Low voltage switching of a pump, on a countdown

AI Thread Summary
A new member discusses frustrations with a malfunctioning hot water recirculating pump that relies on low voltage switching. The pump activates when hot water movement is detected but has electronic failures, prompting the need for a DIY solution. The suggested solution involves using a timer relay to control the pump's 110V power, ensuring it runs for two minutes after activation. The discussion emphasizes the importance of safety and the need for a licensed electrician for installation. The member expresses some familiarity with electrical work but seeks guidance on sourcing the necessary components.
AztecDIY
Messages
2
Reaction score
0
New member here. This might be the coolest subject for a forum I've seen in awhile (that probably sounds like robot spam). On to business...

I have been scr*wed by a succession of people over our home's improperly plumbed hot water. It takes forever to get hot water to the faucets. I bought a product to fix that. It uses a valve plumbed into the water heater outgoing line to detect movement of hot water, and it then switches on a recirculating pump to push water around the circuit (so turn water on/off, wait a minute, poof, hot water is there). The pump shuts off after 2 minutes. Of course, the electronics soon failed. The company owner is a nightmare, so I am on my own.

The valve mentioned above has two low voltage wires that complete a circuit when the hot water moves. I want to replicate what the product did, by taking those two wires and connecting them to... something... that will switch power to the pump on (it's 110v) when the circuit is complete, and keep it on for 2 minutes.

Thanks in advance for any ideas!
 
Engineering news on Phys.org
110Volts can kill. You need a licensed electrician to install it.

What you need is a timer relay:
http://en.wikipedia.org/wiki/Relay
http://www.allaboutcircuits.com/vol_4/chpt_5/3.html
Presumably of the NOTO type

Your local electrical store will probably have some in stock. They are used to delay bathroom extractor fans to stay on after the light is switched off among other things. If you shop around on the internet you could find cheaper ones. There are over 1300 timer relays ranging from $16 to $2.5k USD here:

http://www.digikey.com/product-search/en/relays/time-delay-relays/1049305
 
Last edited by a moderator:
billy_joule said:
110Volts can kill. You need a licensed electrician to install it.

What you need is a timer relay:
http://en.wikipedia.org/wiki/Relay
http://www.allaboutcircuits.com/vol_4/chpt_5/3.html
Presumably of the NOTO type

Your local electrical store will probably have some in stock. They are used to delay bathroom extractor fans to stay on after the light is switched off among other things. If you shop around on the internet you could find cheaper ones. There are over 1300 timer relays ranging from $16 to $2.5k USD here:

http://www.digikey.com/product-search/en/relays/time-delay-relays/1049305

Thanks. I've done a lot of electrical work, just none of this type -- I get the dangers for sure.

The NOTO makes sense. I'm not even sure there's an electrical store around. Everyone seems to source at Home Depot now. :-(
 
Last edited by a moderator:
I used to be an HVAC technician. One time I had a service call in which there was no power to the thermostat. The thermostat did not have power because the fuse in the air handler was blown. The fuse in the air handler was blown because there was a low voltage short. The rubber coating on one of the thermostat wires was chewed off by a rodent. The exposed metal in the thermostat wire was touching the metal cabinet of the air handler. This was a low voltage short. This low voltage...
Thread 'How Does Jaguar's 1980s V12 Dual Coil Ignition System Enhance Spark Strength?'
I have come across a dual coil ignition system as used by Jaguar on their V12 in the 1980's. It uses two ignition coils with their primary windings wired in parallel. The primary coil has its secondary winding wired to the distributor and then to the spark plugs as is standard practice. However, the auxiliary coil has it secondary winding output sealed off. The purpose of the system was to provide a stronger spark to the plugs, always a difficult task with the very short dwell time of a...
Back
Top