ozone control for geothermal dehumidifier

[salty joe]

I am approaching the tail end of a big reef tank build. A main goal is to see how few watts can be used to run this tank. Excess humidity will have to be dealt with. So I built a geothermal dehumidifier and it works! I made 100 feet of 4" x 10" aluminum duct and ran 3 zigzag runs on a 33' uninsulated block wall that is below grade. Then I built an insulated stud wall on the other side of the ductwork. 4" PVC pipe connects the ductwork to the fishroom and the air is moved by a blower. The entire system slopes to a low point where condensate flows down the floor drain.

Unless it's disinfected, the ductwork is sure to become a mold bomb. So I have an ozone generator mounted in the fishroom at the intake of the dehumidifier. The O3 generator has a dedicated receptacle and its' wire is dangling into the basement waiting to be hooked up. There is a Ranco de-humidistat controlling the blower. I need a way to adjustably turn on the O3 generator that also forces the blower to run (override the de humidistat). It would be ideal if the blower ran an additional 30 min or so after the O3 generator turned off. My best guess is that 1-3 minutes of O3 generation a day would do the trick. All this would need to happen at the same time every night. I have an electronic appliance timer (with a battery that saves turn on/off times in case of power outage) if that helps.

If anyone is interested in this and wants to kick it around, I’d appreciate it. The only solution I could come up with is to get a second blower and put it and the O3 generator on an appliance timer. That would not allow me fine O3 adjustment and the second blower would add a lot of resistance, hurting efficiency.
Joe

 

[alec_t]

Hi Joe. Interesting project. Congrats on the successful dehumidifier build. I know you PM'ed some specs for ozone control components to me, but could you post links to them here for other forum members to see?

 

[salty joe]

Thanks Alec, here they are.

https://www.ebay.com/itm/1909413524...eName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

https://www.ebay.com/itm/3510211224...X:IT&_trksid=p3984.m1439.l2649#ht_5109wt_1087

**broken link removed**

**broken link removed**

 

[alec_t]

First thoughts:
1) Appliance-timer set to close S1 contacts for 30 mins at preset time.
2) S1 operates 2-pole relay.
3) Relay poles respectively switch on blower (via Variac) and start ozone-timer.
4) The pole which switches the blower is commoned with the humidistat switch.
5) Ozone timer switches ozone-generator.

 

[alec_t]

Second thoughts. Forget 2-pole relay.
System could be like this:

Here's a suggestion for the ozoniser timer:

 

[salty joe]

Thank you Alec.

Will this trimmer work? I like it because it's easy to fine tune.

https://www.ebay.com/itm/10-x-100K-...ultDomain_0&hash=item3ccab9148e#ht_1360wt_809

How about this 5v coil, is it good for this project?

**broken link removed**

I found a 5V, 2.4A switching power supply in my junk pile. It puts out 5.16V. Will it do the trick?

Could an LED be added to indicate when the ozoniser is on?

Thanks a million!

edit-Are the diodes 1n4148?

 

[alec_t]

Trimmer and power supply look fine. The reason I suggested a 5V supply was because they're common (e.g. mobile phone chargers). Any DC supply of 5V up to 12V would do (of course the relay's rated coil voltage would have to match the supply voltage). A 'LED in series with ~220 Ohm resistor' across the ozoniser relay coil will indicate the ionizer status.
Regarding the relay, the switch-on current for the Variac/blower is unknown, although the running current is ~0.6A. The relay contacts as per spec are rated for resistive loads up to 12A and general use up to 10A, so hopefully will cope with the inductive loads presented by the Variac/blower and the ozoniser.

Edit: If I understand the relay datasheet correctly you can expect the coil temperature to rise by ~30C in use.

Edit2:
Come to think of it, do you already have a spare high-Ohms multi-turn trimmer? If so, what value? (Should be able to mod the circuit to use it).

 

[salty joe]

I do have that 100K trimmer, I wanted to be sure it would work as the plan calls for linear.
The only parts I need are the 330K resistor and the 5V coils. I am ordering them now.
The 220 ohm and LED to indicate ozonizer status would go between the wires that connect the osonizer timer and 5V coil, is that right?
Thanks.

edit-The 330K resistors will be here in a few days, the coils will take a while. After the timer is built, is there a way to test while waiting on the coils?

 

[alec_t]

I do have that 100K trimmer, I wanted to be sure it would work as the plan calls for linear.

Even if it's a logarithmic type it will work. It would just mean that the useful adjustment range would probably be cramped at one end.
Yes, the LED+resistor connect between '+5V' and 'Rly-' on the schematic.
For testing without the relay, just hitch up the 5V supply to the timer and watch the LED. The timer is held in a reset state for about 1/4 sec after power-up to ensure the CD4020 starts counting at zero, then starts the counting; but the LED should come on immediately power is applied to the timer. Your supply may take a fraction of a second to rise to 5V.

 

[salty joe]

The 330 K resistors arrived so I'm getting started.
On the ozoniser timer, does R4 connect to pin 11 of U2 and U1a/R1 connect to pin 10 of U2?
Other than that, I think I understand how to put this jewel together. Thanks!

Edit: Should any pins on U2 be grounded other than pin 8?

 

[alec_t]

does R4 connect to pin 11 of U2 and U1a/R1 connect to pin 10 of U2?

Spot on. I did my usual trick of forgetting to show the pinouts on the schematic .

Should any pins on U2 be grounded other than pin 8?

No. The unused pins are all outputs, so can just be left unconnected.
Good luck with the build.

Edit:
Although the ioniser timer allows for a run time of up to ~40 mins, that time will of course be terminated prematurely (because of loss of the 5V supply) if the appliance timer is set for a shorter time.

 

[salty joe]

Thanks much. I'll get the timer done while waiting on the coils.

Edit: The timer's done and the LED came right on

Should we have a fuse on this?

 

[salty joe]

Thought I'd post a couple pics while waiting on the coils.

First pic is the ozonier. The ceramic element that produces O3 is suspended above the intake of the dehumidifier. Unintentional reflection is from polished aluminum lining of skylight.

Second pic is ozone timer. I was trying to show both sides of the board with a mirror.

 

[alec_t]

Looks good, Joe. We even get a glimpse of you as a bonus!

Should we have a fuse on this?

Sorry for the late reply on this; I missed your post somehow. As the only significant current drawn by the ioniser timer is the relay coil current (2 x some tens of mA), the 5V supply (wall-wart) is only lightly loaded. In the US would you normally run a wall-wart via a fuse? Here in the UK each mains plug contains a fuse, so a wall-wart would normally be fused via that. You should play safe and feed the Appliance timer switch contacts (hence the wall-wart) via a low-amperage fuse. The line feeding the contacts of the relay which switches the ioniser should have a fuse suited to the ioniser current rating. The line feeding the humidistat and the contacts of the humidistat-bypass relay should have a fuse suited to the blower rating. The latter fuse should be a surge-resistant type, to allow for inrush motor and variac current.

 

[salty joe]

This is the coil I just got. Hopefully, it will work for this project.
**broken link removed**

Printed on it is 10A 250VAC, 10A 125VAC, 10A 30VDC, 10A 28VDC and in more bold print SRD-05VDC-SL-C. I could not find a data sheet for it.

The back of this part shows a pin on either side of the coil and the top has an indentation directly above one of those pins. I assume the indentation indicates polarity, but is it + or -? There’s also a third pin between the coil pins that connects to half of the switch, so I guess that pin can be left disconnected.
The fourth and fifth pins (for the switch) have symbols that closely resemble your schematic, so I think I’m OK there.

The appliance timer only shows L (which I assume means live 110V AC). No ground and no neutral going into the appliance timer? I just want to be sure before chopping things up.
Thanks a million!

 

[alec_t]

Coil polarity does not matter.
Here's the relay connections:
http://i01.i.aliimg.com/img/pb/291/460/404/404460291_540.jpg

No ground and no neutral going into the appliance timer?

My laziness again . Yes, L is Live, and there should be ground and neutral for the appliance timer.

Edit:
Here's a labelled pinout of the relay

 

[salty joe]

Thanks for clearing up the appliance timer and coil polarity. And thanks for the labeled printout. I would've left the wrong pin disconnected.

I hope to get after this over the weekend-we are real busy with graduation stuff. Bittersweet, that's for sure!

 

[salty joe]

I am a little confused by the schematic that shows everything hooked together. I'll certainly re-do all connections if need be, If you could let me know if that's needed, I'd very much appreciate it.

At present, the Variac is plugged into a 110V receptacle and the blower is plugged into the Variac. The humidistat is connected to the blower. These three components work exactly as planned like this.

The schematic shows the humidistat connected to the Variac. It looks like it to me anyway. Should I open the Variac and connect the humidistat to it?

Thanks.

 

[alec_t]

As you have it won't the variac be permnently on/?

 

[ramuna]

Hi Salty,
Its hard for me to visualise the layout of your humidity condenser setup clearly, from the description you have given. But it appears to involve damp/wet aluminium tubing, if I have understood you correctly. If this is the case, then you may like to read about the interaction of ozone with damp aluminium here:
https://www.ozonesolutions.com/info/ozone-compatible-materials

The most obvious choice of metal for wet/damp ozone compatibility would appear to be stainless steel. But that is unfortunately much more expensive than aluminium.