Honeywell 8148A setup questions.

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Old 02-10-16, 10:35 AM
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Honeywell 8148A setup questions.

The 8148A aquastat on my boiler crapped out... relay would switch on, but the circulator pump would not energize (no power on C1/C2), so boiler was getting up to temp but no water was circulating thru the system even when the zones called for it. I stopped at a plumbing supply house on the way home and picked up a replacement. The replacement is slightly different even though the same part # (pic #1 is new label, pic #2 is old label from inside of cover).

I have a couple of questions perhaps someone can answer.

The boiler seems to be short-cycling. Kicks on, run for several minutes, turn off, and then back on again in 5 minutes. It seems to be cutting off at 180 and back on again at 170, from what I can see. I've read the 8148A has a built-in temp differential of 8 degrees, but, honestly, I don't recall the boiler cycling on and off so much with the "old" aquastat -- even when it was working correctly. Has the 8148A always had an ~8 degree cycle point?

Can someone explain the how to properly set the temperature on the "new" 8148A. I'm unclear on what the purpose of the little lever is on the dial. The old 8148A didn't have this little lever, it was just set to 180 degrees (see 3rd pic). I set the new 8148A to 180 by putting the dial at 180 (based on the "old" setting), and it seemed to shut off at 170. So I turned it up to 190, and now it seems to shut off at 180... What's the little lever thing supposed to do? (see 4th pic)

Finally, the "old" aquastat has some odd wiring (see 5th pic)... runs from L3 to B on the temperature wheel housing. I did not recreate this 'jumper' on the new 8148A, I did not understand the purpose (I thought the relay clicked on when the thermostats called for heat, thus energizing 'B', and the temperature setting would determine whether or not to fire the boiler or just turn on the circulator pump... so why this jumper was there, I'm confused (boiler does not have tankless hot water -- it used to have a zone for an external hot water heater years ago). Could this be why the boiler seems to be short cycling?)

Would appreciate some education from those "in the know".
 
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Old 02-10-16, 11:59 PM
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I'm unclear on what the purpose of the little lever is on the dial.
High Limit Dial Stop. (Figure 15)
(Always turn power off before removing cover, see figure 5)


Product Data and Specifications-Product Data for L8148A, L8148E, L8148J Aquastat Relays (English) [pdf]


L8148A1124/B -- High Limit Aquastat Relay with 15 F fixed differential
 
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Old 02-11-16, 12:03 AM
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the "old" aquastat has some odd wiring (see 5th pic)... runs from L3 to B on the temperature wheel housing
Repair of Bad PC-board Trace.
 
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Old 02-11-16, 12:39 AM
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Yes your boiler is short cycling.
 
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Old 02-11-16, 07:31 AM
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Thanks for the response. I think I've got it now... The dial itself is the equivalent to the LIMIT OFF on some forced hot air controllers, and the lever is the equivalent of the LIMIT STOP.

What I found confusing was the lever was in the 180-190 degree range, so it was unclear to me if the lever played a role in the shutoff temperature, compared to the "old" 8148's simple dial.

As the lever is currently set, should I read that as a LIMIT STOP of 185, even though I may turn the dial itself up to 190?

Last evening I pulled the aquastat off again, cleaned out the well as best as possible, and then replaced the conductive paste.... performance in terms of short-cycling was much better, so I suspect I was getting poor connectivity on the sensor in the well and that was throwing the controller off.

Problem solved in time to survive the sub-zero temperatures predicted for this weekend
 
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