Weil Mclane P-WTGO-3 controller question


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Old 10-29-09, 05:00 PM
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Weil Mclane P-WTGO-3 controller question

Hello, folks. I've been lurking around here a bit and soaking up a bunch of extremely useful information. But now I've got a question that I haven't seen asked before.

I have a Weil Mclane P-WTGO-3 boiler that heats my home via baseboard hot water. It has a Beckett AFG burner unit, and a Honeywell Triple Aquastat Type L8124A, C controller. It is a single zone, single loop setup.

The unit previously provided domestic hot water. I have have a high-efficiency electric hot water tank that provides these duties now.

My question is should I change any of the settings on the triple aquastat? When the unit was providing DHW, The high was on 200, the low was 180, and the diff was 15.

I now have it set for 180 on the high, 140 on the low, and the diff at 20.

Am I close with the settings, or can I lower the low setting further? My ultimate goal is to lower my fuel consumption. Seeing that the unit is now not providing hot water and I've added insulation in addition to sealing up any air leaks in my 1200 square foot home, the unit is now probably oversized for the job.
 

Last edited by The_Bishop; 10-29-09 at 05:31 PM.
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Old 10-29-09, 06:44 PM
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Lower the LOW all the way down and run the diff at like 15 or so.

Your existing aquastat is known as a 'triple' aquastat and could theoretically be changed out for a 'single'. The single would allow your system to be run as a 'cold start', meaning it will shut off completely in the absence of a heat call.

There is a caveat though:

SOME boilers will begin to 'weep' water from the seals between the sections when converted to cold start after living a long life as a warm start. This is because the cast iron shrinks and allows leakage.

It's a double edge sword.

You could swap out the aquastat for an L7224U, and try running it as a cold start. If you do find the boiler weeping, then turn the warm start function ON ... (this aquastat allows turning these functions on and off... electronically). If you DO decide to go this route, make sure you find a BRAND NEW one, because there are some enhancements Honeywell recently made to the firmware... one is that you can now add OUTDOOR RESET via an add on module. This is very new, so you may have to hunt around for info on it.
 
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Old 10-29-09, 06:55 PM
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Originally Posted by NJ Trooper View Post
Lower the LOW all the way down and run the diff at like 15 or so.

Your existing aquastat is known as a 'triple' aquastat and could theoretically be changed out for a 'single'. The single would allow your system to be run as a 'cold start', meaning it will shut off completely in the absence of a heat call.

There is a caveat though:

SOME boilers will begin to 'weep' water from the seals between the sections when converted to cold start after living a long life as a warm start. This is because the cast iron shrinks and allows leakage.

It's a double edge sword.

You could swap out the aquastat for an L7224U, and try running it as a cold start. If you do find the boiler weeping, then turn the warm start function ON ... (this aquastat allows turning these functions on and off... electronically). If you DO decide to go this route, make sure you find a BRAND NEW one, because there are some enhancements Honeywell recently made to the firmware... one is that you can now add OUTDOOR RESET via an add on module. This is very new, so you may have to hunt around for info on it.
Sounds neat. Gotta love Honeywell.
 
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Old 10-29-09, 06:59 PM
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Ok, I'll change the settings on the controller.

I don't want to eliminate the triple aquastat; I've got things plumbed up so that if I need to I can utilize the in-boiler coil in case we have an extended power outage. My generator will run the boiler, well, and lighting just fine but it's nowhere big enough to run the electric tank.

Again; thanks for the help!
 
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Old 10-29-09, 09:14 PM
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OK, so if you plan to use the tankless coil during power outages, why couldn't you still use the 7224 and turn off the low limit until such time as that power outage occurs? It's just a few button pushes away...

Say hello to the little fishies at the hatchery next time you drive by it...
 
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Old 10-30-09, 04:23 AM
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Didn't think of that angle. I always figured that you needed the triple when you were running the system for DHW.

I'll be sure to tell those fishies you said Hi.
 
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Old 10-30-09, 09:59 AM
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Right, you do [need the triple]. The 7224 will work as either single or triple depending on how it's configured.
 
 

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