# Aquastat selection and installation



## dogwood (Nov 27, 2009)

I have some questions about aquastat installation and selection perhaps some of you may know the answers to. Here's is what I do and don't know about them, and what I need to accomplish. I know aquastats act like switches for 24 volt circuits, are used with relays sometimes for higher voltages, can be single, double, and triple pole, and can turn on and off circs. I think you can get them as either well mounted or pipe strap ons. Please correct me if I'm wrong.

I am trying to do something simple. This to have one aquastat turn on or off the two circulation pumps servicing either side of my DHW flat plate, and at the same time tell a motorized ball valve to open. (That ball valve allows water to flow to the line servicing either or both the W/A HX or the DHW flat plate HX). I think I would prefer a well type aquastat as they are more accurate.

What I dont know is:

1. How do you set on the aquastat the temperature you want to turn on and off on, or do you buy one that has the temps you want preset. 

2. I am not sure what a well looks like or how it would fit into the pipe. The Honeywell aquastats I looked at on the PexSupply site looked like they have real long tubes connected to them. I can't picture how they'd fit into a pipe. How do you plumb them in? I thought maybe you'd put a tee into the pipe where you wanted to gather the temperature reading, and tighten the well into the tee and put some transfer medium into the well that holds the temperature probe of the aquastat. Never having done this, I just don't know. Can't remember the name of the transfer paste either. It was a short word. What and what size fittings would the well normally go in to?

3. I am placing the aquastat into the pipe going to the DHW side of the flat plate hx. That flat plate is being added on a new pipe connecting between where the drain and pressure relief valve currently are on my propane fired water DHW heater. I think I read in a previous post, which I can't yet locate, the aquastat should go towards the bottom fitting of the tank. Is that correct? I will tee off the drain and pressure relief valve on this line when I make the change.

4. . What lower and upper temperatures should the aquastat be set or preset to? I remember, I think, HR saying, you can get up to and maintain 160 degrees in the tank with a tempering (mixing) valve in place. I have purchased a tempering valve to moderate the hot water output of the tank. Would 160 degrees be the top setting for the aquastat then? I would think that makes sense. What should the lower setting be?

5. I read terms like "break on rise" and don't know what they mean. I dont know how these aquastats or their wells physically fit into a pipe, or how to select the one needed from all those available, and there are lots. I've got an idea on how they function electrically from reading the "Quick and Basic Hydronics Controls" book by Carol Fey, purchased off Dan Holohan's site, but not the physical installation.

If anyone can explain the selection and physical installation of one of these in a "Volkswagen Repair for Dummies" manner I'd be beholden. The pumps I'm turning on or off are a Grundfos 15-58 on low speed (24volt) and a Laing low-flow recirculation pump (115volt). The Honeywell motorized ball valve is 24 volt. What would you recommend as a good aquastat (and relay if necessary) for this application and how do I select between them? Meanwhile I'll keep searching for the relevant previous posts. Thanks.


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## tbsdolmar (Nov 27, 2009)

A break on rise aquastat opens the points on a temperature rise and make on fall closes the points on temperature fall. These go into a well mostly either 1/2" or 3/4" or you can get a strap-on type that clamps on a pipe. They also have a temperature differential of 5 to 30 degrees or a preset 5 degrees if there isn't a wheel inside of it to adjust.


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## in hot water (Nov 27, 2009)

an aquastat is just a switch the operates by temperature, instead of you fingers, like a light switch.

Typical "cap" tube stats have a small copper tube with a fluid inside.  When the fluid warms and expands it pushes a switch either open or close.

I like digital setpoint controls better, you get digital temperature display, a lot of adjustabilty on temperature and differential.  Also sensors can be extended sometimes up to  300' with t-stat wire.  Most offer NO or NC functions, and can be used as cooling or heating.  Open on temperature increase or decrease.

I like the Ranco or Johnson Controls brand.  Honeywell, Penn, Azel, HeatTimer and many others build setpoint controls.

Sometimes with wood fired equipment a differential control works better.  With an aquastat or setpoint the control will call until it satisfies.  So if the fire goes out, the pump will keep running.

With differential controls a sensor on both the source and tank operate the load.  So the pump starts when the boiler warms above the tank temperature, and stops when the tank is within say 5- 8 degrees of the boiler.

 hr


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## dogwood (Nov 28, 2009)

TbsDolmar, if I understand what you are saying the well goes into a 1/2 or 3/4 inch fitting? Would this fitting be a tee facing upward maybe? Would it be a tee with a short piece of pipe sticking up from it as long as the well. How long are these wells anyway? Would the bottom of the well stick a bit into the bottom of the pipe whose water temperature is being measured. I'm sure if I could just see one of these it would be obvious how they go in. If I got an aquastat with a wheel on it Could I then set the temperature for the circs and ball valve to turn on and open at let's say when the DHW tank temperature got as low as 130 degrees, and then shut them off when the water is heated to 160 degrees? Does this arrangement and these temperatures sound reasonable? I will have a tempering valve in place so no one gets scalded.

HR, nice to hear from you. What would you set the temps at for opening and closing the switch for the DHW application I have described? Could I set the temps for whatever I needed with one of the digital setpoint controls? Do these digital setpoint controls connect to an aquastat, replace the aquastat and well, or use a different type of aquastat to service them? Remember I am a novice developing a new set of skills. These skills currently don't include how a digital setpoint controller or an aquastat is installed. But now that you you have broadened my horizons and mentioned them, I will look for the brand setpoint controls you named, and their installation and spec sheets, if available, and try and dope this out. I do like to do things well, even the first time around. From what you describe the setpoint controls sound like a good option. Any further explantion on their installation geared to the uninitiated would be appreciated. Thanks to you both. 

Any other answers from anyone else on any of the questions I've asked above would be more than welcome. Soon as I get the electrical portion of this install figured out and planned, and its components purchased I am ready to get busy. Have about everything else needed to start.

Mike


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## tbsdolmar (Nov 28, 2009)

You could use a tee with a bushing for 1/2 or 3/4, just make sure there's enough clearance for the well so it doesn't bottom out. The well is basically a copper tube that's closed off on the end and the bulb from the aquastat goes in the open end. It has threads and a flange for the aquastat to mount to. You can get these temps on them since most are adjustable from 100 to 240 degrees. The 6006 models have a SPDT which make on temp increase or decrease. They have 3 terminals on them.


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## dogwood (Nov 28, 2009)

Thanks tbsdolmar, this is beginning to make much more sense to me. What brand are the 6006 models? Are they Honeywells? I will look them up at your suggestion. 

Mike


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## dogwood (Nov 28, 2009)

Bondo, thank you so much for helping sort this out. I didn't know you could run line voltage directly through aquastats as well. I am a bit confused on how to switch two 24 volt loads (the Grundfos 15-58 and the Honeywell motorized ball valve), and one 120 volt load (the Laing recirc pump) loads off the same aquastat. I was speculating I might need the aquastat, in addition to turning on the two 24 volt loads, to flip a relay to bring the 120 to the Laing. However, I really haven't a clue on configuring this and there probably is a simple way. If anyone does know I'd love to hear. Thanks

Also the Honeywell ball valve is a modulating ball valve. I am going to use it in the full open or full closed positions only, so I was thinking I would not need a modulating controller to operate it. Not that I know what a modulating controller is. I just came across a reference in Ms. Fey's book about needing to use one with a modulating valve. Does anyone think it would be all right to do without the modulating controller in this circumstance? 

Mike


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## in hot water (Nov 28, 2009)

Here is an example of a cap tube (capillary tube) aquastat.  This one has a short sensor and is designed to mount right onto the well in a tank, for example.  You can buy aquastats with longer sensors for remote mounting, up to maybe 6- 10 feet.

Another type of cap tube control is called a "strap on" stat.  Basically they tuck that sensor into a piece of foam on the back of the grey box and you strap the whole control onto a pipe.  The sensor just touches the outside of the tube.  Handy if you do not have a well.

Use a well with the sensor in the fluid stream for best temperature sensing.

Don't put the well in a vertical pipe or tee, as they can trap air and not read properly.  I prefer to see them in the side branch of a tee, then a small air vent on the top, vertical part of the tee if it is at a high point. 

A cap tube aquastat has dry contacts and they do not need voltage to "power" them.  They can still switch in a power outage, but you need currwnt from somewhere to run the load   Cap tubes are nice for overheat, of back up system controls.

A digital setpoint needs voltage to operate the processor.  I prefer them, for about the same $$ the cap tube type as they have a lot more flexability.  And the digital readout is handy for monitoring or troubleshooting.  Their sensors can slip into a well, or strap on the outside of the pipe.

In the end they are both switches, operated by temperature.

 hr


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## dogwood (Nov 28, 2009)

Thanks for the further explanation and pictures HR. I will definitely tee off the well horizontally rather than vertically and put the sensor end into the fluid stream. Does a digital setpoint have electronic analogs to the throws and poles a cap tube aquastat uses for switching? How many loads can a typical one switch. I'm now trying to figure how many of each, throws and poles, to use as described earlier in this post, or the equivalent configuring that a digital setpoint might use, to control two 24 volt and one 120 volt load simultanously. Would the digital setpoint need to switch a relay in order to switch on the 120 volt load? Thanks HR, or anyone out there who may know the answers. 

Mike


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## dogwood (Nov 29, 2009)

Thanks again Bondo. I finally found that old thread by Medman, https://www.hearth.com/econtent/index.php/forums/viewthread/40993/, discussing where to place his aquastat. He was using a sidearm, but that shouldn't impact too much where the aquastat goes. I was thinking of placing the aquastat well in the pipe closest as I could get to where the DHW drain is currently connected. I think Stee suggested this approach in the aforementioned thread. The other choice would seem to be near where the pressure relief valve is currently connected near the top of the DHW tank. I don't think I should be drilling a hole in the tank for a well. Someone else used a sensor glued to the side of a tank even. What are anyones thoughts before I go screw this up, Go near the top fitting, or the bottom. Or something else entirely? 

I guess I will have to adjust the temp settings on the aquastat accordingly. Advice would be appreciated. And Medman if you're out there, did you come to a favorable resolution of this question for your setup. What did you end up doing, and is it working for you?

Mike


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## timberbuilt (Jan 13, 2011)

Do they have low voltage aquastats?  The ones I have used basically switch on and off 120 volts but is it possible to have a aquastat similar to a thermostat which sends low voltage?  OR maybe to be more specific, I want to control a circulator by temperature through a Taco 506 box (24 volt in the top, 120 volt out the bottom), how do I do this?


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## Silver_Is_Money (Feb 13, 2011)

Aquastats are only switches (unless they are combination devices known as Aquastat Relays, the existence of which can confuse some people who only need an aquastat).  As switches they shouldn't care much at all if they are wired for 24 VAC or for 120 VAC service.  That said, if you are controlling a 120 VAC circulator via an aquastat that is giving it a signal to either turn on or off at some desired temperature, then why is there a need to take the circuit down to 24 VAC just to pass it through a relay that is going to bring it back to 120 VAC?  If the aquastat is accomplishing what you need it to accomplish as a switch (and a relay is not necessary), then why not just wire the aquastat (switch) with 120 VAC, and then wire the pump as the load to the circuit that is made (or broken) via the aquastat (switch)?

Looking at this another way, there are only 3 basic things required to make (or break) a complete circuit.  Supply, switch, and load.  If the supply and the load are both 120 VAC, then in most simple applications the logical choice for the switch should also be 120 VAC.  I'm assuming that you merely want the aquastat to either close (make) at some temperature and start a pump, or open (break) at some temperature and stop the pump.  If that is all you are doing, then (in my opinion) a switching relay like the Taco SR506 does not seem to be necessary for the application.


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