Webasto installation help needed

[bottomacher]

Hi Folks. I'm about to install my webasto in my mc9. I have a water heater with heat exchanger, and I want to route the hot water from the webasto through it constantly and occasionally through a heat exchanger in the bedroom above. I also want to route it through the engine block. That's the problem. Can any of you who have done it please tell  me how you piped the coolant from the webasto to the engine area? As always, pictures are so helpful to those of who are struggling...
Thanks
Don

[edroelle]

I used the heating pipes that were already in the bus.  Going forward in center of engine and water returned at the right side engine low.  The pipes were about 1 1/2".

I would suggest you install a number of valves so that you can bypass your engine in the summer, heater in the summer, water heater if you have a leak, etc.

Keep in mind, the standard pump that comes with the Webasto runs out of capacity at about 110' of pipe/hose, round trip.

I think Craig Shepard designed his system similar to an Aquahot with 3 or 4 magnetic pumps - 1 for each zone.

Ed Roelle
Flint, MI

[Zeroclearance]

Don,  per Webasto web forum that is being shut down (lack of use) recomends that one taps into the heater core loop.   This would mean that you would install the Webasto inline to the bus/coach heater core.   The cold return gets cycled back into the engine block.

However, they suggest that one looks to see how the OEM applications routed the factory installed Webasto.    I would like to see some pictures of factory installed Webasto on MCI or "other"

[buswarrior]

I have been involved in two different minimal MC8 installs, one good, one not so good.

The good one, the Webasto is in the middle bay, installed inline in the "hot" forward direction heater line. All coolant going to the stock heater core and defroster flows through the Webasto.

The Webasto may be used to pre-heat the engine, the Webasto may be used to heat the coach interior with the engine off via the coach blowers controls bypassed and externally powered, the engine may heat the coach interior as intended stock.

In the bad one, the Webasto was installed in the middle bay, plumbed into both sides of the heater lines, hot and cold, and flow could not be adequately directed anywhere, depending on what you tried to do, flow bypassed the heater cores, flow wouldn't go to the engine for pre-heating, if you tried closing valves, it wouldn't work the other way, reversing the connection hot for cold didn't really help either...

Moral of the story, think really hard about what you are trying to do, and think hard about how your design ideas will NOT work. Water will flow through the wrong pieces, certain items placed inline shouldn't have been, the pumps can't push the water where you need it, or not at sufficient flow...

Make drawings of your ideas, float them on here for feedback.

Closing valves seasonally is ok in a bus conversion, fooling with valves in the course of an hour, or each day, you need to think again. Or SHE will tell you to think again later...

My advice is to lean hard to manifold everything, along the lines of everything gets flow if everything is open, quarter turn shut off valves in every circuit, supply and return for isolating leaks, think hard about where those valves you will want to manipulate periodically would be best to be controlled from...shaft extensions let them come up through the floor while the valve and plumbing stays neatly and flow efficiently down below. For those items you decide to place in-line, popularly the water heater, fabricate a proper sized by-pass, everything leaks eventually! And depending on where the Webasto is in relation to the pump/pumps, you want valves around each of those too.

Do not be cheap! The price of all those valves pays off exponentially the first time you are forced to close two of them to stop a leak, or to replace a part.  For a break down situation, two quarter turns, a quick top off of coolant or water, and you are back on the road. At what cost in quarter turn valves?

Remember, you need some method for expansion, keeping the engine's own radiator expansion tank available by way of the return lines always staying open saves a lot of trouble and expense. To take a certain device off line, so to speak, would usually only require one valve to be closed, to block the flow, but still allow expansion back to the tank.

As an example of easy valve use, in the cooler weather, the engine would be in the circuit while driving to take advantage of the free heat for the water heater and perhaps some radiant heat, the engine would be taken out of the circuit while parked in order to economize on energy used to keep things warm while parked, and back in the circuit to pre-heat in the morning. Do you want to go outside and hike a bay open to fool with a valve? In your pajamas, in the cold, in the AM? Or, under a seat, in the closet, wherever you put it, reach down to the floor, one quarter turn valve, operated manually from inside the coach would be lovely, and accomplish your goals.

The trick in your designs is to remember that sometimes, supply is return and vice versa!  Add the generator's waste heat to the equation.... and you are saving some bucks in the really cold!

Great topic!

happy coaching!
buswarrior

[Sean]

I recommend you keep your house hydronic loop (and thus Webasto) separate from the engine loop.

You can still get all the benefits of using waste engine heat for the house system as well as engine pre-heating by installing a heat exchanger between the two systems.  Plumb the engine side of the heat exchanger in to the existing heater loop.  If you want engine pre-heating, you will need to add a small electric pump in this loop as well, to move engine coolant when the engine is off.

There are many benefits:

• No need to use expensive diesel coolant in the house loop.  Cheap antifreeze mix is fine.
• No need to test and add SCAs to house loop.
• House side pump does not have to work to pump through the engine loop every time it runs.  You run the separate pre-heat pump only when needed.
• No heat lost in the Webasto system through the engine block when pre-heating is not in use (99% of the time).  This is a huge heat sink and a substantial loss.
• Only need to replace normal amount of coolant at engine coolant change interval, not an extra 5-7 gallons in the house loop (the change interval on the Webasto is much greater).
• No need to drain, then re-prime and re-bleed entire house system when draining engine coolant.
• A leak in the house system will not shut your engine down or keep you off the road.
• Requires no additional valves -- never have to remember to open or close valves.

This is how our system is plumbed, and we get all the heat we need while driving through the heat exchanger.  In fact, if we drive every day, we seldom need to run the Webasto at all, as we get plenty of hot water while driving, and the residual heat in the system and expansion tank is usually enough to heat the bus overnight.

With regard to getting just hot water vs. hot water plus coach heat, this is usually achieved with a two-way or "Y" valve -- a valve with one input and two outputs.  Plumb the HWH as the first item in the loop, then the Y valve.  One side of the Y goes on to the rest of the loop (fan heaters, etc.), the other side of the Y goes to a "short cut" bypassing the rest of the loop.  Those two pathways come back together at a "T" just before the expansion tank.  Our valve is labeled "Summer/Winter."

I should add that the Summer/Winter valve is the only valve in our Webasto system (unless you count the proportioning bypass valves for the water heater and radiant heater in the bathroom, which, once set, are never moved).  The original heater shut-off valves are still in place on the engine loop.

-Sean
http://ourodyssey.blogspot.com

[Gary '79 5C]

Sean,

What ambient temps allow for you to heat the bus interior with the "stored" heat of the exp. tank & engine ? Of course, insulation and personal preference of interior temperature will be factors.

I have a 5C without an engine heat Xchanger, and I worry about being stuck due to a leak in the cabin. An alternate is to install isolation valves. Recently, I was in 25* F and the Webasto came on about 2 hours after shutdown, but I had just driven 1/2 hour, back from dinner. A longer drive would delay little longer, but not the evening. We like the interior cooler than most, at 58*-60*. And that is at the passenger's direction.

My DD was thankful in the AM for the heat input as it started without problem.

[Sean]

Gary,

We try to stay out of freezing temperatures if we can, although we've been in them several times.  So when I said that we might not run the Webasto at all, I would say that's really with daytime temperatures running in the 50s-60s, with overnight temperatures dropping into the 40s.  Usually the bus is plenty warm when we arrive, and the residual heat in the system is enough to last until bed time -- we never run the heaters overnight.  If it's chilly when we get up in the morning, we might have to run the Webasto for 45 minutes or so.  Of course, we have a very well insulated coach -- we furred the walls out an extra half inch before spray foaming, and our windows are covered with double-cellular blinds.

In sub-freezing temperatures, I would start the Webasto about two hours after parking, and leave it running over night, to keep the bays from freezing, with all that entails.

The more coolant you have in your house system, the longer it will last.  We have about a 5 gallon expansion tank, but it's not uncommon to have two or three times that amount in either expansion or thermal tanks.  Of course, the trade-off is that it takes that much longer for the system to first heat up when you start it.

-Sean
http://ourodyssey.blogspot.com

[bottomacher]

Thanks to all of you for the replies. One thing I forgot to mention is that I plan to remove the bus heater core and install one or two school bus units somewhere, probably under the floor and ducted to inside.
Sean, what did you use for a heat exchanger, and where is it? I had hoped to tee into the bus heater water lines in the rear bay, but access to the supply pipe is miserable. The return isn't bad. I don't know the capacity of the webasto circulating pump. Can you please tell me where to find an auxiliary pump (12 or 24 volt)?

[Sean]

Sean, what did you use for a heat exchanger, and where is it? ... Can you please tell me where to find an auxiliary pump (12 or 24 volt)?

My heat exchanger is in the engine bay, mounted to the ceiling.  I'm not certain of the brand or capacity any longer; I'm going to say it's about 2' long and 3" in diameter.  We bought it, along with the 24-volt pump and most of the other bits and pieces to make a working system, from Sure Marine in Seattle.  Sure is very experienced with these systems and can help you size the components -- just tell them you have a motor coach.

-Sean
http://ourodyssey.blogspot.com

[buswarrior]

Also for consideration in an isolated system are the flat plate style heat exchangers.

Who has links?

happy coaching!
buswarrior