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Topic: Using heat from engine coolant system to heat water (exchange) (Read 654 times) previous topic - next topic

Using heat from engine coolant system to heat water (exchange)

It seems that some FTs have this option already installed: of using engine heat to heat the water in the water heater when traveling.  Thereby arriving with hot water and no need of using electric or propane to heat water.  I am replacing my 20-year old gas only water heater with a new water heater.  This new heater is an electric/gas combo which also has the heat exchange inlet and outlet.  I wonder if this option is worth the trouble.  My 20-year 270 does not have the plumbing for this.  However, a couple of T's and a valve and some 5/8" heater hose and about 10 clamps cannot amount to too much cost.  Gotta drill a couple of holes....

After reading a few notes from my favorite experts on this forum (Brett, Neal, and Barry+Cindy and the suggestion that these notes were more than 120 days old and that a new topic may be needed) about sharing the hot engine fluid heat with the cabin heater up front, and schemes for success with this, I searched the internet for more problems.  Seems that other systems (brands of motorhomes) caution about the water being heated to 180-degrees instead the normally regulated 150-degrees on the tank controls.  This worries some folks.  It now worries me with my 20-year plumbing (grey butyl) working at this temperature.  However, we gave up the 5 and 600 mile days after the first year.  Usually a day's driving now is 250 miles max.  So would the water in the tank get to 180 degrees in three or four hours?

Using engine heat to provide hot water seems efficient and worthwhile and something I could get used to.  Perhaps it could help to keep the engine cooler climbing a hill or two.  Anyone have any experience with engine heated water or practical tricks to add?

Andy1
Carolyn and Lewis (Andy1) Anderson
1996 U270 36'

Re: Using heat from engine coolant system to heat water (exchange)

Reply #1 –
Quote from: Lewis Anderson –
It seems that some FTs have this option already installed: of using engine heat to heat the water in the water heater when traveling.  Thereby arriving with hot water and no need of using electric or propane to heat water.  I am replacing my 20-year old gas only water heater with a new water heater.  This new heater is an electric/gas combo which also has the heat exchange inlet and outlet.  I wonder if this option is worth the trouble.  My 20-year 270 does not have the plumbing for this.  However, a couple of T's and a valve and some 5/8" heater hose and about 10 clamps cannot amount to too much cost.  Gotta drill a couple of holes....

After reading a few notes from my favorite experts on this forum (Brett, Neal, and Barry+Cindy and the suggestion that these notes were more than 120 days old and that a new topic may be needed) about sharing the hot engine fluid heat with the cabin heater up front, and schemes for success with this, I searched the internet for more problems.  Seems that other systems (brands of motorhomes) caution about the water being heated to 180-degrees instead the normally regulated 150-degrees on the tank controls.  This worries some folks.  It now worries me with my 20-year plumbing (grey butyl) working at this temperature.  However, we gave up the 5 and 600 mile days after the first year.  Usually a day's driving now is 250 miles max.  So would the water in the tank get to 180 degrees in three or four hours?

Using engine heat to provide hot water seems efficient and worthwhile and something I could get used to.  Perhaps it could help to keep the engine cooler climbing a hill or two.  Anyone have any experience with engine heated water or practical tricks to add?

Andy1


It is on my 1981 used it for 18 years no problems. Standard heater hoses just run through the water heater to the dash and then back  to the engine.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Using heat from engine coolant system to heat water (exchange)

Reply #2 –
I think it was standard on most of the coaches.  For coaches with propane water heaters (Atwood) there is a 3-way model that has the connection for the engine heat as well as propane and AC heating.  There's a separate valve in the water heater compartment that turns off the engine coolant to the water heater.
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Using heat from engine coolant system to heat water (exchange)

Reply #3 –
I just replaced my water heater with the same 6gal Atwood that it came with 26 years ago.. It has the engine water heat exchanger  as did the the old one. I 'm not sure if I will every actually take advantage of this feature but I thought, why not? I'll admit the hoses were already there. The heat exchange option made the water heater about $60.00 (i think) more then the one without.
I'm on my own so the 6 gallon seems to work fine. The old one must have had a thick wall of crust in the tank as the new one seems to make twice as much hot water as the old one.
Andy 1989 U300 40'

Re: Using heat from engine coolant system to heat water (exchange)

Reply #4 –
Quote from: Dave Katsuki –
There's a separate valve in the water heater compartment that turns off the engine coolant to the water heater.

Dave,

I have seen that valve, but never knew what it did. Are you saying that if I turn it on, the hotwater heater water will flow through the dash heater to warm it up while driving? Or is it separate from the dash heat?

Thanks,

Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Using heat from engine coolant system to heat water (exchange)

Reply #5 –
TT.
 It doesn't seem to work that way. By that I mean, the water heater heating water for the engine and dash heater. I wish it did, kind of a preheat situation for the engine and a jump start for the dash heat. We have had the hot water heater on before starting the engine and the systems didn't seem to be preheated. Maybe because the engine water pump wasn't pushing the water around. Is that what you meant.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Using heat from engine coolant system to heat water (exchange)

Reply #6 –
Bob,
 
I am not sure. This discussion reminded me that I had such a valve, but do not really know what it is supposed to do or how it works. All explanations greatfully accepted.
 
Thanks,
 
Trent

Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Using heat from engine coolant system to heat water (exchange)

Reply #7 –
Trent,
I'll give it a try........
The valve controls the engine coolant flow to the heat exchanger in the water heater. The coolant lines to the water heater are "T"ed into the lines going to the front heater core from the engine. When the engine comes up to temp and the T-stat opens coolant flows to both if the valves are open. The water heater is connected in parrallel to the heater core not in series to it. Therefore opening the valve will "rob" some of the heat from your dash heater. There is a tag on my water heater exchange valve that states such. I've tried it with the valve closed and it didn't seem to make any difference. It does however do a good job of heating the hot water while traveling, if you have that valve open. :-)
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Using heat from engine coolant system to heat water (exchange)

Reply #8 –
Go with an on-demand water heater...you won't be sorry
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: Using heat from engine coolant system to heat water (exchange)

Reply #9 –
We have an Aquahot in our coach but the idea is the same. Engine coolant heats the Aquahot coolant which heats domestic hot water.  The Aquahot coolant is hot so in colder weather it also adds heat to the coach interior using heat exchangers.  A couple hours of driving and we have hot water.  In the morning it is still hotter than warm.  You are making engine heat, why not put it to additional use.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Using heat from engine coolant system to heat water (exchange)

Reply #10 –
Quote from: Lewis Anderson –
So would the water in the tank get to 180 degrees in three or four hours?

I had that setup in my old Wanderlodge. The water will be whatever temperature the engine is after 1 hour. If you house piping can't stand that temperature, it will melt. The Wanderlodge had copper piping.

TOM
SOB (Some Other Brand) division
1995 Wanderlodge WB40
8V92 :D

Re: Using heat from engine coolant system to heat water (exchange)

Reply #11 –
Quote from: OldManSax –
I had that setup in my old Wanderlodge. The water will be whatever temperature the engine is after 1 hour. If you house piping can't stand that temperature, it will melt. The Wanderlodge had copper piping.

TOM


Foretravel pipes do survive that heat although through thermal loss I doubt the true engine temperature gets through the heat exchanger and travels to the faucet. Whatever hoses and pipes were used in 1981 never melted.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Using heat from engine coolant system to heat water (exchange)

Reply #12 –
Our OEM MotorAid water heater, after a day on the road, puts out fairly warm water, but you're in no danger of scalding yourself.  The really big advantage, as I see it, is the main heating elements (propane or electric) have a lot less work to do when you fire them up after getting parked.  Only takes our (propane) heater 10-15 minutes to heat the already warm water to "cut-off" temp - ready for hot showers!
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"