Solar hot water + Condensing boiler - how does it work?

Andr3w

Andr3w

Andr3w

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Evening all,

Recently moved into a new place that has a solar panel on the roof which heats a large storage tank of hot water (This only provides hot water, not central heating).

We also have a condensing boiler (Ideal Logic 12).

What I want to know is how do the two work together? It's been a cloudy rainy day today and the temp in the hot water tank is showing about 23c. I turned the boiler on downstairs and waiting 30minutes and checked the hot water tank - it was down to 22c.

I ran the hot water tap and it came out boiling - i'm guessing the condensing boiler is 'heat only' and not providing hot water to the storage tank.

What I want to know is, when I run the hot tap is the water thats coming out just from the boiler, or is it the 22c from the storage tank + water from the boiler?

I've read all the manuals in the house and nothing explains how it actually works!!
 
Seen quite a few systems, without seeing it in person I would hazard a guess that the hot water tank feeds the cold input to the condensing boiler, the condensing boiler would then further heat up this already heated water, so the warmer the solar heats the water the less work the condensing boiler would have to do. You would need good pressure (height) for this set up to work. Is the tank on the floor above the boiler?
 
This is the most common approach:
"When the water temperature in the cylinder is below 50˚C the solar system feeds the combi with pre-heated water which means it has to work less hard to bring the water in the cylinder up to the desired temperature. Once the cylinder temperature gets above 50˚C a diverter valve is used to bypass the combi and send the solar heated water directly to the hot water outlets."

a lot of modern combi boilers can accept hot water on the supply side.
 
KelDG said:
Seen quite a few systems, without seeing it in person I would hazard a guess that the hot water tank feeds the cold input to the condensing boiler, the condensing boiler would then further heat up this already heated water, so the warmer the solar heats the water the less work the condensing boiler would have to do. You would need good pressure (height) for this set up to work. Is the tank on the floor above the boiler?
Click to expand...

Yes the water tank is up stairs, boiler downstairs.

a1ex2001 said:
This is the most common approach:
"When the water temperature in the cylinder is below 50˚C the solar system feeds the combi with pre-heated water which means it has to work less hard to bring the water in the cylinder up to the desired temperature. Once the cylinder temperature gets above 50˚C a diverter valve is used to bypass the combi and send the solar heated water directly to the hot water outlets."

a lot of modern combi boilers can accept hot water on the supply side.
Click to expand...

It's not a combined boiler!


Also, this morning the water tank is showing 21c as its been cloudy the last few days, the boiler is OFF yet we all managed nice hot showers this morning!

This stuff is like voodoo!!
 
cloudyness in water is one of two things; something in the water (sediment, local water supply issue etc), or air in the water. If you pull yourself a glass and watch it clear how does it clear? From the bottom up = air, from the top down = something

No idea on how the hell that boiler works, I'd go with your voodoo suggestion!
 
Is that thermometer actually reading your water tank, or the water coming from your solar panel? It can't be measuring the temperature of your water tank if your hot water is hot but that temp reading is 21deg. It sounds like you've got an immersion heater on in your water tank. Check around it for a cable+switch.
 
Cloudy outside, the water is clear :)!

The temp monitor has 2 values, one for the solar panel and one for the tank!

See why I'm confused lol
 
I bet it's an immersion heater. Run your hot tap for a while, while listening to your tank and/or watching your electricity meter.

Can't really be anything else if all other things are off!
 
Could be the temp reading is wrong - my grandparents have solar water heating and it usually manages a good bit more than ~20C unless its really dull - but I can't imagine it would get warm enough to not need some boosting (for showers, etc.) if its been like the last few days here.

Those temperature readings sound more like the ambient indoor temps for the last few days.
 
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Andr3w said:
Yes the water tank is up stairs, boiler downstairs.



It's not a combined boiler!


Also, this morning the water tank is showing 21c as its been cloudy the last few days, the boiler is OFF yet we all managed nice hot showers this morning!

This stuff is like voodoo!!
Click to expand...

Combi or not it's the same thing the usual approach would be for the boiler to accept warm water as the input and top up the heat.

It sounds to me like either you have a faulty temp guauge or a perpetual energy machine or there is something you missing! What fires your central heating?
 
Haha!

Just ran some hot water to do the washing up, the water was scolding hot.

Boiler is OFF (even at the wall switch)
Immesion switch is OFF (a red light is even lit when it's on)
It's been rainy/cloudy for two days and the hot tank says it's 30c.

Like I said the water was scolding hot.

I'm scared.

I'm running away :(.
 
What's your gas/electricity consumption been like over the past few days? Surely the solar panels aren't that good at heating water...
 
I'm no expert but I hve done some research in the past.

It is not uncommon for the system to have a thermal store, a big cylinder. At the bottom you have a coil connected to your solar colletor. When on the heat slowly brings the tank temp up. A middle coil is connected to your boiler as the main duty heat source. A top coil is connected to your mains pressure hot water system. Col d water enters the top coil is heated by the store and goes to the tap. Sometimes you also have an immersion heater near the top to rapidly heat the water near the top coil.

The water in the store is never used only to store and transfer heat .

You need to know where your thermometer is, it might not be telling you what you think. It could be broken. The solar collector will just help reduce the heating burden in the winter and in the summer will probably prvide all your needs.

*without seeing your system, that is all supposition*
 
Zefan said:
What's your gas/electricity consumption been like over the past few days? Surely the solar panels aren't that good at heating water...
Click to expand...

Despite the weather lol it is after all August (I think) - still a fair bit of energy falling on those panels/pipes especially if it clears up for a bit during the day. With proper thermal storage they aren't bad from my experience.

Still can't imagine you'd be getting a decent shower temperature without further boosting though.

EDIT: I am way down in the South so might be different in other parts of the country but just asking someone who has a solar water heater and they've been seeing 35C or more over the last few days to their recollection even with it moderately cloudy.
 
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