Honeywell L7248L aquastat features / settings?

fredweNovember 15, 2012

I hope fellow forum viewers can help me, where Honeywell unfortunately has declined to provide information. Our oil company installed the aquastat along with a Solaia boiler & Riello burner, but they don't seem up-to-date on the L7248L features.

The aquastat's full model number is "L7248L 1070 1." The L7248L is connected to a Taco SR506 6-zone relay, one of whose zones is indirect DHW. The SR506 connects only to the TT terminals on the 7248; right now the aquastat's ZR is not used. In the interest of saving energy and money I am investigating Honeywell Outdoor Reset modules.

Question: When I step thru the aquastat settings the only ones listed are HL_, F-C, and ELL. Could you please explain why duu, tPL, and tPt are unavailable? I do understand that the Reset settings (such as OtL, BtL) should be shown only when an approved reset module is detected on the Enviracom bus

2d question: are Thermal Purge and Outdoor Reset mutually exclusive?

Thank you very much for your help!

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fredwe

Thank you for replying. I have been to that web page several weeks ago. I have scrutinized the install manual very carefully and have not found an answer to the questions I posed on this forum. If you actually can answer them then I would much appreciate hearing from you.

    Bookmark   November 18, 2012 at 8:02PM
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zl700

The answers are there in the instructions, they have to be used and enabled. if you arent using DHW inputs, duu, tPL, and tPt wont show unless function is turn on, see page 5.
The intent of thermal purge is to insure usable residual heat in the boiler is circulated until it is sufficiently
depleted from the system before the burner is allowed to fire. Nothing to do with outdoor reset.

Its all there if you fully understand what your reading and comprehend heating functions.

    Bookmark   November 21, 2012 at 11:33AM
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fredwe

Thank you for following up. I admit maybe I'm just dense, but if duu does not appear in the list of settings, I do not understand how to enable ZR for DHW. Perhaps the controller senses whether there is a wire attached to its ZR terminal and shows duu only under those conditions.

As for thermal purge, the instructions on p. 5 say "tPL** Thermal Purging Limit Temperature (�F or �C), "OFF" if disabled." The way I read that is, to turn on thermal purge, adjust tPL to something other than OFF. If tPL is not in list of settings I am baffled how to enable it. And yes, I think I do understand the purpose and operation of thermal purge.

I had asked whether you could setup the L7248L to do BOTH thermal purge and outdoor reset. Pages 5 seems to say, NO:

**Settings available for adjustment only when the
W8735S1000 AquaReset Outdoor Reset Kit is NOT
installed.

Sorry if I just don't understand. I really appreciate your effort to help.

    Bookmark   November 23, 2012 at 3:35PM
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fredwe

Well, now I can answer my own question. Sometimes a letter to the CEO gets you the cooperation you need - I spoke to a Honeywell product manager in their Environmental & Combustion Controls division.

The reason I don't see the settings I expected, is that my aquastat (date code 0829), while only 4 years old, has neither of the features that interest me. Although this basic (electronic) design was introduced in 2004, it was not until 2010 that Honeywell added Outdoor Reset capability, in spite of the fact that residential O.R. has been available for over half a century. Go figure.

As for Thermal Purge, it made its appearance only this year (2012) and not voluntarily. Federal energy efficiency regulations mandated this feature.

So, for my purposes, unfortunately my aquastat has all the features of Honeywell's analog design from 25 years ago, and if I want Reset I will have to buy a current-production L7248L.

    Bookmark   December 7, 2012 at 10:17AM
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