Shower not triggering water pump

[oisinl]

Hi, first time poster here. Hopefully I've posted in the right forum.

Right, I've an issue with our shower system. Above is the schematic. Builder is in the wind.

The shower is a mira platinum wireless controlled, the pump is a Stuart Turner monsoon s3.0 bar twin (Monsoon S3.0 bar Twin | Twin Shower Pump | Stuart Turner - https://www.stuart-turner.co.uk/product/monsoon-s3-0-bar-twin-46416).

When the shower is turned on via the wireless controller there is no flow. In order to get flow either the tap needs to be turned on or the shower head brought below the wall exit.

Am I right in assuming that there is insufficient water head?

And would raising the cold water tank up a metre or so solve this issue?

I could potentially change the height of the pump, but everything else is fairly fixed without major work.

Thanks

 

[steadyon]

1. The minimum head between the base of the cold water storage cistern (CWSC) and the outlet for your pump is 0.5.
1a. You have 0.2 metres to the rain head, so that won't start the pump.
1b. You have 1.0 metres to the movable head (per your diagram (3.0 - (1.2 + 0.8))). This should be enough to start the pump, provided it can provide a flow of 0.6 litres / minute. Given that it won't start the pump, there is probably sufficient resistance in the pipework / controller to limit the flow.
2. Use the shower, and lower the movable shower head until the pump starts. Measure / calculate the distance the head has to be dropped to start the pump, and that is the distance you would have to raise the CWSC to get it to start when in its bracket. Add again the distance from bracket to rain head to get the amount it would need to be raised to start the rain head.
3. If you use the figures from 2. above, I'd suggest adding at least 1/2 metre for contingency.
4. Also, look at the height of water in your CWSC. If there is some scope to raise the water level without getting too close to the overflow, that might also gain you a few mm of head.

 

[oisinl]

Brilliant, thanks so much. Will give that a shot.

 

[Ben-gee]

Swap the pump for ST Monsoon universal, which is a negative head pump.
You obviously haven’t got a decent plumber involved in the project or this would have been specified from the start....

 

[oisinl]

Cheers. Yeah, long story on that one. Many issues with the plumbing, if it's as simple as switching the pump, that's a win for me.

I appreciate the responses, it's a pain needing to turn on the tap to get the shower to run.

 

[EvilDrPorkChop]

Cheers. Yeah, long story on that one. Many issues with the plumbing, if it's as simple as switching the pump, that's a win for me.

I appreciate the responses, it's a pain needing to turn on the tap to get the shower to run.

I assume you've got the Mira Platinum for High Pressure? You should have bought the pumped version, I doubt it'll ever work correctly with the way you are trying to do it.

 

[oisinl]

I assume you've got the Mira Platinum for High Pressure? You should have bought the pumped version, I doubt it'll ever work correctly with the way you are trying to do it.

Yes, just checked. It's the Mira Platinum HP/COMBIMIXER.

Ok, so maybe not as simple as swap the pump. I might raise the cold water tank as suggested above. Not sure I can raise it to make the rainfall trigger the pump, but I have space to get enough head for the detachable shower head to kick the pump on. If I lower that shower head by 0.4m it works fine.

Yeah, I'm starting to understand the multitude of problems. Unfortunately, the plumbing was done as part of a renovation, I just bought what the plumber told me to buy. That main builder is in the wind so not much help anymore.

Appreciate all the replies.

 

[ShaunCorbs]

Changing the pump to a uni / negative head will fix your problem

 

[EvilDrPorkChop]

Changing the pump to a uni / negative head will fix your problem

Even with the digital shower being HP version you think?

 

[ShaunCorbs]

Even with the digital shower being HP version you think?

Yep as negative head pumps pressurise the outlet pipework to there pressure rating eg 1.5 bar and asoon as it drops below that eg 1.2 bar the pump kickes in

 

[EvilDrPorkChop]

Yep as negative head pumps pressurise the outlet pipework to there pressure rating eg 1.5 bar and asoon as it drops below that eg 1.2 bar the pump kickes in

I guess so, just thought it might confuse issues with the digital box but guess it's only the same as a pressurised system.

 

[Timmy D]

Another vote for negative pump.