Diesel heated central heating

Is the house currently setup as a single standalone house? If so, how has the radiator pipework system been designed? As since you say that the house is in multiple levels, some of the heating pipes are probably in the ceiling/ floor between the upper and lower levels. Meaning to separate the pipes so heat metering could be installed, would probably involve having to rip open the ceilings to access the pipes.

And how would you get power for the boiler? As since it would be a common service. You would need to get a 3rd electricity connection installed for it. Or at the very least, install a sub meter on the power to it from 1 of the tenancies. But then you would have to arrange with that tenant to reimburse them for the power used. And they might then refuse to sell you power. Or they sign up to Globug, (prepay power) and the other tenants will then keep on complaining about the heating not working, as the credit has been used up on the first tenants Globug account.

And then you would need to add 4x zone control valves and a bypass valve. As you will need 2 heating zones and 2 hot water zones. And wiring, and some sort of control logic (even if it is some relays and switches).

And you still won't have solved the problem of the boiler probably being undersized when trying to heat both hot water cylinders and run the radiators at the same time. While the boiler would likely be oversized if it is trying to run just 1 radiator zone or just 1 hot water cylinder. Meaning it will either short cycle, on an overheat thermostat. Or it would just go into lockout. (no heating until the system is reset, some systems say in lockout even if the power is turned off and on again).

I have also yet to come across a property that uses actual heat meters in NZ. (always interested to know of any that do though). I have seen some apartments that have metered hot water. But that is just by using 2 water meters per apartment.

RedMoose

Aredwood