Engine Block Heater Switch

[Joel Ashley]

However, with my Hydro-hot in diesel mode, and the system in the normal mode of operation, it heats the engine by circulation of same coolant that heats the water in the Hydro-Hot while you are driving down the road.  Therefore, you do not need a switch in the Hydro-Hot control panel.  

Karl

That's news to me.  The optional Engine Preheat switch activates a dedicated pump that pushes engine coolant between the hydronic unit and the engine when the engine isn't running to circulate coolant itself.

Joel

[Steve Huber Co-Admin]

Tom, Roy,
Thx for the info!
Steve

[Steve Huber Co-Admin]

Karl,
Maybe I misunderstood your post, regarding preheating. If so, disregard this.  
As I understand the system, only the Hydro Hot 200 series has a preheat pump that when activated, (w/burner on) circulates engine coolant through the Hydro Hot to assist in warming the engine. This is an independent coolant loop in the Hydro Hot and not connected to the coolant loops that run to your heat exchangers to heat the coach interior.
The Hydro Hot units w/o a pre heat pump (e.g. model 500) also have an engine coolant loop coming into the unit. However, this is not for preheating as the only way of circulating the coolant in this circuit is by running the engine.  Again, this is separate from the coach heat exchanger coolant circuit. Pre heating on these is accomplished by heating the intake air. By running the engine coolant to the Hydro Hot in these models, you can have hot water and some heat when driving w/o having the diesel burner on.
That is my understanding.
Steve

[Karl Welhart]

Steve,

I agree completely with your statement.  However, my experience is that after running the Hydro-Hot all night in diesel mode in very cold outside conditions, upon starting in the morning the engine pre-heat cycle is very short and the engine temp comes up very quickly compared with the same situation not having the Hydro-Hot in operation.  

Perhaps there is some heat exchange via the Hydro-Hot coolant and the engine coolant without the engine running.  Not exactly sure about the mechanics of this heat exchange process, but the engine coolant and the Hydro-Hot coolant must be connected somewhere...

Maybe someone smarter than myself can help us out with understanding how this may be the case.

Karl