Ratio of Propylene Glycol to Water?

[tdiaz]

... I'm filling the sump with distilled water, and got a gallon of the RV antifreeze, so it's got dowfrost, propylene glycol and something else in it. I don't want stuff to grow in the water system.

I've got a 20 gallon sump with submerged pump, the water flow detector on the output end and the end of the tube submerged so that no bubbles have to be pushed out of the laser tube once it's free of them.

[zax15uk]

It is the 'something else' that would concern me.

I have used HydrX™ anti-fungal additive and PC-ICE non-conductive coolant with no ill effects. They are used in PC/CPU/Memory cooler applications, but probably not economical with your setup.

If you use the RV coolant, I would not use more than a 1 in 5 ratio and probably more like 1 in 20.

Do you have a coolant temp and flow interlock and/or alarm? (worth the investment)

Zax.

[DaveDoesIT]

Question:
Why are you using anti-freeze? If the water is getting that hot then you need a heat exchanger to cool the water as it circulates.

If it is to prevent freezing then your electronics are not going to like being that cold and it is risky using a glass laser at very low temps.

I use deionized water and a 5 gallon bucket for a 50W glass laser. As Zac says, flow and temp switches are essential.

To answer your question the anti-freeze aspect of Ethylene Glycol (EG) is at it's maximum at around 50-50 water to EG. With more EG than water the freezing point rises (gets warmer) rapidly.

[tdiaz]

The reason for the antifreeze is just something to keep crap from growing in the water.

The cooling is a 24 gallon sump that will eventually become a chiller system, but right now thats all I have, need to get ahead on things.

It's Propylene Glycol, Water, Dowfrost RVR and "proprietary rust and corrosion inhibitors".

[DaveDoesIT]

The reason for the antifreeze is just something to keep crap from growing in the water.

If you keep the thing clean and the water in the dark, nothing can grow. As I said I use deionized water from the supermarket about 5-bucks for 5 gallons. I have been messing with glass lasers for 10+ years and have yet to have anything "grow." You can see on of mine on Sam's Laser FAQ section on CO2 lasers. That was probably about 7 years back. I use black tubing and a lid on the bucket with a submersible pump. No Uv, no growth even if there was anything in the water. It will not hurt putting stuff in there I just don't see the need for it. Don't rush into chillers they will bring on a whole new dimension of problems. Dew points and condensation being the first PITA. On one of my lasers I used an old transmission cooler from the motor wreckers and a 10" fan. I rarely got more than a 10-deg rise in water temps.

[tdiaz]

On one of my lasers I used an old transmission cooler from the motor wreckers and a 10" fan. I rarely got more than a 10-deg rise in water temps.

Thats probably where I'm headed anyway, it just seems simpler. It's distilled water by the case from Wally World..

.. I just need to see why it's not firing at full power now. "new" tube and power supply, and I can still tease it with paper and as long as I keep moving the paper does not even scorch. It should just go "poof!" ..

It's in a black bucket, with clear sections of tubing as I want to see bubbles and flow due to paranoia. Hell, I even asked for a water flow switch to be sent with the stuff.. I installed it, it says the min. flow rate is .5 GPH, I fill a 3 litre bottle in 45 seconds, the thing won't trip. Stupid switch.

[DaveDoesIT]

I installed it, it says the min. flow rate is .5 GPH, I fill a 3 litre bottle in 45 seconds, the thing won't trip. Stupid switch.

You need to go for an absolute switch not a flow rate. No flow, no power. Same for the temp.

If you are in the US, start here...
http://www.omega.com/green/flow-level.html

Dave

[tdiaz]

It is an absolute switch, it just takes more than .5 GPH worth of flow to get it to close the circuit. So it will shut down if flow drops but before it totally stops unless the stoppage is instant, it would then happen at the same time.

I do need to get a temperature switch too, and just hook it inline with the water flow. Though with 24 gallons it will be quite a while before the water temperature rises enough.

[DaveDoesIT]

OK, got it. I thought you meant you had a flow-range monitor that you could set to cut off at a certain flow.

The ones I use are "Gems" model FS-3. I don't know what rate they shut off at but it is pretty low. I can't remember where I got them but I seem to recall they were only 20-bucks or less.

here ya go...
http://www.gemssensors.com/content.aspx?id=1112

Minimum flow rate 0.05 gpm.

Dave