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Csaba


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Hi. I'm new to this forum and most things electrical, so apologies at the outset if any of the issues raised sound a little stupid ...

I'm busy with a garage project. I have a 12v 102Ah deep cycle battery feeding into a Victron BlueSolar charge controller (MPPT 75 l 15) then into a Shureflo 12V water pump through a Rhomberg 30amp power relay. The water is pumped to a Speedheat 3,5KW electric shower head. Although I haven't connected it as yet, I also have an Enersol 260W solar panel feeding into the charge controller.

The issue that I'm experiencing is that the once I fire up the circuit the pump fills up the PVC pipes with water (from a sump) leading to the showerhead - the power relay starts to click away continuously opening and closing the circuit .... The pump capacity (45PSI at free flow) and the showerhead pressure (min 50kPa - max 800kPa) appear to compatible. If I then replace the showerhead with a free flow shower head, the system runs smoothly and the relay operates as expected - switches on and stays on.

What is causing the relay to run intemittently? Is it power related; is it pressuring related even though the pump capacity and the showerhead pressure are compatible?; is it a wiring related or is there something else I should be looking at? Dr Google solves many of my problems but he has let me down on this one. I really would appreciate a simple dumbed-down response advising what to check, adjust, change, etc.

Many thanks.

 

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25 minutes ago, Csaba said:

Hi. I'm new to this forum and most things electrical, so apologies at the outset if any of the issues raised sound a little stupid ...

I'm busy with a garage project. I have a 12v 102Ah deep cycle battery feeding into a Victron BlueSolar charge controller (MPPT 75 l 15) then into a Shureflo 12V water pump through a Rhomberg 30amp power relay. The water is pumped to a Speedheat 3,5KW electric shower head. Although I haven't connected it as yet, I also have an Enersol 260W solar panel feeding into the charge controller.

The issue that I'm experiencing is that the once I fire up the circuit the pump fills up the PVC pipes with water (from a sump) leading to the showerhead - the power relay starts to click away continuously opening and closing the circuit .... The pump capacity (45PSI at free flow) and the showerhead pressure (min 50kPa - max 800kPa) appear to compatible. If I then replace the showerhead with a free flow shower head, the system runs smoothly and the relay operates as expected - switches on and stays on.

What is causing the relay to run intemittently? Is it power related; is it pressuring related even though the pump capacity and the showerhead pressure are compatible?; is it a wiring related or is there something else I should be looking at? Dr Google solves many of my problems but he has let me down on this one. I really would appreciate a simple dumbed-down response advising what to check, adjust, change, etc.

Many thanks.

 

Hi Csaba, could you describe the relay circuit? Is it only a relay or a pressure relay?

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It appears that relay comes with a range of coils variations.

I am suspicious you may have a 12Vac version instead of a 12Vdc version, unusually there is actually a 12Vac version of this relay..

Especially seeing as you have named AC as a suffix for your model.

I cant really think offhand, where you'd get hold of 12 Vac to prove it. There are things but I can't think of something you wouldn't have to get quite  intrusive to get at.

Maybe test the lower voltage taps of an ac welder with a voltmeter if you have one handy?

If it turns out to be an AC coil, or even if you have no way of testing.

If you can take the cover of the relay and fashion a solid copper ring around the outside the coil with as thick copper as will fit.

Don't disturb the original coil it must still be insulated from the original coil.

Just one turn soldering the ends together. You might be able to make it a work for a DC voltage. I have never done it, but its theoretically possible.

Make a generous continuous solid electrical circuit around the AC coil, its called a shading coil and is the difference between an AC core and a DC core.

This is real old school MacGyver stuff, but no harm in trying if its not working anyway, let us know how you get on.

 

Edited by phil.g00
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I think actually I may have what I said above about a shading coil arseways,  it is an AC core that needs a shading coil. Its along time ago since I messed with these things.

You could damage an AC core with DC, because there is no steady state inductance to limit the current through the coil.

Still worth checking the voltage rating of the relay's coil though.

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1 hour ago, phil.g00 said:

You could damage an AC core with DC, because there is no steady state inductance to limit the current through the coil.

Right. The typical place where you see this is 24V irrigation valves. They inductance in the coil adds extra resistance, so they show a much higher impedance at the 24VAC they are designed for than at 24VDC. You can actually damage them with DC.

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Thanks for the input gents, even though the discussion is now a little above my pay grade... 

Interestingly, whilst the cover of the relay has 30A-AC imprinted on it, the covering over the coil has 'DC12V'. Not sure if the two descriptors are related. It does seem like a DC relay ...

To my original question though, could you please explain what would cause the relay to clatter away once the citcuit is fired up?

I am also considering bypassing the relay altogether as I'm not sure why it was installed in the first place. Would this be advisable, or not? 

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12 minutes ago, Csaba said:

To my original question though, could you please explain what would cause the relay to clatter away once the citcuit is fired up?

It's really hard to know without a circuit diagram... but it could be that once the relay closes, and the load (whatever that might be) is drawing power, it drops the battery voltage causing the relay to drop out. As soon as the relay opens, the load is off, the battery voltage bounces back and now there is enough juice for the relay, the relay closes again, and the cycle repeats.

Stick a volt meter on the battery and see if there is a fluctuation in line with the chattering of the relay. An even better way is a small incandescent lamp, because the brightness of such a lamp is proportional to the square of the voltage, so it shows dips in voltage in a very clear visual manner.

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27 minutes ago, plonkster said:

It's really hard to know without a circuit diagram... but it could be that once the relay closes, and the load (whatever that might be) is drawing power, it drops the battery voltage causing the relay to drop out. As soon as the relay opens, the load is off, the battery voltage bounces back and now there is enough juice for the relay, the relay closes again, and the cycle repeats.

I like this theory too, it only starts the air is purged and the motor actually starts to work ( draw more current).

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Some feedback ... I fired up the circuit and connected a voltmeter as suggested. I ran it for approx 1 minute and the voltage only fluctuated between 12,29V and 12,3V, no peaks or troughs and virtually no loss of voltage for the duration of operation ... 

As mentioned above, the load is a 12V Shureflo water pump which when the circuit is connected, pumps water from a sump to a pressurised (electric) shower head. If I replace this shower head with an unpressurised free flowing head and fire up the circuit, the relay does not clatter away and the whole system operates uninterrupted ... It therefore appears that if the water pump operates under higher pressure it seems to require more power and this is where the relay starts clattering. Hope this makes sense ... 

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3 minutes ago, Csaba said:

Some feedback ... I fired up the circuit and connected a voltmeter as suggested. I ran it for approx 1 minute and the voltage only fluctuated between 12,29V and 12,3V, no peaks or troughs and virtually no loss of voltage for the duration of operation ... 

As mentioned above, the load is a 12V Shureflo water pump which when the circuit is connected, pumps water from a sump to a pressurised (electric) shower head. If I replace this shower head with an unpressurised free flowing head and fire up the circuit, the relay does not clatter away and the whole system operates uninterrupted ... It therefore appears that if the water pump operates under higher pressure it seems to require more power and this is where the relay starts clattering. Hope this makes sense ... 

Could you measure Voltage in pump?

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49 minutes ago, Javi Martínez said:

. Is It possible feed pump directly from 75/15 "Load"?

Don't know... can't remember the current rating of that contact.

The other obvious test to do: Put the Multimeter on the coil side of the relay. Does the relay switch off because it gets too little voltage (ie voltage sag as per my previous theory), or does it switch off because the voltage goes to zero (ie something is switching it off, perhaps the load output on the MPPT, assuming @Javi Martínez's guess of a circuit is correct).

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