adding solar to existing hot water system

[r.bartlett]

chaps,

over here everyone is on electric mains pressure hot water and my leccy bill is 120 euro's a month a lot of that is hot water heating, that's just about to get worse as we have added another water heater to cope with demand now daughter has moved into the renovated finca:-(

So the addition of solar is a no brainer when I can get a unit for 800 euros.

http://www.milanuncios.com/calentadores-de-agua/panel-solar-de-efecto-termosifon-165-lt-78082428.htm

however my concern is the integration of the unit to the existing. Do I simply break the cold feed to the electric boiler and run that to the solar unit then back to the boiler (left off if necessary).the solar comes with an expansion device so that should be fine but how is temperature controlled?

14134 existing boiler + new

14135

[mikeref]

RB. I have a 300 L solar roof mount with a back up 2KW electric element on a controlled supply.
Controlled supply means power is automatically switched off for around 6 hours per 24. Saves $ by using a lower cost Tariff.
I set my electric thermostat to 50 C tho the CB is mostly switched off. There is NO control to regulate solar input so water temperature can easily reach 80+ Degrees C during Summer. Plumbers these days have to install a Mixing valve so that hot water cannot enter a premises beyond 50 C.

Yeah, Plumb cold water to Solar and insulate solar collector outlet to your "Boiler."

[frank]

Hi Richard
Over on mainland Spain where my brother lives I designed a 3 port valve into the hot water supply from the solar collector which diverted the hot water into the gas boiler if the hot water was not hot enough, i.e. cloudy days. The valve operates from a pipe stat set at 40C.
If the solar water is above 40C then it goes straight into the feed to the taps. Below 40C and the valve diverts it into the DHW inlet to the boiler which tops it up on demand.
Blending valves are installed in the bathrooms but not in the kitchen.

You could install a similar setup by using a 3 port diverting valve on the outlets from the solar and the electric storage

[chemi-cool]

numero uno company:

http://chromagen.com/

[r.bartlett]

numero uno company:

http://chromagen.com/

Looking to buy these for my pool
http://www.milanuncios.com/calentadores-de-agua/placa-solar-187343904.htm

[r.bartlett]

Hi Richard
Over on mainland Spain where my brother lives I designed a 3 port valve into the hot water supply from the solar collector which diverted the hot water into the gas boiler if the hot water was not hot enough, i.e. cloudy days. The valve operates from a pipe stat set at 40C.
If the solar water is above 40C then it goes straight into the feed to the taps. Below 40C and the valve diverts it into the DHW inlet to the boiler which tops it up on demand.
Blending valves are installed in the bathrooms but not in the kitchen.

You could install a similar setup by using a 3 port diverting valve on the outlets from the solar and the electric storage


is this what you mean -from the Ariston solar range leaflet:

14137

[r.bartlett]

RB. I have a 300 L solar roof mount with a back up 2KW electric element on a controlled supply.
Controlled supply means power is automatically switched off for around 6 hours per 24. Saves $ by using a lower cost Tariff.
I set my electric thermostat to 50 C tho the CB is mostly switched off. There is NO control to regulate solar input so water temperature can easily reach 80+ Degrees C during Summer. Plumbers these days have to install a Mixing valve so that hot water cannot enter a premises beyond 50 C.

Yeah, Plumb cold water to Solar and insulate solar collector outlet to your "Boiler."


Thanks Mike that's pretty much what I thought. We get 350 day a year of sun so the payback should be quite high. I believe they all come with a heater eliment to assist but will endevour to not use it.

I also want a couple for a pool so will buy some s/h and use a HE or if I don't need the tank perhaps I can mod them to just use the tubes?

[frank]

Yes, option A

[MikeHolm]

RB, having put in 100s of solar systems, I will say that the best system is one with flat panels and not vac tubes (they require a lot more maintenance) and you need about 1m2 per person of panel area. Also, the more you can store the better with about 50L/m2 at a minimum. The tanks should be in series so the powered tank only sees heated water and it also make the control much easier. When the solar system sees only the cooler water in the first tank it works at it best efficiency. The second tank is just top up, if needed.

[r.bartlett]

RB, having put in 100s of solar systems, I will say that the best system is one with flat panels and not vac tubes (they require a lot more maintenance) and you need about 1m2 per person of panel area. Also, the more you can store the better with about 50L/m2 at a minimum. The tanks should be in series so the powered tank only sees heated water and it also make the control much easier. When the solar system sees only the cooler water in the first tank it works at it best efficiency. The second tank is just top up, if needed.

Thanks mike.

Can you expand on this with enough for a layman to understand. I am worried about the maintenance thing. Is this a temperature related one as we never get below 10c so the only potential concern is high winds.(most sold here are vac tubes)

also there is no water heating used (just heat pump splits) so not sure if this affects the 50l/m2 thing?

at present we have 2 x 75l electric tanks so intend to replace with 1 x 200l solar

[mikeref]

I think Mike H is talking about separate solar Panels and hot water storage in a closed circuit, recirculating water from panels to Boiler via a small pump. If there isn't enough heat via solar by X time, Electric elements cuts in.

Buggered if i know what the second tank does.

[mikeref]

My kit is the same setup as this picture. Hot water storage on the roof. No problems with high winds as it survived several severe Cyclones. Good for 200+ Km/h wind gusts.

http://www.solahart.com.au/downloads/album/BasecampNepallowres_12b5_albumLarge.jpg

[chemi-cool]

It's a great invention, maybe the best solar power use, I use electricity backup less than one month a year.

[MikeHolm]

Thanks mike.

Can you expand on this with enough for a layman to understand. I am worried about the maintenance thing. Is this a temperature related one as we never get below 10c so the only potential concern is high winds.(most sold here are vac tubes)

also there is no water heating used (just heat pump splits) so not sure if this affects the 50l/m2 thing?

at present we have 2 x 75l electric tanks so intend to replace with 1 x 200l solar

Sure, there are 2 main types of solar thermal. The first is for more northern climates where we pump the liquid to a HX down by a tank which could (possibly) feed a second powered tank and the second which is more common in your area which is to have the solar storage tank on the roof (which is called a thermosyphon system). Either system can be made with flat panels 2 or 3m2 or with vacuum tubes. Flat panels last longer and need less maintenance because they don't run at very high temps (up to 120C) where VAC tubes can run at double that which causes thermal stresses and regularly, one or two tubes needs to be replaced. This isn't a problem if it is quite accessible but if not, why use them.

If you say you rarely get down to 10C, go with a thermosyphon system (flat or vac panels). This way you can keep your existing tanks and have the supply side attached to the output of the solar system. It is a completely passive system with no controls needed except for the electric element. An antiscald valve on the output of the small tanks might be advisable if you have enough mains pressure for it to work well.

I'm not a fan of vac tubes because when they go, you often can't tell. They are cheap as 90% come from china.

If you have the roof space, you also could put a PV powered system in. It costs a bit more but it has the benefit of no plumbing and the power can feed other things once it heat up the tank (which would be in a lower area). You would need a DC-DC converter to keep 240V on the element but not much else. More about that if you are interested.

I will try to post some pics if I can find them.