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Author Topic: Hydronic Heating System  (Read 2544 times)
Tikvah
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« on: April 28, 2012, 08:31:15 AM »

I'm designing my heating system for the coach.  I'm not so concerned about what brand system you use.  But, if you would be willing, would anyone share your schematics for your house and bus heating system?
We have engine heat, heat from another source (Webasto, etc), and heat from a water heater of some kind.

Sometimes the "other source" heats the coach, other times it pre-heats the engine, and other times the engine takes the full load.  Also, most systems heat domestic water or use an additional water heater.  Engine heat can pre-heat the water heater, etc.   How do you control all that?

I would love to see a drawing and details.

Dave

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« Reply #1 on: April 28, 2012, 09:35:50 AM »

First I can't understand why the concern a heating system up in the sunny northland.  Grin

I don't have drawing yet; I will do as built drawings as I am still building. 

I have a 16 gallon three-way for domestic hot water (propane, 110 AC and engine heat). It gets hot water from a loop consisting of a Webasto boiler, engine connected heat exchanger and
a four port 19 gallon 220 AC water heater. When driving the heat exchanger supplies heat to the loop.  If 50 amp service is available, the AC water heater takes the load. When boondocking
the Webasto supplies the heat with the 19 gallon water heater acting as a heat sink to give the Webasto longer run cycles. During the summer or when heat is not required the three way
heater supplies domestic hot water from propane or electric. Engine pre-heat is via a pump in the engine/heat exchanger loop that is switched for pre-heat.
The bus heat is looped from the 19 gallon water heater to manifolds supplying the in floor piping, four toe kick heaters and large factory heater that was used to heat the bus bathroom.   
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« Reply #2 on: April 28, 2012, 09:42:40 AM »

I'm interested in this topic as well. I'm in the process of installing a diesel generator with a heat exchanger that I plan to heat the domestic hot water and a few toe kick heaters. I plan on using electric toe kick heaters too.

Mark
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« Reply #3 on: April 28, 2012, 09:56:38 AM »

Just to consider-current cost of a new AquaHot system with heat exchangers, engine heat, domestic heat is around $11,000.00 (as quoted last month in Phoenix by AquaHot at The Rally).  And then there is yearly maintenance of the burner, pumps, valves, etc.

I like simplicity-even if it means some interaction by me (mainly having to throw some switches or valves at times).  I have probably the simplest, most reliable system (least amount of maintenance) and lowest cost system.  I like it so much, I'm duplicating it on my truck conversion. For heat I'm using a 40,000btu Suburban propane furnace with four outlets.  Might use a second smaller one to heat the basement-but will determine that later.  My engine has a 120vac block heater.  My fuel tanks have Arctic Foxes (coolant loops) that keep the fuel from freezing with a 120vac circulating pump from the engine.  My water heaters are 2-10gal electrics straight from Home Depot-one plumbed into the next with the final one wired through the inverter for hot water while driving.  Total cost of domestic hot water, air heating and engine block heating- less then $2,000.00.  And if my bus is any indication of maintenance-there isn't any-except for draining the water heaters once a year.  Good Luck, TomC
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« Reply #4 on: April 28, 2012, 12:28:04 PM »

Having played the LP Gas furnace & electric baseboard heat with LP Gas water heater for years, I finally got into the Aqua Hot system with 120 Volt backup element, it is the best overall between engine preheat and engine keeping all warm when driving, then the diesel fired Aqua Hot works when engine is off.
What is there to not like.  Yes there is some added costs for annual maintenance, but in the end, it is pennies, so who cares.  Being comfy and happy beats being cheap and uncomfy.
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« Reply #5 on: April 28, 2012, 06:08:28 PM »

I have a Webasto Scholastic Series (DWB 2010) in my RTS and it runs off the engine/radiator system.  All I did was add a water heater that gets engine heat and a couple of heater units in the bus.  I can separate the engine from the interior heating system and it is the nicest interior heater I ever had.  Try this link and ddown load the school bus installaton to get an idea of how it works.  It beats an Aquahot system by $5-7k.

http://www.webasto.us/general/en/html/8259.html
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« Reply #6 on: April 28, 2012, 07:11:33 PM »

Thanks for the link Geoff. The Webasto (Esberspacher) Thermo Top C is looking good to me. It's 5000 watts output, the Scholastic is about 13,000 watts.
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« Reply #7 on: April 28, 2012, 08:11:08 PM »

Just to clear up some misconceptions:

1. The DBW 2010 and Scholastic are two different models, not two names for the same model.  These are made by Webasto.

2. Eberspacher (also known as Espar in the US) and Webasto are two different companies and make two different product lines.  They overlap in many areas, and both make diesel-fired boilers of similar capacities.

3. 5,000 watts is about 17,000 BTU/h, not enough to heat the interior of a 35'-40' motor coach in anything but the mildest weather.  For a 40' coach you really want a DBW-2010, which at 45,000 BTU/h (about 13,000 watts) is much more appropriate for this volume in near-freezing conditions.  If you don't ever plan to be in weather this cold, a diesel boiler is probably not economically justified at all -- get heat pumps instead of air conditioners.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #8 on: April 28, 2012, 08:24:43 PM »

Drat, I liked the look and fuel consumption of the Thermo Top C. That 5000 watts is three toe-kicks, but getting all of that 5000 watts into the bus wouldn't happen, forgot about the losses and inefficeincies. Webasto, though, looks like they market Ebershacher units, 'cause they're listed on they're website.
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« Reply #9 on: April 28, 2012, 09:40:42 PM »

... Webasto, though, looks like they market Ebershacher units, 'cause they're listed on they're website.


Maybe I'm out of date, but I just went through the Webasto web sites, both US and Germany, and did not see any Eberspacher products.  Lots of third-party companies, however, market products from both manufacturers.  Are you sure you aren't looking at a third-party site?

The "Thermo Top C", BTW, is a Webasto product, not Espar, as are the Thermo 300/500 series.  Eberspacher is best known for D3W, D5E, and Airtronic product lines.

-Sean
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« Reply #10 on: April 28, 2012, 09:55:47 PM »

Sean, I'm not going to argue with you, when you're right & I'm wrong. Grin
I think I was misled somewhere on ebay.
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« Reply #11 on: April 28, 2012, 10:19:12 PM »

Sean, I'm not going to argue with you,


FWIW, I am not trying to be argumentative, just accurate.  Mostly because, as I have said here many times, these threads are archived, and new folks come to them sometimes years later.  When the original participants have long since moved on, it can be confusing for a newcomer to sort out the facts.

Quote
I think I was misled somewhere on ebay.


And that makes perfect sense.  One of the "tricks of the trade" on eBay is to put all the major competitive brand names for whatever you are selling in the listing, even though what you are selling is from just one of those brands.  So if you are selling a Creative Zen MP3 player, but you know that more people search for Apple's iPod music player, you might list is as "Creative Zen just like iPod" or some such, to bring the iPod-search traffic to your listing.  Technically, this violates eBay's TOS, but I see it all the time.

With specialty items like diesel boilers, that don't get much search traffic to begin with, the temptation to list something as, say, "Webasto Eberspacher Espar Thermo Top Diesel Heater" is great indeed -- it's unlikely that the brand-name-police at eBay will even know what this is, and you'll get a lot more hits on the listing.  The exact same reasoning applies to Craigslist and other for-sale sites on the web. Take anything you see there with a grain of salt, and it always pays to do your own additional research when buying anything at on-line auction.

(Edit:  So I just did a quick surf over to eBay and there is one particular seller, "Heavytruckparts," who likes to add "Eberspacher" and "Espar" to all his Webasto listings, and "Webasto" to all his Eberspacher listings.  Not only is this against eBay rules and illegal, it's potentially confusing and also extremely annoying to anyone actually looking for something specific.  There are few things as frustrating as having to wade through hundreds of irrelevant search results due to this sort of keyword-spam when you are trying to find a part.  Hopefully eBay will bring him in line shortly.  BTW, I didn't think his prices on the Webasto items were particularly good, either.)

-Sean
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« Reply #12 on: April 29, 2012, 04:41:02 AM »

Nice discussion about different kinds of heaters - but I really had high hopes that some of you have schematics of your system.  I know some of you do... I've seen them.

I don't currently have the financial resources to purchase any of the above brands.  I have a couple very nice LP on demand heaters.  One will be domestic, the other will be for heating.  I think I have a plan, but I'd like to see what others have done so that I don't have to re-invent the wheel.

Thanks for the brand suggestions, and where to find them.... but anyone have a drawing?
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« Reply #13 on: April 29, 2012, 08:38:41 AM »

Tikvah...
we have a skoolie (40 ft) and are converting nice but cheap (we used to remodel high end houses for a living plus owned/ran cabinet shops). It sounds odd but we are going to reuse the heat exchanger that was in our bus when we bought it. Many skoolie converters toss them so you might want to check with the skoolie.net forums to see if someone near you has one laying around. The exchanger is simply a radiator with 12vDC fans already on it (in our case 2 of them) using "A Simple RV Hydronic Heating System" as a general example, we will use a 6 gallon electric water heater to heat the fluid (pet safe antifreeze) that will flow thru the heat exchanger (same as designed but using the water heater instead of the engine for heating the fluid). It will blow the heat thru ducts that we will pipe thru out the bus with PVC pipe (also to the water bays). Air return is located under my cedar chest with a furnace filter laid over it. Right now heat is not a priority, cooling is, we have been trying to figure out a cooling system to loop into the heat system and think we have got it. just need to build it. Our goal is to keep our power consumption down low. Since we tend to stay in parks more than we are on the road, using an electric water heater is best for us (we put an LP/AC water heater in our Class C in 2006 only to realize that we have NEVER used the LP side of the water heater). We still have the Bus' front heater plumbed to the engine and will add a small LP heater to the bathroom area (to boost the warmth for times when the heat isn't running but too cool to not have a bit of heat for showering). I'm also putting a very small electric "wood stove" looking thing in my fireplace mantle for the tiny living area. Again, that is for times when we do not want to kick the main heater on because we only need  a bit of heat (I can turn on the "flames" without having heat) because we sleep best at about 65F in the winter. We are on a 30 amp set up and plan to keep it that way. Our cooling system is the tricky part. We think it will work and will allow us to power the AC unit off a smallish 5500/6000 generator without pushing out of it's 50% load range (best fuel consumption). Still collecting the parts. If it will cool us here in the NM desert heat, it will cool us anywhere. I need to get everything together and get it installed in the next month or so. It's already hit 100F a few times.

I refuse to put something in the bus that costs more than we paid for the shell. Based on my continually updated conversion costs spread sheet, we should be able to convert for right at $5K not counting the cost of the shell. The generator will bump us up to almost $6K.
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« Reply #14 on: April 29, 2012, 01:07:12 PM »

1. The DBW 2010 and Scholastic are two different models, not two names for the same model.  These are made by Webasto.

Damn, are we getting picky there, Sean?  The Scholastic Series uses a DBW 2010 plus it has a pump and enclosure.  True, not the same part number, but WTH?

--Geoff

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« Reply #15 on: April 29, 2012, 06:39:57 PM »

... are we getting picky there, Sean?  The Scholastic Series uses a DBW 2010 plus it has a pump and enclosure.  ...


As I wrote in another thread, not trying to be picky or argumentative, just accurate.  Mostly for the sake of newbies who come back to these threads in the archives, sometimes years later.

Not only are these different part numbers, but there are other differences as well.  For example, the DBW-2010 is available in 24 volts, whereas the Scholastic only comes as a 12-volt model.  For many bus owners, this is an important distinction and could be a point of confusion if they were looking for a Scholastic model.

For the benefit of anyone following along the Scholastic is a package system marketed by Webasto specifically for the school bus market (as in actual school buses, not conversions).  It is intended to be more "plug and play" for school bus fleets, and thus includes a pump, some additional control wiring, an interconnecting hose from the pump to the boiler, and, as a nod to "school bus yellow", the boiler housing is finished in yellow as opposed to the silver of a stock DBW boiler.

The DBW-2010 and its sibling, the DBW-2020, are boiler-only models which include the control relay module, but nothing else.  You add a circulating pump to this mix, which Webasto is happy to sell you but is usually made by a third party, and optionally an enclosure.

FWIW, most DBW installations in converted coaches will use a higher-capacity pump than the one that comes integrated into the Scholastic series.

Again, not trying to step on anyone's toes, just trying to be more accurate or complete with the information.  Hydronic heat is a complex subject and can be daunting for a first-time converter, and having partial information or terms mixed up can add to the challenge.

-Sean
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« Reply #16 on: April 29, 2012, 07:34:30 PM »

Sean, I would like to say you made a very nice response.  But I can't.

--Geoff

... are we getting picky there, Sean?  The Scholastic Series uses a DBW 2010 plus it has a pump and enclosure.  ...


As I wrote in another thread, not trying to be picky or argumentative, just accurate.  Mostly for the sake of newbies who come back to these threads in the archives, sometimes years later.

Not only are these different part numbers, but there are other differences as well.  For example, the DBW-2010 is available in 24 volts, whereas the Scholastic only comes as a 12-volt model.  For many bus owners, this is an important distinction and could be a point of confusion if they were looking for a Scholastic model.

For the benefit of anyone following along the Scholastic is a package system marketed by Webasto specifically for the school bus market (as in actual school buses, not conversions).  It is intended to be more "plug and play" for school bus fleets, and thus includes a pump, some additional control wiring, an interconnecting hose from the pump to the boiler, and, as a nod to "school bus yellow", the boiler housing is finished in yellow as opposed to the silver of a stock DBW boiler.

The DBW-2010 and its sibling, the DBW-2020, are boiler-only models which include the control relay module, but nothing else.  You add a circulating pump to this mix, which Webasto is happy to sell you but is usually made by a third party, and optionally an enclosure.

FWIW, most DBW installations in converted coaches will use a higher-capacity pump than the one that comes integrated into the Scholastic series.

Again, not trying to step on anyone's toes, just trying to be more accurate or complete with the information.  Hydronic heat is a complex subject and can be daunting for a first-time converter, and having partial information or terms mixed up can add to the challenge.

-Sean
http://OurOdyssey.BlogSpot.com

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« Reply #17 on: April 29, 2012, 08:11:48 PM »

 Hi Dave--- I am not sure what you want for a schematic but I dug this out at shop today.and took a couple of pictures for you. These are only my thoughts. You have to design the system to make it do what you want it to. If you are going to use the engine to heat, you cannot interfer withits normal ability to cool and regulate its own temp.I live in Canada EH it gets cold here and I wanted to be able to start my engine in cold weather thus PRO HEAT. I had two extra three way air operated control valves left over from my steamfitting days, so I used them. . Valves 1&2 are opened and valves 5&6 closed to heat engine with pro heat. Other than to heat engine this order is reversed and all other valves stay open and control is by air valves. The heaters are Princess Auto about 9000btu (I think) The heaters I hung upside down in bay and aimed them at something that I could make a false floor in and blow heat a couple directions, like a vanity, kitchen cupboards or a seat. I hung heaters in bay because if they spring a leak I prefer antifreeze in bay not upstairs.I used 110 volt ac base board thermostats to control heater fans, they can handle the fan amps. Water like electricity will follow path of least resistance thus you need a balancing valve at each heater or you will get hot and cold spots in coach. Hope  this is what you are looking for.
   Larry B  
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« Reply #18 on: April 29, 2012, 08:16:33 PM »

A couple more pictures. The one picture has nothing to do with heating ,it contols my leveling jacks and slide
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« Reply #19 on: April 29, 2012, 09:16:50 PM »

Sean, just curious,

What is the size of the pump (gal/h or ltr/h) of most DBW2010 installations in conversions ?


FWIW, most DBW installations in converted coaches will use a higher-capacity pump than the one that comes integrated into the Scholastic series.


The specs in the Webasto manual are little confusing -  Scholastic vs DBW2010

Shed any light ?


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« Reply #20 on: April 29, 2012, 11:26:50 PM »

What is the size of the pump (gal/h or ltr/h) of most DBW2010 installations in conversions ?
...


They're all over the map, and depend greatly on who designed and installed the system.  Also, GPH is a relative figure, since it depends on the apparent head of the system.  My pump, for example, is rated at 25 GPM at a head of around 8', but that drops to just 5 GPM at a head of 25'.  "Head" is a measure of backpressure in the system based on an open-ended pipe of the listed height, but in a closed-loop system like a hydronic heat system, is is really a function of size of tubing, number and tightness of bends, orifice size of the devices, number of independent paths, etc., which goes to your second question,
Quote
The specs in the Webasto manual are little confusing -  Scholastic vs DBW2010 ...

and this is exactly why: Webasto makes and sells component parts, and relies on its independent dealers to do the system engineering.

Figuring the backpressure of the system in order to properly size the pump requires advanced engineering in a specialty known as fluid dynamics.  That's not my particular expertise, and so I know just enough to be dangerous here.  I can tell you that most service and supply shops don't have this expertise, either, and so they rely on engineering rules of thumb, sometimes garnered over decades of experience.  They just know that with so much tubing of such a size and with this many devices you need a pump of X capacity.  Usually they err on the side of caution and recommend a slightly larger pump than is required.

The Scholastic is Webasto's attempt to take the guesswork out of this one segment of the industry.  They looked at the engine and heating configuration of the most common school bus models and sized a complete system that would work, out of the box, with the majority of them in most conditions.  This is facilitated by the fact that there is not a lot of variation in design, layout, and capacity of school bus heating systems -- they are all pretty much alike.  Bus conversions, OTOH, are all over the map in terms of design, layout, fluid capacity, devices, and whether the engine loop is integrated or separated by a heat exchanger.

Figuring the correct pump for your installation is probably the single most difficult part of a home-brew hydronic heating installation.  This is one area where your hydronic parts supplier or Webasto dealer can probably help by making a recommendation based on experience with similar layouts.

Probably not the answer you were hoping for, but I hope it helps a little, at least.

BTW, FWIW, I have a single-loop system with a "summer" bypass valve, two heat exchangers (one for the engine and one for the hot tub), a marine water heater, five fan-coil units, one radiant heater, and an expansion tank.  My boiler is a DBW-2010.  The pump I use is a centrifugal type with a stainless impeller, made by MP.  I'm pretty sure it's an MP FRX75.  The pump cost more than the boiler, and I'm on my third one (they really, really, really do not like being run dry).

That said, lots of pumps will probably work for most applications, just with varying levels of efficiency and lifespan.  Our system probably sees more use than most, anywhere from 200-500 hours per year; for a coach that only gets occasional use a less heavy-duty model would probably suffice.

-Sean
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« Reply #21 on: April 29, 2012, 11:58:08 PM »

...
I would love to see a drawing and details.
...


Dave, it took me a few days to dig into my documentation.  Unfortunately, I could not find a drawing other than some hand chicken-scratch we did when we installed it that would not translate well here.  That said, I can tell you the layout in a less graphical way.

My system is arranged in a single loop, with a Y-valve to bypass the house heaters for warm-weather use (allowing the system to still be used to make hot water).  Starting from the lowest point in the system and running to the highest, my loop runs, in order:

Pump -> Boiler -> HX(e) -> DHWH -> HX(h) -> Y -> FCU(x5) -> Radiant -> T -> Expansion Tank

Where:
Pump = MP centrifugal pump
Boiler = Webasto DBW-2010
HX(e) = engine heat exhanger (30,000 BTU/h)
DHWH = marine water heater with integral heat exchanger
Y = Y-valve. This short-cuts past the house heaters
HX(h) = hot tub heat exhanger (30,000 BTU/h)
FCU = Fan coil unit.  There are a series of five of these through the coach
Radiant = radiant baseboard heater
T = "Tee" in the line where the bypass from the Y-valve joins back in
Expansion Tank = ~3 gallon tank with pressure cap at the high point of the system.

Obviously, the expansion tank connects back to the pump input.

Quote
Sometimes the "other source" heats the coach, other times it pre-heats the engine, and other times the engine takes the full load.  Also, most systems heat domestic water or use an additional water heater.  Engine heat can pre-heat the water heater, etc.   How do you control all that?


In a heat-exchanger system, the short answer is that all you need to do to get heat from the engine while driving is to turn on the hydronic circulating pump, without also turning on the boiler.  To pre-heat the engine, you need to turn the boiler and the circulating pump on, but you also need another small electric pump to circulate the engine coolant as well, since the engine water pump is not running.  So the "pre-heat" function involves turning on this extra pump.

Overall thermostatic control of the system involves one or more house thermostats, a thermostat on the water heater, and a thermostat on the coolant loop itself connected to the fans on the FCUs.  Theses later two thermostats are often called aquastats because they measure water temperature rather than air temperature.  Many hydronic dealers, for example Sure Marine, will sell you the thermostats and required relays as an integrated control package.

The basic layout is to multiplex the house thermostats and water heater 'stat into a single "ON" signal to the boiler control.  The boiler supplies a control signal to the circulating pump.  Each house thermostat also signals "on' or "off" to the fans of the FCUs depending on zone.  A relay prevents the FCU fans from running until the coolant aquastat closes, indicating sufficient coolant temperature to provide heat (this just keeps the fans from blowing cold air).

Wiring all this together is straightforward, but the circuit diagram can get large and complex depending on number of zones.  I don't have one handy or I would post it, but I would be happy to provide any more details that you need to make a working system.  Also, I'm pretty sure Dave Galey has diagrams of both the fluid side and the electrical side of a basic hydronic system in his book on the subject.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

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« Reply #22 on: April 30, 2012, 07:30:35 AM »

Dave,

I found 2 old schematics that I am sending you.   They need explanation from learnings after installation, so they are not ready for prime time posting.

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« Reply #23 on: April 30, 2012, 08:11:45 AM »

For those us you have the Scholastic Series DBW 2010 and are entirely pleased with their hydronic system I would like to add that the provided coolant pump with the unit produces 15-20 GPM, which has always been adequate for a basic converted bus heating system.  Plus my RTS (like other buses) has a factory coolant pump that can be used in conjunction with the Scholastic pump for pre-warming up the engine faster.  I have mine set up so the Scholastic heater can just warm up the interior, or the engine and interior at the same time.  I feel using the basic layout of the Scholastic Series with a few extras is the simplest and adequate system-- I think the heat exchanger method that the Aqua-Hot system uses is much more complex than necessary and way too costly and bulky.


--Geoff
'82 RTS AZ

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Geoff
'82 RTS AZ
Sean
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'85 Neoplan Spaceliner "Odyssey"


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« Reply #24 on: April 30, 2012, 12:07:56 PM »

For those us you have the Scholastic Series DBW 2010 and are entirely pleased with their hydronic system I would like to add that the provided coolant pump with the unit produces 15-20 GPM, which has always been adequate for a basic converted bus heating system.


Just to clarify my earlier comments, the pump included with the Scholastic series is, indeed, adequate for many conversion installations.  It is better suited to a handful of larger heaters, though, than many smaller ones, and the additional restrictions imposed by marine water heaters and multiple heat exchangers can challenge it.

In short, the Scholastic series is a good solution (and can be very cost effective) if the included pump is adequate for your needs.  If the included pump is not adequate, then buying the components separately might be a better choice, so that a larger or more robust pump can be specified.

Quote
... I think the heat exchanger method that the Aqua-Hot system uses is much more complex than necessary and way too costly and bulky.
...


FWIW, this is my take on Aqua-Hot as well.  It's a great company, with wonderful customer service, and buying an Aqua-Hot product takes a lot of the engineering or guesswork out of a hydronic system, but you pay a premium for that.  Individual components are generally cheaper, especially if you shop around.

-Sean
http://OurOdyssey.BlogSpot.com
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Full-timing in a 1985 Neoplan Spaceliner since 2004.
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« Reply #25 on: May 01, 2012, 07:53:11 AM »

Nobody's mentioned this company.

They have all the manuals on line.  Perhaps you can get ideas from them.


http://itrheat.com/products/oasis-heating-system/
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