Circulation pump

[acmetowers]

Just a few questions!

Is it correct in saying that you need a backup power supply for the circulation pump if for some reason you have a power cut while there’s blazing sun, i.e. will the collectors overheat?? If this is the case are the only two options 1) a backup power supply or 2) PV powered pump in the first place.

Looking through the FAQ about using a solar pump you mention the use of a 220v 10w pump, a 20w PV panel and an inverter to power the circulation pump, is this the correct specification for your circulation pump (10w), and do you sell the inverters??

Lastly

The Resol Delta BS/4 has the function of variable speed output for the pump, is this a worthwhile option? If so I take it your pumps are compatible with this.

Many Thanks

[Ivan]

Generally you tend to get power cuts in the winter and during stormy weather, when overheating is not such a problem.  However, if there is a powercut when the sun is shining the temperature in the manifold will increase to a level where the circulation fluid will begin to boil. About 1/2 hour at this time of year during the day will give you temperatures in excess of 170C, and I have seen temperatures eventually reach 216C! This is inconvenient to say the least, but it will not damage the panel.

The backup power supply is designed to get around this problem. However, bear in mind that you will be using 3-4watts constantly with the power supply rather than <2watts for the controller alone - so it will increase your electricity consumption, albeit not a hugh amount. We have carefully selected a very low power unit to ensure minimum losses - many cheaper UPS systems will use up to 80w in standby!!

We do not recommend PV-powered pumps - they cannot cope with vacuum tube heat, and tend to fail after a few days. Also PVs produce very little heat in overcast weather - whereas the panels can get very hot in summer overcast weather. This is due to activation energy of the Si and the much lower efficiency of PVs compared to vacuum tubes.

The BS4 will reduce the cost of pumping, by running the standard pump at lower duty cycle - down to 30% of its intended rating - so a 40w pump will run down to about 6w, by being pulsed on and off by the controller. It is a matter of preference. It requires some more care in setting up - hence installers will normally fit the BS3 controller, which is more straightforward. For DIY use, the BS4 can be more rewarding, as you have a lot more time to 'fine tube' your own installation for different weather conditions. I have asked resol for recommendations, but unfortunately they do not have any, so it is a bit of trial and error.

Ivan

[Amaterasu]

Even though I have not actually got my solar bits yet. Waiting for the July shipment!.
I have been planning ahead.
I bought a 1000VA PC UPS for less than £40 (inc P&P) on ebay. Its a rackmount model so will not take up too much space.

I know it wont last too long but at least it may mitigate any damage. Fortunately our power cables are underground here so the chance of a disruption is less than overground supplies.

G

[Ivan]

The UPS is exactly what you need. If the batteries are knackered (this is usually the reason they end up on ebay - they cost a fortune to replace), then it is easy to fit a set of external batteries (such as our deep cylcle batteries) - just make a hole in the case, and some extra long leads or lead extentions.

I would suggest you check the power consumption of the UPS before you enlist its work full time. The power consumption can vary enormously. Our backup power supply (UPS) system has been selected on the basis of very low power usage  - 6-7watts. Many inverters and UPS systems require 40-80watts even when no power is being drawn. If you add this up over 365 days, it can end up costing a lot - £30-40 per year. An efficient UPS as an alternative would cost much less.

If you want to check the AC consumption of the power meter, one of our power inverters are invaluable for doing this

Ivan