I don't see a bus heater over cooling a genset or any engine for that matter. Think about engines that run raw water cooling. Raw water will always be much cooler than your closed loop fresh water system.
Yes, it will suck all of the cooling heat out of the cooling loop.
28,000 btu/hr is about 11 hp. The engine that drives that genset is about 10-15 hp. Typically 1/3 of the input fuel is converted to hp, 1/3 to heat in the cooling system, and 1/3 goes out the exhaust. So the hp output roughly equals the coolant load.
Virtually all of the cooling load in the glycol loop will be sucked out by the Heater Craft Heater. And that assumes that the genset is putting out its maximum KW. If the genset is only running at say 5 hp (to supply a 2 KW load) then ALL of the coolant load will go to the heater and the engine will never warm up.
It will be like running down the highway on a cold day in your car with the thermostat stuck wide open.
A 10,000 BTU heater might be ok, but not the 28,000 BTU one.
I wasn't sure. Are the normal connections for an external heater before or after the thermostat?
If after, then you are right. The engine will come up to temperature but there will not be enough heat to fully supply the Heater Craft unit. But there will be some heat.
Is there any point in this situation to throttling the flow with a valve? It seems that the coolant either goes to the main heat exchanger or it goes to the Heater Craft unit. The more that goes to the Heater Craft, the better.
I have no clue about what ever brand. But the loop by rights should be on the open loop side of the system. Before the heat exchanger. Imho. With Ts and valves to isolate the loop when u done need heat. Atleast thats how i would do it.