Hi everyone,
I have looked into this problem myself and have found that the electronic 'blipper' a very useful tool. It can be bought at Maplins for around £35. There are even different types which would lend themselves to possible variable speed/flow rates. I just have the single channel type but am considering the dual or triple channel varient. If you connect your pump via a ballast resistor which I robbed from an old sierra heater motor fan circuit you have the option of four speeds. Slow (which in actual fact is too slow to run the pump) medium (which is good for ground floor work) fast (good up to three storeys) and total bypass of the resistor which is like direct to battery.
It would not be unconcievable to connect three speeds to the maplin three channel remote controller. Like I said before I just have the single on or off controller with the speed set via the sierra switch in the back of the van.
In terms of aerial and distance from the van which it works.... I may well have cheated here. I have an old vauxhall combi with heated rear windows and have wired the aerial to one of the heating elements. (obviously having disconnected from the heating circuit and isolateing from the earth on the other side of the element) This doesn't worry me as the cab is boarded seperate to the load space and I can't look out the rear windows anyway.
Effective range is 70meters in an open enviroment, but does work with the house inbetween to around 50 ish.
Put it this way, I'm happy. Best thing I ever did. Tip* put the blipper on a long boot lace around your neck and you have easy access to it without messing in your pocket to switch on and off every time. (yes I know I look like medalion man, but it works)
Details of maplin item below (three channel)
Three Channel Wireless Remote Control Kit
Complete 3 channel remote control system
Switches up to 12A at 230Vac mains
Up to 70m range
Only £35.99
Order Code: L28BK within 7 Days
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