Resident script pump circulation

[Domoticatorino]

Code:

valveStatesTag = 'pompa_circolazione_giorno'
pumpGA = '2/0/1'

opened, first_timestamp = false, 0

valveStates = grp.tag(valveStatesTag)
for v = 1, #valveStates, 1 do
 valveState = valveStates[v]
 if valveState.value then
   opened = true
   if first_timestamp > 0 then
       if first_timestamp > valveState.updatetime then first_timestamp = valveState.updatetime end
   else
       first_timestamp = valveState.updatetime
   end
 end
end

if opened then
   opened_5_minutes = (os.microtime() - first_timestamp) >= 120
   if opened_5_minutes then
       grp.checkwrite(pumpGA, true)
   else
       grp.checkwrite(pumpGA, false)
   end
else
   grp.checkwrite(pumpGA, false)
end

Hi, I use this script above and it seems does not work. I use 120 sec to check without loosing too time. Unfortunately Pump does not start.
What do you think?
Thanks.