Automatic boiler shutdown upon loss of cooling water

[Cardinalbags]

I've been lucky enough to come across a flow switch that has two alarms and relayed switchpoints. The alarms can be configured based on decreasing or increasing flow rate, decreasing or increasing temperature, or used as contact indication mode for low level or high level. The flow meter's range of measurement is 0.0009 to 3.0 litres per minute.

I am only using one of the alarm set points on flow mode and tied the instrument head into my cooling water supply line to the still. I calibrated the flow meter by backing off my cooling water until I could see vapor just starting to escape from the top of the condenser and then increased the flow again. I dialed in the flow meter to set the low flow cut out point to be at this slightly higher flow rate.

Then I tied in the power to the boiler to the relay contacts of the flow meter. If the low flow alarm gets tripped, then so does the power to the boiler. The power for the boiler is fed off of the flow switch.

I did all of this because on two occasions I have lost cooling water. The first time, i was running the still at the same time as my wife was running load after load of laundry and we emptied the well. That is what prompted me to tie into my 1000 gallon underground cistern (I recycle the discharge water back to the tank so net 0 litres of water down the drain.) The second time I lost cooling water is due to the pump from the cistern losing power due to its GFI plug tripping. That pump is outside and 100 feet away from where I am running the still run powered up using an extension cord off of an outside GFI plug for the house. Fortunately I was there at the still both times and could take immediate action.

I have read about some folks leaving their stills unattended only checking on it every half hour or so as they did yard work or puttered around the garage etc. Based on my above experience, I would not recommend anyone do this unless they have a very robust safety system and automated shutdown setup.

My next step is to wire in a new dedicated GFI circuit for powering up the boiler, flow switch and cooling water pump all on the same circuit.

[ErnieV]

Sounds like a great safety system, but it would need to have a gas valve included for me, I boil with propane bottle

[Cardinalbags]

Yep. A 1/4 turn solenoid valve would do the trick. It would have to be spring loaded to fail closed on loss of electrical power to be failsafe.

[bellybuster]

I have a solonoid gas valve that I picked up for my brew rig,pretty sure it is fail safe closed

Cool safety system

[Prairiepiss]

My next step is to wire in a new dedicated GFI circuit for powering up the boiler, flow switch and cooling water pump all on the same circuit.

I would put them on separate circuits. If the pump trips a common GFCI circuit. You would lose everything. Making the shutdown system null and void.

[Maritimer]

Hi Cardinalbags,

Do you know the name and part number of the flow switch?

M

[Cardinalbags]

It is a Fluid Components International model FLT93L. This is an industrial version housed in an explosion proof casing. There may be other models out there that would be fairly economical.

The contacts are only rated for 7 amps at 115/120V i.e. good for up to 700ish watts of power. If your electrical boiler is much more higher powered than that, then should be using another higher rated relay for the boiler power line.

[Cardinalbags]

My next step is to wire in a new dedicated GFI circuit for powering up the boiler, flow switch and cooling water pump all on the same circuit.

I would put them on separate circuits. If the pump trips a common GFCI circuit. You would lose everything. Making the shutdown system null and void.

While your statement is true, I purposely plan to do this as then I have double redundancy in the system. While a loss of power will shutdown everything immediately, there is still a scenario where the power to the pump is not lost, but still a loss of cooling water due to a hose break or loss of suction to the pump etc. That is where the true value of the flow switch comes into play.

For propane fired systems, a flow switch would be the only way to shutdown the propane and it should be on own circuit separate from the pump circuit, unless the solenoid valve is definitely fail close upon loss of signal.

[Maritimer]

Hi Cbags,

That flow switch must cost a bundle. When I Google it, I get lots of places selling it, but nobody has a price.
I see that you can get a flow switch for about $50 from McMaster-Carr.

M

[Cardinalbags]

Hi Cbags,

That flow switch must cost a bundle. When I Google it, I get lots of places selling it, but nobody has a price.
I see that you can get a flow switch for about $50 from McMaster-Carr.

M

Probably would cost a bundle. I was lucky to be able to trade/barter for it with some old junk that that I no longer considered valuable. As they say, one mans junk is worth a cool flow switch to some other man.....

The McMaster Carr ones would probably work fine. You would have to pick one with a low flow preset, say the 0.1 gpm model which works out to 378 ml/minute. They are all low amp models so would have to be used with a relay for most applications.