Weil Mclain Ultra 155 - Blown 3AMP fuse

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Old 10-25-18, 10:47 AM
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Weil Mclain Ultra 155 - Blown 3AMP fuse

Hi
I have installed Two Weil McLain Ultra 155 as attached diagram. I am using it one as LEAD and other as SHADOW. Shadow will kick in if
LEAD boiler runs more than 10 min.

Intially I connected only three zone and it was working great for one week. Finally I got some time to hookup my all 12 Zone Valves (Honeywell- 4 Wire (Two Yellow and two
red)) and turn on the boiler. It ran about 10 min. and all of sudden It stopped working, screen went blank and only Fan was runninng. It blew up 3 AMP Fuse.
I disconnected all zones and connected only hot water Zone (Note: Hot water tank plumbed as one of the zone not used as DHW) and replaced Fuse with new one. Now everything
is working. Now I am afraind to connect all zone. I need to find out root cause before I connect all zones.

My question is how do I troubleshoot this issue without blowing up fuse again and again ? What could be the issue.

I have Four 40VAC transformer, 3 Zone valve connected on each one. Same Zone valve were connected on same 4 transformer with 25 year old boiler and I never had and issue.
I checked voltage on each transformer and 3 of them showing 24V and one of them is not. Did it blew up one tranformer ?. I heard ticking noise
while boiler was running on transformer which is no longer showing 24V.

I do not see any issue with how I have wired Boiler since all function works as expected. Also, I beleive all zone valve wiring is correct too.
It seems if I connect more zone, it is sending more resistance (???) to boiler which is overloads the circuit ? How do I protect that ? Should I wire
RELAY between RED/WHITE wire of Zone valve to RED/WHITE Boiler wire ?
 
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Old 10-25-18, 11:10 AM
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The diagram is too small for me to make out.
 
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Old 10-25-18, 11:39 AM
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Please see page 26 in below link. I have two boiler setup.

https://www.weil-mclain.com/sites/de...3-manual_1.pdf
 
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Old 10-25-18, 12:20 PM
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Figure 27, p. 26, shows individual circulators for each boiler, no zone valves. I'm still a little confused, but if one transformer is dead, I would replace it. It would be helpful if you posted a sketch showing how you have the transformers, zone valves, and fuses wired up. If you are blowing a fuse, it seems possible that you have a short somewhere? You said the transformers were 40-V? Did you mean 24-V? What is the amp rating of the zone valves? What is the VA rating of the xfmrs? how many zone valves do you have on each xfmr?
 
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Old 10-25-18, 04:55 PM
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Page 26 applies to piping...... no mention of any electrical connections.

The two yellow wires from each zone valve gets connected in parallel to all the the other valves. It doesn't matter if there is one zone valve or 20. The two yellow wires are for switching only. No thermostat wiring should be connected to the yellow wires at any point.
 
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Old 10-26-18, 09:30 AM
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I think I found root cause of problem. Wire going from external transformer to three zone valve was shorted due to wire clip I installed to organize the wire. Apparently nail from Wire Clip went in middle of transformer wire and I did not realized it. That caused transformer to blow up but not sure how it went into boiler and blew up the fuse of boiler. I have ordered new 120 --> 24 V 40VA transformer. Will install and see how it goes. Rest of the three transformer connected 9 Zones are working good.
 
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