Undersized Solar Pumping Station Pump - should I replace?

BigGeorge

Have a solar thermal panel set up, 3 sets of tubes ( 28 small tubes on each) in parallel, with a solar pumping station back at the solar tank. Its is a long run & the pumping station is putting out about 8 lt/min. I have the system drained down & flushed as the flow rate had dropped to about 6lt/min. Its in 3 year & working.

The pump is a Wilo solar specific pump. To go for a more powerful model - about 40% extra head - is about €200. I think the flow rate should be about 12-15lt/min. Is there anyone with experience to say this is a change worth making & will I harvest much extra heat

The heating vessel is a very large stratified tank so can absorb massive amounts of heat, currently about 30C at the bottom of the tank with 60 at the top. I cannot change the sytem configuration so make major changes unfortunately. Advice really appreciated.

Reposting here as had no luck with help over in plumbing

macnab

Taken from Builditsolar.

Quote
There are a lot of recommendations around on what the flow rate through water heating solar collectors should be.
I'm aware of these:

- Heliodyne recommends a range of 0.025 gpm/sf to 0.075 gpm/sf

- SunEarth recommends 0.025 gpm/sf for their collectors

- Solar discussion groups often talk about 0.02 to 0.03 gpm/sf a good number.
End Quote.

Personally I would put the old pump back in, the payback time on a €200 replacement is going to be quite long. I am not an expert.

BigGeorge

Thanks, the old pump is still in , not spent the €200 yet, looks like those numbers confirm a rate of 13t/min versus the 8lt/min currently getting. The solar is a really big proportion of our heating & hot water , but I just can't quantify the benefit of swapping it out

ccsolar

BigGeorge wrote: »

Have a solar thermal panel set up, 3 sets of tubes ( 28 small tubes on each) in parallel, with a solar pumping station back at the solar tank. Its is a long run & the pumping station is putting out about 8 lt/min. I have the system drained down & flushed as the flow rate had dropped to about 6lt/min. Its in 3 year & working.

The pump is a Wilo solar specific pump. To go for a more powerful model - about 40% extra head - is about €200. I think the flow rate should be about 12-15lt/min. Is there anyone with experience to say this is a change worth making & will I harvest much extra heat

The heating vessel is a very large stratified tank so can absorb massive amounts of heat, currently about 30C at the bottom of the tank with 60 at the top. I cannot change the sytem configuration so make major changes unfortunately. Advice really appreciated.

Reposting here as had no luck with help over in plumbing

Hi Big G
Can you post a photo of pumping station and controller?
It's not worth changing the pump if your getting 8 ltr min but if it dropped to 5ltr then you have an underlying problem with a jammed non return valve or blocked filter on pumping station.
Cc

BigGeorge

sorry for delay. The system was flushed, filters, NRVs cleaned out...I think its just a long run & pump is underpowered. Advice appreciated, trying to attach photo