engine coolant plumbing question

[John Z]

I recently purchased two NOS bus heaters to be used in my 4104. The coolant lines running to the front htr/def core are probably 1 1/4" or maybe 1 1/2"; i haven't looked at them yet. The original htr control valve was about 1/2' itself, with the lines leading to it at 3/4". The new ball valve i replaced it with is 3/4"; so this is less restrictive than the stock setup.

I want the return line to the engine to supply the two new heaters which have 3/4" lines. So the question is, would you run the return coolant line "through" the 3/4" heaters or would you "T" off the return line and run the branch line through the heaters? Of course if i go the branch line route it would require an inline pump to push coolant through the htr cores or the coolant will just take the least resistive way back to the engine.

My preference would be to run the coolant return line through the heaters and not have to mess with a pump and controls for it. My only worry is will the addition of two more heater cores increase the resistance in this loop? I don't want to lose any heat at the front htr/def. What say you all?

John Z

[David Anderson]

When I yanked out my OEM heaters from my Eagle 10 I replaced the 1 1/4" lines with 3/4" and left one of the 2 12volt circulator pumps to push the coolant through the loop.  I have two 8000btu Danhard heaters up front in the cockpit with the pump wired into the heater control.  When I turn on the heaters the water is already hot even before the pump begins to turn so the natural flow from the engine water pump is sending water to the front of the coach and back.  The heater blows on my feet and the other blows on the windshield.  It will burn my feet after a while, so I imagine running yours in series should serve you well.  I suggest some way to turn your blowers off individually to give you some sort of zone control.  I use 180 degree t-stats on my 6v92, so I always have hot water going through the engine accessory water lines.  When I had 170's  in the engine I couldn't keep the cockpit as warm as I liked. 

David

[gmbusguy1]

John, Hello

I have just recently done what you are trying to do. only with a 8v71 in our Buffalo

first of all the 6-71 does not move much water thru the system to provide enough heat that your 2 heaters need and keep the temps up

in my opinion you will need a second coolant pump either in a proheat or webasto type diesel fired boiler
or a aux coolant pump, these pumps are magnetic drive and will move about 8 gallons per minute

in our Buffalo I installed a proheat into the supply line from the engine to the dash defroster not tapping into the return line at all

my thought was the supply will be a higher temp for more heat in the heaters

I did have to do a little re-plumbing in the engine compartment to have the engine and the proheat not fight each other you may or may not have to do the same depending on how (or who) has been plumbed

please feel free to contact me if you need any help with this project

Chris
231 846 0880 

[gmbusguy1]

John, the copper you are refering to in your post should be 1 inch O.D and is available at any plumbing supply

Chris

[buswarrior]

Excellent plan, to use engine heat to stay warm.

Some thoughts to guide the design:

How are you going to control the heat when it gets closer to warmer? You may find flow control to be required, not just turning off your fans, if the heat exchangers are up in the coach.

How are you going to maintain flow to the defroster/front for keeping the windshield clear without roasting the rest of the coach?

The stock system had the big heater in parallel with the defroster core, and each had their own flow control, the defroster a manual one beside the driver, the big heater, an electric or air powered valve controlled by a thermostat. Many coaches came stock with an electric pump to help with the flow, so the engineering is already done. Transit scrapyard near you!

I'd think parallel might be the way to go.

happy coaching!
buswarrior

[John Z]

Buswarrior, i have a 3/4" ball valve installed to replace the OEM control valve. In summer time this will be shut off, or partially opened to allow a small amount of heat if needed for warmth or def.

I plan to install another valve between the coolant lines to work in conjunction with the front one. This line that ties the two coolant lines together would be between the front def/htr and the new installed heaters.

In winter for max heat, the front valve by the driver would be open, and the second valve would be shut, forcing all coolant to travel to the front core before heading back through the new heaters.

In summer the front valve would be shut, and the crossover valve would be open which would allow the enging coolant to circulate through the two new heaters. My current plan is to mount the heaters in a baggage area and duct the heat upstairs where needed. The reason for the second crossover valve, is i hope to come up with a way to dump all the heat out through a bay door to the outside, in order to assist with engine cooling. The heaters are rated up to 80,000 btu, so they could add a lot of cooling effect.

As to control, i just finished wiring in the dash switches to control seperate relays for each of the new heaters. When the install is completed i want to have seperate switches for each of the 3 or 4 fan motors on each heater. The first one i want to get going is to run heat up to the navigator chair!

David, thanks for your input. Based on your experience it does sound like a series hookup should work. I think that is how i will install them,,, a lot less hassle and mess. And if it doesn't work that way, i can always change it later.

Does anyone have any recommendations as to what brand/size/model pump would work out well if this coolant loop needs a boost? I don't have the original pumps that were in there.

[tekebird]

why not have them as a seperate circuit?  Like it was orriginally?

are you having engine cooling issues?  Why not fix them?

is the bus heat already gone?

as far as the 6-71 not moving water....it surely does....at least mine did....no issues pushing heat all the way up front in North east winters all by itself ( no booster pump)

[JohnEd]

I am with john Z, what is the source for the water pumps?  The mag coupled pumps seem ideal as there is zero chance for leakage.  How much do they go for? 

Thanks,

John

[belfert]

I am with john Z, what is the source for the water pumps?  The mag coupled pumps seem ideal as there is zero chance for leakage.  How much do they go for? 

March magnetic coupled pumps in 12 volt DC are around $250.  I looked at a few other brands and they all seem to be close to that price.

[NJT 5573]

John, the return hose route is not one I have seen used. Normally a hot pressure pickup for water out is at the top of the engine. Normal return is at the bottom of the engine close to the water pump.

[gus]

Chris,

My 4104 w/671 still has both the original defroster (W/only one fan motor working) and the bus interior hearing system intact, including that monster fan motor. No optional coolant pump.

It keeps the bus so warm I can only run the large fan a few minutes at a time before I have to turn it off. (The original air-temp controls don't work anymore).

I don't use even the one fan on the defroster, all I do is open the front air vent and the moving air pressure provides all the defrost I ever need.

As far as I can tell the whole system is original except the defroster heat control valve has been removed.