What should I watch out for when replacing Honeywell Aquastat Controller?

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Old 09-02-14, 03:05 PM
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What should I watch out for when replacing Honeywell Aquastat Controller?

I've had intermittent issues with my oil fired boiler supplying DHW over the summer: The boiler wouldn't start. If I tripped the reset it would fire but after a week or two it wouldn't. Called service and they determined the Honeywell controller wasn't working properly and needed to be replaced.

50+ year old boiler with a DHW internal coil.

Technician also diagnosed a bad circulator pump (Taco 007 Cast Iron)

Price quoted was about $1,000 to replace both. Controller alone was quoted at close to $600 and I declined.

Found a new in the box controller on ebay for $135 shipped and it showed up today. What I need to know is what to look out for when installing it.

The model numbers (and revisions) on both controllers are exactly the same, so I'm pretty sure the wiring will be simple.

Not sure about the pipe coming out of the boiler that connects to the back of the Honeywell Controller...How is that secured to the controller? What should I be watching out for when doing the swap?

Thank you in advance for any help on this!

Old controller:













Since the two controllers are identical, I'm assuming that the wiring will be exactly the same. I plan on marking each wire on the controller that is still on the boiler and transferring the same wires to the new controller. The pipe that somehow connects to the back of the new controller is what has me a bit stumped: New Controller...



 
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Old 09-02-14, 03:17 PM
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Go wire for wire. It's pretty simple. The only thing I would do is run the burner without connecting the cad cell wires ( ff) to make sure it shuts off on safety. Also make sure it turns the burner off on high limit.
 
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Old 09-02-14, 03:30 PM
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Did the new Aquastat come with a supply (maybe a tube) of heat transmitting thermal paste ?

That compound is what goes into the well of the boiler to ensure that the probe of the Aquastat is able to read the correct boiler temperature. There's usually just a set screw holding the Aquastat in that correct position.

Did the new Aquastat include some basic instructions ?
 
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Old 09-02-14, 03:50 PM
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Originally Posted by Vermont View Post
Did the new Aquastat come with a supply (maybe a tube) of heat transmitting thermal paste ?

That compound is what goes into the well of the boiler to ensure that the probe of the Aquastat is able to read the correct boiler temperature. There's usually just a set screw holding the Aquastat in that correct position.

Did the new Aquastat include some basic instructions ?
Not many new aqua stats come with the paste. I've never used it. It really doesn't do anything
 
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Old 09-02-14, 04:14 PM
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There's usually just a set screw holding the Aquastat in that correct position.
Well, that comes sorta close to answering the guy's question... but no cigar for you.

In this picture, you see that Philips head screw on the side? That's the 'set screw' that dburr is talking about. It's a 'clamp' mechanism. Look at the new one and you will see how it works.

You loosen that screw and the clamp will retract (you may need to hold the screw head to the chassis of the a'stat).

After loosening that screw, the old one should slide right off.

Don't bother with the paste... it's more trouble than it's worth. Just make sure that the temperature sensing bulb is fully inserted into the 'well' and that it STAYS at the bottom of the well.

Be very gentle with that thin copper capillary tube... you kink it and you have a $135 paper weight. You can gently bend it, but don't kink it!

And hold off on that pump... I think he was just trying to 'upsell' the job. What was his evidence that the pump is bad?
 
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Old 09-02-14, 04:19 PM
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Yes, included in the box are the instructions. There is no thermal paste, but there are two (2) rubber caps that I presume would cover a couple of electrical knock-outs if necessary, a blue-headed wire nut and what appears to be a lock washer.

The instructions do mention the side screw that holds the probe into position..I found this part a bit fuzzy:

Fit controller case into immersion well so that immersion well clamp slides over flange of immersion well. Huh?????

Securely tighten immersion well clamping screw.

I'm thinking the pipe from the controller to the boiler in my pics is the "immersion well" is that correct?

The probe is the copper tube on the back of the controller...??

It slides into the tube that is connected to the boiler and located on the back of the controller...

Next question assuming I can figure this ^^^^ stuff out....How do you drain the boiler and is it really necessary when you look at the pics of the plumbing??
 
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Old 09-02-14, 04:25 PM
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RE: the pump

With the cover off the Technician could flip each relay (boiler, circulator) independently. When he flipped the one on the left (picture left) the boiler would start and run fine (as long as he held the relay).

When he flipped the one on the right and held it, the circulator pump made a LOT of noise. I've ordered new internal pump parts and hope that fixes it.

Technician explained to me that this controller is rather old school....It controls both the burner and the circulators...where newer boilers have independent controllers for boiler and circulators.

Lucky for me it is in the 80's for the rest of the week and no real need for the boiler just yet.
 
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Old 09-02-14, 04:28 PM
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Fit controller case into immersion well so that immersion well clamp slides over flange of immersion well. Huh?????
It will all come clear when you take the old one off.

On the end of that 'pipe' (which IS the 'immersion well') there is a 'ring' on the end that the clamp will fit into.

How do you drain the boiler and is it really necessary when you look at the pics of the plumbing??
You should not have to drain the boiler. That's the whole idea of the immersion well. It's closed inside and the bulb is not exposed to water.

This of course is not exactly what you have, but should give you an idea of what you're dealing with.


image courtesy of newegg.com
 
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Old 09-02-14, 04:31 PM
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When he flipped the one on the right and held it, the circulator pump made a LOT of noise. I've ordered new internal pump parts and hope that fixes it.
What kind of noise? Like 'grinding' ? or more like air bubbles moving through the pipes ?

Should have just ordered a new pump. Price is damn near the same.

Yes, you WILL have to drain the boiler to change the pump. NO... WAIT...

Luckily you have valves above and below the pump, CLOSE those valves and you shouldn't lose much water. You will lose SOME, but not much.
 
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Old 09-02-14, 04:34 PM
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I have some advice for ya...

Start a "New Boiler Fund" NOW.
 
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Old 09-02-14, 04:47 PM
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I've heard circs make noise if the loop is air bound. Check the pressure in the boiler. Most feeders will have a little lever on top of them. Flip that up real quick to see if the boiler continues to feed. Other than that you might have to replace the circ or just the guts.
Sometimes it's kind of a pain to get the new aqua stat on the well. Just make sure the screw is loose enough and don't break the tube. It's full of mercury. I'll tell you from experience that it hurts pretty bad when that bulb breaks and you get mercury in your eye
 
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Old 09-02-14, 05:26 PM
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Thank you to all that took the time to reply!

Just to be sure>>>

I'm going to kill the power to the boiler and controller>>>

Take notes/pictures of how the three sets of wire leads (white/black) enter into the controller are connected>>>

Unscrew this side screw and slowly walk the controller out of the "well" ??

For anyone that has BTDT I know this appears as though I'm suffering from some sort of brain damage...just trying to make sure.. ;-)

Loosen this screw and once the electrical connections are free the controller can be removed?

 
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Old 09-02-14, 05:49 PM
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Fit controller case into immersion well so that immersion well clamp slides over flange of immersion well. Huh?????

Haha Ė I know what you mean. That is the same exact statement that meant absolutely nothing to me. I think those boys ought to spend a little time re-working that section of the manual.

I loosened the screw on the bottom of the Aquastat, the screw that you can see on the right side of this pic, and then tried to slide the Aquastat forward and off. No way. When after a lot of trial and error I finally got it off, I could see why it wouldnít slide forward. Gravity just keeps those teeth down in any groove and itís just a simple matter of pushing upward on the screw when itís backed out, which then pushes the teeth upward, which then allows you to slide the Aquastat forward.

But I guess Iím just a little mentally slow and the job was a beeotch!

 
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Old 09-02-14, 05:51 PM
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Not at all Rob... I'm overly cautious when doing something I've never done before too. It all started about 40 years ago when I thought I could repair an automatic transmission. I can... NOW Sometimes the best way to learn is to royally screw up.

You've pretty much got the idea. Just loosen the screw enough to get the clamp out of the way. If it hangs up, just loosen the screw some more.

You'll be fine.
 
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Old 09-02-14, 06:02 PM
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We all forgot the simplest and most important step. Push up on the screw. You got it but I didn't think about that part.
 
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Old 09-06-14, 08:42 AM
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Job finished and I have hot water!

A big THANKS to everyone that helped me out on this. I've successfully installed the new Aquastat controller and it is working as it should. Was pretty pumped when I flipped the breaker for the boiler, turned the red emergency switch back on and the boiler fired right up. Ran for about 12 or so minutes and got to 180 deg and shut off.

Running DHW all day and the controller is doing its thing...turning the boiler on and off as required.

Thanks again for taking the time...much appreciated.

 
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Old 09-06-14, 09:46 AM
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Good job Rob...

Let's talk just a little about the settings on the new a'stat...

What are your HI , LO , and DIFF settings at currently?

It looks like you had 190, 160, and maybe 15? on the old one?

Is that what you've used on the new also?

Your LO setting should be as low as possible consistent with adequate supply of hot water to the home (domestic supply).

I would try 140 LO and 20 DIFF and see if your hot water supply is still adequate.

Turn the HI down to 180.

These settings should save you a decent amount of fuel.

If you don't get enough hot water for domestic use, you can bump the LO up in 5 degree increments, but not closer than 20 from the HI setting. In other words, if the HI is at 180, you can't set the LO above 160.

What about the pump? Still making noise?
 
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Old 09-06-14, 09:53 AM
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In this picture:



on the left side of the boiler it appears that there is a 'tempering valve' installed for the hot water supply... that's good, and probably the reason that y'all haven't been scalded by super hot 175F water...

Can you read the temp scale on that valve? If so, what is that valve set at?
 
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Old 09-06-14, 12:47 PM
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Tempering valve is set to about 140..There is no gauge on it, just a dial (Watts Tempering Valve).

I've changed the controller settings to what you suggested:

H 180
L 140
Differential 20

Will see how it works out.

The pump is so quiet now I can't hear it with the burner running. Once the burner went off the pump was 10x quieter than before. Very happy with the results so far.

Did forget to shut off all the valves before taking the pump apart...That was bit of a surprise ;-)
 
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Old 09-06-14, 01:35 PM
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Originally Posted by NJ Trooper
". . . What about the pump? Still making noise? . . ."
What do you do; open a Case File on each one of these problems that requires solution ?

I'm impressed; most of the professional service people I've encountered recently can't remember details between here and their shop. We joke that many have the retention capacity of a Day Fly !

You give us hope.
 
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Old 09-06-14, 03:44 PM
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Tempering valve is set to about 140
You could try backing that down a bit also. Rarely does one need more than 125F domestic hot water. Exceptions might be laundry and dishwasher.

You might find that you actually have MORE hot water available with a lower setting on that valve. This is because there will be less flow through the coil, and more cold water being mixed in at the tempering valve. Less flow through the coil gives the water more time to pick up heat from the boiler.

Did forget to shut off all the valves before taking the pump apart...That was bit of a surprise ;-)
Ohhh, I didn't realize you had also rebuilt the pump already... good deal, now you won't have to bathe today!


I'm impressed; most of the professional service people I've encountered recently can't remember details between here and their shop. We joke that many have the retention capacity of a Day Fly !
Thanks V, after 60 some odd years I'm happy to say that the three remaining synapses I have left are still functioning well in spite of heavy 'pickling'!
 
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