PV- real world figures

Gumbo · 21-10-2017 09:50PM

Agree I have my immersion to switch off at 65 degrees. So while the eddi says max temp achieved, it’s obviously at 65 degrees at that point in the cylinder. It may not be a full 200L at 65 degrees but it’s been certainly enough to get 2 adult showers, 2 kids waging and the usually kitchen uses.

I’d be very interested in these digital temp displays as I’m currently looking for similar.

a148pro · 22-10-2017 08:53AM

freddyuk wrote: »

Better option is 2 x horizontal immersions then you can switch from top to bottom with solar diversion.

Freddy, can you set this so the first one will be heated by solar until certain temp and then the second one? That would seem to be optimum solution?

Gumbo · 22-10-2017 11:02AM

a148pro wrote: »

Freddy, can you set this so the first one will be heated by solar until certain temp and then the second one? That would seem to be optimum solution?

Yes, my eddi unit can divert the power to two heaters. You set which one first and then it diverts to the second once the first one hits max temp.

a148pro · 22-10-2017 11:12AM

Sounds class - that's an alternative to say the i-boost thing mentioned by Conor in his thread? You are happy with?

freddyuk · 22-10-2017 08:49PM

unkel wrote: »

Technically you are correct, but people should be careful with this advice. You can't just up the temp of the water in the cylinder to 80C. First of all, most cylinders can't take that and secondly, if they can, you can only do so with soft water (you do mention this)

When you say they "can't take that" what exactly does that mean?

unkel · 23-10-2017 02:02AM

Cylinders are certified to a specified temperature by their manufacturers. Go over that temp at your peril. I don't know what will or can happen if you exceed thos maximum temperatures. But for one, your home insurance won't cover you if something goes wrong if they know that you have used your hardware outside of their scope of use.

A lot of Irish people would just do a "shure it'll be grand" at that, but you're from the UK, freddyuk, you're probably a bit more mature / responsible?

rolion · 23-10-2017 08:49AM

Any of the PV owners here really believes that their system will manage to power-up a second output / second immersion connected to the cylinder !? Any idea from "real world figures" how many hours, wattage and thermo laws needs to work together to get the little Joule on the shower pipe ? There was a conversation recently,on another thread about this...guys,until March / April, our PVs will barely keep warm the invertor, not even thinking of warming up a second immersion.... sorry.

Gumbo · 23-10-2017 10:37AM

rolion wrote: »

Any of the PV owners here really believes that their system will manage to power-up a second output / second immersion connected to the cylinder !? Any idea from "real world figures" how many hours, wattage and thermo laws needs to work together to get the little Joule on the shower pipe ? There was a conversation recently,on another thread about this...guys,until March / April, our PVs will barely keep warm the invertor, not even thinking of warming up a second immersion.... sorry.

Its October now and mine is still heating the water?
At what stage do you envisage the cut off to be, November maybe?

You can already see the difference with the low lying sun alright.

air · 23-10-2017 10:46AM

I think if anyone has high enough hot water demand to get use out of a second immersion it would make more sense to install solar thermal.

a148pro · 23-10-2017 08:59PM

I think ideally you'd have both, but as you can't use excess hot water to power the house, but can use excess power to heat the water, if forced by the install cost to choose one or the other I'm inclined to go PV

air · 23-10-2017 09:04PM

Agreed, I have both but wouldn't bother with thermal if starting again to be honest. When the PV output is low I'd generally run the GFCH which heats water relatively cheaply when it's running for space heating anyway.

Gumbo · 23-10-2017 10:21PM

I decided for PV over thermal recently during a complete renovation.
Cost wise, it was working out nearly the same.

The 30 tube kingspan system was going to set me back €3700 after the grant but that included a 300L stainless steel cylinder.

My 3kw PV system with eddi immersion divertor set me back €2900 all in fitted. But I then upgraded my existing cylinder to a kingspan 200L insulates cylinder that cost me a couple of hundred euro.

The pros and cons is that the thermal system looks neater in the sense that the roof panels are smaller. The PV system is at the limit of the planning exemption area. The PV has less moving parts and is a Fort and forget system. The thermal requires plumbing and servicing going forward.

unkel · 24-10-2017 12:04AM

They are both very good prices!

One thing that seems to never come up when people compare PV vs tubes, is that tubes generate a lot more usable energy per m2 of roof. A 30 tube system would only take up about a quarter of the roof space compared to a 3kW PV system, yet it generates more energy (which is directly used to heat water with very little loss)

PV only really makes sense if you have a feed a feed in tariff or if you have your own storage (battery). But I'm always the first to shout that solar tubes only make sense if you use lots of hot water...

Gumbo · 24-10-2017 12:07AM

unkel wrote: »

They are both very good prices!

One thing that seems to never come up when people compare PV vs tubes, is that tubes generate a lot more usable energy per m2 of roof. A 30 tube system would only take up about a quarter of the roof space compared to a 3kW PV system, yet it generates more energy (which is directly used to heat water with very little loss)

PV only really makes sense if you have a feed a feed in tariff or if you have your own storage (battery). But I'm always the first to shout that solar tubes only make sense if you use lots of hot water...

Long term plan is to get a battery.
Or use the Leaf

Evd-Burner · 24-10-2017 02:15PM

air wrote: »

I think if anyone has high enough hot water demand to get use out of a second immersion it would make more sense to install solar thermal.

Couldn't disagree with you more. The PV has a multitude of benefits and has very little maintenance.

My sister has solar thermal from a new, she saves about 200 or so a year on heating the water. However she has stated that it is costing 150 to service it every second year. Not to mention if a pump or anything goes. Solar thermal just has far to much to go wrong and far to much maintenance needed.

air · 24-10-2017 02:32PM

I agree it's high maintenance but she's being ripped off. She should be able to get it looked at whenever her boiler is being serviced. There isn't anything to service on an annual basis as far as I'm aware, just needs a visual inspection.

unkel · 25-10-2017 12:15AM

Evd-Burner wrote: »

it is costing 150 to service it every second year.

That's madness. Has she a cheap Chinese system? On a Kingspan thermomax system, the max temp on the tubes can only be 135C, so the coolant is that too at the max. And it would only reach this kind of temperature very occasionally. Not like every day like in your car (where you still only change coolant every 3 -5 years even though there's only a few liters of coolant in your car. Much more in your solar thermal system)

Which means you do not have to change the coolant every 2 years. Once every 7-10 years maybe. And it won't cost anywhere near €150 to change the coolant, more like €50 (when you have a plumber in the house already servicing your boiler or doing another job)

unkel · 25-10-2017 12:17AM

I'd have PV panels on the roof tomorrow if they made any economic sense at all. It just isn't here without FIT, although one justification could be crypto-mining. Where you need 24/7 mining to let the hardware pay for itself. At least with PV you can use some of the expensive day rate excess production for your mining so it isn't wasted heating water or giving it back to the grid

rolion · 25-10-2017 08:33AM

unkel wrote: »

That's madness. Has she a cheap Chinese system? On a Kingspan thermomax system, the max temp on the tubes can only be 135C, so the coolant is that too at the max. And it would only reach this kind of temperature very occasionally. Not like every day like in your car (where you still only change coolant every 3 -5 years even though there's only a few liters of coolant in your car. Much more in your solar thermal system)

Which means you do not have to change the coolant every 2 years. Once every 7-10 years maybe. And it won't cost anywhere near €150 to change the coolant, more like €50 (when you have a plumber in the house already servicing your boiler or doing another job)

With all due respect,that is not entirely true and/or correct.
Im not arguing the price but you will need regular maintenance.
For that type of €50 maintenance done by a plumber i will prefer to pay €150 to get a pro that knows how to use a presurised flushing pump,knows the inside-out of the controller and of the solar mixer and not lastly,to "read" the colour of the coolant in the buffer plastic container.
I know that savings are been minimised but the satisfaction of knowing that from March to October my gas boiler will be turned off and the gas bills are in lower 2 digits ... nothing beats that !

As a bonus, the safety of a well running system and avoiding any blue or green or pink leakeage in the living room...

And...my Joules solar tubes have reached higher than 135 (a preset temperature in the controler where they stop working ) and went all the way up to over 200ish. Coolant is certified for working at higher temperatures.

unkel · 25-10-2017 08:42AM

rolion wrote: »

And...my Joules solar tubes have reached higher than 135 (a preset temperature in the controler where they stop working ) and went all the way up to over 200ish. Coolant is certified for working at higher temperatures.

Yes it is. But my point is that coolant needs replacing far more often in a (cheaper Chinese) system that reaches over 200C than if only up to 135C (which is a feature of the Kingspan Thermomax system). My system comes with a 20 year warranty too. Must look up the small print, if it says anything about required maintenance...

rolion · 25-10-2017 08:43AM

kceire wrote: »

Its October now and mine is still heating the water?
At what stage do you envisage the cut off to be, November maybe?

You can already see the difference with the low lying sun alright.

The MAIN and primary effect of the solar tubes over the bad eather / winter is the initial "themo warm-up" of the lower temperatures... from the coldish 10ish to higher maybe lucky 30ish. And, from there, top-up with the boiler and/or PVs .

Imagine your car engine and consumption.When you start moving the car,in the first gear,the car runs at 3000rm and with a consumption of lets say 20l per 00km. Once the car moves with any speed,the gas consumption is much lower,going down to less than 10l at a higher speed but varies with rpms. Is the initial inertia, being thermic or temperatures,as the laws of the physics.

25-10-2017 09:01AM

unkel wrote: »

I'd have PV panels on the roof tomorrow if they made any economic sense at all.

I just acquired 725Wp for €280.

Solar thermal does outrank PV in terms of efficiency and hence works in Winter where PV doesn't.

unkel · 25-10-2017 10:02AM

I've had my full 360 cylinder of water heated up in December and January to beyond scorching temperatures, but it is very rare (maybe one day of glorious sunshine in each month that did the trick). On the other hand, it is also quite rare to have a day that contributes nothing to the water temps. A day of non-stop rain I suppose.

Sir Liamalot wrote: »

I just acquired 725Wp for €280.

Well, yeah at those prices it does make sense. Can you acquire me a system like that?

25-10-2017 10:19AM

No probs. But if you don't want to splash out on grid tie, I seriously doubt you'll be interested in a stand alone system.

a148pro · 26-10-2017 09:19AM

Actually lads - given that I've just finished first fixing, I'm probably asking this too late - but what wiring do I need to do for solar PV?

I assume I have to get a feed down from the attic to the fuse board, or would it be to the meter (may be in same location, I'm not sure)?

Can the diverter be powered off the existing spur for the immersion?

Is there anything else I should wire for now in anticipation of this?

Many thanks

air · 26-10-2017 09:54AM

a148pro wrote: »

Actually lads - given that I've just finished first fixing, I'm probably asking this too late - but what wiring do I need to do for solar PV?
I assume I have to get a feed down from the attic to the fuse board, or would it be to the meter (may be in same location, I'm not sure)?

You need wiring from the panels to the inverter and from the inverter to your consumer unit (fuse board).
You could put in conduit instead at this stage.

a148pro wrote: »

Can the diverter be powered off the existing spur for the immersion?

Yes

a148pro wrote: »

Is there anything else I should wire for now in anticipation of this?

Roof hooks for the rails would be the best thing you could do in advance, but if the roof is already on you've missed the boat.

a148pro · 26-10-2017 11:21AM

I'm getting roof done next week but assumed as most systems are retro fitted there's nothing to be done in advance?

Also I gather the inverter should go in the attic?

Anything I might think about for display purposes, showing electricity being generated etc or can that be done wirelessly? I mean if I had to mount something somewhere I'd have a think now about where

Do I need to get a wire back to the meter for FIT or are existing wires 2 way?

PS have sent a few PMs to lads who've had systems installed looking for recommendations if any, thanks in advance

air · 26-10-2017 11:41AM

If you put in the hooks as you are putting the roof covering on it will be a big labour saving, a massive labour saving if you're planning a slate roof. The same goes for the cable entry from the roof into the attic space for the cables from the PV to the inverter.
The inverter can go anywhere. I wouldn't put it in an attic unless it's going to be well ventilated and relatively cool.
Most inverters have wireless display options nowadays, you've plenty of time to research that though.
All electrical wires are bidirectional.

a148pro · 26-10-2017 11:45AM

I might be safe so as I think I asked the lads to put a plug in the attic which hopefully I'll be able to use instead as the feed. But best to get someone on site quick to look at everything. Thanks.

air · 26-10-2017 11:56AM

The plug probably only has a 2.5mm2 cable to it.
I'd run a minimum of a 6mm2 cable to the attic for the inverter, on it's own RCBO, but consult your electrician to have it sized properly and run properly.
I don't have the specs to hand but IIRC the voltage drop specifications for an inverter are more stringent than those for loads of equivalent wattage. You don't want the voltage to rise too much between the inverter and your ESB meter when the PV is at full output. You won't go wrong oversizing the cable and the cost should be relatively insignificant.

PV- real world figures

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