My old 4 wire 240V mechanical line voltage thermostat stopped working. I want to replace it with a digital thermostat. Problem is I don't know the amp rating of the old thermostat. I checked with maker and they have no info...too old. Is there a way to check amp rating of old thermostat? A very good electrician installed the two 8 foot baseboard heaters, thermostat, 2-pole 20 amp circuit breaker and all wiring about 25 years but he is nolonger around.