I see. I'll just use one by the heater then. I was going to go with this one because it had good reviews and was cheap.
http://www.amazon.com/gp/product/B0039LH8PM/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
However, your comment about quality has me worried. Should I use a higher...