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Author Topic: Mixing/connecting cooling systems  (Read 3832 times)
PCC
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« on: December 11, 2009, 07:10:01 AM »

Can I take the heating system water lines from the engine, that are used to provide interior heat for the coach, and somehow use the same heat distribution pipes that provide interior heat and use the water from the generator (when the engine is not running)?

I was thinking that being able to interconnect, somehow, the coolant systems would also keep the non-running engine warm, and if both were running, the coolants could simply share the heat.

I am using heat exchangers for heating domestic water while drivng, but is there a way I can do something similar between the two diesels (engine and generator) so the domestic hot water can also be heated by the generator?

There will have to be valves (similar to the thermostatically controlled valves in the heating system controls), or high tech plumbing done, to separate the systems to protect in the event of a system leak. These valves would have a driver controlled override to shut them off manually in the event of a problem.

I thought about installing solenoid valves to shut off the interior heating coils from whichever engine (main or generator) is not running, with small bypass hoses to deal with water expansion.

Am I totally crazy? or can it be done?
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« Reply #1 on: December 11, 2009, 07:16:26 AM »

While that sounds good on paper, the generator does not produce anywhere near the heat that the main engine does.  If you did hook up the generator to your heating lines, you would end up with luke warm water going through the lines and a generator running to cool.  I would suggest just keeping the heating lines hooked to the main engine and if you want heat when the big engine is stopped, get a Webasto Diesel fired coolant heater.  Good Luck, TomC
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« Reply #2 on: December 11, 2009, 07:19:02 AM »

I don't see why it can't be done.  The old 4104 had the air conditioning engine tied into the coach cooling system, they each had their own radiator and fan.

My concern would be with keeping the generator running hot enough, especially since you would not be putting as much electrical heating load on it.  Probably the worse thing you can do to a diesel generator is under loaded and over cooled.
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PCC
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« Reply #3 on: December 11, 2009, 07:39:48 AM »

Thank you - but perhaps I should mention that the generator is a 75 HP four cylinder diesel with a radiator as big as the entire bay door, so I could cut off some of the air flow to raise the water temperature.

I already have an exchanger to use the hot water to heat the interior heating system, and, when the engine is running, to heat the domestic water.

Does that information make a difference in your thoughts?

Sorry, I forget to mention those specifications.

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bobofthenorth
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« Reply #4 on: December 11, 2009, 07:54:34 AM »

Unless I'm missing something here - which wouldn't be the first time - the generator temperature will be controlled by the generator thermostat.  It will just see the house cooling loop as a very big radiator but that won't change the operating temperature of the generator engine.  The generator won't provide much if any heat to the house but I don't see how it will affect the operation of the generator engine.


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R.J.(Bob) Evans
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« Reply #5 on: December 11, 2009, 08:04:05 AM »

Thank you Bob,

The generator does operate at the usual 160F (71C for you, Bob), so it does have the temperature to heat the coach, and it has the radiator size to keep that temperature. I could put a higher temperature thermostat in to increase the available heat.

The size of the radiator was to say that there is sufficient volume of water, and heat created during operation, to make a good dent for the interior warmth, I think.

It is the interconnecting that I have never done before. I am trying to get these cooling systems to share the warmth with the interior in an easy to operate or switchable manner, and find the pitfalls of interconnecting the two independent systems.
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« Reply #6 on: December 11, 2009, 09:24:09 AM »

Thank you Bob,
The generator does operate at the usual 160F (71C for you, Bob), so it does have the temperature to heat the coach, and it has the radiator size to keep that temperature. I could put a higher temperature thermostat in to increase the available heat.
The size of the radiator was to say that there is sufficient volume of water, and heat created during operation, to make a good dent for the interior warmth, I think.

The thermostat rating won't change the waste heat available to heat your coach.  You are right though that a large radiator would seem to indicate that there is waste heat available.  My point was that the thermostat will attempt to keep the generator at the correct operating temperature.  The heat you have available for the coach is limited to what would normally be wasted through your radiator.  As far as your generator is concerned the coach hydronics are just a really really big radiator.

My personal opinion is that you won't get much usable heat out of your genset but that is just an opinion.  I have looked at interconnecting my generator & engine cooling systems - in my case the goal was to get rid of the genset radiator entirely.  It seemed to me that the risks and expense of interconnected systems outweighed any potential benefits but again - just my opinion.
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R.J.(Bob) Evans
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« Reply #7 on: December 11, 2009, 10:35:20 AM »

Changing the thermostat does not change the heat available; the heat available is a funcation of the engine and load.  The thermostat controls the coolant temperature by metering coolant into the cooling system when the coolant temperature inside the engine has reached the set point of the thermostat and shutting off the coolant into the cooling system when the temperature has dropped below the set point.  Ideally the cooling system is sized to the engine's needs and the thermostat stays in a midpoint of opened and the heat generated matches the cooling available; if the cooling available is not enough for the heat generated the temperature will rise and the thermostat will go the full open but the temperature will continue the rise but because the temperature of the coolant in the cooling system (generally the radiator) now has a greater delta to the exchange medium (air with a radiator) the cooling system gains a little more capacity and the temperature may stabilize at this higher temperature (above the thermostat's rated temperature) if not the temperature rises above the coolant's boiling point. When the coolant boils (converted to steam) it provides a great deal of cooling as the convertion the steam takes a great deal of heat but with a limited amount of coolant available this cooling does not last very long. If the cooling system is larger than the engine's needs the thermostat closes completely and the coolant in the cooling system has a significant drop in temperature before the thermostat reopens and very cool coolant enters the engine which may cause thermal shock to the engine. This is why you see the big rigs with most of the radiator covered or shutters closed.  Anyway those are engineered systems and I would proceed with caution.
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« Reply #8 on: December 11, 2009, 11:35:02 AM »

Depending on the fittings in your genset, perhaps it would be easier to plumb a separate heater core to your genset and then just take advantage of that heat when the it's appropriate.  That is what I plan to do with mine.  Good luck!

Glenn
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Len Silva
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« Reply #9 on: December 11, 2009, 12:29:38 PM »

I wonder with a 75 horse generator, how are you going to keep enough load on it to even get to normal temperatures?
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« Reply #10 on: December 11, 2009, 12:58:21 PM »

The generator will maintain a basic continuous load on it, between 10 Kw and 16 KW (+/-), when parked and occupied.

When running all the A/C systems, the load will be at about 30 Kw. When running with everything on. I will need about 42 Kw.

I figure it will be able to stay warm.

And no, it is not a hybrid bus !! (LOL)

It is a working home, and will have a lot of electrical appliances that will run almost all the time.

The generator has the heater hoses already connected to the engine, so it is an engine designed to be used with a heater. That is what gave me the idea that I could find heat for the interior from this engine.

I hope it runs cool, for the generator's sake, but I hope it runs warm enough to bring the engine coolant temperature into the coach.

Am I wrong to presume that a thermostat set for 160F will warm the engine up to that temperature before opening to the radiator, and then keep it about there?

If that is so, then would that (160F) not be the average/minimal water temperature fed into the coach for heat?

Is that not hot enough?

If not, would not a higher temperature thermostat raise the generator engine's water temperature even more?

Are my presumptions all wrong here? Do I need to rethink the system completely?

I await your inputs.
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« Reply #11 on: December 11, 2009, 01:17:03 PM »

The thermostat will crack open  at 160F and reach full open at about 175 F.  In between it will regulate flow. 
Assuming the genset is under light load, the thermostat could remain virtually closed causing no flow to go through the genset radiator.
The bus heat will get coolant flow regardless of thermostat opening. The cooling effect of the bus heaters could be enough to cause the engine to run below 160F

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bobofthenorth
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« Reply #12 on: December 11, 2009, 02:19:33 PM »

If you put some kind of a thermostatically controlled valve on the link between your genset and your hydronic system to restrict the outward flow of engine coolant when the engine temp is below 160 then I don't see a problem.  Otherwise I think you are going to run your genset cooler than it is designed to run but again, that's just my opinion.  What you want to do is mimic the operation of the engine thermostat with another thermostat that regulates access to the "really big radiator" which is in fact your hydronic system.

 
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R.J.(Bob) Evans
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« Reply #13 on: December 11, 2009, 02:35:00 PM »

Keith,
One thing that puzzles me in yer post is you mention;
"When running all the A/C systems, the load will be at about 30 Kw. When running with everything on. I will need about 42 Kw.

I figure it will be able to stay warm."


Uh isn't heating and cooling at the same time counter productive?
Just curious.
Grin  BK  Grin

btw I still haven't took pics, I loaned my mom my digital camera and she won't be back w/it until monday!
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« Reply #14 on: December 11, 2009, 03:06:26 PM »

BK - I was just trying to show the anticipated load of the generator - Hopefully, the heat and the A/C will not be operating simultaneously, but then it might, if the humidity is too high.

Looking forward to the pics.

Thank you
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For some, patience is a virtue.
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Thank God - He is always patient.
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