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Outdoor Reset Control of Circulators

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Blue Tornado, Apr 5, 2013.

  1. Blue Tornado

    Blue Tornado Guest

    Does anyone have an easy design that is economical to control the zone circulator(s) with outdoor reset? Considering that many boiler operators are using storage that would take the "boiler control" out of the equation for the reset, or not? The outdoor reset controls on the market do not come cheaply and the Taco reset pumps are about $500 bucks a piece.

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  2. velvetfoot

    velvetfoot Minister of Fire

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  3. Blue Tornado

    Blue Tornado Guest

  4. __dan

    __dan Feeling the Heat

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    Hey BT, it depends on your existing setup, what you have and want to modulate. I looked at the manual, the 256 control above does on/off control and would be intended for on/off control of a condensing rated boiler that does not otherwise modulate the firing rate.

    I have no idea about your primary fuel source/type, and if you have primary/secondary pumped loops with circulators for zone control. I have oil primary with an OAT reset secondary loop and circs on the zones. So, I use one (per boiler) Tekmar injection pump controller for variable speed control of the standard Taco 007, used for the VS injection pump. The control would be similar to the Tekmar 356. Looking at the 356 manual, it does not have boiler return water protection. There are pictures and piping diagrams in my post list. I'm saying there are a variety of ways to do it, not saying how to do it. Not enough information.

    It all depends on what you have now for piping and equipment and what you want to control, boiler, mixing valve, or pump control. If you are expecting me to say at this point, hire a licensed guy, regular electricians commonly have trouble and smoke the controls on relatively easy multiple zone valve and damper controls. I get called to fix that. I would recommend hiring a good heating controls electrician. And my view is always, concern for doing what is right and not what is lowest cost. It's in my nature to overbuild.

    At that point it's a no brainer, the right equipment and controls are a huge fuel and money saver pretty quickly. With the wrong controls, you can easily burn that in one month in fuel.

    Maybe try posting a piping diagram. Is this for existing, or a new build in the future?
  5. Blue Tornado

    Blue Tornado Guest

    Hi Dan, thanks for your input.

    The goal is very basic; to control a zone circulator with outdoor reset. The supply temp will be from storage at 140-190 degrees. Ideally it would be variable speed ecm cruising on slow and steady, yes? My thought is that water temp sensor, outdoor temp sensor, thermostat calls demand and a control are what is necessary. Keep in mind I am not a plumber or hvac professional and will do anything myself rather than pay someone else. Not that I am just a cheapskate, but it is good to know what is going on with our technical and mechanical devices. Hence a DIY'er and eternal student.

    The 256 and 356 differ in that the 356 has variable speed?

    Does the "fixed" "varying" temperature of storage hinder ODR? Or, asked another way. Does the inability to control supply temp as in boiler control hinder ODR? ODR controls generally interact with boiler and circulation, yes?
  6. __dan

    __dan Feeling the Heat

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    OK, the 256 doing on/off will not work for your application. The 356 doing variable speed control of a single Taco conventional (permanent split capacitor type) circ is one of the choices I would look at for your application. If you're wondering what else I would look at, I bought my Tekmar injection pump controls new on EBay, so I would look for a deal, but most likely, something Tekmar. Depending on what else is going on, there are injection pump controls with more features, but the 356 would be a standard application as described.

    As far as I know, I am not aware of an ECM type circ that does outdoor reset or works together with an OAT reset control. The ECM type cicr is far better at variable speed compared to conventional, it is made for variable speed, it just seems the market is not mature yet for ECM's. They do not offer all the different features now, wihch they will in the future. This question would have to go to the manufacturer's product representative, what is available today in an ECM circ with either internal or external OAT reset control.

    The reset control will not care at all about the tank supply temp, including variances. It will simply calculate (reset) target setpoint supply HW after the circ, where the thermistor is, and ramp pump up or down to maintain the target temp. When supply is hotter at the tank, it will requires less speed to achieve setpoint, and more speed when tank temp is lower. It will not care otherwise.

    If you had more than one circ to reset, because of the cost of the control, I would look at resetting a secondary header and take the regular speed zone circs or valves from that header.

    And, imo, I would prefer the control and circ be separate for easier servicing. Easier to change a standard circ than a specialty circ with the control built in.

    The zone thermostat trips the mix demand in the control. Have to look specifically at the manual to see if the control wants a voltage or closed contacts there. That starts the injection pump, but there are no smart features, like boiler protection, which you could use to stop the pump when the tank is cold.

    If you want to disable the pump operation when the tank is cold, you may want to uprgade from the 356 to a reset control with boiler protection, and use the boiler protection thermistor to sense the tank temp.

    I usually look at the whole, and in my own work, love puzzles, but hate assembling a puzzle when some of the pieces are missing. Still not enough information.
  7. __dan

    __dan Feeling the Heat

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    This is the control I have on my system, one for each boiler, oil and wood, doing variable speed injection pumping into the reset secondary header.

    http://tekmarcontrols.com/products/hvac-systems/361.html

    I don't otherwise know enough about your system to recommend something, but disabling the zone pump for low tank temps may be necessary, which the 361 may do with boiler return low limit protection, using that thermistor.
  8. __dan

    __dan Feeling the Heat

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