Aqua Hot

[Gary Winzenburger]

Because anti-freeze expanse as it gets hot, the pressure of the cap determines when, and how much of it goes into the expansion (overflow) tank. If the cap is rated at 7#, the anti-freeze in the heating chamber (radiator)will leave sooner and at a lower temperature. It will not flow back until it cools down and the cap allows the backflow valve to open from the overflow tank. That's why they make the statement about destroying the heating chamber if you use a lower pressure cap - there's less liquid in the heating chamber at the time when you need it.

[Keith Oliver]

Ed:

Measured in Kpa your 13# cap will no longer be unlucky, at 89.63184464Kpa.

[Edward Buker]

Thanks Orman, they designed the system so I will head for the #13lb cap. Thanks for sharing the info.

Later Ed

[Edward Buker]

Keith, that made me feel better....I'll use Kpa from now on to improve my luck :-)

O.K. I admit to having a high level of curiosity....... So I called tech support at Aqua Hot and asked for the background behind the 13lb cap. It turns out that they used to use a 7lb cap for years but it was much easier to obtain the 15lb cap so that was part of the story. There was also a tech bulletin sent out by engineering citing that there would be an increase in thermal capacity using the 15lb cap given the system would have a higher boiling point. With a 30% antifreeze concentration the boiling point would be approx. 218 degrees F. You add 3lbs for each pound of pressure so for a 7lb cap the boiling point would be 239 degrees. For a 15lb cap the boiling point would be 263 degrees F. The temp cut off limit is 190F for the button thermostat and the safety cut off thermostat in series with that is set to open at 220F. So we are well protected from boil over in either case. Regardless of either pressure cap the inside of the boiler should be fully wetted.

Tech support was not completely sure what engineering had in mind so he is having someone in engineering tell me their tail. Tech support saw no problem and told me to use the 7lb cap. If I get some added news I will pass it along.

The surprise that I got from tech support was regarding how much fluid should one expect to add a month due to normal evaporation. They said it can be as high as 1 to 2 quarts and that would be considered normal. Seems like a lot but you can be in a dry climate and the solution sits at 190F most all the time. Maybe I have no leaks, but I will keep my eyes open.

One last thing, it is easy to pour a 50/50 mix for convenience but a 30/70 mix is actually 10% more efficient in heat transfer. That should translate into hotter water through the tankless coil and less burner run time.


Later Ed

[Larry Fisk]

This year we had the Wabasco motor go out for the diesel burner. I had it checked by an Aqua Hot Tech in Indio, CA and he recommended replacing the motor, noozle, control box, everything as one unit. He said that if he just replaced the motor eventually all the other associated parts would go bad and I would end up having to replace them piece by piece. By replacing it all at the same time Aqua Hot would cover the unit with a 5 year warranty. So almost 4000 dollars later I have a whole new Wabasco unit plus he drained and replaced the float with a brass one and put in new antifreeze. No more problems since this was done. Oh, he also replace the electric element for me.

[George H. Wall]

Ed, In the 30/70 mix is the antifreeze the 30%??  

[Edward Buker]

George,

The 30% to 50% antifreeze solution is what Aqua Hot recommends. It needs to have enough antifreeze to protect the system from freezing while being stored. I live in the south and a 30% solution will protect down to about 0 degrees F which is fine for me but not everyone. If you do go to a 30% solution you need to use distilled water. The third chart in this article from Hella is a good one.

http://hellafunctional.com/?p=629

It basically boils down to the fact that water is much more efficient at absorbing and transferring heat then antifreeze is. With the cost of diesel fuel you should run your concentration no higher than you need to in order protect your system. While the burner is running, the more efficiently you can extract the heat the shorter the run time will be to get to temp. This is the reason that race cars do not use antifreeze, mostly water with a wetting agent. Every little bit helps...in this case maybe 8-10% less run time to get to temp but at the same time we have not done anything to cut the heat loss of the unit just sitting there. These units are not insulated very well but I probably will not go there....

Larry,

Sounds like you will be set for quite awhile. I have had to replace my ignition transformer, the flame detector sensor, and the electronic control unit. There is truth in the fact that these components take a beating in this environment and do fail.

Later Ed

[George H. Wall]

Thanks for the explanation, ED!!