Esper/Eberspaecher aux heater

[Jim Blackwood]

I now have the burner running but so far no heat in the coach.
Inside it was pretty clean. The wiring connectors were very bad off so I replaced them with Weatherpak, used those because it was easy to use various gage pins in the same body. A 6 pin for the main connector and a 2 pin for the water pump.

Blew a fuse in the process because I thought the main disconnect was off instead of checking it, but it turns out the fuse is right there in the compartment with the disconnect. I really like the gas sealed fuse holders btw. Only thing that's missing is a way to make use of the LED equipped fuses.

The Esper controller was acting squirrely at first, not sure why but as I attempted to pry it out of the housing with a knife blade it suddenly decided to settle down and start working, the MAN light came on, the burner fired off and the other light came on. Ran it through a couple cycles. Exhaust got hot, and I fussed around with the various heater switches and controls trying to get some warm air. Wasn't til I got back to the house that I thought to check the water pipes for heat so I'll do that in a bit. Could be the pump isn't running. Either that or it could be something with the bypass switch. There is also apparently a set point that must be exceeded before flow switching occurs but I'm lacking any more instructions on what exactly that means.

Found in the manual where it said the Esper was fitted beginning in '97. Guess they forgot to tell the assembly guys, mine's a '96 and has it.

I would really like to find a complete set of instructions for the Esper manual timer. (Round with two light touch buttons, no other controls. Square two digit window, SET and MAN buttons to the right. Bezel does not move.) That and the as-installed system Theory of Operation would be a tremendous help.

Jim

[buswarrior]

Look for closed valves in the plumbing...

Quick solution to a challenged AC system is to close the heat valves... rather than fix whatever is wrong in the temperature regulation...

Also, the order in which the hot water flows from the Espar, and then to where does it go?

Heat the engine bias, or heat the coach interior?

It may require further mods to get solid interior heat to the interior while camping.

Happy coaching!
Buswarrior

[richard5933]

Also, check to see if you have a secondary pump that circulates to the house side. We had a small Bosch 12v pump on ours, and the switch/power source for that pump were totally separate from the main system. The switch (if you have one) to circulate to the interior could be on one of the interior blowers, could be on the dash, or could be somewhere else. Sometimes these things are a bit of a scavenger hunt.

[Jim Blackwood]

Good News Everyone!
(If you haven't watched Futurama I can't explain exactly what that means.)

Suddenly I have heat!
Well, I know for sure that the pipes are getting warm all the way to the front of the bus, the main heater matrix and the driver's heat/AC matrix, the front fan blows, and I think the main one does as well, didn't double check that one.

Only had it powered up for maybe 5-10 minutes but the return was warming up nicely as well. Both manual valves were open. Not sure about the state of the solenoid valve, I will check that out later, say on a day when I plug in the power cord and fire it up to work on the bins. Could be this weekend, could be next week. I have a half tank of fuel so all I need to concern myself with is the batteries. So far they are holding up just fine.

The solenoid valve is in the return to the engine block after the supply to the coach "y"s off, so all it seems capable of doing is shutting off water flow directly to the engine. Next time I fire it up I'll compare the temps to see if I can tell if the solenoid valve is open. Obviously I'd like to force it to be closed if it isn't already. The return from the coach goes through the engine block. Fine for OTR, maybe less than ideal for parked. It would take an additional solenoid valve and a bit more plumbing to change that though so for now it's fine, as long as I get control of that existing solenoid.

I find the plumbing diagrams I've seen and the plumbing as it exists is not an exact match. As with the controller, chances are good I just don't have the right manual, or there was a revision.

Jim

[richard5933]

Congratulations! You've licked this one in pretty good time. Glad to hear that you've got heat. I agree that the branch to the engine should be closed unless you are intending to pre-heat the engine, otherwise you'll just be pumping all that heat out the back end through a massive heat sink.

Would love to see some photos of how the plumbing is set up once you find all the bits and pieces.

[Jim Blackwood]

I'll have to sketch out a diagram, every time I try to visualize it I get confused.
I think the exhaust from the solenoid valve ties to the return from the coach. That was the last thing I was looking at. Then it goes down to the water pump.

I will get this figured out, but it'll be awhile before I isolate it completely from the engine, just because I'm not ready to drain the coolant.

Jim

[Jim Eh.]

Why do you want to isolate it from the engine? Or is there no valves or an easy location to clamp the lines off and install them on the engine branch? Is the Espar unit easy to snap a photo of?

[Fredward]

Our Country Coach has a Webasto powered hydronic heat system. One big loop with three pumps. The pumps all run when the system is in heating mode and it heats the engine all the time. I agree with Richard, our engine is heated all the time and it just throws off heat all the time to the atmosphere. Bad design. I have looked at isolating the engine from the coach because we don't need to be heating the engine constantly. 

Interestingly our system has a freeze prevention circuit that if you have the coach heat turned off, but the Central Heat turned on, it closes two solenoid controlled valves and only circulates hot water to the wet bay to keep it from freezing.
Fred

[buswarrior]

Beware the dangers of designing an accidental engine overheating situation, in the pursuit of other objectives...

The whole coolant boiler topic is a complex matrix of hardware, plumbing and goals.

I wrote a bunch of stuff back in maybe 2010? that might be part of the thinking.  http://busnut.com/forum/index.php/topic,3262.0.html

Jim, this solenoid valve you refer to, is this the one that controls the coach heat, or something else?

Heating the engine block continuously costs money, in that the heat the engine is giving off back in the engine room, is being wasted to the outdoors. Now, this isn't necessarily a problem, it depends on how frequently and for how long, you might be burning fuel to do this. An occasional weekend camping trip is hardly worth the cost/benefit of isolating. However, if many days or months of cold weather living are in the plans, it starts to pay for itself, to isolate the engine from the heating system.

Now, the complexity of the isolating system...

Solenoid valves are lovely, until they fail... the ones used must be intended for the temperatures of the 160 degree coolant boiler, or the 200 degree engine, depending, and sized correctly for proper coolant flow, both the engine and the coolant boiler require minimum flow rates so as not to overheat. These are going to co$t... It is easier on them to control the return side, after the heat has been used for something, than to control the supply. Manual valve on the supply side to isolate the component, solenoid if you want, on the return.

Don't plumb anything in, that you can't turn valves to isolate so you can remove it without draining the whole coach...

What are the consequences of any one certain solenoid valve to fail? How often does this valve really need to operate, and will a manual valve, strategically positioned so that a long stem goes up thru the floor and under a couch or in a cupboard, so you don't have to go outside to change your configuration, do the job?

In designing a system that will also scavenge waste heat from the engine or the generator, where are the places an unintended hot feedback loop can be created? For instance, once the domestic hot water tank is up to temp... the hot coolant flow through there is not shedding any heat, and goes right back to the engine return without any cooling... and will stopping the flow to a device cause a starvation of coolant to the engine involved?

As they say, there's no free lunch.

My old MC8 had a simple install to make a mobile classroom for the PO. Webasto brand boiler in the middle baggage bay, plumbed inline to the hot pipe going forward to the coach heat and defroster. a simple circuit to power the coach blowers with the engine off, plug the coach in, or run the generator, stock temperature control, and the same fresh air intake as going down the road, important with a dozen trainees breathing in the chairs, let the class begin. The engine block was being heated too, but it was a simple install that didn't change what the engine saw in return coolant flow.

Then, my parts bus had a Webasto brand boiler installed for similar purposes, but the boiler was plumbed in parallel to the coach heater core, in the middle bay... Any guesses how cold it was in the coach, when driving down the road? Unintended feedback loop, the hot coolant took the short-cut through the coolant boiler in the middle bay, right back to the engine, and very little came forward... creating a disturbing summer time overheating situation, if the coach was driven too far/too long on the highway...

It was finally figured out to close one HVAC valve back in the engine room, (the return is handy inside the side access, but either would work) so that the interior would heat when being used stationary, and to block the feedback loop in summer. Never got any further before it was condemned, and became the parts coach.

These both were in a fleet environment, mostly before the internet, and it was all seat of the pants, feeling around, with no budget and no authority to order changes. So, learn and adapt we did.

If I'm involved in another install for busnut use... the layered approach would be my goal. The coolant boiler would be the big hammer, reserved for engine pre-heat, wet bay protection, and the ability to engage the stock HVAC, with a modulated control on the outside fresh air intake. This would back-up a modest marine stove, diesel fired, gravity fed, from a small tank built into the overhead somewhere convenient, that would be replenished periodically via an electric pump. The marine stove may also be equipped with a generously sized water coil to aid in wet bay freeze protection.

(having listened to fans, generators, engines, NOISE, all my career and at bus rallies... a busnut really wants to investigate the marine stove and heater options... heat comes with SILENCE... and gravity fed requires no power consumption to make heat. not much to go wrong...)

If it is properly cold, boondocking, the generator is running, making electric options available. A collection of electric heating suitable for power pole use only goes so far in the real cold. 30 amps won't cut it... but it is a part of the busnut's arsenal. At $20 each, why wouldn't there be a cube heater fastened into a corner of the wet bay, waiting for the command?

I'm not likely to bother with using generator waste heat, as much fun as that would be to dream up and execute... I don't want to mess with the "back-up" life support.... 

And, if all that craps out, well...run the big engine and seek shelter... wondering what sins are being punished this time...?

Domestic hot water? Frugality suggests boring electric, with a dedicated, used, old school, big name, modified sine inverter (cheap) to make water underway, or whenever power is available. I used to think about using a flat plate heat exchanger in conjunction with an electric tank, but at the price points involved in the components today, vs 20 years ago, why bother?

But, like all over-thinking busnuts, ask me next week, I'll lean a different way?

HTH

happy coaching!
buswarrior

[richard5933]

Our 4106 had a pretty simple set up after reading all that. We had the factory loop for the bus engine and OTR heat. There was a loop for Webasto which heated the interior of the bus when needed. And then there was a small third loop which joined the other two together when we wanted to use the Webasto to heat the engine. The small third loop was setup to use a small Bosch pump and an electric solenoid to open/close the loop. There was an auxiliary 12v pump installed in the bus main loop which was on whenever the smaller third loop was on to circulate the coolant back to the engine without having the engine on.

The whole thing reminded me of how the heating boiler was setup in my old shop. Big loop which went between all the heating units. Small loop which went between the boiler and the expansion tank. The only overlap was about a 12" section of pipe where the two loops exchanged heat. The small loop in the bus served as this overlap when the Bosch pump was running and the solenoid opened the valve.

The whole thing worked like a champ. Heat only the interior or heat both interior and engine. If the engine only was needed, I ran the system with the interior fan all the way down.

There are as many ways to plumb these things as there are people using them, so creativity is sometimes needed.

[Jim Blackwood]

The first round of photos came out too dark to see but I'll try again later.

I can now properly describe the plumbing however. Imagine one big loop short circuited by a solenoid valve and you have it. Engine to electric pump to heater to heater cores and back to engine pump. Two manual valves, one on each leg of the heater cores can completely cut off flow there. The solenoid valve opens a bypass back to the engine pump. Based on my infrared temp measurements the S. valve is open with power on, ign off, engine not running. (Engine pre-heat) In this mode, flow to the heaters would be minimal.

There may not be any as-installed method to close the solenoid valve prior to engine start. Or there might be. I have no documentation. So a necessary first step is to trace the solenoid wires back and find a place to install an indicator or possibly find one if it already exists. Then determine if a manual switch is needed to do a forced off condition.

After that, full flow will be diverted to the heaters, assuming the S.valve is in working order. That is phase 1. If it is not, and requires replacement, that triggers phase 2 as the coolant will need to be drained. For phase 2 the circuit will need to be modified to bypass the engine so all the heat will be kept in the loop between the heater cores and the Eberspaecher, possibly by using a 3-way valve on the return to the engine pump, diverting it to the electric pump inlet.

Later I can consider such refinements as bay heat and/or in-floor heating, gravity/thermosiphon plumbing and the like. For now I'll be satisfied to close the solenoid. Cost/benefit will determine future upgrades. I expect to minimize cold weather usage.

Because all my water tanks will be stainless it makes some sense to install bungs for heating elements. Probably the least expensive method to insure against freezing except for empty tank conditions. Have to think about that one some.

Jim

[buswarrior]

Richard, was the coach interior heating shared by the engine and the Webasto, or separate heat outputs?
How was this switched?

Shared devices is what complicates matters.

Dedicated separate heating devices takes most of the fancy valve and plumbing decisions out of the mix.

Not mentioned so far, is the need for an expansion tank function. Taken care of, if at least one valve stays open back to the engine, have to add something, if total isolation of the gear down the back happens.

happy coaching!
buswarrior

[Jim Blackwood]

Right BusWarrior, that's what I forgot to mention! Can't isolate it from the expansion tank, which generally means that one path to the engine MUST remain open.

Jim

[richard5933]

Richard, was the coach interior heating shared by the engine and the Webasto, or separate heat outputs?
How was this switched?

Shared devices is what complicates matters.

Dedicated separate heating devices takes most of the fancy valve and plumbing decisions out of the mix.

Not mentioned so far, is the need for an expansion tank function. Taken care of, if at least one valve stays open back to the engine, have to add something, if total isolation of the gear down the back happens.

happy coaching!
buswarrior

Working from memory here...

The Webasto's main loop was to the coach interior heating. There was a small surge tank on that loop so it could run isolated from the bus's loop. When running just the interior heat, the coolant went in a circle: Webasto > Interior Heat > surge tank > Webasto.

The bus's loop was the factory loop which ran the coolant from the engine/main surge tank to the front heat and back again.

The only thing that connected the two loops was the small loop that joined them by way of the Bosch pump. I'll call this the exchange loop. When I flipped the switch for engine heat, the solenoid opened the valve in the exchange loop, the Bosch pump kicked on, and an auxiliary pump in the main bus loop kicked on. The heated coolant from the Webasto loop was slowly mixed with the bus's loop by way of the exchange loop. Didn't happen particularly fast, but the engine did warm up. Also, when the switch was flipped for engine heat, the interior fan could be shut off. The interior thermostat was taken out of the system when the engine heat switch was flipped, and the Webasto would run until the temp in all the coolant reached the set point.

Since I no longer have the bus, there is a limit to how much detail I can give. I do remember marveling over how incredibly simple the system was that they installed to bridge the Webasto heat to the bus's coolant lines. The Webasto was installed midships, and they tapped into the bus's coolant loop by installing two T fittings into (I believe) one of the copper coolant lines running through the tunnel above the bay. Each of the T fittings was about 12 inches apart and was where the exchange loop mixed coolant with the bus's main coolant loop. (This last detail is what reminded me of exactly how the boiler at my shop was connected to the main heating loop throughout the building.)

[buswarrior]

Thanks Richard. What were the interior heat devices that kept the coach warm while camping?

In these combined systems, the coolant flow only needs controlled on one side, either supply or return, the other can be left open, accessing the expansion function of the engine. Expansion doesn't require flow, it just requires a path.

In Richard's 4106, if the engine pre-heat circuit was engaged, did the stationary interior heating still work to some degree? My guess is it did, sort of... to go with your description that the engine loop was slow to come to temp. Coolant was likely flowing everywhere, albeit with less effect.

I suspect it was plumbed with a shared supply, and the shared return blocked on the engine side by the solenoid valve. The extra pump was used to boost the now shared flow out to the engine loop. Disabling the stock HVAC thermostat at this point, ensures the regulating valve in the return is open, and the stock booster pump runs to allow flow.

Interesting strategy. Thanks for sharing.

Happy coaching!
Buswarrior