Aquastat Setting with a SuperStor and More

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Old 02-28-16, 03:04 PM
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Aquastat Setting with a SuperStor and More

I have an Oil Fired Boiler forced hot water system (Hydronic) with typical baseboard radiators. Almost standard fare with 3 zones (1st for finished basement, 2nd for first floor and 3rd for second floor) in my typical New England Colonel. Honeywell L8124A Aquastat on a York AP-590 Boiler with tankless domestic hot water.

Almost normal, reason 1, because the former owner installed a SuperStor domestic hot water heater. This means that there are now 4 zones, 4th being the SuperStor. This works exactly like another zone with the ‘thermoset’ that call for heat as part of the SuperStor. And while the original tankless is still plumbed up it, it was done properly such that it is cut out of the domestic hot water circuit and vented to atmosphere. Works just fine.

Almost normal, reason 2, because I installed an Intellidyne IntelliCon HW+ Hot Water Hearing System Economizer some years ago. It has a feature that allows for using a SuperStor and it is all set up per the manual. Works just fine and has saved me a noticeable percentage of oil during a heating season (~15%).
In the past I had not studied nor modified my Aquastat settings. Until now. I have now read the various excellent articles on Hi, Low, Diff and disabling the Low that can be found on the InspectAPedia site.

So posting what I have set the Aquastat to in hopes to get comments that I did it correct or wrong.

And I think these settings apply regardless of the Intellidyne Economizer. Of note is that since I have a SuperStor, while I could conceptually disable the Low Limit, I did not want to because (1) the concern over boiler cooling down to ambient (condensation, etc.) and then being called upon as the SuperStor called for heat and (2) it seems that the SuperStor will produce domestic hot water sooner, as in longer to run out, with the family of 5 folks feeding off it (think consecutive showers). Note: with the SuperStor we have never ‘run out’ of domestic hot water, even in the summer.

I have also crafted a modified version of Honeywell’s ‘set point’ diagram. It occurred to me that a lot of my confusion over the Low Limit is simply due to their diagram showing an “up arrow” for the Differential Setting. This implies the bottom ‘line’ (switch makes R-B and breaks R-W…) is the low limit and the differential takes it to the line above. In fact it is opposite. Differential ‘drops’ the Low Limit. Add to that they show another “differential” for the High Limit that I think adds to some of the confusion, when I fact that is hard wired.

So onto my setting and justification. Looking for advice that “makes sense, this is good” or “Bill, you need to go back to school”

High Limit Setting: set to highest possible WITHOUT exceeding 200 on Boiler. In my case this is ~ 185, after observing a number of cycles. Note: I have not only the Boiler temp gauge but also the Intellidyne has a senor on the boiler output. And when the circulator is running these closely track one another. Logic from reading on this site is that the hotter the boiler water the better the efficiency and heat transfer to the air. See this link Aquastat settings: Best High, Low, & DIFF Settings on a Heating Boiler Aquastat?

Low Limit Setting: Set to lowest possible. In my case this is ~ 110. Logic is that (1) no tankless but do have SuperStor (read above) and (2) do not want to deal with issues of boiler going to ambient.

Differential Setting: Set to lowest possible. In my case this is ~ 10. Logic is that do not want the boiler to drop too low in temp. Not sure what temp things will start to condense but I figure that is the boiler only gets down to 110 – 10 = 100 that is still hot enough. If NOT, then I need to raise the Low Limit NOT the Differential.

Thanks for reading and if you have some other ideas would appreciate your comments.

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Old 02-29-16, 09:12 AM
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hi ESG-

I’m not much help, just a newbie. I don’t think they changed the control, I think they probably just clarified the Low Limit and the differential. This page from the manual -

95-6571.11 G.R. Rev. 12-01

is certainly different form yours.

[ATTACH=CONFIG]63455[/ATTACH]
 
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Old 02-29-16, 05:07 PM
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zoesdad,

that is kind of my point: that the diagram in the manual is somewhat confusing, so I modified it But I have again re-read it and some other articles on InspectAPedia website where they explain the Aquastat. And the moderator has been very helpful.

Bottom line is I did not capture the 10F delta in the Low Limit that is 'baked in' regardless of the DIFF setting, so I will redo it and correct my post.

My overall dilemma is that with the SuperStor I really do not need a Low Limit BUT I do not want to have issues with Cold Starts and Condensation, etc. Example: one gent offered that I need to keep it about 128F to preclude Condensation.

So hoping there are others with SuperStor set up and understanding their approach.
 
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Old 02-29-16, 05:53 PM
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Bottom line is I did not capture the 10F delta in the Low Limit that is 'baked in' regardless of the DIFF setting, so I will redo it and correct my post.
All the diff does is change the lo limit temp burner off time.

If you set your low to 110 the boiler will fire when it cools at 100. And burner will turn off at 110. This is with a 10diff. ( the circ will not come on if a call for heat until 110f)

As long as the indirect or there is no call for heat it will do this indefinably..

Now say with a 110 lo and a 25 diff. Boiler fires at 110. Now the boiler will turn off at 125f. Additionally the circ will not run until the boiler reaches 125 if there was a call for heat...

IMO your best off making the boiler cold start... That site you linked too is kind of hokey...

To make a cold start you need to remove the blue and white wire from low and diff and tie them togther... This will save you fuel...

Condensation issues arise from cold return temps from the loop.
 
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Old 02-29-16, 05:58 PM
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Old 02-29-16, 06:09 PM
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Intellidyne IntelliCon HW+ Hot Water Hearing System Economizer some years ago.
Not a fan and it makes things complicated... Where do you think you saved the 15% of oil?


Whats the make and model of boiler?

How many circs?
How many zone valves?

Any controls such as a taco panel to control the circs or zonevalves?
 

Last edited by lawrosa; 03-01-16 at 02:12 PM.
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Old 03-01-16, 08:53 AM
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...the diagram in the manual is somewhat confusing, so I modified it...
I didn’t read your post carefully enough. I see what you did with the diagram. I agree, I think the original is somewhat confusing. I think trying to show two different cases on that diagram for the limits of the adjustable Diff (Diff=10 and Diff=25) IMHO wasn’t very well done. Just my opinion.
 
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Old 03-02-16, 03:13 PM
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OK guys – looks like I have way too much time on my hands lol, but I think their diagram could be redone something like this, and I’m sure there are better ways, maybe where you pin the example numbers right on the rectangle. Who knows, lol:


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Old 03-02-16, 05:59 PM
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zoesdad,

And to think I was going to spend my w/e redoing the diagram. No more! It looks like u nailed it! Thanks for putting it together


lawrosa,

Make and model of boiler > New Yorker AP-590 (107,000 BTUH for DOE Cap.)
No. of circs pumps: 1
No. of zone valves: 4 that includes the SuperStor and the basement which only occaiaonlly gets run
Any controls such as a taco panel to control the circs or zonevalves? No

The 15% comes from factoring two elements together:
1) the Intellidyne IntelliCon HW+ Hot Water Hearing System Economizer has a display on it that cycles thru a few readouts, included a "You have saved xxx" based on an internal algorithm. It says 23% which I think is a little bit of a stretch, which leads to no. 2
2) based on a review of my oil consumption over the first few years after I installed it vs. before. Clearly this is problematic with so many factors, etc, but was also clear I was using less.

Is 15% exact? No way but I am believe that it is right around there if not above.

For the condensation, I have been recently reading it is due to the cold return hitting the heat exchanger as you are confirming. But if the burner was firing it would seem to me that it would evaporate and not be an issue. I guess I still am not following all the dynamics and what seem to be concerns over cold starts and condensation.

I get this will really only be an issue when I turn off my room thermostats and the only calls for heat are for the SuperStor during the 'summer'

Boiler is 25 years old and we are planning for new boiler in a year or two so I do have some concern over treating it gingerly.

Thank for your time and advice...
 
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