Discuss HWS trips 20A CB after a few minutes in the Electrical Appliances Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
0
Hi there,

I have a Vulcan (2009) Hot Water System (HWS) which is now tripping the 20A CB on my switchboard. The switchboard has been replaced one month ago (no problems since today, though).

The tripping happens 1-2 minutes after I switch the CB back on. Does it means I can rule out any short circuit / earth connection problem? I would assume that should trip the CB instantly?

I have set the thermostat to the lowest temp (60, was 80 before) and examined the wires (nothing suspicious). The thermostat is labelled: "240V – resistive load 30A", does it means the HWS might draw up to 30A? thus the CB being too low?

Thanks a lot for you help!

Thierry
 
TL;DR
HWS trip 20A CB, HWS is labelled as "240V – resistive load 30A", do I need to change CB to 30A?
No. That just means the thermostat is capable of carrying 30 amps.
It would be helpful to know the rating of the actual heating element if possible.
 
Hi there,

I have a Vulcan (2009) Hot Water System (HWS) which is now tripping the 20A CB on my switchboard. The switchboard has been replaced one month ago (no problems since today, though).

The tripping happens 1-2 minutes after I switch the CB back on. Does it means I can rule out any short circuit / earth connection problem? I would assume that should trip the CB instantly?

I have set the thermostat to the lowest temp (60, was 80 before) and examined the wires (nothing suspicious). The thermostat is labelled: "240V – resistive load 30A", does it means the HWS might draw up to 30A? thus the CB being too low?

Thanks a lot for you help!

Thierry
What size in KW is the heater?
 
1st thing I would be doing is sticking a clamp meter on it and seeing what load is being drawn.
 
3600 Watts is around 15 amps, so should not trip a 20 amp breaker. Sounds like it's a faulty element. Insulation resistance test will prove it.
 
Last edited:
3600 Watts is around 15 amps, so should not trip a 30 amp breaker. Sounds like it's a faulty element. Insulation resistance test will prove it.
It’s a 20A breaker.

if I had To give it odds,
80% chance of faulty heating element
19% chance of faulty breaker
1% something else.
 
Thanks for hints, really helpful.

It seems the problem solved itself: after I reset the CB to ON again a few time, it just stop tripping and remained ON since then.

I guess if it happens again I would go with a clamp meter (didn't knew these existed), if it draws more than 20A, I could assume faulty heating element, right?

With a broken thermostat, I would assume it would not draw more than 20A, but might just over-consume power over time?
 
Agree with @newfutile thought, the RCBO used here will trip with earth leakage current of 30mA. This could happen with a dodgy element and is readily confirmed with an insulation resistance check.
 

Reply to HWS trips 20A CB after a few minutes in the Electrical Appliances Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock