Hi All,
Thanks you everyone for the swift response!
Sounds like this is not likely a fix I can handle solo. There are few options
at the university I can try for the repair before having to go external.
The first breaker to trip was an RT-692 120/240VAC 20 Amp 1 Pole Circuit Breaker.
It took a few iterations to confirm which device was responsible for tripping it.
The tests I described in the original post used a power strip with built in 15 Amp breaker.
Kind regards,
Luke
Luke Fulton, PhD
CHEM BLDG R003
NMR Core Facility Director
Unit 3060
COR2E & Department of Chemistry
55 N Eagleville Road
University of Connecticut
Storrs, CT 06279
________________________________
> From: main_at_ammrl.groups.io on behalf of Michael Groves via groups.io
> Sent: Friday, July 17, 2026 12:04 PM
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] BCU II Power Issue
Hi all,
I'll second what Bob said--HVAC people are a great resource in this case.
This doesn't sound like they typical failure we see from BCUs--frequently
they either stop cooling or just fail to power up altogether. My first guess
would probably be a failing capacitor and this is definitely something your
HVAC guys should be able to help with. Because it's tripping the breaker
and not blowing the fuses in the unit that does seem to indicate a capacitor
issue to me. What's the rating of the breaker that's being tripped?
Cheers,
Mike
On Friday, July 17, 2026 at 10:00:01 AM MDT, Bob Berno via groups.io wrote:
Hello Luke,
I have had many issues with our BCU-2 chillers over the years. In fact, very
recently I was able to scavenge enough spare parts from two failed units to
get one of them operational again.
I suggest that you talk to the people in charge of maintaining your building
HVAC systems. They have been very helpful in diagnosing the issues with
our faulty BCU (1 and 2) chillers over the years. And they can source replacement
switches and relays, which almost always are the root cause of the failure.
Good luck,
Bob.
On 2026-07-17 10:57 a.m., Fulton, Luke via groups.io wrote:
Hi All,
This week our BCU II started experiencing electrical problems. Roughly 5
minutes after turning on cooling the circuit breaker trips and cuts power.
This is reproducible and happens even when given its own circuit without other
devices. It does not matter whether operating in remote mode when turning
on VTU or manually selecting cooling strength at the BCU II itself. The Status
LED consistently blinks Green from start right up to power loss. I presume
the BCU II is drawing an excessive load, but can't explain why. There
were not any surges or interruptions to building power coinciding with when
it first appeared (afaik), and this is the only device affected. In case it
matters: NEO console, TBO probe, TS 4.4
-I've checked the dust filter. It was cleaned recently and has a long ways
to go before clogging enough to choke air flow.
-I set the BCU II to flush for 24+ hours in case of ice blocks. No changes observed.
It's less than 2 years old. Fingers crossed the problem doesn't require sending
it out for repair.
Anyone have any suggestions on what to try next?
Kind regards,
Luke Fulton
Luke Fulton, PhD
CHEM BLDG R003
NMR Core Facility Director
Unit 3060
COR2E & Department of Chemistry
55 N Eagleville Road
University of Connecticut
Storrs, CT 06279
-- Dr. Bob Berno Manager,
NMR Facility
McMaster University,
ABB-156
1280 Main St.
West Hamilton,
ON L8S 4M1
T: 905-525-9140 x24158 or x24686
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Received on Fri Jul 17 2026 - 12:22:52 MST