Folkes arrived on 11/22/2021 to install new 80gal peerless indirect water heater. Upon arrival I started by draining down the old water heater and isolating it on every side. After it was drained I started by removing the old water and putting the new one in its place. I piped in for the boiler supply and return and added a drain valve on the return side. I then piped in the hot and cold side for the domestic side of the water heater. I added and drain on both due to there not being a drain on the bottom of the water heater. I then began to fill the unit by drain all of the air out on both the domestic and the boiler side of the unit. After filling the unit and removing all of the air. I connected the thermostat wire to the indirect and let it start to heat up. After a few mins customer stated that everything started to heat up. I also let the customer know that we will have to come back and put in the expansion tank due to there not being enough room as well as not being able to shut