I looked on a few different HVAC web sites and I don't see parts listed except for  thermostats and complete electric baseboards.If hydronic, then yes, but you'd have to know how to drain the boiler, solder heating element to pipes, and refill/bleed all the air out.  

The old tenant had been there 6.5 years and so there was cost in getting the unit back to rental condition, one of the units also had the thermostat go out.

Now based on the triggering of one of 3 separate thermostats (in as many areas), the forced air is directed to a specific level/area to meet the (a/c / heat) demand.

And I don't waste money on things that don't matter- hardwood floors, Nest type thermostats, wifi, etc.

I also have WiFi thermostats so I can remotely change the temperature when no one is there to save on the electric bill.

I changed the rods and thermostats, still going strong 6 years later.

Water Heater Not Producing Hot Water   Quick Fix:     - Check the thermostat settings

Automatic set-back thermostat (generally both tenants worked, no sense in cooling a place while no one is there.4.

I had jacked up the insulation to about 24" (90% plus of HEAT GAIN is through the roof), I had SOLAR SCREENS on all south and west facing windows, all of my windows and doors were well caulked to prevent air leaks, all of my units had electronic/automatic set-back thermostats, whenever I replaced a roof I went with a ridge vent to improve air flow through the attic.

The boiler system has baseboard radiator heat & 3 new thermostats that must stay since they were all completely replaced.