Zs on ground source heat pump

[davidjones89]

Test readings on ground source heat pump are showing R1 + R2 as 0.03 ohms, zs reading taken at rotary isolator for the pump is 0.27 ohms. Protective device is a 63A type d mcb, run of cable is approx 7 metres, wired in 16mm t & e, ze is 0.11 ohms, max for a type d is 0.15 ohms so i'm well over but how come given all the other readings. Advice needed please :banghead: :icon9:

 

[telectrix]

try taking a reading from the busbar. i.e. after the MCB but before your circuit. the difference, if any, between that reading and the Ze will be due to internal res. of the MCB. this can be enough to throw your Zs above limits. alternatively, record R1+R2 and calculate Zs.which would give a value of 0.14ohms.

 

[Des 56]

Sorry for the intrusion into this thread,but could someone give me some understanding of whats involved with these heat pumps please

Now this is a subject where I'm an absolute know nothing,but I think I will be involved in wiring one of the contraptions in a couple of months, so I will need to get educated

63 amp mcb and 16mm twin + earth ground source heat pump ?
What is a typical rating of the pump or pumps with such large cable and mcb being used and is there any items I need to be aware of specific to these systems

Thanks in advance