it's not that the series 60 does not provide enough engine heat......the Webasto is a suplimental heater to provide heat without idling the engine or for quick cabin heat in the morning
That true for motorhome or some non-city-transit use.
About why not enough engines heat (BTU or British Thermal Unit) to maintain heat in transits coaches. Most northerner version use 80K to 140K heaters. Definition of BTU…is; http://dictionary.reference.com/search?q=British%20Thermal%20Unit
1) They have double twin doors & that perhaps open more than close plus poorly sealed from factory.
2) Engine’s greatest BTU output is only during acceleration
3) Axle ratio is low speed version so to achieve greatest acceleration between city block stops which mean less laboring time & rarely in over-drive than intercity coach
4) Four cycle is about half BTU of two cycle during acceleration. Even still 2 cycle transits use 80K or larger heater
5) All coach equips with glass expose half of its wall…mean greater BTU difference.
6) Very low “R” factor in between walls’ metal or fiberglass.
What about size of heater for given 40 ft coach…if you remove all but approximately 32 sq ft of thermo pane side glass with 1 ½ inch polyurethane foam in walls & ceiling, 45K BTU heater should be all you need for mild cold climate areas.
However learning from many users that have transits over-size take-out such as 80K or higher. That it starts & stop too often will cause chamber to dirty up quicker than smaller 45K that run longer & fewer cold starting. Excessive cycling equal wasting more unburned fuel to blacken until reheat chamber to a point of cleaner burning.
However…in bare shell format…80K is best in mild cold climate areas.
Plus 80K is noisier than 45K unit at the inlet & exhaust.
The larger heater the more battery power drainage for given time. All electric motor require 1/3 to 2/3 more amperage to start until reached full RPM. So fewer cycling is the better.
Another thing to be known is whatever unit’s flow rate is…it must be that flow rate or greater in your heat exchanger system or YOU WILL have problem with several pre-cycling before it reach coach’s thermostat setting. What happing is on-demand (limited storage tank) boiler water’s temperature is already reach high limit before enough cooled inlet flow rate to keep it from triggering high limit safety switch. This the cause premature failures to starting due to sooted fire chamber & clotted igniter & restricted or plugged exhaust. So be sure you check unit’s flow rate so you can design exchanger system to match it or greater.
However those diesel heater equips 2 or more zone system contain larger tank surrounded burner unit to have a supply of heated water = call an oil-fired boiler that similar as home type but equip with electric element while in RV park with eddy kilowatt power source. These “boiler” types not require minimum flow-rate in exchanger circuits.
Aqua-Hot & Hydro-Hot are design to zone for a price.
Restricted fresh air inlet & exhaust will cause unburned fuel & can be fire hazard.
For free information…20 sq ft of well sealed single pane glass areas equal 18000 BTU of heat or cooling loss for every 27° F degrees difference for a given condition. Remember that ONLY glass…not including non-glass wall.
Another freebie; Coolant Flow, Electrical Power & Fuel on all brands of Diesel Heater;
PS…even though it from Proheat…it practically same suggestion to other brandshttp://www.proheat.com/SHARED/HTML/X45FAQ.htm
Sojourn for Christ, Jerry