But in the 5-unit, I pay utilities.The thermostats (there are two boilers and two thermostats) are in two separate units.  

Because I have large temperature fluctuations in all months except July and August, I can only assume they will be flipping the thermostat from hot to cold, as night and day ..I had never written into the lease specifics for house temperatures (I never thought I would honestly see someone up a thermostat up that high lol), but I know in my province of Manitoba that during the winter, temperature must be room 21 Celsius during the day and a minimum of 18 Celsius at night.

When a heat pump can't keep up with the outside temperature and using a fireplace or wood stove is not an option, I usually use infrared space heaters that have a thermostat. 

With the water coming out of the element/thermostat cover near the top of the outer shell that still does not tell you where the tank is leaking.

This is a DC low-voltage set-up - not unlike a door bell, thermostat, central vacuum switch, etc - 18 gauge (or 16 for the longer runs) should be sufficient unless you are worried about drop over 70ft (which should not be an issue).

One thing you can do that helps, is make sure when you put in a new programmable thermostat that the owners/tenants understand how to program, and have the instructions :)

A heating thermostat has a differential; the temperature difference between beginning and end of cycle.

Where the cutoff is depends on age of heat pump and thermostat being used.

hi all the factsit is 105 today tennant complains that her thermostat is set at 77deg and the air runs all day and only gets to 80 ,, she is a wuss if you ask me but she has small kids so okthe air con guy was called last time it was 105 and he topped it off the freon and said it was working fine and to drop the temp 25 deg was just about the max one could expect a unit to doso do i just tell her thats whats up it gets hot deal with it ,,any ideasthey pay the rent on time and keep the place nice but im not shelling out 5k for a new unit for her so she can get that 3 deg she is after

Well you do any troubleshooting like check the on switch or thermostat first?