Aquastat Setting with a SuperStor and More

ESGWheel

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 http://inspectapedia.com/heat/Aquastat_Settings.php

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.

ESGWheel

Hatter,
Thanks for the reply and I confess my ignorance:
* what does "CH" stands for? and
* what would be the condensing range I need to stay above?
I figured if the boiler never got below 100 it would not be in that range. Perhaps that it is at 100 at its lowest but will really drop in temp upon a call when the cold water from the zone hits it? But the burner would be running, so should not matter?

Thanks for your time in getting me on the right track.
bill

ESGWheel

LOL, got the DHW part but CH threw me.
So key is for lowest temp at 128 or above
I'll have to redo my picture
Thanks for your advice and time