Are you all pleased with your solar panels for hot water heating

Good year so far.
No maintenance required.
Normally I get start of March to end of October solely on solar but have to start blipping the gas boiler from Halloween on.
Haven't had to do this yet this year.
€300-€350 estimated savings with abundant hot water from April - Sep.
Today got the 250l up to 49C.
Happy days.

unkel wrote: »

Install last week. Pretty impressed so far. 40 tube system from a well known Irish manufacturer :pac:
25 year warranty

360l slimline stainless steel cylinder (biggest that would fit in the hotpress)

Even on a very cold winters day like today that started with scraping the car windows. Outside temp is 5C now, tubes are 46C (sun shining) and they've already warmed up the water in my cylinder from 13C to 32C this morning with plenty of sunshine left in the day

Sounds like your 40 tubes have a good aspect and angle.
Do you have a heat dump solution/strategy for the summer?

The heat dump is more to protect the tubes, the fluid and the pump I think.
I don't have one and on a good summer day once the cylinder hits max, the fluid will stop circulating.
I've seen 220C at the tubes and early on the pump had to be replaced due to the excessive heat.
Overheating of the fluid will shorten its lifespan as far as I know.
I've heard of others dumping excess heat via a rad in the attic but am not sure exactly how that works.

I just came upon your post in this thread from 2 years ago:

josip wrote: »

Ah, but that changes everything.
In your first post you said 2 toddlers but now we find out they're both girls
In my limited experience, hot water consumption for females is higher than for males and this will halve shorten your payback timeframe.

I've 3 girls myself. None of them teenagers but in 4.5 years from now, all 3 will be teenagers

I have a pumped shower (2 bar Stuart pump) and the original 120l cylinder in the house was only good for 1 shower of 10 minutes. Which is ridiculous in a 5 people family. So I needed a 300l / 360l cylinder anyway. I got a good deal on my installation and I reckon the extra cost of the solar (minus the subsidy) will be paid back in not much more than 5 years. Even though I have a 98% efficient Viessmann gas boiler

We like our showers / baths, so we do

893bet wrote:

What temperature is normal at the collector?

It will always be about 8 deg above the temperature of the store. I know you were possibly hoping for someone to tell you the temperature today but again, that would be very inexact since someone could say that it's 80 deg when it started at 60 deg, while mine is 50 deg because it started at 25 deg.

Then it also goes down to the number of tubes, and the side of the store.

So you've got a serious problem with your setup or wiring.

I am assuming that most systems are pretty much identical. When the roof temp is about 8 deg higher than the bottom of the store, the pump should kick in automatically until it's only about 4 deg higher. If run much longer, it has the possibility of sending cooler water back to the store as the pump over runs the sensor.

The only other possibility here is that your top of store is set to 60 and therefore, the system has locked out. If you have an imerson or a central heating bypass fitted through the store, then i would nearly expect your system never to be much lower than 60 in the first place, meaning the system is pointless.

So what is the cutoff temperature ?

josip wrote: »

Good year so far.
No maintenance required.
Normally I get start of March to end of October solely on solar but have to start blipping the gas boiler from Halloween on.
Haven't had to do this yet this year.
€300-€350 estimated savings with abundant hot water from April - Sep.
Today got the 250l up to 49C.
Happy days.

300e saving, is about 5,357 kWh of energy when using gas (at 0.056 per kWh). What is your setup that generates this much energy and what did it cost to install?

josip wrote: »

30 Chinese tubes on a 36 degree roof 5 degrees west of due south.
1 Chinese controller.
1 Kingspan 250l steel solar cylinder with foamy stuff.
The tubes and controller were €3,300 net of SEAI grant to install.
The cylinder was an additional €1,100 I think.

The main consumers are a pumped shower for a 3 person household and a fairly long pipe run to the kitchen hot tap.

Thanks! It's interesting to see the figures here. I'd really like to get my hot water from solar. So real figures are great to see.

If I am working out the numbers correctly, it will take 14.6 years to see a return on your investment of 4,400e with 300e saving a year?

metricspaces wrote: »

Thanks! It's interesting to see the figures here. I'd really like to get my hot water from solar. So real figures are great to see.

If I am working out the numbers correctly, it will take 14.6 years to see a return on your investment of 4,400e with 300e saving a year?

I don't expect to ever see a return on the investment to be honest.
Every few years the fluid will need to be replaced and that one callout for the plumber will wipe out most of the savings for that year.
I doubt if the pump will last 15 years.
The tubes are rated for 20 years on average but they'll probably start to fail individually from year 10 onwards if they haven't already, reducing the efficiency of the system in the critical Oct-Mar months.

If I was installing it now, I'd give more consideration to PV, but 7 years ago PV technology performed relatively poorly in Ireland compared to the evac tubes.

I installed it so that I no longer wince and nag when certain family members brush their teeth in warm water with the tap running full or 'rinse' off the plates in the sink with fire-fighter levels of pressure from the hot tap.

Seriously, it's very hard to put a price on the peace and harmony those solar tubes have brought to our house.

quentingargan wrote: »

A 30 tube system will produce about 1800kwhrs per year. That hot water from oil or gas would have cost about €162 per year. Maintenance (changing glycol) will be at least €200 every 3 years. So savings nett about €100 per year.

I'm including the cyclinder cost in my RoI calculations.
Previously there was only a lagged copper cylinder and the gas cost of heating it was twice what you've calculated above.
Did you factor in any loss in that calculation?

josip wrote: »

I'm including the cyclinder cost in my RoV calculations.
Previously there was only a lagged copper cylinder and the gas cost of heating it was twice what you've calculated above.
Did you factor in any loss in that calculation?

No - you are quite right. The cylinder would make a big difference to lost energy and is well worth doing, but bear in mind that you can get a well lagged single coil immersion for a lot less than a solar cylinder. These figures are all very ballpark. Some people use very little hot water, some families have two baths a night.

metricspaces wrote: »

If 93% of people in the pole for this thread are happy with their solar panels for hot water heating, does this mean they are happy with them on some criteria other than economic value?

It seems you need to wait 15-40 years to break even, and that is assuming your system does not break at any point and operates at constant level of efficiency for entire period.

Is there any system you can install for hot water heating that would see a return in the 5-10 year time frame?

People all to often rely on the Economics.

If we always relied on the Economics then we would not take holidays for example. We take them to take the stress out of life and for a good feeling.

I imagine not having to worry about an extraordinary gas bill or oil bill dropping on the door step is nice. His install cost the same as a good holiday.

metricspaces wrote: »

If the rationale for being happy with the system is something other than economic, then the pole makes sense.

For the vast majority of people economic criteria is going to be the main driver in purchase like this - not saving the planet or feeling good. As a consumer, I can't say it is immediately obvious if any of the solar systems are economically viable for your average household.

The initial impression I get from the industry is "install this system and in a few years it will have paid for itself". This seems very far from reality.

When i put PV into my next house purchase the rational will not be economical. It will be totally driven by self sufficiency and smugness of my ESB bills. The feel good factor of zero concern for leaving powered units on or forgetting to turn something off because the big ball in the sky is looking after it.

Il skip a years holiday for that satisfaction with no problems.

Imagine running a family car for free as in zero bar tax and insurance....

metricspaces wrote: »

...The initial impression I get from the industry is "install this system and in a few years it will have paid for itself". This seems very far from reality.

Do any of us believe the salesmen and evangelism from any industry, not just solar heating?

I think the larger your family, the faster you will break even if that's wwhat's important for you.
A 5 year break even would be doable with a family of 10/11 I'd say. And a 1500l tank. With 180 tubes to heat that. On top of the 400sqm house.

unkel wrote: »

My 40 Irish tube Kingspan + Kingspan controller + highly insulated 360l stainless steel cylinder was only a few hundred more than yours

We needed the cylinder anyway as we only had a poorly insulated 120l copper cylinder and we have a household of 5 (4 women) and we use a lot of hot water
(2 bar pumped shower and bath)

Payback on the rest of the system (net of 360l cylinder) is somewhere in the 7 - 10 year range for us. And replacing the glycol every 3 years is completely unnecessary when the temp of the glycol never exceeds 135C

It's good to see that the Kingspan tubes and controller have become a lot more cost effective than they were in 2010.