We hired a contractor to install our water to water heat pump. After installation the unit runs for about a minute then shuts off for 5 minutes. It then kicks on again with a surge that dims the lights in the house. When it was first installed the temperature raised to the limit it burned up a transformer within the unit. The contractor replaced it and added an aquastat but it continues to turn off and on every 5 minutes. We installed it to cut down on heating costs not increase our electric bill. My husband has asked him to install a heat exchanger with a domestic hot water heater. Has anyone else used this type of system and have you used the heat exchanger?