Condensate pump doesn't retain water after shut down

[LChaminés]

Hi all,
We installed some condensate pumps in mini-split AC to drain the water upwards but something went wrong.

One of the pumps (they're 3) stopped working after a week or so, we thought it overheated and "burned", we changed the pump, and after that all pumps worked but after a whyle (after the AC unit had been shutdown) the AC indoor units would start to drip (we think the water in the pump pipes backtracked into the unit (note that the pumps have external power, always ON).

Since we had to move the pumps earlier (because of noise) we used a conection to "extend" the pipe that goes from the remote detection unit (level float) to the pump, that may be the reason why the water comes back (since the pipes should be always filled with water.

Any ideas about this, right now none of the pumps is working, we're gonna go there again and change one (trade it for a sauermann), change the pipes (no cuts or unions, full lenght pipe) and see how it goes for 1 or 2 weeks.

If anyone has any similar experience I would appreciate the help.

Have a nice day!

[nike123]

Check installation instructions of those pumps against what is done on field. I bet that there is the answer.

[The Viking]

What's the maximum lift on the pumps?
What's the actual lift?
Is the hose as it leaves the pump going straight up to the highest point and then fall back down again?
Your "connector", does that restrict the water flow? (is it's internal diameter the sam as the hose's)

Questions, questions, questions...
Sorry but without seeing the installation we haven't got much of a chance diagnosing it.

[LChaminés]

Hi and thx for all the help,
the max lift is 1 meter (3 feet??) and the real lift is maybe 1.5 meter (4.5 feet??), the conector does restrain a little (let's say 1 milemitter), the pipe goes up then it makes a small turn down (like a cane..) and enters the pump, than it descends 20 centemiter (less than a foot??)

[The Viking]

the max lift is 1 meter and the real lift is maybe 1.5 meter

OK...
And the problem is then....

[Tayters]

OK...
And the problem is then....

Indoor unit was fitted too low down. Ha ha!

[install monkey]

few tips- check the pump is wired to the 240 or 220v mains and not the signal, ensure any filter gauzes are clean, sump float switches correct way up and clean- most pumps can syphon 1 mtr up from the sump/float- ensure the breather tube is fitted, also no kinks on the hoses, finally the outlet must be above the height of the pumpotherwise syphoning can occur- causing the pump to run on start up until it primes itself with water, the water cools the pump motor- finally prove theres no blockages from debris and the drain hose doesnt sag, most pumps have an anti cyphon valve so you shouldnt fit an additional one

[LChaminés]

Thanks again for the help, i don't think the 1/2 extra meter is the problem since it did pump water (all 3 pumps) whyle we were testing them (1 hour or so), but the one will be testing allows 2 meters so we'll see if it fixes the problem, I really think we messed up with the piping, the conector might have been a wrong move, also, since the pipe makes an inverted U turn just before the pump (we had to put the pumps outside the roof, because of sound spread, and isolate the "exit hole" on the roof (it's like an Inox cane so rain doesn't fall inside) and isolate the pumps (they're inside a pipe above the roof)