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Surge Protection Devices

 
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Air Source Heat Pumps (ASHPs)
Last Post by Batpred 4 months ago
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Batpred
 Batpred
(@batpred)
Noble Member Member
Joined: 2 years ago
Posts: 1200
12/06/2026 3:23 pm  

Posted by: @transparent
↑

Posted by: @batpred
↑

So would the presence of DC components require RCDs to be fit?

Erm... I can interpret that question in more than one way, so I'm unsure of the angle you're taking.

All Type-B RCDs and RCBOs will correctly trip ii there is an element of Direct Current superimposed onto the mains 50Hz waveform.
I've deliberately changed the wording to clarify the concept.

 

The reasons that earth-leakage devices are fitted to circuits is usually to

  • protect the cable in the event of fire / over-heating
  • prevent death in the unlikely event of a person touching a live wire or connector
  • prevent the metal casing on an appliance becoming live due to a short-circuit fault

 

That decision is the same irrespective of whatever aberrations are present on the sine wave.

In the case of our installation site, I see value in having the RCD fit, so we will have it. In many other cases, since I understand isolators are typically installed near the heatpump (EST guidance), unless the RCD would remove the need for such isolator, it seems to mostly add to costs without significant value.  

But my angle was actually on whether an RCD could be justified solely based on the likely DC components?

 


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kW export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; Vaillant Arotherm Pro 7kW; 100Amp head, HA lab on mini PC


   
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Transparent
 Transparent
(@transparent)
Illustrious Member Moderator
Joined: 5 years ago
Posts: 3430
12/06/2026 3:28 pm  

Posted by: @batpred
↑

But my angle was actually on whether an RCD could be justified solely based on the likely DC components?

No.

The shape of the waveform has no bearing on the decision to use an RCD.

 

BTW. I'm still unsure why you're making "DC Component" into a plural.
Could you give an example for me please?


Save energy... recycle electrons!


   
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Batpred
 Batpred
(@batpred)
Noble Member Member
Joined: 2 years ago
Posts: 1200
12/06/2026 9:13 pm  

@transparent 

i just mean dc in the wire


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kW export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; Vaillant Arotherm Pro 7kW; 100Amp head, HA lab on mini PC


   
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