Max heatbed output of the Melzi board

Hi Guys

I'm building a 400x400x400 machine and for the heatbed at the moment I'm powering it by using 4 little heaters connected on mains. The bed only reaches 56 degrees (IR sensor) and so far after over 100 prints in PLA I have not had any curling or detaching so that's great, however I need it to be controlled by the Melzi really and a 300x300 silicone heat pad would be sufficient to spread I think. They draw about 12v and 20amps:

[www.amazon.com]

I'm struggling to find out what the max draw I can take from the Melzi board would be. I'd prefer not to have a second PSU and a relay board if possible, although I have already specced out that option. I'm trying to keep costs to a minimum.

Anyone know this information ?

Thanks

Adam

I don't know the max draw, but I recently came across a fairly reasonably priced way of increasing it (reprap.me).

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