z820 install of multiple P40 GPUs power trouble

[DunMath]

I am trying to install 3 x Nvida P40 GPUs into the Z820 V2, Win10. It has the 1125 PSU with 240 volts giving 1450w available and standard 3 x accessory 6 pin power supply. 

The P40 requires 225w each on 1 x 8 pin connector (Total under 700w).

I have 3 of dual 6 pin to 8 pin Power cables adapters

plus accessory PSU - XTYPOWER 'Sure PSU' model ST1800W with 10 of 6 pin power cables.

Even though the HP standard answer is the Z820 accessory cables are 75 w but can handle up to 150w. When I connect ;

1 x p40 GPU to any 2 of the 3 HP standard 6 pin acc power supply (using the  6 to 8 pin adapters) it just beeps even though there should be enough power (incl PCIe 75w). or

1 x p40 GPU to 2 of the connected to the ST1800W via the 2 x 6 pin to 8 pin cable - no beeping but st1800W cables hot + plastic smell.

3 x p40 GPUs with 1 of 6 pin connected to 1 HP standard 6 pin acc power supply and the other 6 pin connected to the ST1800W PSU. It beeps and has melted the wires from the st1800W with in a few seconds.

When I test the Acc power cables with a multi-meter I get no voltage?

It sounds like to me that there is an issue with the z820 acc power perhaps? Cables or PSU?

Is there a BIOS setting to turn on?

the ST1800W and its cables are not up to 75W each?

Any help would be appreciated. Dunc

[DGroves]

i have touched on this subject several times in previous power related posts please use this forums "SEARCH" function to read them

the z800 820 840 systems use "Multirail" power supplies not single rail (which is now the more common type)

due to this, you have a hard limit on what wattage can be pulled from each power supply rail

and since the P40 can draw up to 250 watts (not 225), trying to use three of them (750) the available wattage the GPU power rail can supply

next, you description of what happens appears to show the z820 power supply crowbarring (shutting down) due to a excessive power draw/short somewhere

start with just the z820 without ant addon power supply

if the system boots using one card/adapter remove that card, then NOT USING that cards power connection/adapter connect a sec p40 and adapter to the system and boot

repeat with the third card adapter, this tests that each card adapter and gpu power plug is functional

 HP does not recommend or support more than 2 high wattage cards via the GPU connections

connect two p40 cards to the GPU cables in this order

one card to the cable that has only one 6 pin plug (GPU rail #1) using a 6-8 pin adapter

one card to the cable that has two 6 pin GPU plugs (GPU rail #2) using a 6-8 pin adapter

the sec GPU 6 pin connector on rail 2 is connected to  both cards using a dual 6 to 8 pin adapter

it's apparent that your attempt to connect a ext ST1800W power supply is improper and causing a direct short which can damage the z820 and all it's parts and the ext power supply

i have seen adapters that allow a  atx 24 pin connector to power on ext supplies but they are not compatible with the HP workstations non atx power supply

[DunMath]

Thank you D Groves for your contributions. I have previously tried the accessory supply in every combination of the 3 - and none worked. Tried again. I have got 1x nvidia P40 working by using all of the accessory cables 3 into 2 into 1. Plan to install a 1 x P2000 (75 watt) and a 1 x P4 (75 watt) for a total of 37 Gb x Gddr4. I have bought an additional Hp 1275 PSU -could someone design an upgraded PSU with 3 x 8 pin cables?

[EXCITERESEARCH]

My summaries were incomplete/incorrect, so I'm temporarily replacing with this comment because there's no way to delete a post.