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Newbie needing help - arcing relay

[email protected]

May 11, 2017
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May 11, 2017
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Dear all,

I would be very grateful for some advice....

I have just replaced my PCB on my hot tub with a new one from China (old Chinese hot tub - first mistake!). The components are supposedly rated for a max draw of 6kw for the heater.
When connected to a 3kw heater, the relay arc's every 20 to 30 seconds, with a nice corresponding flash :(

What I am not sure of is if the relay is duff, or if it is struggling with the current draw, or if the draw is not high enough to prevent the relay from clicking in and out and arcing. Details below:
Relay:
HF105F-1
012D-1HS
30A 240V AC

Heater:
H30-R1
Amps: 13.6
Power 3kw

Also worth noting, the same relay powers a circulation pump, details below:
DH1.0
Amps 3.8
Power 0.75kw

The arcing happens both with the circulation pump attached and disconnected.

I have 2 diametrically opposed thoughts:
1. The current draw is not high enough for the relay to simply stay on when turned on, which is causing the arcing - install resistor?
2. The relay is struggling with the load for some reason, and is arcing, therefore connecting the existing relay to a heavy duty contactor, and the heater and pump to the contactor may solve the problem?

I'd be really grateful for some advice and guidance, as I am a beginner at all this.

Many thanks,
[email protected]
 

duke37

Jan 9, 2011
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If the relay is arcing when it is supposed to be hard on, then look at the relay coil supply to ensure that the contacts are closed.
A more powerful contactor will only push the problem elsewhere if it is due to an intermittent signal.
 

[email protected]

May 11, 2017
3
Joined
May 11, 2017
Messages
3
Thanks for the reply Duke. I hear you, but not sure how I can resolve it if there is a problem prior to the relay :( Are you suggesting that the problem is prior to the relay, or maybe something in the coil within the relay itself? It feels like the EMF that should be holding the relay closed is failing?

Just out of interest, I disconnected everything from that relay and powered it on, it clicks in fine and doesn't arc. Then I tried to connect the circulation pump ( 3.8A and 0.75kW) and the relay starts arcing, although not quite as much as when the heater is connected.

The circ pump works fine when connected to a different relay, so I don't think it is a problem with the pump that is causing an issue in the relay.

Am I right in thinking that it is failing under load? Therefore change relay, or leave existing relay in place and connect it to a contactor (assuming the load required for the contactor doesn't make the existing relay arc)?

Does this make any sense at all, or am I barking up the wrong tree completely?
 

Minder

Apr 24, 2015
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With that kind 0f load I would expect arcing.
Repairing a few recent appliances of which just about all were relay problems, I found that not only the relays appear woefully small for their current ratings, especially when inductive loads (motors) are involved.
If you have sufficient room I would fit larger capability and physically larger relays or even go with SSR's.
M.
 

duke37

Jan 9, 2011
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The relay is driven by 12V DC, I would check that this is consistent, allowing the relay to stay in. Something is upsetting the relay when it should be conducting. Is the temperature controlled by switching the power on and off rapidly?

I would not advise a newcomer to measure when it is operating.
12V DC is ideal to drive a SSR. The 12V DC may be powerful enough to drive a big contactor.
 

Harald Kapp

Moderator
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Nov 17, 2011
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Where does the arc appear?
Across the contacts (how would you notice? most modern relays have an opaque housing)?
Across the pins on the contact side?
Across the pins on the coil side?
Does the arcing happen when the relay contacts are open, closed, or in both cases?

First I'd make sure the relay is correctly powered on the coil side - without an actual load. Check the actual coil voltage against the rated coil voltage. You should read at least 90 % of the rated voltage or more.
Next check whether the relay is subject to mechanical vibrations. Some relays are sensitive to vibrations and the contact force changes with the vibrations even up the moment where the contacts open momentarily. That may lead to an arc.
Also check your power supply. Is it stable or does it show dropout from time ti time? Do the dropouts correspond with the relay's arcingß
 

[email protected]

May 11, 2017
3
Joined
May 11, 2017
Messages
3
Hi gents,

Many thanks for taking the time to reply.
The relay is white opaque plastic, but you can see the arc through the plastic (!), and certainly hear the arcing. If I can upload a video on here, I'll film it for you?
I'm assuming this is a NO relay. There is no arcing until there is a load on the contact side. There doesn't appear to be any significant vibrations, and the other relays on the board work fine (same type of relay), although they are connected to different pumps etc.

Thanks for the advice gents, I'll try and test the existing relay.

Cheers,
[email protected]
 

Minder

Apr 24, 2015
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+1 on the test for low coil voltage, it looks like 12vdc for this relay, the coil and contact are on the front so it should be possible to measure easily.
Is it dropping out and in sporadically when it shouldn't?
M..
 
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