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BANGKOK 26 June 2019 17:20
Yellowtail

Another Pump Cycling Issue

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Have good municipal water supply that feeds the ground floor tank.

 

Mitsubishi pump pumps water from ground floor tank to roof tank. 

 

Float valves in both the ground floor and roof tanks control the water levels.

 

The issue is that when the roof tank is full, the ground floor pump shuts off and on for almost an hour until the float valve settles down and flow stops completely. It looks like it used to have an electric control, but is in not operational and (apparently) incomplete.

 

The problem is that I do not want to get on the roof to repair or replace the electric control. 

 

The plan is to install an on-delay relay and contactor to control the pump such that it (the pump) will only come on once an hour. 

 

Anyone think of a reason this would not work or why it might be a bad idea?

 

 

 

 

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1 hour ago, Yellowtail said:

The problem is that I do not want to get on the roof to repair or replace the electric control. 

Why not?  Approx cost 400 Baht.

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OP, get the guys from the local pump shop, they will work out the solution, get up on the roof etc, all for a couple of hundred baht. 

It sound like either adjustments to the float or the pump.

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A pump delay timer would work if the demand from roof tank will allow it. I would add override switch to the timer and start with 30 minutes then increase if required. This will only work if the pressure switch never cuts the pump when ball valve is fully open.

 

Another method would be adding additional pressure storage at the pump to increase time between cycles as ball valve closes.

 

Constant pressure control is another method but not straightforward modification on a regular house pump.

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10 hours ago, Fruit Trader said:

A pump delay timer would work if the demand from roof tank will allow it. I would add override switch to the timer and start with 30 minutes then increase if required. This will only work if the pressure switch never cuts the pump when ball valve is fully open.

 

Another method would be adding additional pressure storage at the pump to increase time between cycles as ball valve closes.

 

Constant pressure control is another method but not straightforward modification on a regular house pump.

3

 

The roof tank lasts us two days, so that should not be an issue.

 

I did plan to add an override.

 

Not sure what you mean by: "This will only work if the pressure switch never cuts the pump when ball valve is fully open."

 

There is no pressurized storage now, beyond what is in the pipe from the pump to the tank. I'm not clear how adding a pressure tank would help, unless it had an air bladder of some kind.

 

I think constant pressure might be cost prohibitive. 

 

Thanks for the help.

 

 

 

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13 hours ago, Peterw42 said:

OP, get the guys from the local pump shop, they will work out the solution, get up on the roof etc, all for a couple of hundred baht. 

It sound like either adjustments to the float or the pump.

Thanks, but I've had three guys out, one said nothing was wrong, one said I needed to repipe (still waiting for the quote) and the last said I need an electrician.

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19 minutes ago, Yellowtail said:

Not sure what you mean by: "This will only work if the pressure switch never cuts the pump when ball valve is fully open."

I assume the timer will prevent the pump from starting again after the pressure switch stops the pump. It would be undesirable if this happened before the tank filled to the start of ball valve closing.

 

19 minutes ago, Yellowtail said:

There is no pressurized storage now, beyond what is in the pipe from the pump to the tank. I'm not clear how adding a pressure tank would help, unless it had an air bladder of some kind.

So you are running a pump and pressure switch without any pressure vessel. By adding additional pressure storage like a 20L bladder tank, the pump would cycle less as ball valve started to close.

 

You do not say what kind of pump arrangement you are using to send water to a roof above five floors.

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18 hours ago, Fruit Trader said:

I assume the timer will prevent the pump from starting again after the pressure switch stops the pump. It would be undesirable if this happened before the tank filled to the start of ball valve closing.

 

Almost. The timer will prevent the pump from starting for a period after the pressure switch comes back on.

 

18 hours ago, Fruit Trader said:

So you are running a pump and pressure switch without any pressure vessel. By adding additional pressure storage like a 20L bladder tank, the pump would cycle less as ball valve started to close.

 

You do not say what kind of pump arrangement you are using to send water to a roof above five floors.

1

That is correct, although I assume the pump has an integral pressure vessel. 

 

The bladder tank would be full of air, correct? I can see how that could work. I think I can try this with a length of pipe.

 

The pump is a Mitsu EP-355Q5, and it will pump 750l to the roof in 20-30 minutes. The WP type might be better given it has a bladder but the EP is less than 2 years old and I would rather not replace it. Long term I want to do a full repipe.

 

 

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1 hour ago, Yellowtail said:

The pump is a Mitsu EP-355Q5, and it will pump 750l to the roof in 20-30 minutes. The WP type might be better given it has a bladder but the EP is less than 2 years old and I would rather not replace it. Long term I want to do a full repipe.

The EP has an integrated pressure vessel with a bladder. The WP series has no bladder, it sits on the pressure vessel and needs bleeding occasionally. The EP is designed for things like an instant hot water shower  

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3 minutes ago, sometimewoodworker said:

The EP has an integrated pressure vessel with a bladder. The WP series has no bladder, it sits on the pressure vessel and needs bleeding occasionally. The EP is designed for things like an instant hot water shower  

But the WP would have a much greater volume of air to compress than the EP, yes?

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I may be missing something here, but why have a roof tank? why not just connect the pump to the outlet from the roof tank, your still pumping the same volume of water.

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2 minutes ago, CGW said:

I may be missing something here, but why have a roof tank? why not just connect the pump to the outlet from the roof tank, your still pumping the same volume of water.

A bigger reserve of water and we still have water in the event the power or pump goes out.

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Posted (edited)
34 minutes ago, CGW said:

I may be missing something here, but why have a roof tank? 

Yes you are. There a often power cuts sometimes several hours long with a roof tank you can still have a shower or use the toilets and wash up any time. The water can also be cut from time to time so with 7,500 litres at low level and 1,000 in the roof we would be OK for a couple of months (one water cut was about 5 weeks)

 

Though with my system I have a small cheap pump that fills the high level tank if the village water pressure is too low. Then I have a pump in the roof to pressurise the water system.

 

if you have a constant power and water supply things are different but TIT.

Edited by sometimewoodworker

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2 hours ago, Yellowtail said:

The pump is a Mitsu EP-355Q5, and it will pump 750l to the roof in 20-30 minutes. The WP type might be better given it has a bladder but the EP is less than 2 years old and I would rather not replace it. Long term I want to do a full repipe.

The EP-355Q5 series is in the compact range which is likely to include flow and pressure control.

 

If fitted, the electronic module has a reed switch flow sensor along with input from the pressure switch. You will need to decide the best place to introduce time delay as the module will be looking for flow when pressure switch calls the pump on.

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