Pump HP vs Heater KW Permissible Combinations

Maximum pump / heater combinations for common lower powered spa installations

 

AS/NZS60335-1 refers to rated power input deviations which permit a small increase in acceptable overall current draw above the actual rated power supply.
This means that a 10A or 15A plug in spa control system is able to have a total load a small margin greater than those plug ratings, as per below information.
The below info outlines the maximum amperage that the pump associated with the heater can draw.
It’s important to note that the maximum load of other combined pumps, blower etc, also does not exceed the 10A or 15A rating.

Just because an existing spa has installed from manufacture, or an alternate supplier advises that you can use larger pumps, does not make it accurate information. AS/NZS60335-1 gives clear data relating to maximum load.

In almost all circumstances the combined current draw is allowed to exceed the rated input by a maximum of 5%
10A plug in system can consume a maximum of 10.5A
15A - plug in system can consume a maximum of 15.75A (7)

 

10A plug in power supply

1.5kw heater = 6.25A
4.25A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
4.25A single speed pump with blower (1.0hp MAXIMUM pump)
1.5hp two speed pump with blower (1)
3hp two speed pump with NO blower (2)

2.0kw heater = 8.33A
2.16A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
2.16A circulation pump with 6A single speed jet pump and blower (3)

Maximum load with a 10A standard plug in power cable cannot exceed 10.5A

 

15A plug in power supply

1.5kw heater = 6.25A
9.5A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
11.0A single speed pump with blower (4,7)
3hp 2 speed pump with blower (5)

2.0kw heater = 8.33A
7.4A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
7.4A single speed pump with blower (typically 1.5hp or low performance 2.0hp MAXIMUM pump)
3hp 2 speed pump with blower (5)
2 x single speed pumps – pump one 7.4A (P1 & P2 combined 15.75A)
2 x single speed pumps and blower – pump one 7.4A (P1, P2, & blower combined 15.75A)
1 x two speed pump, 1 x single speed pump and optional blower (combined high speed 15.75A)
1 x low flow circ pump, 2 x single speed jet pumps and optional blower (combined 15.75A)

3.0kw heater = 12.5A

3.25A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
3.25A circulation pump with 3hp single speed jet pump and blower (6)
3hp 2 speed pump with blower (5)

Maximum load with a 15A plug in power cable cannot exceed 15.75A (7)

 

20A power supply (generally hard wired)

3.0kw heater = 12.5A

8.5A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
8.5A single speed pump with blower (typically 2hp MAXIMUM pump)
3hp 2 speed pump with blower (1)
2 x single speed pumps – pump one 8.5A (P1 & P2 combined 21A)
2 x single speed pumps and blower – pump one 8.5A (P1, P2, & blower combined 21A)
1 x two speed pump, 1 x single speed pump and optional blower (combined high speed 21A)
1 x low flow circ pump, 2 x single speed jet pumps and optional blower (combined 21A)

4.0kw heater = 16. 7A
4.3A maximum pump load - pump (or low speed for a 2 speed pump) associated with heating

Permissible combinations:
4.3A single speed pump with blower (1.0hp MAXIMUM pump)
3hp 2 speed pump with blower (5)
1 x two speed pump, 1 x single speed pump and optional blower (combined high speed 21A)
1 x 4.3A circ pump, 2 x single speed jet pumps and optional blower (combined 21A)

 

(1) Heating is with pump low speed only. Low speed is typically 2A.
(2) Heating is with pump low speed only. Low speed is typically 2A. High speed of a 3hp pump is typically around 10A, so no blower or other load can be added.
(3) Heating is with small circulation pump typically 2A. Jet pump and blower combined load cannot exceed 10.5A.
(4) In this combination the total load is permitted to be a maximum of 17.25A. Therefore, a substantially larger pump amperage is acceptable.
(5) Heating is with pump low speed only. Low speed is typically 2A.
(6) Heating is with small circulation pump typically 2A. Jet pump and blower combined load cannot exceed 15.75A.
(7) Maximum load is able to be 15% above rating when the pump has a higher current rating than the associated heater. For a 15A circuit this equates to 17.25A. This rating onlyapplies to the combination with this footnote marked against it. In ALL other cases, the maximum load input amperage deviation permitted is 5%.

Other combinations may be possible. Provided total load never exceeds the circuit current rating by a maximum 5%.
We recommend that were possible, maintain the maximum current draw below the circuit rating. 

 

The figures above assume the electronic spa pack is load shedding the heater (heater disabled as soon as a load other than the associated pump or pump speed is turned on). Load shedding is standard on most spa packs but needs to be checked as it can be over-ridden.
Variations are available with some spa packs offering load limiting which prevents a pump or blower operating to limit overall current draw to an amperage within the correct limit.

As an example:
15A power available (maximum 15.75A load)
2.0kw heater 8.3A
2 x 7.0A single speed pumps
1 x 4.0A air blower
Load shedding the heater as soon as pump 2 or blower are turned on.
P1, P2 and blower combined = 18.0A which is to great (max permissible is 15.75A)
Load limiting prevents all 3 outputs running simultaneously. e.g. you can only run p1 and p2, P1 and BL, p2 and BL, but cannot run P1, P2 AND Bl. 
This reduces maximum load to 14.0A and is therefore safe and legal.
Only a limited number of spa packs are capable of offering load limiting capabilities.