanks.

 I'm not sure I fllly understand the need for both sunamp and ASHp. I've read a number of the threads relating to both and it just confuses me a little at the moment. tank and ASHP i get. Sunamp by itself, I get. Sunamp and ASHP - can't quite understand

 sunamp is a a hot water tank --just much more compact+ much less heat loss than normal tank ,even a very well insulated one .

that ,s how I understand it 

ASHP is a another way of heating water  in a very cheap way compared to LPG and oil,and could be run from saved PV if you have battery system  --in theory .

your Off grid situation is the situation  why I posted about the nexgen heating  system ----maybe  that could be a viable alternative  for off grid.

i have now come across an old ruin  --which could be that way,off grid --about 10steps with the paraglider and i would be soaring at 200metres

 

I asked in same thread about cost comparison of suspended wood floor  verus insulated slab +ufh  system.

so far no replies  for or against 

 

My gut feeling is that the costs would be in favour of the suspended floor +direct electric floor heating --if  off  grid  and you are intent of going major pv + batteries

 

 

[Big Neil]

6 hours ago, JSHarris said:

Using a high temperature Sunamp as a hot water heating system definitely has some useful advantages, with the heat losses being lower and the unit being physically smaller than an equivalent hot water tank.  Being a low water capacity thermal store also means that it doesn't require a Part G3 sign off on installation, or ongoing inspections, which is useful.

Gotcha. Big Sunamp for hot water then

 

6 hours ago, JSHarris said:

My personal view is that the case for using a low temperature Sunamp as a UFH buffer, charged by an ASHP, is probably a bit marginal in many cases.  There are circumstances where it will work fine, and be a good solution, but I would guess that most people fitting an ASHP and UFH would be better off just running the UFH directly from the ASHP.

 

What about cutting the ASHP pump out of the equation, such that the source for the UFH is just a low temp Sunamp. In both running cost and initial investment terms how does this workout Vs just the ASHP for the UFH and a Sunamp for the hot water?

[ProDave]

3 hours ago, Big Neil said:

What about cutting the ASHP pump out of the equation, such that the source for the UFH is just a low temp Sunamp. In both running cost and initial investment terms how does this workout Vs just the ASHP for the UFH and a Sunamp for the hot water?

A sun amp is just a heat store.  Without the ASHP how would you propose heating the sun amp?  

[Big Neil]

16 minutes ago, ProDave said:

A sun amp is just a heat store.  Without the ASHP how would you propose heating the sun amp?  

 

Electricity. It confused me to be honest, but look at the first post by Jeremy there, and he says that's how he does it.

[ProDave]

3 minutes ago, Big Neil said:

 

Electricity. It confused me to be honest, but look at the first post by Jeremy there, and he says that's how he does it.

We are talking about the low temperature version of the sun amp here, where the temperature range is within limits for an ASHP to charge it. So why would you not use that with a COP of say 3, and instead choose to use direct electricity?

 

Jeremy charges his high temperature sun amp with direct electricity because the temperature is too high for an ASHP so there is no alternative. 

 

I am in the camp that things there is not much benefit to a heating buffer tank, and my ASHP feeds the UFH directly.

[Big Neil]

I was thinking about reducing installation complexity and also the balance of cost. Is the cost of buying, installing and maintaining an ASHP to charge the sunamp actually any cheaper than the extra cost of electricity if not using this option?

 

As JEremy mentions the cost may be marginal between sunamp +ASHP vs just ASHP. I just wandered the just Sunamp powered off the mains/solar option

[ProDave]

It is right to look at running cost vs installation cost.

 

In my case annual heating cost is about £250 with ASHP.  If we assume that runs at a COP of 3, then that would cost £750 pa with direct electricity.  So the ASHP is saving me £500 pa   *

 

In my case the ASHP cost under £1000 so in 2 years it has paid for itself.

 

*of course it also saves money on the DHW heating so payback time will be even less.

[Jeremy Harris]

19 minutes ago, Big Neil said:

I was thinking about reducing installation complexity and also the balance of cost. Is the cost of buying, installing and maintaining an ASHP to charge the sunamp actually any cheaper than the extra cost of electricity if not using this option?

 

As JEremy mentions the cost may be marginal between sunamp +ASHP vs just ASHP. I just wandered the just Sunamp powered off the mains/solar option

 

If using electricity for heating, then why bother with heat storage at all?

 

If the idea is to be able to use off-peak electricity during the day for heating, then you can make this work just by having an ASHP and UFH set into the slab (which is what we do) .  That way we only use about 1/3rd of the amount of electricity, so it's even cheaper.  As an ASHP is around the same price as a Sunamp, it seems a bit of a no-brainer to go down this route.

[Big Neil]

2 minutes ago, JSHarris said:

If the idea is to be able to use off-peak electricity during the day for heating, then you can make this work just by having an ASHP and UFH set into the slab (which is what we do) .  That way we only use about 1/3rd of the amount of electricity, so it's even cheaper.  As an ASHP is around the same price as a Sunamp, it seems a bit of a no-brainer to go down this route.

bang on - thanks

[TerryE]

I use E7 low rate to heat my 2×SunAmp PVs, and to be honest we seem to use so little hot water that there isn't really the cost justification of adding a buffer tank for preheat even when we install our ASHP.  So the big pluses for this approach are (1) simplicity; (2) No Part G3 requirements so I could do everything myself. (3) still relatively low running costs for our usecase.

[Jeremy Harris]

5 hours ago, TerryE said:

I use E7 low rate to heat my 2×SunAmp PVs, and to be honest we seem to use so little hot water that there isn't really the cost justification of adding a buffer tank for preheat even when we install our ASHP.  So the big pluses for this approach are (1) simplicity; (2) No Part G3 requirements so I could do everything myself. (3) still relatively low running costs for our usecase.

 

Same here re: the preheat buffer tank, @TerryE.  When I installed it I assumed it would be more useful than it is, but we've stopped using the ASHP to heat the buffer tank solely for hot water preheat now; it only provides preheat if the ASHP has been running the UFH overnight, and that preheat is then only used to shave about 1 kWh or so off the first shower energy use.  With hindsight I've have been better to have put the Sunamp in the ground floor cupboard where the buffer sits, as it would have been a lot easier to install downstairs.

[Barney12]

OP, this is exactly my setup. Two 12kWh Sunamp powered only by grid electric which feeds my UFH and DHW. No buffers, no complicated stuff.

 

The system still not properly used in anger (as I’ve not fully moved in) but it coped fine in the cold spell we had a while back. I’ve found that simply dumping a couple of hours of 30 degree heat into my ufh loops will pull the temp up by around 1-2 degrees. 

 

The plan will eventually be to divert excess solar gen in to the Sunamps (IF Sunamp ever come up with a solution that actually works! Unlike the solution I was sold by Sunamp ) and then top it up with off peak electric.

 

in my passive standard house I factored (with @Nickfromwales significant help) that the savings on annual inspections and hardware costs meant that it was a good solution.

 

However as I’ve said elsewhere I intend to add an ASHP to my setup 1) because my confidence in Sunamp as a product has been seriously dented 2) because I’d like the ability to cool my slab. 

 

If if I was starting again I would definitely have gone down the route of charging low temp Sunamps with an ASHP. 

Edited April 20, 2019 by Nickfromwales
Don’t shoot the messenger please ?

[Nickfromwales]

20 hours ago, Barney12 said:

However as I’ve said elsewhere I intend to add an ASHP to my setup 1) because my confidence in Sunamp as a product has been seriously dented 2) because I’d like the ability to cool my slab. 

 

If if I was starting again I would definitely have gone down the route of charging low temp Sunamps with an ASHP. 

Edited just now by Nickfromwales 

Not forgetting the PCM34 has been out of circulation for what seems forever .

Other low temp models will surface soon enough but I’ve no useful info on that yet I’m afraid. 

Rumour has it that improved, and now ‘on board’, controls are in production so I’ll update ASAP on that as I get some training ( hopefully ). 

I just got trained up on the fitting of a trio of SA units fed only from a split high temp ASHP for load-shifting off E10. I’ll post some pics when I get copies ( as my daughter was deleting them off her iPad at home as I was taking them after I had linked it to my Apple ID to set it up and had not logged back out ??? ). Lost loads before I realised where they were going ? 

Need to see if there’s a way of recovering lost pics off iCloud. Gutted. 

[newhome]

15 minutes ago, Nickfromwales said:

Need to see if there’s a way of recovering lost pics off iCloud. Gutted

 

They should be in the ‘recently deleted’ album in iCloud (or on her iPad). 

 

 

[Jeremy Harris]

16 minutes ago, Nickfromwales said:

Rumour has it that improved, and now ‘on board’, controls are in production so I’ll update ASAP on that as I get some training ( hopefully ). 

 

 

I can confirm that there are new controllers being produced now.  I should have mine, together with a new sensor array, some time next week.  I'm aware of one new controller that's already been delivered to another customer, too.

 

I have to say I've been impressed with the very recent contact I've had with Sunamp, they now seem to be taking things onboard and working to make improvements based on feedback from customers.

[Barney12]

16 minutes ago, JSHarris said:

I have to say I've been impressed with the very recent contact I've had with Sunamp, they now seem to be taking things onboard and working to make improvements based on feedback from customers.

 

I've had radio silence. Feeling left out ?

[Jeremy Harris]

16 minutes ago, Barney12 said:

 

I've had radio silence. Feeling left out ?

 

I'll PM you.

[PeterW]

2 hours ago, Nickfromwales said:

Need to see if there’s a way of recovering lost pics off iCloud. Gutted. 

 

Go to your pictures on your phone

 

scroll down and you’ll see a folder marked recently deleted ...

 

should still be in there