Here is a pic of my set up. I have 2 Teenage Girls and never run out of hot water. Mine is first then the furnance and I also plummed the incoming boiler water to the top of the sidearm and leave the bottom. Some will say that it wrong but it works. I am no thermo expert. LOL. but many years ago when I was in the navy you always entered colling water at the coolest point of the heat exchanger and flowed to the hotest part. and the reverse for heating. so I plumed all my stuff that way. Good luck Because it saves me 25 bucks on the old electric bill ! Oh and dont forget the anti scald device. I have had 183 degree water come from the kitchen sink.