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Old 12-28-14, 02:11 PM   #301
buffalobillpatrick
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I am not using the paddle wheel flow sensors, as I felt that they are trouble prone.
I'm using the analog pressure sensors that I referenced in post #232 above on both Source & Load water pumps.


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Old 12-28-14, 06:54 PM   #302
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Quote:
Originally Posted by buffalobillpatrick View Post
I am not using the paddle wheel flow sensors, as I felt that they are trouble prone.
I'm using the analog pressure sensors that I referenced in post #232 above on both Source & Load water pumps.
I think this is a great idea. No moving parts.

Unless you need to do calculations that require precise flow measurement, like precise COP, knowing exact flow rate just isn't needed.

I suppose you could get an approximate measure through some testing and determine how pressure relates to flow in your system.

The programming for pressure sensors should be much easier, too.

Best,

-AC
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Old 12-28-14, 08:00 PM   #303
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Quote:
Originally Posted by buffalobillpatrick View Post
One of these on pipe at pump output:

30PSI Pressure Transducer or Sender for Oil Fuel Diesel Gas Water Air | eBay


Take pressure reading with pump off, turn on pump, take a 2nd pressure reading, calculate Delta, calibrate with good known flow.
That's a fuel pressure sensor! For what kind of vehicle might I ask? I bet you could find one of those bad boys at autozone for 8.99 if you knew what kind of car it went in. Ingenious.

I must have been working nonstop that month, I'm still playing catch-up today.

EDIT: OK, I'm caught up now. And here come the questions:

So for the water-source variant, the analog fuel pressure type sensor will be used for proving coolant flow downstream of the heat exchanger, yes? To me, this means an interrupt will not be needed to count flow pulses, which will greatly simplify debugging. A simple periodic sampling can be done instead, which can be used during the start-up routine to determine a baseline setting while the compressor is locked out.

Another detail comes to mind: do you still want temperature sensors in the same places as these pressure sensors also? And in other places also? Sounds like a lot of analog pins.

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Old 12-29-14, 10:01 AM   #304
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No interrupt needed.

I measure 6 temperatures around the HP refrigerant loop:
1. Compressor Out / Condenser In
2. Condenser Out / IHX Hi Side In
3. IHX Hi Side Out / TXV In
4. TXV Out / Evaporator In
5. Evaporator Out / IHX Lo Side In
6. IHX Lo Side Out / Suction Line to Compressor

I also measure 4x water temps. Source In & Out, Load In & Out

Analog 0-5vdc pressure sensor on output pipe from water pump.
Code Steps:
1. With pump off, measure static OFF pressure.
2. turn on pump, wait X seconds, measure ON pressure.
3. The pressure delta between these 2 readings represents the plumbing back-pressure (head) that your water pump & plumbing stabilize at.

1 psi = 2.31 feet of head

This delta pressure won't vary unless pump stops working or a blockage condition.

My code, which I don't have access to on Holiday road trip, verifies that the pressure delta stays +- 10% for each water pump.

This is a Go/Nogo test, actual water flow is unknown, so COP can't be determined.

Last edited by buffalobillpatrick; 12-29-14 at 10:40 AM..
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Old 12-29-14, 11:05 AM   #305
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16 analog sensors can be read via the 16 channel Mux chips that I have been using, but I have had one of them go bad. So I got a couple of Arduino Mega's to play with.
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Old 12-29-14, 04:01 PM   #306
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Quote:
Originally Posted by buffalobillpatrick View Post
No interrupt needed.

I measure 6 temperatures around the HP refrigerant loop:
1. Compressor Out / Condenser In
2. Condenser Out / IHX Hi Side In
3. IHX Hi Side Out / TXV In
4. TXV Out / Evaporator In
5. Evaporator Out / IHX Lo Side In
6. IHX Lo Side Out / Suction Line to Compressor

I also measure 4x water temps. Source In & Out, Load In & Out

Analog 0-5vdc pressure sensor on output pipe from water pump.
Code Steps:
1. With pump off, measure static OFF pressure.
2. turn on pump, wait X seconds, measure ON pressure.
3. The pressure delta between these 2 readings represents the plumbing back-pressure (head) that your water pump & plumbing stabilize at.

1 psi = 2.31 feet of head

This delta pressure won't vary unless pump stops working or a blockage condition.

My code, which I don't have access to on Holiday road trip, verifies that the pressure delta stays +- 10% for each water pump.

This is a Go/Nogo test, actual water flow is unknown, so COP can't be determined.
BBP,

I'm curious why you want all the temp sensors? Seems like maybe 1 or 2 would cover most hazard situations. Are the rest for general data logging?

Also, it seems to me, regarding pressure sensors, that after the 'time period' the system should shut down to avoid damaging the circ pumps.

However, there needs to be some kind of over-ride provided through software or hardware, so that troubleshooting can be performed.

-AC
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Old 12-29-14, 07:10 PM   #307
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The 6 refrigerant sensors mostly are for my curiosity, I want to adjust Superheat via TXV measured after Lo side IHX to about 30*C and measure Sub-cooling.

I will have standard high & low pressure cut-out switches.

A/C Sure, shut down if water pump is not working as expected.

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Old 12-30-14, 03:16 AM   #308
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Default flow sensor

I'm using a flow sensor for one year now in my heatpump. It was running end of last winter, for one month during summer (for cooling). Was stopped for monthes. It was running from mid October, without any problems.

Suddenly it stopped to send out pulses a month ago. I tought, that's all...
I decided to unmount it out of curiosity, to see what went wrong. I found a small stone approx. 8mm jammed the padles. I don't know where it come from. Material is like chalk. Othervise the sensor looks like new. After reinstallation, sensor works flawlessly. If it happens again, I will install some rough filter to pipes.

To be ontopic. For me, the flow information is a must to be able to calculate heating power. It's mandatory to finetune the HP to maximum efficiency or to find problems. I have some nice graphs and conclusions to come...
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Old 12-30-14, 10:52 AM   #309
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Actually, flow can be approximated closely using a pump flow/head performance chart and your measured output pressure reading.

Many common pumps like Grundfos, Taco, etc. provide these charts.
1psi = 2.31' of head

Find your measured pressure on the pump curve & read flow on X axis.

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Old 01-05-15, 10:51 AM   #310
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I just figured out how determine Flow for a Taco 008 pump from Head pressure in 12 lines of Arduino Code.

Uses an array & Interpolates between elements for higher accuracy.

I will post code after I have access to my computer back in Colorado.


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