DHW systems - thoughts?

[gregh]

9 hours ago, Gill said:

Adding solar to the mix increases the payback time on the ESHP

I believe at least the Edel has terminals to receive solar excess as well. Still not sure the payback is worth it, but one to consider.

[Gill]

2 hours ago, gregh said:

I believe at least the Edel has terminals to receive solar excess as well. Still not sure the payback is worth it, but one to consider.

 

Thanks - the Edel is a few hundred pounds cheaper which would reduce payback. Do you happen to know about install or maintenance costs? It would be good to factor that in. 

 

 I may well be missing something on the ESHP but I see max temps around the 65 mark. I can't see an figure for UVC but assuming 90 based on manufacturer datasheet mentioning 'pressure relief value set at 7 bar / 90°C'.

 

I'm think I read on another thread that the eshp might not be the best fit to max out your spare solar due to temp limitations. 

 

The other aspect I don't fully understand on the excess solar is if that hooks to an immersion (so 1:1) or if that can flip the heat pump power input automatically giving your solar input an increased COP. 

[gregh]

10 minutes ago, Gill said:

Do you happen to know about install or maintenance costs? It would be good to factor that in.

That is my biggest concern with EASHP - in theory the install shouldn’t be much different, aside from a couple of extra holes for the air supply/exhaust. However I can imagine your average plumber not wanting to take the risk on something new like this, and the handful who have experience with these charging a premium… might still explore it

[RichardL]

FWIW If you look at the manuals - dimplex edel and vaillant arostor have suspiciously identical compressor/circuit board layouts, would be interesting to know if there's much more than marketing between them - looks like a shared technical design at some point - or off the shelf product?

Edited April 9, 2023 by RichardL

[Gill]

23 minutes ago, RichardL said:

FWIW If you look at the manuals - dimplex edel and vaillant arostor have suspiciously identical compressor/circuit board layouts

Good to know.  I'm sure when I was looking previously at the edel, it brought up a list of 'additional product of interest' including required exhaust kit and (optional) wifi hubs. I am a big hater of hubs. Why do I need to route simple api calls through a propriety hub! I have to assume its not required for every day operating. I don't think that's an edel specific issue. Valliant probably the same. 

 

More to the point... There's more to the cost than just the unit as is probably true with the UVC. 

 

23 minutes ago, gregh said:

That is my biggest concern with EASHP - in theory the install shouldn’t be much different, aside from a couple of extra holes for the air supply/exhaust. However I can imagine your average plumber not wanting to take the risk on something new like this, and the handful who have experience with these charging a premium… might still explore it

 

When I spoke to my plumber last year he had zero heat pump experience and his son was just starting to look into it but they had zero demand. Not one single customer. Spoke to a few others who echo this. Those with the experience are hard to find or are operating under 'Green /renewable solutions' type companies which in my limited experience adds a hefty premium to the work. 

 

36 minutes ago, Gill said:

The other aspect I don't fully understand on the excess solar is if that hooks to an immersion (so 1:1) or if that can flip the heat pump power input automatically giving your solar input an increased COP. 

 

I may have answered my own question. Should take my own advise sometimes and RTM. 

 

'This function enables the appliance to operate in 
auto-production mode, which means that it will use the 
energy produced by the PV function to supply the heat 
pump as well as the electrical back-up, in order to heat 
the water in the tank.' 
 

So potentially increased COP from solar but reduced storage if max temp can only be 65.

 

I should probably size up roof space suitable for solar and work out what I could be storing on a day where we have little sunlight demand. 

 

 

Edited April 9, 2023 by Gill

[RichardL]

My reading of the manual is there are 2x dry contacts on both V & D machines, which are the PV input - but presumably also the simplest way to override the onboard timer with a 'heat now on immersion' command without hubs/cloud etc.

Both manuals seem to talk about 2x levels of PV input but not much/any more detail I could see.

One of the dry contacts on that board is shorted by default -  might indicate that could be a simple external control/timer input? (or might not - I'm really guessing - no direct experience)

Update - theory? - one of the contacts is immersion and the other is the compressor/A2W via the onboard timer - hence why its normally shorted?


I really don't want my heating or DHW connected to wifi - worked far to long in IT to think its a good idea to add layers of complexity on a basic switch.

Edited April 9, 2023 by RichardL

[Gill]

8 minutes ago, RichardL said:

I really don't want my heating or DHW connected to wifi - worked far to long in IT to think its a good idea to add layers of complexity on a basic switch.

 

IT myself for a couple of decades - currently cloud compute with a strong emphasis on security and regulatory compliance. I like a happy medium where I have the option but I maintain full featured control without WiFi.  Not a fan of black box solutions where I can get in there and inspect the security setup. That rings alarm bells for me. 

[RichardL]

8 minutes ago, Gill said:

security setup

Personally Its not just the security - its trying to avoid my house being a debugging and configuration scenario with potential for everything being reliant on a single point failure (or reconfiguration if it changes).

I can see some advantage to cloud and certainly local wifi, not a total luddite , but laying a bit of signal bell wire once with a switch and a central time-clock is pretty much guaranteed not to break with software updates or router changes etc.

Nothing against full automation - just not for me in my house.

[JohnMo]

1 hour ago, RichardL said:

dimplex edel and vaillant arostor have suspiciously identical

Not sure but this may be the source, or just another using the same unit.

 

https://www.auer.fr/en/products/heat-pump-water-heaters/edel-water-heat-pump-water-heater/

[JohnMo]

54 minutes ago, Gill said:

spoke to my plumber last year he had zero heat pump experience and his son was just starting to look into it but they had zero demand

Interestedly I had the same discussion with the electrician who wired my ASHP up the other day, similar output, senn a couple on new builds but nothing more.

[Gill]

A very basic solar gen calculation from energy saving trust based on postcode. South facing unstructured roof. I estimate 5mx 4m could site panels. This is by no means using any smart sizing based on my energy requirements. It does indicate I've potential to bank a fair amount of excess as hot water (over the sunny months).  Now I need to work out how this folds into the maths 🤔

 

Size of the system

4 kWp

Energy generated by the panels

3,213 kWh / year

 

[Gill]

27 minutes ago, RichardL said:

Nothing against full automation - just not for me in my house.

 

My washing machine is wifi enabled (not a factor in my purchase). Has never worked. Full manual control was a requirement otherwise I would have a very large paperweight in my kitchen. I would never want to rely on WiFi (and certainly not cloud! ) for critical home functions. 

[Iceverge]

2 hours ago, Gill said:

A very basic solar gen calculation from energy saving trust based on postcode. South facing unstructured roof. I estimate 5mx 4m could site panels. This is by no means using any smart sizing based on my energy requirements. It does indicate I've potential to bank a fair amount of excess as hot water (over the sunny months).  Now I need to work out how this folds into the maths 🤔

 

Size of the system

4 kWp

Energy generated by the panels

3,213 kWh / year

 

 

Try PVGIS for an another useful tool. It will give you more granular data. 

https://re.jrc.ec.europa.eu/pvg_tools/en/

 

 

 

Just to put the cat amongst the pigeons here's an option from Daikin that may suit you. 

 

[Gill]

24 minutes ago, Iceverge said:

Try PVGIS for an another useful tool. It will give you more granular data. 

https://re.jrc.ec.europa.eu/pvg_tools/en/

Will need to play around with that a bit as I'm not familiar with a lot of the solar terminology. Basic defaults for my location with roof pitch giving me this. 

 

24 minutes ago, Iceverge said:

Just to put the cat amongst the pigeons here's an option from Daikin that may suit you. 

 

Edit - looks like I can discount that due to lack of water capacity. 

 

Offered with a choice of domestic hot water storage capacities of either 90 liters or 120 liters

 

Sometimes I think I should just flip a coin. I should probably add a factor of 'hours spent trying to comprehend viability and ROI' to each solution but I don't think I want to see those numbers quantified 😂

Edited April 9, 2023 by Gill

[Iceverge]

What is your TOU tariff at the moment and what will the occupancy of the house be for DHW purposes? 

 

 

 

[Gill]

29 minutes ago, Iceverge said:

What is your TOU tariff at the moment and what will the occupancy of the house be for DHW purposes? 

 

 

 

 

Eco 7 tarrif at 0.44 day and 0.15 night. 

 

Occupancy of 2. I calculated we use 6 kWh daily for our current system. That may increase a little when we refit the bathroom to bring in a deep soaking tub but that'll be a luxury and not ever day use. 

[Iceverge]

Ok excellent. We have somewhere to work from.

 

Option 1. UVC only

Option 2. ESHP only

Option 3. UVC plus solar.

 

Assuming UVC and solar last 20 years and the ESHP lasts 10.

 

Option 1 . UVC 300l costs £700 plus annual cost for 2200kWh ( all on TOU ) is £330. Adding the cost of the cylinders over 20 years is £365/year. (300L stored at 70deg is about 14kWH so plenty of capacity to ensure TOU is used only) 

 

Option 2. ESHP costs £2500 and runs at a COP of 3, annual cost of £110 ( all on TOU) . With a 10 year lifespan the annual cost is £360. Also a 270l ESHP at 49 degrees will only store 6kWh so any more use you would move to day rate which would wipe out any savings. 

 

Option 3. UVC plus PV. (No feed in tariff) Assuming a 4kw array with a diverter would cost £6k.  You should be able to use about 2700kWh per year in the house with some timed dishwashers etc. The difference from option 1 will be 500kWh of energy you don't need to buy at 15p/kWh so a nett positive of £75/year. (£6000/20 +£700/20) +£75  is an annual cost of £410. If you get a feed in tariff of equal to E7 rate you could make that £335/annum. 

 

TLDR

 

1. 300l UVC. £365/annum.

2. ESHP £360/annum

3. UVC plus PV £330-410 per annum. 

 

 

No wonder you're confused, it's far too close to call and for the price difference of a bottle of nice wine it isn't worth worrying about.

 

 

I would get a 300l UVC with a timer switch and forget about it. In fact, that's what we did!! 

 

 

 

 

[Gill]

@Iceverge thanks a ton for the input. 

 

I was converging on UVC ( and solar eventually - that's a whole different thread of questions !) but I 100% suffer from over analysis and this is a classic example. Stuck in a loop when the margins are so close.

 

I'm going to chalk this one off the decision list and enjoy a glass of that nice wine. 

[Iceverge]

I'm glad it helped. 

 

edit:

Bugger just spotted a mistake. 

PV reduces the cost to £260-£180 so you're on the right track. 

 

Edited April 9, 2023 by Iceverge

[Gill]

35 minutes ago, Iceverge said:

I'm glad it helped. 

 

edit:

Bugger just spotted a mistake. 

PV reduces the cost to £260-£180 so you're on the right track. 

 

 

PV seems a no brainer. I'll admit I've done zero research on it partly because I need to work out if extend into the roof is financially feasible at some point and if so whether the current advice I've had about that doing a full reroof is our only option. 

 

One item off list.... Two more added on. 😁

 

[gregh]

11 hours ago, Gill said:

I can't see an figure for UVC but assuming 90 based on manufacturer datasheet mentioning 'pressure relief value set at 7 bar / 90°C'.

 

Can anyone with experience comment, is this safe to do? Ie. heat the water in UVC up to 90°C to store the energy? Thinking more about the tank, assume you would fit a thermostatic valve to keep taps and showers safe.

[JohnMo]

Aren't the cylinder rated at 90 degrees and protection is set to vent the pressure at 90, so if you were to store at the temperature the protection system would operate. So not a practical idea.

 

Not sure how you would heat it that hot anyway as most immersions only can be set to 80 and have a thermal trip set at a hard 85 trip, which requires the immersion to be manually reset.

 

If you replaced the immersion from a higher rated one from a thermal store, you would be circumventing you certification.

 

Thermal store possibly, UVC no.

[Gill]

9 minutes ago, JohnMo said:

Not sure how you would heat it that hot anyway as most immersions only can be set to 80 and have a thermal trip set at a hard 85 trip, which requires the immersion to be manually reset.

Thanks @JohnMo

I certainly don't want to be triggering any built in system safety release.

 

So with that info I could potentially set solar immersion to 75 and eco 7 set at the recommended lowest input to avoid any legionaries type nasties? 

 

Edit:I will  be getting someone with far more clues than me to fit and configure the system and keep me from blowing a hole in my roof. 

Edited April 9, 2023 by Gill

[JohnMo]

There are a couple of schools of thought on legionnaire and the need to have an overheat cycle.

 

Heat geek did a good write up and video. Looking at all the whys and what it's.  Plenty on this forum also.

[Iceverge]

For PV integration I would have 2 X thermostats on the tank. Have a good thermostat mixing valve (TMV) on the tank too. 

 

Have one thermostat on E7 set to cut out at 50 Deg. At 300l this will give about 7kw of storage. Plenty to ensure you're never without water. 

 

Then set one for the PV at 75-80deg and this will give you another 9kw of storage for the PV. This will be enough to never get to the point of needing E7 most of the summer. 

 

If you bumped to 400l tank then you could have 12kW of storage but then cylinders get much more expensive. If going this route you might be better off with smaller cylinders in parallel.