Relocating Wabesto

[RichardEntrekin]

This is a quick explanation on why Aquahot says not to run engine glycol coolant in their heating systems. Sometime in the early 2000s Aquahot moved their hot water heating coil from an external to the boiler copper tubing coil to an internal to the boiler loop. You get better heating for longer showers with the internal coil.

However, when they did that, they had to protect against potential contamination of the drinking water system since ethylene glycol can kill you if ingested. When they changed to the internal coil system they changed to running propylene glycol as the coolant.

Not trying to nitpick, but the thread is about designing and building custom heating systems, and one needs to be aware that if there is only one degree of separation between the hot water and the recirculating coolant, then it is prudent to use propylene glycol as the coolant. Propylene glycol is the pink RV antifreeze available anywhere. It won't hurt you if ingested.

[Jim Blackwood]

If the water heater is part of the system this does make sense. If it is not then this does not apply. Much depends on the configuration. How are typical RV water heaters that include an engine coolant loop configured? Extra thick internal loop maybe? Just asking here. Probably prudent not to drink hot water out of the water heater. I got out of that habit as soon as I was aware of the lead issue. Might make sense to have a check valve on the water inlet to the heater.

As for routing, on the DL there is not much needed to convert to RV use. One more valve to isolate the engine loop and a bit of re-plumbing, I believe is all it takes. As it stands circulation is always through the engine and the coach can be isolated (no heat). You want it the other way around, or better still for cold climates, the ability to isolate either. Doesn't take much to do that once the coolant has been drained.

Jim

[Geoff]

Geoff

I'm open to all options.  I need to have my Webasto rebuilt anyhow so now is the time to think about a different way to plumb a system.  If you could help me design a system that does all those things then I am all ears.  From what I understood from reading on this forum was that if the two systems (engine coolant/interior coolant) were not separated what would happen if you had a leak in one system?   Then both would be down, correct?  I spoke to a member on this site who has a system set up as I described using a flat plate exchanger to keep the two systems separate.  While traveling through Alaska he had a failure with the engine coolant loop and because his system was separated by the flat plate exchanger he was able to run the interior system and keep his family warm until he was able to fix the engine issue.  That to me seams like a smart way to set up a system.  Am I wrong or missing something?

The engine coolant loop on an RV water heater is simply an aluminum pipe welded to the OUTSIDE of the water heater, so there is no chance the glycol is going to get into your fresh water.  Only people like Aquahot use a heat exchanger to heat the fresh water and they run separate systems because of this.  Same for the engine preheating-- another heat exchanger.

Anyway, I not only have the engine/Webasto loop to heat water; but my heater is also electric and propane.  I don't like the complexity of an Aquahot.  You can do everything an Aquahot does with a Webasto much easier.

[sledhead]

very hard to ex plane but how I did it was from eng .to ball valve to preheat pump ( on only to preheat eng. ) to ball valve to marine 6 gal. water heater loop to ball valve back to eng.

I use the 6 gal. water heater as a buffer tank for Propylene glycoll to hold the heat in the system and to add enough propylene glycoll so the boiler does not short cycle .

proheat boiler out to ball valve to 11 gal. marine hot water tank loop to 6 gal. w/h tank above ( buffer tank ) then ball valve and back to proheat

clear as mud right

pic shows buffer tank on top with domestic 11 gal w/h tank under and boiler in front


the 11 gal w/h tank is my domestic hot water tank     

[Jim Blackwood]

Clearly you should just throw money at it. All that shiny stainless is sure to impress. But where is the rationale for extra fancy heat exchangers? Are they not just as likely to spring a leak as a tube welded inside a hot water tank? To be honest I'm less than impressed with the way RV hot water heaters are made. Sure they work, but they seem to be barely a step beyond the old external coil units with the cast iron gas burner. After driving for hours you might have shower water but that little external loop is never going to heat your interior. So how about something custom made, and since it's in a bus and there's plenty of room, size is no concern. Just to make sure it's obvious if the coolant gets into the drinking water it's probably best to use oil as the heat transfer medium. That way it'll really be noticeable if there's a leak. Hey, motor oil ought to work fine, right? Better yet, it can be run anywhere from atmospheric pressure to about 15psi while the water tank is held to about 60psi so if there is a leak it'll go the other way. What? You're already doing that? Well maybe the antifreeze will migrate in there anyway. Hell, maybe it'll creep over the outside of the bus to get in the fresh water tank through a vent or something. Let's just Rube Goldberg the Hell out of it, what do you say? Make a big insulated stainless enclosure with a big ole coil inside with an oil bath around about a 60 gallon water tank, that way the engine coolant can transfer heat to the oil then to the water. Might even get enough heat transfer that way to run a pump and send the water through a bunch of passive radiators in the coach. In fact, let's just go passive all the way and use convection flow. The pipes will have to be a lot bigger but what the heck, there's plenty of room, right? Sheesh. I can't believe some of the things I see. What's wrong with a simple fireplace, am I right? Hey, it worked for Gramps...

No, seriously though I hope y'all got a laugh out of that, but if you want a completely safe system some of that does make sense. Use pressure differences and an inert fluid to transfer your heat, and keep it simple. A coiled tube has no weld seams to leak. But you can very quickly go overboard with this stuff. If your water system maintains 60psi and your engine coolant never goes over 15 psi, how is antifreeze ever going to get into the drinking water? Scratch that, shower water. Put a check valve in the water heater inlet and it'll never get close to the drinking water. Maybe you could keep the antifreeze and the drinking water at opposite ends of the bus and just transfer heat by osmosis. How hard can it be?

Jim

[buswarrior]

And remember the root of all this was to scavenge "free" heat from the engine while driving earlier in the day...

And it went from there...

This is complicated subject, with many variables and does not lend itself well to the typed words in a forum.

Don't even dream of raising it on the fools' social media...

Happy coaching!
Buswarrior

[luvrbus]

You can do about anything with a Webasto or ProHeat boiler hot water with the little March pumps and aqua stats for less than a 100 bucks,you are not sending a man to moon 

[sledhead]

Clearly you should just throw money at it. All that shiny stainless is sure to impress. But where is the rationale for extra fancy heat exchangers? Are they not just as likely to spring a leak as a tube welded inside a hot water tank? To be honest I'm less than impressed with the way RV hot water heaters are made. Sure they work, but they seem to be barely a step beyond the old external coil units with the cast iron gas burner. After driving for hours you might have shower water but that little external loop is never going to heat your interior. So how about something custom made, and since it's in a bus and there's plenty of room, size is no concern. Just to make sure it's obvious if the coolant gets into the drinking water it's probably best to use oil as the heat transfer medium. That way it'll really be noticeable if there's a leak. Hey, motor oil ought to work fine, right? Better yet, it can be run anywhere from atmospheric pressure to about 15psi while the water tank is held to about 60psi so if there is a leak it'll go the other way. What? You're already doing that? Well maybe the antifreeze will migrate in there anyway. Hell, maybe it'll creep over the outside of the bus to get in the fresh water tank through a vent or something. Let's just Rube Goldberg the Hell out of it, what do you say? Make a big insulated stainless enclosure with a big ole coil inside with an oil bath around about a 60 gallon water tank, that way the engine coolant can transfer heat to the oil then to the water. Might even get enough heat transfer that way to run a pump and send the water through a bunch of passive radiators in the coach. In fact, let's just go passive all the way and use convection flow. The pipes will have to be a lot bigger but what the heck, there's plenty of room, right? Sheesh. I can't believe some of the things I see. What's wrong with a simple fireplace, am I right? Hey, it worked for Gramps...

No, seriously though I hope y'all got a laugh out of that, but if you want a completely safe system some of that does make sense. Use pressure differences and an inert fluid to transfer your heat, and keep it simple. A coiled tube has no weld seams to leak. But you can very quickly go overboard with this stuff. If your water system maintains 60psi and your engine coolant never goes over 15 psi, how is antifreeze ever going to get into the drinking water? Scratch that, shower water. Put a check valve in the water heater inlet and it'll never get close to the drinking water. Maybe you could keep the antifreeze and the drinking water at opposite ends of the bus and just transfer heat by osmosis. How hard can it be?

Jim


I tried the quote but lost the post sorry

Jim

this is a very simple system as far as hydronic heat goes . I did not include how the inside coach heat works as that is more completed .
marine water heaters have been used by boat and rv people for years with very little problems and the cost is very low and the ones I used are all aluminum . the anti freeze can not get to the fresh water unless both water heaters fail at the same time . any heat exchanger can fail
maybe the best heater and cheapest would be a 120 volt cube heater but I am not on a poll all the time . my cost on the complete system including the coach heat was only approx. $3800 for all new . to me it was cheap compared to any other hydronic system on the market today

dave   

[chessie4905]

Or 1000 hours of generator time with electric heat. Or propane furnace and 1000 lbs of propane.