I replied to that other forum re your circuit. It was started by Bob Muir or Peter Muir. Is that you, otaio?
Can you confirm that the timer starts when the reed switch contacts go open, and its intended purpose is to keep the motor off for the period of the timer?
Thank you for your continuing interest. and various suggestions.
Yes the 'user idents' are all me.
I offer the following description of the problem and my solution which may be of interest to the curious and prompt further discussion. (Apologise for referring to flow and pressure switches -- there are only flow switches).
Installation:
A domestic shower is supplied by an electric pump. The pump motor is turned on or off by two flow switches wired in parallel. One flow switch is in the cold feed to the shower head. The other is in the hot feed. The feed pipe work from the pump to the shower head is about 25 feet.
Correct operation:
User turns shower mixing valve on. Gravity induced water flow operates flow switches and turns pump on. User closes mixing valve water flow stops. Flow switch detects no-flow condition and pump motor turns off.
Actual operation:
As above until user closes mixing valve. Water flow stops. Pump stops but then proceeds to cycle on and off approximately three times a second. (Due to travelling pressure waves in the long pipe work. These waves are detected by the flowswitch(es) which momentarily close and open). Turning pump supply off and on cancels cycling and system becomes stable.
Corrective action:
Various mechanical solutions tried but to no avail.
Desired effect of cicuit
When the flow switch(es) open when the mixing valve is closed they are isolated from the control circuit for three seconds. This prevents the pump starting and allows the pressur waves to die. At the end of the period the flow switches are automatically reconnected and the pump becomes available for use once more.
Restraints:
The solution must use the installed flow switches and pump.
Electrical charateristics of plant:
Flow switches are reed switches in with series 470 ohm resistance in a common encapsulation.
Pump motor is a capacitor start and capacitor run.
Operation of circuit
Shower mixing valve opened
Normally open flow switch closes on water flow. Flow switch relay (RL4) energised. Normally open contact RL4/1 closes puts feed onto motor relay (RL3) and trigger relay (RL2). Motor contact RL3/1 closes motor starts. Trigger contact RL2/1 opens.
Shower mixing valve closed
Normally open flow switch opens on water flow stopping. Flow switch relay (RL4) denergises. Normally open contact RL4/1 opens removes feed to motor relay (RL3) and trigger relay (RL2). Motor contact RL3/1 opens motor stops. Trigger contact RL2/1 closes initiates timer. Flowswitch interlock relay (RL1) energises. Contact RL1/1 opens for approximately three seconds. At end of period RL1/1 closes and circuit ready for next operation.
Hi Bob B, your shower problem is allmost bound to be due to trapped air in the pipe run allowing the water to run back and forth. Travelling shock waves would not operated a flow switch as there would be no flow.
Thanks for your observation. The water circuit has been flushed through a number of times without correcting the problem. The unions on the pump been 'broken' and the system bled at this point. This hasn't cured the problem.
I agree you should solve the cause rather than treat the symptom but I have had no success in acheiving a solution this way and the problem is now six months old. So I've opted to treat the symptoms electronically.
That is very kind of you to put yourself to such trouble. Much appreciated.
I don't know how you post to this site. It would be useful to know.
In respect of the EZ site the file size limit is 100,000 bytes. You click the browse button and that attaches the file.
Couple of questions
What type of computer Win or Mac
What is your file format?
What is the scan resolution?
What is the document ie width X" by height Y"
The file is a .bmp, but only 19Kb. I tried as you suggested but the preview did not show the file. I'll try again on EZ. If it comes out as a text description only with no attachment then I'll have to email the drawing to you.
I prototyped it yesterday and it work first time.
An elegant solution which demonstrates what can be achieved when you really know your subject.
Reed switch closes – motor contact closes
Reed switch opens – motor contact opens
Then for a period of approximately seven seconds repeated closing of the reed switch has no effect on the motor contact – exactly as intended.
Thank you again for your support. I will make a donation to charity in your honour.
