168lt solar cylinder size 2 people bath in winter WBS HELP PLEASE

[Chanireland]

 banghead:Just a quick question looking for opinions,
have just ordered 168lt solar cylinder for 2 people 2 bed cottage will get 15 or 20 47mm tubes in the summer and a large WBS wondering now  should i have  gone for larger cylinder not allot of space but really want enough hot water for bath in winter.
If the bath is say 140lt and the water in tank is 50 or 60oc and the coil from stove only heats say 100lt how much water can i get from the tank with cold added to 38 oc for good hot bath.
hope that makes sense.
or does any one have a 168lt solar cylinder and how do they feel the size has worked out for them....
if i rush i could change my order tomorrow and get a little bigger say 184lt.

sure this is a simple  maths thing and/or experience thing.

Thanks for any thoughts.

should i change my order for a larger cylinder

[wyleu]

I'd go for the bigger option, simply because the whole of the solar game is really about storage rather than energy generation.

Consider the time you have your bath. Because you will have to store the energy from the last of the sun till the time you stop filling the bath.

[Justme]

banghead:Just a quick question looking for opinions,
have just ordered 168lt solar cylinder for 2 people 2 bed cottage will get 15 or 20 47mm tubes in the summer and a large WBS wondering now  should i have  gone for larger cylinder not allot of space but really want enough hot water for bath in winter.
If the bath is say 140lt and the water in tank is 50 or 60oc and the coil from stove only heats say 100lt how much water can i get from the tank with cold added to 38 oc for good hot bath.
hope that makes sense.
or does any one have a 168lt solar cylinder and how do they feel the size has worked out for them....
if i rush i could change my order tomorrow and get a little bigger say 184lt.

sure this is a simple  maths thing and/or experience thing.

Thanks for any thoughts.

should i change my order for a larger cylinder

I am more worried that with 8L per tube you will be very under powered & might never get a full tank of hot water even in summer.

A bigger tank will be even worse. You need to up the number of tubes to more like 5L per tube or even less if you want solar hot water in more than just the summer.

[Chanireland]

well yes but an oversized tank to tubes meens les heat dump so less wast and cheaper, also could buy more and add them on if they wernt sufficiant. but the solar part is next i just need a tank in so i can wash me grubby mits

yeh  thought the more you store the better..
but come winter and the sun is having a holiday probably south america or india who knows. so the WBS is the heat sours because the  WBS coil is further up the cylinder say only 100lt is being heated will this give me 150 lt of Bath temp water when cold is added this is  my concern.

i also asked them to put an extra immersion bus on it low down so if in the future i get a wind mill it could heat dump into it. i is right up a windy  mountain.

but 168lt will i get a big bath (140lt 40oc) and possibly do the dishes from 100lt of WBS hot water??? , probably a hunter 14 with only 4 rads or might be Stanley  range style coss its in the kitchen.. not sure yet...
thanks guys

[desperate]

What size cylinder do you have at the moment, and is it ok or not? this should guide you to how much hot water will be sufficient for your use. As the last couple of post indicate it is always a compromise sizing a system.
I would have thought a 100 litres of hot from the WBS would be ok for 2 people.

Desperate

[Chanireland]

im renovating a cottage, so no cylinder as the last occupants  didn't have electricity or  running water 35 years ago, bare stone and roof off. Doing 98% myself BIG learning curve ...
 
have a couple of rooms ready bedroom, living space and a small bathroom ready to plumb , just putting extra joists in above what will be the klitchen to take hedder tank so plumberish guy will help get a temp kitchen bathroom going but the copper i thought put it in its final right places and the right tank in the right spot and  not have to change it just work around it....

Desperate
"I would have thought a 100 litres of hot from the WBS would be ok for 2 people."
does that mean i would get a large bath from it 140lt ?

thanks

i know nothing is defnate except what happens if ya fall out of a plane at 20,000mt with no parachute.. ya get cold...

any 168lts out there

[Greenbeast]

we have a 172l for 2 people but we have 36 x 58mm tubes

[Brandon]

direct tapping the WBS will enable you to effectively heat the entire store bar the solar reserve (usually 50-60l at the bottom)

[KLD]

Don't you fear, the maths is actually quite easy   
Right then, you want 140L for a big, deep bath. Let's say the cold mains water comes in at 10°C. FIll the bath with 40°C (actually too hot to stay in for long, but then it won't stay that warm forever either.) So, you need to provide enough heat to raise 140L by 30°C.
If your store was 140L, and you could extract all the hot water from it, then it would cool down by the same 30°C. If your store was smaller, then you'd need it hotter to make up for the shortfall in volume. The heat content is proportional to volume times temperature difference. With your estimated 100L of WBS heated volume, you'd need 30°C*(140/100) = 42°C temperature difference. Give it a little extra, and run the tank at 60°C (i.e. 50°C above incomming mains water temp). Now, extract 100L of 50°C, add 40L from 10°C cold, and enjoy.

And the WBS, if it's not a tiny one, will quite likely have a higher output to water then the solar panels. The energy content of your bath is 100L*50°C*4200J/L °C / 3600000J/kWh = 5.8kWh. If you had 6kW into water from a big stove, it'd take an hour to reheat the store.

Regarding the solar panels, I agree with the others here and recommend more tubes. 20x  58mm tubes are roughly equivalent to 30x 47mm tubes. We've got 40x 47mm into 216L, and that seems about right. Should you need it (e.g. going away during summer), then installing a heat dump is no big magic.

Klaus

[Chanireland]

direct tapping is an interesting idea, i actually asked them to put an extra tapping just incase in the future the plan changed.
 
slightly off topic ~But is it posible to set up like  this and if so whats the simplest way.

WBS priority heating rads when house up to temp swich to also heat DHW (this could be manual)
incorprating a heat dump rad for WBS/ thermoshoning DHW/ pumped rads/ solar heat dump by circulating rad heating circut utilizing possibly  the tdc3...

should i start another thread for that thought above?

thank you

[Chanireland]

thanks Klaus

funny at school me maths was great and now post calculatos and computer the mind  boggles
gues its easy if ya know that formula.
INFORMATION IS POWER...

going to have a plays with your maths there and try and play around  with the temps etc.
so it sounds like 168 will do the trick, not sure about wether i get TMV , its not a thermal store but tha maths stays the same.

thanks