On Fri, 13 Apr 2018 15:14:25 +0100, newshound wrote:

On 10/04/2018 00:03, Johnny B Good wrote:
On Mon, 09 Apr 2018 20:49:34 +0100, newshound wrote:

====snip====

A small 12 volt boat bilge pump would go down your existing 75 mm sump
pipe. I guess you could suspend it either above or below the "steady
state" water level. Then have it switched on by a suitable float
switch.

That's a no, no afaiac simply on account of the need for a hefty 12v
power supply.

Hefty? A wall wart will give you 2 amps, which will drive one of the
small pumps. It's not as if you need a huge flow rate.

It's true that I need a modest flow rate that can be sustained
sufficiently to outpace the rising water level but even the modest 16.5
litres per minute at a 50% duty cycle of the small 12vdc pump that I did
land up buying from MachineMart today claims a 4.5A requirement (which I
thought was quite modest). Since I already had a 13.5v 10A smpsu to hand,
along with a 12AH SLA in serviceable condition, it seemed worth taking a
punt at a mere £20.39. :-)

TBH, I doubt a small enough pump to keep the current demand within the
2A limit of a 12v wallwart would be up to the job. However, despite my
original rejection of your advice, I reconsidered it in the light of the
specs shown in the manual I downloaded this afternoon (one of many such
pdfs btw) and bought this pump:

https://www.machinemart.co.uk/p/cl-msp12-pump-kit12v/?instore=Liverpool

which slides rather neatly down my sump standpipe.

I just need to extend its supplied 3 metre outlet hose another 10 metres
to pump out from the standpipe location to out of the backdoor. All I
could manage this afternoon was a basic test on the more accessible coal
hole puddles which suggests that it's likely to suffice for the job in
hand.


Also, there are plenty of cheap "damp" alarms on ebay, I've just
bought one to fit into a friend's condensate drain to give him early
audible warning of a frozen outlet.

I think I could homebrew my own float switch, possibly from W/M water
level sensors if not an actual float operating a microswitch.

That's going to be a project for another day. The problem with using
electrodes dipping into the water to detect the level, as one sump pump
manufacturer demonstrated to its trusting customers, is the risk of false
detection due to water film bridging across the electrode insulator.

A float operated sensor is more reliable if designed carefully or else
the use of a pressure sensor as used by the washing machine manufacturers
can prove an effective alternative. I'll probably pick the simplest to
implement, a simple float operated switch, but it depends on how complex
a controller I decide to fabricate. I need not only to prevent dry
running but also to limit the duty cycle to a max of 15 minutes per half
hour of run time with this pump so there'll likely be some electronics
involved that otherwise wouldn't have existed which would have made the
float operated microswitch the obvious solution.


I'm hoping my experiment with W/M pump and wet 'n' dry vac succeeds. My
Franken- solution looks an ever more elegant option each time I search
for a suitably priced sump pump. A single W/M pump might not be
sufficient but given a free supply, suitable hose and jubilee clips,
I'm sure I can cascade enough of them to do the job. :-)

I have to confess the Franken-solution has a certain appeal to me too
:-)

I did find the W/M pump but not assembled onto a board as I seemed to
recall, just the bare pump and its inlet hose. TBH, it was all starting
to look a more fiddly job than I CBA to spend time on, hence my
continuing search for a ready made solution, culminating in the purchase
of that Clarke MSP12 - 12 Submersible Transfer Pump that I discovered as
a 'Sale Item' on MachineMart's website earlier today (Friday).

As a "Thought Experiment" it was all 'Fine on Paper' but quite frankly,
I didn't have enough motivation to spend any time on translating it into
actual hardware. In the end, it was your suggestion that won the day,
even if it was in a round about way (and tipped by the sale price of the
pump in MachineMart).

--
Johnny B Good