Esper/Eberspaecher aux heater

[richard5933]

The interior heat of our 4106 was an central exchange unit - the coolant ran through this in what looked like an oversized heater core. Air was blown across that and into the coach through ducting. The ducting did have outlets in the wet bay.

If we had the engine heat engaged, the interior heat could still be run. Obviously performance took a bit of a hit since the engine was now sucking heat out of the system. But, the way it was set up the coolant from the Webasto loop did not directly get pumped through the bus's loop. If the heat had been running through the night keeping us warm though, turning on the engine heat for a couple of hours to pre-heat the engine didn't really affect the temps inside the coach.

If I remember correctly, the OTR heating loop in the 4106 circulates through the engine regardless of whether the thermostat is open or closed. Seems like I remember that the heating loop is on the engine side of thermostat and allows the OTR heat to start heating the interior of the bus long before the thermostat opens. That being so, when the Webasto is sending heat to the engine it is not running through the radiator, just through the engine itself.

I drew a really primitive sketch of how I remember things being connected. I'm sure that I'm missing things, but hopefully it will give some idea. The small center loop is where the coolant was shared between the two systems - this was mounted in the bay with the Webasto up on the ceiling and connected between the Webasto loop and the copper heating lines in the tunnel.

[Jim Blackwood]

Hatches are frozen shut today but I may get more photos later.
I think it's possible to make out the drawing, and then there are a couple shots from above. Unlike Richard's setup there is no way to isolate the coach heat from the engine as it sits now, and valving the return to the electric pump inlet (3-way valve) with the solenoid valve closed takes the expansion tank out of the circuit. So the solenoid valve would have to remain open which is easy enough. Seems like a simple enough mod while leaving everything else alone. The only issue that occurs to me is what happens if the 3-way valve is left switched to "coach", the bus is going down the road, the Eberspaecher comes on,  and the solenoid valve closes, presumably to regulate the coach heat or engine heat? Pressure could build up in the coach loop from expansion. I suppose that could be cured with a bleeder line.

What do you guys think?

Anyway, I'm off to look at the wiring diagram.

Jim

[richard5933]

Could the buildup of pressure in he house heating loop be solved by installing a small secondary surge tank to the house heating loop? That's what ours had - it looked just like a small radiator surge tank (maybe 1-1/2g), complete with radiator cap. I believe that the pressure of the surge tank was fairly low and was set just slightly above the rating for the bus's main coolant system.

[buswarrior]

Jim, there has to be at least 2 valves close, supply side and return side, for expansion to be trapped.

The principal of controlling the return side, for valving component longevity, and then the coolant will just go where there is no resistance. The expansion is free to go "backwards" via all that supply side plumbing.

If you close off both supply and return, such that there's no way for a little fishy to swim back to the engine/radiator/expansion tank, then you have a problem.

Richard, the "thermostat" I was refering to is the one that regulates the coach interior heat, the valve in the return line from the big heat exchanger in with the fans. Not the ones in the engine that regulate engine temp.

happy coaching!
buswarrior

[buswarrior]

Jim, the design purpose of the Espar back there may be at odds with what a busnut wants it to do.

It's purpose is to keep the passengers warm. The 4 stroke engines were such a jump forward in efficiency, they don't make heat like the 2 strokes. The engine is completely unable to keep the passengers warm by itself in the cold, unless fully loaded and pounding up the highway. Downslope, you can watch the temp needle drop to boiler cut-in in short order.

Plumbed to supplement the passenger heat, makes it not as good for engine pre-heating, by some measure, that may or may not be meaningful.

But it surely screws up the ability to easily cut the engine out of the coolant flow.

You may find that the current location and space constraints make re-plumbing difficult. Don't be afraid to abandon the location, and put it somewhere else in the coach to better accomplish your goals.

Remember the exhaust is both grass fire hot and many think it stinks. A double win, better plumbing for a campground up-pipe, better plumbing for busnut purposes?

That's why we build our own.

happy coaching!
buswarrior

[richard5933]

...Richard, the "thermostat" I was refering to is the one that regulates the coach interior heat, the valve in the return line from the big heat exchanger in with the fans. Not the ones in the engine that regulate engine temp...

That does change things. I wonder what the default is to the valve controlled by the HVAC thermostat when the power is cut to it? Does it default to open or closed? Or when the air pressure is removed from the valve? O does coolant flow to the defroster core even with the main HVAC heater core valve closed? Seems like it is in our current bus, as when the main heat stop blowing hot we can still make heat at the defroster. If so, then coolant would still be flowing through the pipes in the tunnel. Not sure if the MCI is plumbed the same way. This part of the system is somewhat of a mystery to me that I'll have to explore more.

[buswarrior]

No power, valve is open.

Unregulated flow to the defroster controls.

Foggy memory suggests no air, valve is open.

All the old MCI did not use a booster pump, engine water pump did it all.

Old GM, booster pumps were usually found.

Happy coaching!
Buswarrior

[Jim Blackwood]

[No power-valve open] may be the case here too. Valve open means the engine short circuits the heater loop. Not much heat comes out in the coach. My suspicion is either the valve is not getting power or it isn't closing. The driver who delivered it complained that the dash heat didn't work but the fan blows and the core does get warm if you lay your hand on it. But not hot I think.

Of course, the Eberspaecher wasn't firing then either, so the electric pump also wasn't running.

Too cold today to be messing with it. I should probably check the connector on the solenoid valve. Maybe I can reach it if I open the center floor access panel.

Now, where does the control signal for that solenoid valve come from? So far I don't know but it seems like it'd have to be either from the thermostat or from the engine controller. Does it switch based on cabin heat or engine heat or both? No clue.

Jim

[buswarrior]

Before you get complicated...

What position is the driver's control for the defroster heat in?

And is the cable actually acting on the valve mounted down below the floor?

Is there an air lock in the defroster/heater core?

Remember what the theory of a "short circuit" back there means... overheat...

I would be shocked to find MCI designed a failure point with the Espar system that will overheat the engine, or otherwise compromise operation without it. Interested to find out, but shocked none the less.

I was referring to the big valve that controls the coach heat, that is normally open with no power applied.

If there is a solenoid valve and pump associated with the Espar, then it is likely controlled by the Espar. The coach is only going to provide the Espar a power signal, that the coach is running, and the coach heat is turned on. Whether the conditions are ripe for a burn, (that is, it is cold enough) is up to the Espar's temp sensing equipment. Separately, the Espar's own control may tell it to burn for engine pre-heating. I would expect that all the Espar parts, valves and pumps, turn on the same, whether commanded either way.

happy coaching!
buswarrior

[Jim Blackwood]

Dunno. There could be more buried where I can't see it. But the diagram I drew is accurate, as far as it goes. It just doesn't go forward of the engine compartment.

As such, yes the solenoid valve does indeed short circuit the coach heater core loop, but does leave the Eberspaecher and it's associated electric pump in the circuit.

I've been learning the schematics (very slowly) and it does appear that there is an electric and air operated coolant valve somewhere, as well as possibly a similarly constructed "Bypass valve". So far I haven't discovered where those may be found. But I have found an electric schematic that shows the 3-wire Esper timer, so that's progress anyway. I will have to see if the solenoid valve I've found has an air line, in which case it may very well be the "Bypass Valve" shown.

I'm not yet very familiar with this schematic type and it will take me some time to sort things out. Ultimately an in-depth study of the manual may be required. Such fun.

I think I'll pull that other floor panel today and try to get a better look.

Jim

[Jim Blackwood]

OK, here's another shot. The S.valve in this photo and the sketch is indeed an electric/air/fluid valve and meets the definition of a bypass valve. That's not definitive but it is persuasive. It may be the one shown in the schematics. If you look closely you will see that the plumbing matches the sketch. The other (return?) valve on the coach heating loop is to the left on that curved insulated line in the corner.

So, I need to fire it all up again and see if there is any power on the electric solenoid. Both valves are controlled through relays by the "Temperature Controller", however, there are two temperature controllers so it isn't quite as simple as it might seem. I have yet to see the second one on a schematic. Several references to a temperature sensor (ambient) in the drag link compartment and unfortunately the edges of the drawings are clipped and tracking from one to the next isn't straightforward.

But, bits and pieces all do add up if you can just keep them straight.

Jim

[Jim Blackwood]

One more quick tidbit. I do get power to the electrical solenoid when the main power switch is on, but not without it. Which means the valve remains in the unpowered state until it gets a signal from the controller and has air. I have yet to determine if the presence of air and power does in fact switch the valve. Which also means that I don't know if the valve's unpowered state is open or closed.

I can hear the solenoid click. Presumably when I next fire up the engine I will be able to hear or feel some indication of the valve opening or closing when air is applied. That will be required information to proceed further.

But guesses? My guess is that the valve is supposed to close so heat can be sent forward. I suspect it may not be. And this will have to be fixed before anything else can be done.

BUT, if that is the case there is no way the Eberspaecher can ever be effective in sending heat to the coach with the engine powered down and shut off without some changes, simply because without power and air this bypass valve would be open. Unless application of power is supposed to open it and it is sticking open. But then I have to wonder why. It doesn't seem to fit in with operational uses.

I would think that you would want the bypass valve open unpowered so that the engine would get most of the heat prior to starting the engine. Then open after start until the engine is at operating temp, then closed until the coach is heated, then open or closed as needed, at which time the demand solenoid could be used to control coach heat. But is that the way it is designed to work?

Jim

[Jim Blackwood]

More info. Should I start another thread? I dunno, it's DL specific and heater specific so maybe so... You guys would have to tell me.

Anyway, I found the demand solenoid valve, turns out it was at the top right inside the door of the main evaporator compartment at the front of the rear bay. looks just like the bypass solenoid valve in the engine compartment. I could maybe get the numbers off them and compare to see if they are the same part, that would probably be a good idea. The lines for dash heat "T" off there, before the valve and heater core so coach heat and dash heat are completely independent of each other aside from both relying on coolant temp.

At the front there is a cable controlled manual valve with a single "T" handle left of the seat. The valve is up in the spare tire well.

Now here's the fun part. There is a second cable that operates the fresh air damper looks about the same. Except it has been cut off over in the steering bay and there is no hole in the floor, the stainless trim, or the stainless bracket that the other cable handle is mounted through. Just guessing, I'd say that maybe there used to be an air cylinder that operated the cable to open and close the damper. I mean, clearly a cable was just too simple when you could make it more complicated, confusing and introduce more failure points. Incidentally, it was the damper door attachment on the end of the cable that failed. Guess I can look around there for another air leak, there are bound to be several on this bus. Probably a cable is the best solution here.

Jim

[buswarrior]

Do you have a square button mounted in the front surface of the driver's modesty panel, between the seat and the aisle?

The cable operated dampers were not friendly in the preceding 102 models, seized cables or dampers, drivers pulling the T handles out by the roots...

The D had a pneumatic damper, activated by the square push button switch.

Fresh air is an often overlooked, or ruined, capacity in bus conversions. Many are dank tubes, with little opportunity for air turnover.

Only in the furthest extremes of temperature, when the interior temp is beyond control, would I want it closed, otherwise, lots of fresh air is desirable, both for the health of the coach interior and the health of the inmates.

happy coaching!
buswarrior

[Jim Blackwood]

Yes, those T handles need a drop of oil placed on the cable below every now and then. There are two fresh air inlets. The one to the main HVAC has the pneumatic butterfly valve in a big square box, I have not yet checked that one for proper operation. The other is a flapper below the dash Heat/AC core which is moved by a cable. In some, the end of this cable came up beside the manual heat control valve cable. In some the heat control valve was a solenoid valve with no cable (my assembly guys didn't get the memo). And apparently at least one had the manual heat control and some other means of actuating the damper cable. So far I've not been able to discover what that means was. However, the remains of the cable are there even though there is no hole for it to come through and no cylinder to move it. Adios, YOYO.

So unless I can find something pointing me to a better way, it looks like a cable replacement and holes drilled in the floor are in my future.

Which also seems to mean that the square module in front of the Esper timer has no influence on dash heat other than perhaps closing the bypass solenoid valve once up to operating temperature.

I pretty much understand how this system works now. Both solenoid valves seem to be normally open. At a preset temp the bypass closes, sending heat to the coach and at the set temp the demand valve closes. Dash is manual control after the bypass closes but will output a little heat before that point as will the main HVAC, but it won't feel warm if the blowers are running, especially if the fresh air dampers are open.

For warmup with the Eberspaecher, both valves being unpowered would be open but the resistance of the lines and cores will cause most of the flow to be through the bypass and then through the engine, as it would should the engine cool down.

Now, to make this suitable for camping heat, The return flow needs to be diverted to the Eberspaecher water pump inlet, which can't be done without changing the plumbing. I'll be thinking about the best way to do that.

Jim