Cold weather air blow down/weep

[BayWatch]

For some of you guys that have done this before, please advise me on my current plan. I have Dixmor LED5 timers in each bay. I plan on using the rotary switch output to an off delay timer. The timer would control an air solenoid with lines to the foam brush manifold and HP hose manifold on top of each bay. I would of course have to add fittings and check valves to the manifolds. The current weep system uses a simple thermastat and water solenoid setup. I am thinking of keeping the thermastat setup and removing the wiring from the solenoid and attaching it to another simple relay so that the voltage from the Dixmor timer would only go to the off delay timer when the thermast trips the simple relay (blow down wouldnt run when not freezing). I am thinking of doing it this way so that if only works at a temperature I can set and is activated when the Dixmor timer turns on and then off. The off delay timer would shut off (no air) if the Dixmor timer is reactivated, in case the customer let the time run out and the deposited more money. I think for about $700 in electronics, hose and fittings this could be done if i had to do this setup for each bay (6 off timers, 6 simple relays, etc) or would it also be better to use and 8 input controller, wire each bay into the controller, wire the output to one off delay timer and have the delay timer then blow down all bays at the same time. This setup would be about $200. Any comments are welcomed. Thanks.

 

[cantbreak80]

I suggest you reconsider the air blow-out freeze protection for high pressure hoses. They will freeze in the low point of the bay hose and you will have spent money for a headache. Seriously…unless you use several massive blasts of air from a huge CFM compressor, you’ll never get the water out of the loop in the hose.

But, if you insist on proceeding, your first idea is best. Control each bay individually so that one bay’s usage doesn’t result in needless blow-down for all bays.

Your “all at once plan” may result in freeze-ups. Unused bays waiting for blow-out while one or more bays remain busy may freeze long before the entire car wash becomes idle.

An alternative to blow-out is to inject an anti-freeze solution…windshield washer solution usually works down to moderately cold conditions. This is what I use…although currently for the foam brush system only.

A six bay system would require a small PLC or a Smartrelay with expansion module, solenoid valves for each bay, a Flo-jet pump, check valves, fittings, and a 15 to 30 gallon antifreeze solution tank.

The PLC/SR gets 24vac inputs from a thermostat and the timed outputs from the bay timers. Timers in the PLC/SR program wait for the bay’s timed output to change state, then energize the anti-freeze solenoid for that bay. Another timer in the PLC/SR program controls how long each solenoid remains open. The anti-freeze is delivered to the solenoids via the Flo-jet or similar pump.

My SR program injects antifreeze after 5 minutes of reaching the thermostat’s set point. This prevents injection should the temperature simply “hover” at the set point of 35 degrees. All idle bays are then injected. In-use bays receive their injection immediately after the bay becomes idle.

BTW...A fail safe water weep system should be included for your hp hoses. A normally open solenoid connected to city water and a 120 volt outlet will keep the wash from freezing should you experience a power failure during that cold snap/ice storm.

 

[MEP001]

I already have a PLC system in place that I set up to blow down the bay hose after each use. My plan was to add an antifreeze purge and a second blow-down and not weep water. I already mix windshield washer antifreeze into the foam brush tank the night before a freeze and purge the lines, and I plan to set that up to be automatic too.

I don't think an air blow-down will ever be enough to purge the line completely so that it won't freeze.

 

[Sponge Bob]

I have posted to a similar thread with the same message. I tried this at my 4-2. I engineered what I thought was going to be a simple SS blow down system using an inexpensive Omron programmable relay, some solenoid valves and fittings. I modeled it after my Oasis IBA. I used an Omega digital temperature input for accuracy and a high to low signal from each bay to trigger blowing.
I fought the system from the inception. I solicited the help of a very good control engineer and the system evolved into a complex routine on an AB Micrologix platform where we varied length of blast, duration of blast, delay to blast, time on, time off, overall blast sequence time cycle variable by temperature input and repeat if a bay was not used or blown in a given time. The colder it was the more aggressive the routine became. The system would blow all bays simultaneous if the ambient temp would fall into a blast set-reset window and the bay was not in use. The same routine would be repeated if conditions were met post customer use.
After several freeze ups and many customer complaints, I went back to water weep. I found that I nearly killed my compressor trying to keep the entire place blown down during ideal conditions. I operate in Ohio and we fight constant swings above and below freezing for several months a year.
Not to say that the concept would never work, but it beat me. I found that my 10 hp, 220 3-phase, 2 cylinder 2-stage 30 cfm compressor would work so hard that it heated the air. The heated air would pass thru the cold bay boom and condense in the lines and add to the freezing. I found that a thimble full of condensate in the bottom loop of the bay hose would be sufficient to freeze the bay.
My ultimate failure mode came the day when I was away and the compressor breaker blew from overuse in sub 5 F cold weather. The auto bay entry doors first failed to open from no air, thus halting the touch less wash business. I was selling washes, but not delivering them. It was too cold for regular SS business but a couple of people tried all bays until they finally froze them up. Next the IBA's froze from inactivity and inability to blow down.
If I were to try again, I would select 1 bay and use a dedicated compressor for the development process. I learned that compressed air is a very valuable/expensive utility and water weep is relatively cheap and very robust.

 

[Greg Pack]

I already have a PLC system in place that I set up to blow down the bay hose after each use. My plan was to add an antifreeze purge and a second blow-down and not weep water. I already mix windshield washer antifreeze into the foam brush tank the night before a freeze and purge the lines, and I plan to set that up to be automatic too.

I don't think an air blow-down will ever be enough to purge the line completely so that it won't freeze.

If you could market that for a reasonable price, you would probably have some interest. Water/sewer is 1.5 cents per gallon here, and rising fast.

 

[Robert2181]

It can be done.We have been doig here in Michigan for several years.

 

[MEP001]

If you could market that for a reasonable price, you would probably have some interest.

I think you're right. Someone's already PM'ed me wanting to buy them, but I didn't regard it as serious at the time.

 

[Robert2181]

You can get one direct or from Kleen-Rite