Out of curiosity, how do you have your 28CFM blower hooked up to your HeaterMeter? If I recall correctly, that model of blower fan is 12V 1.65A, which is a lot more than the HM can handle. Do you have it on a separate power source with an optoisolator?
I been using an rotodamper, and will soon be using a RD25 that Ralph built for me. As long as you have an power supply of atleast 1.2amps then there is no problems. I think I have even used an 1 amp without issues.
I would be kinda shocked if that giant blower worked fine, along side a servo, with the stock 1A power supply? I know my HM browned out very easily with a 15CFM blower and the servo going. My advise is if you haven't bought the PS already just shoot for a 2A unit, because the cost increase is negligible and having an extra amp available can do no harm...
EDIT: Now that I think of it, when I was testing the RD25 with the 25CFM blower I did power it with a 1A PS and the servo was too weak to move (because the blower was hogging all the current). When I changed over to the bigger PS everything worked great.
