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#69873 09/22/06 11:23 AM
Joined: Apr 2002
Posts: 257
M
Member
We are trying to fix a problem with a float switch that controls an automatic fill valve in a small (15' X 15") decoraive fountain.

The float switch is installed in the fountain inside of a still tube to prevent unnecessary switching.

The float switch controls two time delay relays and switches about 20mA at 24VAC.

The switch is a reed switch and is designed to handle .5 Amps at 120 Volts.

The problem is the switch starts sticking after a few days or within a week. We don't believe that it is a mechanical problem.

Everyone we talk to agrees that the switch and the design should work but yet we are still having problems.

HELP!

Does anyone have experience with fountain or similar controls? Has anyone came across this problem before?

Thanks
Brian

[This message has been edited by master66 (edited 09-22-2006).]

[This message has been edited by master66 (edited 09-22-2006).]

Joined: Sep 2006
Posts: 98
A
Member
Again, contact the mfg. and get their fix, they pay their tech support folks to have the answers, it builds repeat business, for both of you.

Joined: Oct 2004
Posts: 132
M
Member
Are the relays this switch controls inductive, producing a "spike" back to the reed switch when it opens, casuing arcing? Maybe you need an interposing relay driven by the reed switch, which then feeds your timedelay relays. An interposing relay has a small coil burden, and a diode and resistor to squelch the spike.

Just a guess, perhaps you have already looked at this.

Mike

Joined: Jan 2004
Posts: 54
L
Member
I have installed float switches for similar applications. The float switches were stainless steel and were from Dultmeier Sales. I think the model # was 2A551. Going on 2 years now with no problems.

Joined: Apr 2002
Posts: 257
M
Member
I should have mentioned in the original post that the relays that the switch is controlling is two solid state time delay relays from idec.

We have been in contact with idec and the switch manufacturer and they can't figure it out either. Idec says that thier relays would not cause a spike.

We would like to find a murcury tilt switch that would fit this application but have been unable to find one. We are also considering a probe type switch system.

The switch mfgr said that they ran into a similar problem a few years ago but couldn't remember what they did to solve it. The guy that dealt with the problem was not in today but will be back in on Monday. He thinks that they might have installed a varister across the switch or possibly a capacitor. We will be talking to him on Monday.

leespark,

what was your switch controlling? Was it the same as I have described?

Brian

[This message has been edited by master66 (edited 09-22-2006).]

[This message has been edited by master66 (edited 09-22-2006).]

Joined: Nov 2005
Posts: 827
J
Member
For the life of me, I can't figure out why you have one float controlling two TDRs. You usually see 2, NC, open on high water float switches in series driving a control relay. A NO sealing contact of the relay would be paralleled with the lower setting float switch. You really think of the lower setting switch as closing on low water, instead of opening on high water. There are various switches that allow deadband adjustments with a single float but those are usually touchier to adjust. Is there more to this that you're not sharing? Do you just want to open the fill valve at x" and close it at x" + y" ???

I work with some used oil day tanks that have reed switches in a SS shaft. SS floats with magnets travel berween collars. I have seen them ordered and installed with the wrong contacts. Fortunately I was able to switch the contacts by moving the collars up or down a little. I have never had the units stick. They all pick cube relays @ 120 VAC.

The only pump controls I work with that use TDRs require pre-libe of bearings on long pump shafts. The floats and alternator trigger a >= 1 min pre-lube and then start the pump(s).

Are you using these delays for alarms or to detect if you haven't filled the tank within the allowed time?
Joe

Joined: Feb 2005
Posts: 693
L
Member
If you have a pivoting float arm that works, you could epoxy onto it a mercury bulb switch taken from a mechanical HVAC thermostat, many of which have three contacts for SPDT uses.


Larry Fine
Fine Electric Co.
fineelectricco.com
Joined: Jan 2005
Posts: 5,360
Likes: 1
Cat Servant
Member
FWIW... Much to my amazement, there are different internals used in float switches! Reed switches, sliding contacts, mercury vials... you name it.

The hardest thing to design into a float switch is a 'dead' zone between 'on' and 'off.'

I have had much, much better luck, and better reliability, with the ones using mercury vials.
What is interesting is that the vials have a partition inside, with the effect of making the cylinder act like an hourglass. The float has to move significantly from horizontal for the mercury to flow into the other half. This leads to a 'definite' switching action, rather than a 'maybe.'

If your local plumbing supply doesn't have them, e-mail me for a reccomendation.

Joined: Jan 2004
Posts: 54
L
Member
My situation was in the bottom of an underground vault which houses several pumps for decorative ponds as well as an electric panel, timeclocks etc.

A sump pump was installed at the bottom of the vault. That particular float was installed to allow the pump to run even when a small amount of water entered it. We used a simple "RIB" relay to operate the pump. I know the pump operated quite frequently and as I said no problems to date.

Joined: Apr 2002
Posts: 257
M
Member
The float switch is connected to two TDR's as such.

TDR#1 must be energized by the float switch for a preset time (5 min. solid) before the fill valve is turned on. This was done to prevent the valve going on and off when the water level was at the borderline.

TDR#2 is a shut down timer. If the float switch is not satisfied within a preset time (about 1 hour) this timer shuts down the fountain completely. This was done to prevent over flow.

There is also an off delay timer that is controled by one of the on delay timers. This is connected so as to keep adding water for a preset time after the float switch is satisfied. (about 20 min)

The water level must be within about an inch and a half to two inch area for proper operation.

We redid all of the controls but redid them the same as the original design.

Brian

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