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Multiple Aquastats only one well

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by BoilerMan, Nov 6, 2012.

  1. BoilerMan

    BoilerMan Minister of Fire

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    I only have one well on the Attack. I had three single Honeywell 6006A's on my old boiler, one for system control, one for over-ride, and one for over-heat.

    I'd like to have basically three set points and three N.O. contacts for these independent set points. I have lots of PLC experience, but would like to keep this purely mechanical in nature if possible. All of these contacts will be pilot duty low voltage making and breaking 24V for zone valves.

    These three will be progressively making at 5-10 degree intervals. First for the indirect ZV at 165, next at 180 for tricking the injection control into thinking the floor supply is 5 degrees cooler than it really is, and last at 190 for tricking the injection controller floor is 10 degrees cooler/ and opening largest ZV for upstairs.

    Any thoughts on this or suggestions are welcome. This is basically a three step boiler temp control. I'd like to avoid strap-on aquastats if I can, but that could be an option.

    TS

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  2. BravoWhiskey

    BravoWhiskey New Member

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    You should be able to strap-on the 6006s to do what you're talking about. Anywhere on the supply pipe leaving the boiler would work. If supply pipe is iron may want to dish out 15 thousandths or so with a dremel to give bulb some more contact area, cover bulb with insulation and good to go. Could get one bulb with two mechanical contacts with two separate temperatures using a 8124 but one contact would be NC. But the new electronic aquastats are very adaptable and affordable. Wouldn't an electronic strap-on be suitable for non failsafe functions?
  3. Fred61

    Fred61 Minister of Fire

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    I have the Ecoster2 control on my EKO. Because it doesn't have the flexability and features I wanted for my system, I installed a Tekmar 156 to control the circulators. This gave me more features including differential temperature control between boiler and storage. I left the original control to function as an on/off switch and max temperature/idle point.
    I strapped the sensor for the Tekmar to the outlet as close to the boiler as possible. If I remember correctly, it had a flat on it. Wrapped with insulation. Works good and is very responsive.
  4. Bob Rohr

    Bob Rohr Minister of Fire

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    Are you looking for a multi sensor well? if so here are several that I made to put 2, 3 or 4 sensors in one well. These will accept the 6mm or 1/4" diameter sensors that are fairly common now a days. You could select different size brass tube to fit the sensors you have in mind.

    I prefer sensors in wells if possible, they respond faster and seem to be a bit more accurate. If you strap on be sure to put a good tight insulation over them.

    Attached Files:

  5. Robby

    Robby Member

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    I had to hook up a sensor (1/4 type) on a copper pipe. Did'nt like the result, temp seemed low. Used some heat sink goop and a stainless hose clamp, then insulated over the whole works. I think much better. That should work on any strap on set up.
  6. BoilerMan

    BoilerMan Minister of Fire

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    Thanks guys!
    Bob, I only have one 1/2" tapping which I put a well in.
    Had to hole-saw the jacket for the deep insolation well to protrude to the outside. Would a triple aquastat work for this, the ones I see seem to be for burner control rather than three aquastats sharing a single 3/8" bulb, which is what I'm looking for. I did find the Honeywell 6008G which is for a two stage gas burner, but it has a remote bulb.... Somethign like this is what I'm looking for it has a setpoint and the differential between the setpoint (one set of contacts) and the second set of contacts is adjustable.

    Bravo, there is not a kit made to convert the 6006 into strap-on, I could make something out of sheetmetal, but was thinking that I could sell them on ebay to pay for the aquastat that I really need.

    TS
  7. Bob Rohr

    Bob Rohr Minister of Fire

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    Those cap tube aquastats are pretty old technology, for the same money, or less you can get a digital control, a solar controller like Fred mentioned. Now you have multiple, adjustable outputs differential or setpoint, digital readout, variable speed control, BTU monitoring, some basic data logging, etc Also they have the 6 mm sensors that are thermistors not 3/8" capiliary tube like the 6006 use. You can get two of those 6mm sensors in a well that fits into a 1/2 tapping, or make a well with an extended tube to reach thru the insulation shell.

    A trick for strapping on a sensor is to get an electrical ring terminal, tighten it on the sensor now you have a better surface to bolt or clamp onto a pipe or the flat surface of the boiler.

    In the center is a sensor that I cut the jacket off to show what is inside them. The thermistor inside is at the very tip of the sensor, really only the top 1/4" of that sensor needs to be in contact with the well or surface to accurately read. Really no need to encase the entire sensor tip, but do insulate over it if you strap it on.

    Attached Files:

  8. dogwood

    dogwood Minister of Fire

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    Along the same lines do you or Taylor have any tricks for strapping a snap sensor to a pipe? I thought about using a hose clamp, or using an old fashioned "C" shaped pipe clamp on the underside of the pipe, trying to match it's two holes to the two holes on the sensor, and bolting them together.

    Mike
  9. Bob Rohr

    Bob Rohr Minister of Fire

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    A narrow type stainless hose clamp works fine, screw at the bottom, a dab of heat transfer grease between the sensor and pipe.

    Use a high temperature insulation if it is near the boiler, not the cheap foam stuff from the Home Centers. The fiberglass pipe insulation works also.

    Attached Files:

  10. dogwood

    dogwood Minister of Fire

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    Thanks Bob.
  11. BoilerMan

    BoilerMan Minister of Fire

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    What make and model of electronic aquastat would work. I've looked at some Johnson controls but they confuse me a bit as the terminology seems different. BTW are they actually called "aquastats" or is that just a Honeywell trade name? I'm always leary of electronic controls because of my own work expierence, I've worked in the electrical feild and see many industrial/commercial electronic controls and PLCs fail and bad things happen. However my whole system (including the RK2001at2) is powered through a mechanical set of contacts so when the boiler cools, ALL power to everything is turned off ZV controls, injection control, boiler controller, and system pump all dead with 140 degree boiler.

    TS

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