Ranco ETC Temp Controller to widen the differential for a fixed diff aquastat

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Old 03-11-12, 09:16 PM
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Ranco ETC Temp Controller to widen the differential for a fixed diff aquastat

From another thread..

I said..
Trooper, would that remote control help my system out ?

If you recall, my zones and circ pumps run independently from the boiler.. the boiler's TT is just strapped and it runs hot all the time (10f diff fixed).

If I was to connect this "ETC Temperature control" to my TT control at the aquastat, and strap the sensor to my boiler outlet pipe, I'd have a new boiler range / differential ? Should make the run times a little longer .. ? The existing aquastat would serve as a safety limit control of sorts..
To which Trooper said..
It's something to think about Dave...

If you were to replace the TT jumper with this control, and set the differential wider, with the control set up to BREAK on TEMP RISE (heating mode on the setup), then yes, I believe that this would allow the new control to 'over-ride' the existing one.

One possible problem though... since the sensor will not be inside the boiler, but on an external pipe, it may not sense properly when the pumps are not circulating. The sensor would need to be as physically close to the boiler as possible and very well insulated.

You would want to set the existing HIGH limit aquastat to a few degrees above the temp on the Ranco if you did this. This way you still have the original control acting as a secondary high limit in the event the Ranco were to fail.

Yeah, it might work!
Unit was sitting in my util room for a while now.. finally got to starting the install today.
Im at the point of attaching the sensor to my boiler's output pipe. Im considering using a gear clamp to attach the sensor stick laying along the pipe, and then covering the area with aluminum tape or similar.
Question is.. that sensor 'stick' has wires coming out of the end.. if I 'lay' it along the pipe like this, could the heat damage the wire ??
I cant figure out how to attach it at a 90deg angle, otherwise..
 
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Old 03-11-12, 10:28 PM
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Hello Dave,
I don't know what a gear clamp is.
What i do is, put a good dab of heat sink compund, lay the sensor lenghtwise.
I use a couple to 3 or 4 beefy cable ties and crank them down real tight.
You know they are tight when you have broken a few.
Just make sure the wires don't touch the pipe and it should be ok.
Then i cover the whole thing with one or two layers of 1/2" foam pipe insulation.
Again using cable ties to secure the foam.
Iron pipe has about a 1-2 miute lag, copper pipes respond fairly quickly.
It's important to insulate. Keeps the heat on the sensor.

Peter
 
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Old 03-12-12, 01:51 AM
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What I did with my Ranco unit is, I wire-brushed the portion of the pipe (black iron) that the sensor bulb was placed against, and like Peter suggested, I used a zip tie to tightly fasten the bulb to the pipe, and then covered the attached sensor & pipe with a piece of pipe insulation. I cut a slit in the insulation so that the sensor wire could be run outside of it, so the wire doesn't touch the pipe.

The heat sink compound also sounds like a good idea, but I didn't use any.
 
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Old 03-12-12, 06:59 AM
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Another name for a gear clamp would be a hose clamp ? A metal band with a driven screw to tighten it around circular objects. I also have ty-wraps (zip ties/ cable ties).

Thanks for the comments.. I'll go ahead and lay it lengthwise and then insulate well.
 
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Old 03-12-12, 10:36 AM
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Hi Dave,
IMO, cable ties are better than hose clamps, because they don't pull the heat away from the sensor and the pipe.

Peter
 
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Old 03-12-12, 01:02 PM
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It's possible that the heat on the cable ties might cause them to break apart prematurely.. the good quality black outdoor ones would last longer I guess.
As I was tightening the hose clamp, I had my finger on the outside where the clamp went over the sensor.. and yes it got hot quickly via transfer. Maybe thats a good thing, also putting the heat on the sensor's other 'side' ?
In any case, its operational now.. too late in the season for any realistic data.. but if I stop hearing that boiler coming on for 30 second bursts, Ill be quite happy.
 
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Old 03-12-12, 03:39 PM
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They do also make stainless steel zip ties... I would be concerned about getting hose clamps too tight and crushing the sensor.
 
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Old 03-12-12, 03:57 PM
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IMO, it's a leap that the stainless clamp is transfering heat to the top of the sensor. Rather it is taking heat off the sensor.

Just my opinion.

Peter
 
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