Water Flow Meter

Does anyone know where to get a water flow meter that will close or open a switch when water is flowing? I have an AC unit that uses water to cool itself and it produces 110 deg water if you reduce the flow enough. I'm trying to build a setup that will switch between the on demand hot water heater and the AC unit for the house. The major difficulty is determining if there is water flow to the hot water lines in the hosue..

Thanks,

Mike

Reply to
Michael Kennedy
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At work we had a problem in finding a reliable way to detect water flow. The mechanical types just get eaten up or jammed over time. The electronic ones could not stand the environment it was subjected to (High irradiation). So we set forth and designed a basic 2 probe sensor in a gutted ball value to be used as the body.. shielded the probes back to a safe environment where we use a osc circuit through the probes in to a balanced system. when the waters moves a shift is created in the signal.. etc..

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Reply to
Jamie

Ooh, that sounds like a *good* move... (If you want to damage the HVAC unit, that is!) I'd make sure that reduced flow is within the manufacturer's ratings, before going any further.

There are switches that do just what you describe. Used in industrial applications frequently for both similar reasons, or for safety shutoffs when flow fails for some reason.

Many are simple vane or moving ball magnetic reed switches. You could build one if you wanted with some simple parts. Not sure you'd really want to however.

Reply to
PeterD

Jacuzzi heater safety switch is a NO switch that closes when water flows (i.e. pump is on and working.)

Reply to
Smitty Two

Thanks! I'll look into that. This may be exactly what I need. For use with hot water, and flow switch.

Mike

Reply to
Michael Kennedy

My (very typical) automatic shower pump has a flow operated switch in both the hot and cold sides, to start it up as soon as water flows as a result of opening the water valve. It's based on a small magnet that moves up against gravity in the water flow, and closes a reed switch. When the valve is shut and water flow ceases, it sinks back down, and the reed switch opens. If you know any plumbers, they're sure to have an old pump that they have changed lying around, that you could cull the switch assembly from.

Arfa

Reply to
Arfa Daily

Hmm.. Automatic Shower pump? What exactly is that? I'm not sure we have that here in the USA. Could you describe a little more? Even if we don't have them I could build one eaisly enough with a hdd magnet and a checkvalve and a gutted relay. Just don't know how reliable it would be. Thanks Arfa!

Mike

Reply to
Michael Kennedy

OK. Stored hot water system in house (common). Header tank located on low platform in roof space. Low pressure cold supply for basin / bath feeds derived from same header tank. Shower room upstairs. Shower head only 3 feet below header tank. Result ? Not a lot of pressure at the shower head - certainly not enough to run a fancy 'power' or 'massager' head. Solution ? An automatic shower pump. Take a look here for a picture

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It is a twin impeller pump that is 'broken into' the hot and cold feed pipes to the shower. As long as the shower is off, it just sits there dormant. However, as soon as you turn on the shower valve, water starts to flow through the impeller housings, and up through the reed switch assemblies on both sides. This switches the power to the pump motor via the (presettable) speed control circuit. The pump raises the low feed pressure to over 20 psi. Result ? A nice powerful hot and cold feed to your shower valve, allowing you to have just about any type of shower head fitted, that you like.

I have a dead one here. Not sure how easy it would be to canibalise, but might be able to fix you up with the switch unit from one side. It is very sensitive, and in all the years I've used these pumps, the system has been very reliable.

Arfa

Reply to
Arfa Daily

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I've not come across those devices. Do you happen to know what the resolution is between no flow and minimum recognisable flow. ? That is one problem with ultrasonic Doppler shift flow sensor systems.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook

I couldn't put you a figure on it, but turning the shower valve just a quarter of a turn out of perhaps 3 turns available, equating to just about a dribble of water from the shower head, is enough to activate it - I just went and checked for you, how dedicated is that ??!! :-)

Very reliable system. Never fails to activate the pump. This shower is used every day of the year by at least 2 people, and often as many as 5 people. I am on my third pump in about 20 years. First (cheapo) one developed a motor fault after doing stirling service as the kids grew up. Second one just wore out its bearings, and became very noisy. Current one is heavy duty version, rated for 'continuous' use, and has been in service probably about 5 years. If you know any plumbers, I'm sure that they would have an old one lying around the yard somewhere. All the ones I have owned / seen, employ the reed switch method to control them.

Arfa

Reply to
Arfa Daily

: :Hmm.. Automatic Shower pump? What exactly is that? I'm not sure we have that :here in the USA. Could you describe a little more? Even if we don't have :them I could build one eaisly enough with a hdd magnet and a checkvalve and :a gutted relay. Just don't know how reliable it would be. :Thanks Arfa! : :Mike :

There are a number of flow switches available but only those made of plastics (Noryl) would be considered inexpensive. Gentech International make several inexpensive (approx $50 per one) including the FS-01 and FS-02.

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Farnell, a UK parts distributor, is represented by Newark in the USA

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If you type "gentech international" (without quotes) into the search box you will get a complete listing including the FS-01 nad FS-02.

Reply to
Ross Herbert

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