ProHeat pressure cap?

[JackConrad]

I am finally installing a heating system in our bus.  We purchased a used ProHeat from Nimco and have accumulated a couple toe kick heat heaters as well as 1 larger heater core for the inside of the bus and a heat exchanger to combine ProHeat system and engine cooling system in a bay. Most of the connecting lines are high quality automotive heater hose.  We will have an expansion tank at the highest point in the system to fill the system (the expansion tank will be in the linen closet to double as a towel warmer). The expansion tank uses a standard radiator cap. MY question is "how many pounds presssure should the cap by? (ProHeat operating range is 150-180 degrees)  Thanks in advance.Jack

[Ednj]

Jack,
My system is vented open to atmosphere.

I don't know about a pressure cap.

[Homegrowndiesel]

Hey Jack
Any pressure will do, within reason. You do not need a high pressure cap because you are not trying to raise the boiling point.

Bill

[Nick Badame Refrig/ACC]

Hi Jack,

Ed & Bill are correct, you will be well below the boiling point at 180 deg. so no pressure cap is required.

Good Luck
Nick-

[gumpy]

The cap on my AquaHot is 13 lbs.

It's not necessary for the expansion tank to be the highest point unless that's the only fill for the system. My Aquahot has the
fill on its internal tank, and my expansion tanks is on the floor. As coolant expands it pushes out the cap and into the tank.
As it cools and contracts it sucks it back into the system.

craig

[Nick Badame Refrig/ACC]

Hi Craig,

If you were to build your Proheat/Aquahot systems with a direct loop into your engine without the use of a

flat plate heat exchanger of sort, then it would be necessary to have a pressure cap that is equal to your bus

engine's pressure.  When we heat coolant it will expand. A good rule of thumb is to allow an expantion space

of 20% of your entire capacity.  My Proheat system contains just over 5 gallons of antifreeze/ water mix. So,

I installed a 1 gallon reservoir for expantion. I used a plastic overflow container from a ford Taurus that has a fill

fitting and a breather cap. It's an almost clear in color and it allows me to watch the expantion and contraction

while the unit cycles and I can easily see if the level has dropped from a leak or what not..

Good Luck
Nick-

[gumpy]

If you were to build your Proheat/Aquahot systems with a direct loop into your engine without the use of a

flat plate heat exchanger of sort, then it would be necessary to have a pressure cap that is equal to your bus

engine's pressure. 

Right, but the Aquahot has an engine preheat loop inside it, and I believe Jack said he purchased a heat exchanger for engine heat.

If you were to build it with a direct loop into the engine, then I agree you would need a cap at least equal to the bus. However,
in your direct loop described configuration, you could eliminate the reservoir and cap all together, as the bus pressure tank and
fill cap would sufice. All you would need in the bay would be an air purge.

I don't recommend using a direct loop system like that. Too much risk to leaking out engine coolant, and too difficult to isolate. Your
way, with two tanks and caps would be better.

In Jack's described system, he says his expansion tank is pressurized, which means it does need to be higher than the heater unit.
However, it only needs to be mounted such that the fill cap is slightly higher than the heater itself. It does not have to be higher
than the hydronic lines that go to the heater cores inside the bus, as long as the return lines come in below the coolant level,
and there's no chance for them to suck in air. Once the lines are filled, they won't bleed back into the system if you open the
fill cap on the reservoir. Another neat thing with this is that once the lines are filled, there's no head pressure on the circulation
pump (not that it really matters in the bus system since there's so little elevation there anyway).

Mounting the pressure tank in the linen closet may not be the best location.

First, while it might afford easy access to fill the system, if the tank is too small it might overflow as the coolant reaches maximum
temp (upwards of 210* when heating off the engine). Then you'll have antifreeze all over the inside of the coach (I'm assuming
there is no blowoff line attached to this tank. I think this is normal on the newer cars equipped with such pressurized tanks. Correct
me if I'm wrong.).

Second, it will only be warm for a brief period of time as the system is actually coming up to temp and expanding into the tank. After
that, it will cool down to near ambient temp as there is no circulation through the tank to keep it warm. So the towel warmer idea
won't pan out.

Sorry Jack, no warm towels unless you install a circulation loop through a copper pipe towel bar.

[Homegrowndiesel]

OK GUYS
We are all real close here, I Hate to be an opinionated SOB.
There is no need for a seperate system.  Valve off-on that easy, seperated. No air traps, no need for air vent in bay. I agree with you on the rest Gumpy.

All systems need to work together, or you need to run both systems instead of one. If seperated You will also need a circulating pump on the detroit side to preheat the detroit.
It's all good though, to each his own, Just MY OPINION.

The cap on the detroit then is my corrected answer.

I love this board

Bill

[gumpy]

OK GUYS
We are all real close here, I Hate to be an opinionated SOB.
There is no need for a seperate system.  Valve off-on that easy, seperated. No air traps, no need for air vent in bay. I agree with you on the rest Gumpy.

All systems need to work together, or you need to run both systems instead of one. If seperated You will also need a circulating pump on the detroit side to preheat the detroit.
It's all good though, to each his own, Just MY OPINION.

The cap on the detroit then is my corrected answer.

I love this board

Bill

Hi Bill,

We kind of strayed here, and got away from Jack's intended system. He indicated he bought a heat exchanger for the engine side, so he
does need to have two separate systems, the engine side, and the proheat side, which means he does need to provide the expansion
tank and cap for his proheat system.

As I mentioned before, if they were combined without an exchanger, you could use just the detroit cap, but it would be easier to have one in the bay for filling, also. Otherwise, you have to fill the proheat from the detroit cap and somehow bleed the air out of it in the bay.
Plus, if you valve it off, you can't use the heater because you then have no expansion capability. Of course, you probably would only shut it off
if you were isolating the system from the engine due to a leak or for service so you probably wouldn't be trying to use it then, anyway.

craig

[tomhamrick]

I have the Webasto Scholastic unit which comes with a pump and all controls in one unit, but no storage tank. I purchased a 12 gallon household water heater that I use as my resevoir and have a loop from the Webasto to the water heater. I have another loop from the water heater with a speperate pump that feeds the radiators in the bus. On the radiator loop I have a 2 gallon tank that I purchased from Dick Wright (The Generator Man) and placed it in the dash of my Eagle. It is the highest point in my system and has a 4 pound (if I remember correctly) pressure cap. This tank also has two ports for coolant lines so water circulates through it as well as being the expansion space (could be a towel warmer). It also has a overflow port that I ran through the floor and under the bus.

Tom Hamrick
1984 Eagle 10S

[Songman]

This is all so confusing... My Hurricane has everything built into one unit. I had assumed that the electronics built into the unit would handle all the cutoff stuff as needed. Since I will be using engine heat to heat the coach and the hot water when on the road, I think a manual valve would only be useful only if I needed to work on the engine for some reason. Hopefully the manual will explain all this when the time comes.

[tomhamrick]

I forgot to add that I also have a heat exchanger between the engine and the Webasto so they are seperate systems. I used the water pump from the Eagle heat system to circulate the engine water through the heat exchanger both to preheat the engine and to heat the Webasto from the engine.
Tom Hamrick
1984 Eagle 10 S

[colecruzer]

Hi,
If I want to add the capabillity of heating water with a Proheat system what is the best way of doing it?
Thanks
Rich

[captain ron]

Hi,
If I want to add the capabillity of heating water with a Proheat system what is the best way of doing it?
Thanks
Rich

Flat Plate heat exchanger and install it before your water heater tank then you should pretty much have continuous hot water.

[gumpy]

Hi,
If I want to add the capabillity of heating water with a Proheat system what is the best way of doing it?
Thanks
Rich

A friend of mine bought a new 12 gallon or so electric water heater from Home Depot, stripped the outer cover and insulation off to reveal the tank, and then wrapped about 100 ft of soft 1/2" copper tube around the tank. The copper tube was connected it to the heating system, and so by circulating the heating system liquid through the copper tube coils on the water tank, he can heat domestic water in the tank.
Seems to work well for him and his wife.

AquaHot does something similar, but in reverse. They have a 12 gallon coolant reservoir. There is 130 ft of copper wrapped around the
reservoir, which produces continuous domestic hot water. Works well for my family of 4.