Configuring hot water solar panels

Acuario · 11-01-20, 07:20 AM

I currently have 3 solar water panels connected in series to provide heating to my underfloor heating in the house.

As I write (a nice sunny Sunday at 13h) the water temperature in the floor is 32C and the exit temperature of the panels is 54C. I have a coil heat exchanger in a 100L water tank to transfer heat.

I have now obtained a 4th panel that I will add to the system.

The question is; do I connect the 4th panel in series with the 3 existing panels or do I split the panels into 2 banks of 2 panels.

Any thoughts? Is one configuration better than the other?

Daox · 11-02-20, 08:57 AM

Why put them in series at all? Lower panel and water temperatures generally mean higher efficiency.

Acuario · 11-03-20, 02:08 AM

I'm currently getting around 7C increase per panel. I can't increase the flow through the panels and the HX is quite small bore so there is a limit to what I can pass through it.

My thoughts are:

Add an extra panel in series so exit temperature is higher but flow rate is the same - would I get to 60C +?
Put 2 sets of 2 panels - flow rate through each panel is slower so exit temperature is higher - would I get 11C per panel increase?

Ultimately I will have a delta T of panel exit temperature - tank temperature, tank temperature is normally around 30C so the panel temperature is the important one.

Maybe, as the flow rate isn't going to change, it's pretty much the same one way or another.

Daox · 11-03-20, 10:38 AM

I imagine it won't matter a ton either way. I'd probably put them in whatever way is easier to mount.

jeff5may · 11-05-20, 07:43 PM

Since your hx and the flow through it is your limiting factor, put the panels all in series and force the highest dT across the hx. Make sure it is running counter flow as well to get the highest leaving water temperature. As long as there's no boiling risk in your panel loop, that is.

11-01-20, 07:20 AM	#1
Acuario Apprentice EcoRenovator Join Date: May 2011 Location: Tortosa, Spain Posts: 221 Thanks: 2 Thanked 81 Times in 46 Posts	Configuring hot water solar panels I currently have 3 solar water panels connected in series to provide heating to my underfloor heating in the house. As I write (a nice sunny Sunday at 13h) the water temperature in the floor is 32C and the exit temperature of the panels is 54C. I have a coil heat exchanger in a 100L water tank to transfer heat. I have now obtained a 4th panel that I will add to the system. The question is; do I connect the 4th panel in series with the 3 existing panels or do I split the panels into 2 banks of 2 panels. Any thoughts? Is one configuration better than the other?

11-02-20, 08:57 AM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Why put them in series at all? Lower panel and water temperatures generally mean higher efficiency. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-03-20, 02:08 AM	#3
Acuario Apprentice EcoRenovator Join Date: May 2011 Location: Tortosa, Spain Posts: 221 Thanks: 2 Thanked 81 Times in 46 Posts	I'm currently getting around 7C increase per panel. I can't increase the flow through the panels and the HX is quite small bore so there is a limit to what I can pass through it. My thoughts are: Add an extra panel in series so exit temperature is higher but flow rate is the same - would I get to 60C +? Put 2 sets of 2 panels - flow rate through each panel is slower so exit temperature is higher - would I get 11C per panel increase? Ultimately I will have a delta T of panel exit temperature - tank temperature, tank temperature is normally around 30C so the panel temperature is the important one. Maybe, as the flow rate isn't going to change, it's pretty much the same one way or another.

11-03-20, 10:38 AM	#4
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	I imagine it won't matter a ton either way. I'd probably put them in whatever way is easier to mount. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-05-20, 07:43 PM	#5
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	Since your hx and the flow through it is your limiting factor, put the panels all in series and force the highest dT across the hx. Make sure it is running counter flow as well to get the highest leaving water temperature. As long as there's no boiling risk in your panel loop, that is.