svizoman
Junior Member level 3
Air condition installer told me that I need either:
two parallel cables 5x2.5mm2 with 6x16A brakers or
one cable 5x4.0mm2 with 3x20A brakers.
We are talking about inverter heat pump Daikin Altherma HT, with termal power output of 11kW and with aditional 6kW inline electric heaters.
I have an older house where single core cables are build into the walls rather than multicore cables beeing laid into the plastic cable hose. I am using 2.5 cables and 3x16A brakers. My main house brakers are 3x20A (3 phase 50Hz, 400V) so using 3x20A brakers just for one consumer is not a good idea.
Considering EU regulation for house electric lines we can affor up to 3% of voltage drop for regular 70C termoplastic cables. I found two equations to calculate needed size of vire (in square milimeters) and power it is transported using 3phase, 400V supply.
Since inverter (variabile freq drive) acts as resistive load and electric heater is a resistive load we can neglect sin fi in our equation. So at 400V, 3 phase, 50Hz AC suply with 16A brakers we can transport round 11kW of electric power which should be enough for both heat pump as for additional el heaters.
Using second equation we calculate that 0.5mm2 wire (20 AWG) is more than enough to carry 11kW load at 400V, 3 phase AC at the distance of 10meters, considering EU regulation (up to 3% voltage drop and cable thermal insulation).
So why does offical Daikin installer want two paraller cables of 2.5mm2 with 6x16A brakers or one parallel cable of 4.0mm2 with 3x20A brakers?
Did I miss something?
My question to you is - am I right at my thinking or not.
two parallel cables 5x2.5mm2 with 6x16A brakers or
one cable 5x4.0mm2 with 3x20A brakers.
We are talking about inverter heat pump Daikin Altherma HT, with termal power output of 11kW and with aditional 6kW inline electric heaters.
I have an older house where single core cables are build into the walls rather than multicore cables beeing laid into the plastic cable hose. I am using 2.5 cables and 3x16A brakers. My main house brakers are 3x20A (3 phase 50Hz, 400V) so using 3x20A brakers just for one consumer is not a good idea.
Considering EU regulation for house electric lines we can affor up to 3% of voltage drop for regular 70C termoplastic cables. I found two equations to calculate needed size of vire (in square milimeters) and power it is transported using 3phase, 400V supply.
Since inverter (variabile freq drive) acts as resistive load and electric heater is a resistive load we can neglect sin fi in our equation. So at 400V, 3 phase, 50Hz AC suply with 16A brakers we can transport round 11kW of electric power which should be enough for both heat pump as for additional el heaters.
Using second equation we calculate that 0.5mm2 wire (20 AWG) is more than enough to carry 11kW load at 400V, 3 phase AC at the distance of 10meters, considering EU regulation (up to 3% voltage drop and cable thermal insulation).
So why does offical Daikin installer want two paraller cables of 2.5mm2 with 6x16A brakers or one parallel cable of 4.0mm2 with 3x20A brakers?
Did I miss something?
My question to you is - am I right at my thinking or not.