East West Orientation

Pataman

Hi Guys I am looking for advice. I have 24 tubes on a west facing roof heating a 300L TANK. I have now got a 30 tube manifold to put on the east side to compliment the existing system. I have 2 questions:
1) I am told that afternoon sunshine is stronger so I would be better putting the 30 tubes on the west and moving the 24 tubes to the east.
2) I have been told that I can just install the other manifold but need to change my controller to a dual roof version. Another person told me I need to also install motorised valves to switch between east/west automatically. The first expert told me I dont need the valves as the manifold that will be in the shade is full of insulation and therefore there wont be any heat loss.

I tried to find a list of daily hours of sunshine for Dublin but couldnt find any.

Any opinions would be greatly appreciated.

Thanks
Pat

championc

Pataman wrote: »

1) I am told that afternoon sunshine is stronger so I would be better putting the 30 tubes on the west and moving the 24 tubes to the east.

You could well be right about this although it's more that the general Air Temp will be higher. Best bet though is to look at your roof and actually time the hours that the sun hits your roof - taking account of possible shadows or blockages of sunshine by other houses around you. I'm directly south and would get sun from about 08-18:00. Therefore, with noon, I have 6 hours after noon but not 6 before. And if I was more West facing, I could maybe get a few more hours in June. So it's worth thinking about 54 on one side.

Pataman wrote: »

2) I have been told that I can just install the other manifold but need to change my controller to a dual roof version. Another person told me I need to also install motorised valves to switch between east/west automatically. The first expert told me I dont need the valves as the manifold that will be in the shade is full of insulation and therefore there wont be any heat loss.

Yes, I believe you would need to at least change to a different mode on your current controller. You need it to be able to stop one panel and enable to other. Without a diverter valve, you could end up taking cool in from the shaded side and possibly cancelling out the gains from the other.

So in conclusion, 50 tubes would be the sizing for a 300L store. If your West is facing any way sightly South of West rather than North of West, I'd think 54 on one side is the way to go.


C

Pataman

Agreed about changing the controller and diverter valve.
Interesting thought about all tubes on the west side, I will have to check if i have room.
The roof-line is exactly due south so for a few hours maybe 11-1 both sides would be sunny(at this time of year).

Both sides of the roof should be sunny for most of the day in the height of summer, unless you have a very steep pitch.

Pataman

Its a fairly standard pitch roof

championc

Pataman wrote: »

The roof-line is exactly due south so for a few hours maybe 11-1 both sides would be sunny(at this time of year).

So East side would give about 5 hours from 8 till 13:00 whereas West would give about 9 for 11:00 till 20:00.

Since you already have a system in place on the West, what time does it start to heat up at on clear sunny days, at what time does it loose the Sun at ? You can just watch the controller - looking at the roof temperature or else some other indicator as to when the system is generating heat.


C

quentingargan

The other reason to give priority to the west roof is that you are storing the water for a shorter period.

Some people like to have an east west arrangement as a way of backing both horses. You might get a sunny morning and a cloudy evening, or vice-versa. But apart from that, the general advise would be to put 'em all on the west - warmer air temperature, lower cylinder storage time.

If you are going for east-west, and if your panels are of the heat-pipe variety, you would need an east-west controller. But I think there is very little difference between

1) using motorised valves, and
2) connecting both pump output relays to the one pump, and running both panels in series.

All you are doing is running the water through an extra couple of metres of very well insulated 22mm pipe in a manifold. If you are using motorised valves, bear in mind that for much of the day, both panels will be in use, so you need to ensure there is a balanced flow rate - ensure that both systems have roughly equal bends and pipe runs.

championc

With the hassle of balancing too, sounds like all 54 on the West is the way to go - space permitting.

Pataman

Hi guys, Firstly thanks for all your replys.

My gut tells me to split it between the 2 roofs however as championc says the west side may get more. Just looking at the roof this morning the east side has baked in sun since sunrise and only now the west side is beginning to wake up. It would be an awful pity to ignore 6/7 hours of sunshine on the east side to favour all on ther west.
Damn planners wouldnt let me change the roofline when we were building!!
Quentingargan, i tend to agree with you to run it in series, 1 pump, obviously a dual controller, however I wonder will I lose much heat to the dead side in the morning?

quentingargan

Pataman wrote: »

Quentingargan, i tend to agree with you to run it in series, 1 pump, obviously a dual controller, however I wonder will I lose much heat to the dead side in the morning?

I can't see how you would lose any more heat than you would in a few metres of well insulated pipe. My gut feeling is that you would lose almost as much heat by running two pipes, and with the thermal mass and losses of poorly insulated motorised valves etc. Also, more stuff to go wrong...

I'm open to other views on this, and textbooks I've seen say to use two pumps without differentiating between tubes and flatplates (there are even twin pumpumpstations on the market for this very purpose) but with tubes, I could never see the sense of all that. Flatplates are a different matter, and the heat loss of running through a cold panel would be astonomical.

championc

Pataman wrote: »

Hi guys, Firstly thanks for all your replys.

My gut tells me to split it between the 2 roofs however as championc says the west side may get more. Just looking at the roof this morning the east side has baked in sun since sunrise and only now the west side is beginning to wake up. It would be an awful pity to ignore 6/7 hours of sunshine on the east side to favour all on ther west.
Damn planners wouldnt let me change the roofline when we were building!!
Quentingargan, i tend to agree with you to run it in series, 1 pump, obviously a dual controller, however I wonder will I lose much heat to the dead side in the morning?

Not knowing where in the country you are but I had a feeling that you may have been lucky this morning. If you had exactly equal amounts of sunshine on each side during a single day, I still think the West will work out better given the higher air temperature and, as Quentin says, it will most likely have a lesser time between water being heated and it being used.

When I got my system installed, my main hope was to maximize gain during Spring and Autumn. In ideal weather, we should all have an excess of hot water during the summer months.


C