Shower pump - 'Techflow' brand runs itself !!!

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Hey there,
ive a Techflow branded twin impellor shower pump running the bathroom, gravity fed system, the pump has been replaced about a week ago and the problem is the pump just runs for about 3 secs and stops for 10 secs then back on etc... when there are no taps running anywhere, its constantly doing this and have noticed that with the indirect hot water cylinder filled with only cold water (HW off) the hot side of the impellor pump seems to be hot, the obvious reason for this I would think is because the impellor on the hot side is the one running intermittently even though there is no hot water in the system.
Now correct me if im wrong but think the hot draw off to the cylinder is connected off the top of the cylinder pipework and NOT a flange from the cylinder causing air to be drawn in from the open vent at the top?? this is allowing a pressure drop to the pump causing the intermittent triggering,
what do you think about this conclusion??
 
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would not it be better to fit the hot supply from the cylinder to the pump through a flange as recommended by techflow?
 
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Now correct me if im wrong but think the hot draw off to the cylinder is connected off the top of the cylinder pipework and NOT a flange from the cylinder causing air to be drawn in from the open vent at the top?? this is allowing a pressure drop to the pump causing the intermittent triggering,
what do you think about this conclusion??
Don't really understand what your saying here, can you clarify what type of flange connector you actually have on the cylinder & where the HW supply connection is? Where is the pump located relative to the HWS cylinder, the shower head & the CWS tank in the loft; do you have up & over pipework fron the pump to the mixer valve &, if so, how far below the bottom of the cws tank is the highest point? do you have vents fitted in the top of these loops?

It could be any one of a number of reasons, the most obvious is a pottential negative head situaltion, air locks in the pipework from the pump to the mixer valve or a leak somewher in the system allowing it to de-pressurise.
 
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would not it be better to fit the hot supply from the cylinder to the pump through a flange as recommended by techflow?
Just noticed this post is actually yours as well; are you saying you don't actually have a flange fitted? If not how have you connected the pump supply?
 
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hi Richard, I know its confusing but let me brief you..
Techflolw twin impellor positive head type fitted next to the hot water tank sitting on the floor, 22mm hot feed to pump is taken off the hot feed pipe at the top of cylinder (and NOT a essex flange which is directly from the cylinder). I have not fitted this, my logical thinking is that the way its currently fitted is that its drawing air from the open vent while taps are off causing the drop in pressure and intermittent trigering. there is no air in the pipework from the pump to the taps as I checked that already,

thanks in advance
 
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You can tee off the top outlet but this must be at a 45 degree, downward angle or you'll contunually draw air into the system & run the risk of seriously damaging the pump. By far the best way is to use a proprietory flange &, of these, most manufacturers favour a separate side entry Essex flange.
 

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