Storage tank / thermometers

[Stumpuh]

Good afternoon, I recently purchased a used stss storage tank with blackened copper hex coils. My question is, does the black coating affect the heat transference and if so ,how can it be removed.
I am also looking for a source for off the shelf submersible thermometers

 

[Hunderliggur]

I do not believe the "coating" (corroision) would have much effect. You are more likly to damage the coil by cleaning it, and then it will oxidze again anyway. I am sure someone (like nofossil) will chime in on submersible sensors, or try a search of the site. There are several threads about monitoring (I am not using submersible sensors).

 

[RobC]

In tank sensors. One way to do it is through a drop tube in the stationary part of the top cover of your tank. If your using the temp for sensors ( pump control for example ) it allows you to adjust the height of the sensor up or down to get a desired effect. Plus you can put multiple sensors in the same drop tube.
When re-piping your coils I remember somewhere that you should cover any exposed copper inside of storage tank with a thin layer of silicone caulk to prevent corrosion above water line. There is a need to PH balance the water in the tank and attention to overheating the tank liner.
I used pressurized storage so I can't tell you all the details that are specific to non pressure tanks, but once you get any type storage online it's great.

 

[Stumpuh]

Thanks for your input on the "corosion". That will step up the installation.
What method do you use to indicate storage tank temps?

 

[RobC]

A "solar controller" will provide you with 2, 3 or 4 temp probes and will function to turn you tank charging pump on and off. The solar controller will look for the differential in water tamps btw the boiler and top and bottom of tank. Also you can use the high temp limit on a solar controller as a tank temp dump for overheat protection for the liner. (This is assuming your building a tank that needs a liner.)
In either case the solar controller will give you the temp readouts wherever you mount the control head.
If you want additional temp readouts search Anzel digital or frothing thermometers.

Have you seen the "sticky" notes on the home page of the boiler room ? There is a bunch of good info contained within. There are many who look at this forum and will add there 2 cents if you post some info. The more specific you can be about your set up the more help can be offered.

 

[in hot water]

As to the black coating.. scratch a small portion and see how thick the coating is. A few thousands is all that is needed to start hampering the ability to conduct heat. The thicker the build up the more heat transfer is decreased.

An example would be an electric water heater element. Once they get a thick layer of scale they tend to be less effective, they take longer to recover the temperature, and eventually burn out.

The hotter the water is in the tank the more minerals come out of solution and attract to the copper coils. I'd fill the tank with softened water, if possible.

Most hydronic inhibitors include a film provider. With new or bare metal a very thin protective coating will prevent the metals from being attacked by the fluid, especially with less than perfect ph levels.

If your coil has a thin layer, like someone rubbed chalk on it, let it be. If it has a build up the thickness of paper or more I would clean it off and start with good quality water when you refill the tank.

hr

 

[tom in maine]

Copper heat exchangers in a normal tank situation will get a thin layer of corrosion (or more accurately--tarnish) that is the surface coating that allows copper to last so long.
One issue with EPDM lined tanks is that the EPDM does slowly start to break down, especially in higher temp situations like wood boiler installations. The normal tarnish coating should rub off some black or dark bronze color on your finger and should appear to be very thin.
EPDM as it breaks down will cause a more tarry coating on the copper. I would not mess with it unless it is significantly thick as mentioned earlier.