Camper heating

[oz101]

I need some advice on the best way to set up my camper heating.

At the moment I have a 30L hot water tank which is heated by the engine or by 240v.

I have bought a Webasto Thermo Top E furnace, now is it best to connect it to the engine coolant system and T off that for the heating for the camper, That would be the easiest installation, or should I disconnect my water heater from the engine coolant system and have a dedicated system purely for the hot water and the heating.
I would appreciate any input You have.

 

[SkiFreak]

Heating Schematic

I have a virtually identical setup, so I can tell you what I have done.
Rather that describe everything, here is the schematic of my heating layout...

 

[gait]

much the same, worked well in first build so transferred to Canter.

I used standard car heater valves, one in each "leg". Schematic looks like a top and bottom pipe with everything piped between. Getting the heat from heater to camper has three "fan heaters", too little heat transfer and the diesel heater cycles. I believe that's also why the buffer tank is recommended in Aus. One fan heater can be diverted into shower/loo for drying clothes.

I also piped heated water through copper coils in fresh and grey water tanks - depends where you are taking the vehicle. In retrospect I should also have provided heat to house batteries but not really necessary in Oz.

In total, heat water and camper from engine while driving, heat hot water and camper from diesel heater when stationary, preheat engine from diesel heater if required (not that cold - yet).

Replaced original diesel heater timer (limited to one hour run time and could never remember how to set) with simple on/off switch after discussion with Webasto Aus technical. Heater switch and central switch for all fans can be reached from bed. I replaced the noisy fans on the Webasto supplied fan heaters

In operation hot water tank is always on, change engine and diesel heater valves over at begin and end of a drive.

Only problem I've had in a few years is small air leak into fuel supply after move to new vehicle which only showed up in below zero temperatures - I mixed up pipe sizes and finally replaced all. Don't forget the fuel filter!

My buffer tank is above the level of the vehicle radiator. Any engine cooling water loss appears as low level in the buffer tank rather than lower level in the engine reservoir.

There's an audible whistle (G above middle C) which I think is from the combustion air fan and may be helped with a different design air intake silencer.

I carry a short length of copper pipe and a couple of hose clips so I can separate engine and house in a hurry if need be.

 

[oz101]

Thanks a lot for the advice and the schematic very useful cheers, I just have one (or maybe two)question is there any reason why I can't just use my trucks reservoir rather than putting the aux reservoir in, I'm a bit stuck for space to put it.

Also the coils you're put in your water tanks did you buy the tanks with the coils in or can you get them made up and put in after? I have two water tanks already fitted,

Again thanks for your help.

Adam

 

[SkiFreak]

You need the additional reservoir if you are creating a closed, or as in my case, a semi closed loop when using the Webasto to heat the coolant.
The specs for this setup states that a minimum of 4 litres of coolant is required.

As for gait's water tanks... he made them himself.

 

[alan]

http://www.ebay.com.au/itm/NEW-PLAN...Caravan_Parts_Accessories&hash=item519f8dee1d
This may be of some interest..

 

[whatcharterboat]

Hi Adam,

You need the additional reservoir if you are creating a closed, or as in my case, a semi closed loop when using the Webasto to heat the coolant.
The specs for this setup states that a minimum of 4 litres of coolant is required.

Yep. That's the reason if you make a completely closed short loop. There is a way of cheating but it's a bit hard to explain without drawing a circuit. Basically you need to leave one leg of the loop still open to the engine circuit.....and of course there still needs to be enough coolant in the circuit or the Thermo Top cycles to often but it cuts out having 2 coolant fill points.

Another thing Webasto were trialling was instead of having a water tank with a heater circuit they were going the other way and using a heat exchanger in the header tank.....so they had a big header tank with one of their brick type heat exchangers submerged in it.......so cold went in and hot comes out instantly and the coolant is heated as required by the Thermo Top.

Heater tubes for your tanks wouldn't be that hard to fab either.

 

[SkiFreak]

http://www.ebay.com.au/itm/NEW-PLAN...Caravan_Parts_Accessories&hash=item519f8dee1d
This may be of some interest..

20KW... that will make you nice and toasty in no time.
Might be a bit of overkill in my setup, but I am impressed that it still only uses half a litre per hour. That's the same fuel consumption as the Webasto 5KW unit.

 

[gait]

yup, made my own tanks from sheets of polypropylene cut and welded. Break even on buying the plastic welding gear was three tanks. Just a 75mm coil of copper pipe (filled with sand while coiling). And a home made pp gland (I have a lathe) through the tank wall so there's no break or join in the copper inside the water tank.

My understanding is the heater was originally designed to run for a short time to preheat engines in very cold weather. 5kw through a couple of small fan assisted radiators for our use is a big ask. The coolant circuit gets hot real fast and the heater starts cycling. The startup current is quite high and would be a drain on the solar. The buffer tank is sufficient to delay the cycling long enough that it doesn't matter (not prevent it). Maintain the pipe size from the diesel heater as far as possible rather than the smaller diameter of some of the fan heaters. I insulated the pipes from the diesel heater.

I used Rehau pipe fittings from the local plumbers merchants for tees and reducers, and vehicle heater hose throughout. And what seemed like fifteen gazillion best quality stainless hose clips. Not as neat as SkiFreak's manifold.

A trick I used in the Coaster was to build heater, buffer tank, wiring, and fuel pump into a "module". A frame, minimum connections to rest of vehicle (water in/out, diesel in, 12v supply, heater control), easily installed/removed. Not so necessary on the Canter, heater and buffer tank are easily accessible on the outside of the front wall.

An on/off switch in the 12v supply may be useful.

I couldn't quite wrap my head around the alternative approach. The limit is probably the purge cycle before the burner ignites. I do know someone who trialled it for a while - do you want me to ask?

It may be worth experimenting with a 2kw electric fan heater to see what the vehicle feels like. My diesel heater worked well in a converted Coaster bus with little insulation and lots of glass, but once my fibreglass foam box on the Canter gets warm its hard to turn the heat down - there's something mildly odd to me about opening the windows in -10 deg C.

All these are "minor inconveniences". Just things that need thinking about. I wouldn't be without it. And if I was I'd probably be without a wife.

PS a half liter of diesel is about 5.8kWh, then there's the efficiency losses.

 

[SkiFreak]

Hydronic setup

For anyone wondering about gait's reference to my hydronic manifolds... well, here they are.



I am not a big fan of joins that require sealant. The more joins you have the more likely you are to have leaks. A fact of life unfortunately.
My hydronic setup is located between the chassis rails of the truck, which is not overly easy to access. To that end, I welded up whatever joins I could, using sealant only on the joins I had to leave free for assembly. Not a big fan of PTFE tape either (plumber's tape) as this can cause major issues with valves. Instead, I use Loctite 569 hydraulic sealant.
I have also used heavy duty hose, opposed to the standard heater hose. All of the plumbing in my system is 19mm (3/4").

 

[oz101]

So if I am understanding this right, the aux tank is for increasing the volume of water in the system and not an expansion tank as such? If I have an open system to the trucks coolant system I can position the aux tank somewhere that is a little harder to get to and use the trucks expansion tank for filling the system and expansion?

What valves did you guys use?

I am thinking of using insulated plastic poly pipe the same stuff that I use at work in plumbing solar hot water systems in new house builds, Has anyone had any experience in plumbing a camper with this stuff?

 

[gait]

yes, its a buffer tank to increase the volume and reduce heater cycling. Place in return line.

Valves (as previous post) are standard after market car heater valves. Open/closed and balancing flow. From (Walkers) Auto One, and occasionally eBay - http://www.ebay.com.au/itm/16mm-5-8...=AU_Car_Parts_Accessories&hash=item1c23bdba56

Just something in the back of my head says don't use the poly pipe for the engine coolant water heater circuit. Use in a domestic solar hot water system is static, there are vibrations in vehicle. End connections may not be appropriate. The spec for the poly pipe may show reducing pressure for increasing temperature. It probably softens. I used normal vehicle heater hose - it seemed to create less risk of losing water and then engine. Similar argument to using vehicle electrical cable rather than domestic cable.

Having said that I have used 12mm poly pipe with JG push fit fittings for fresh and hot water. Engine water temperature is somewhere around 80-90 deg C, diesel heater thermostat at about 80 deg C. The JG hot water connections need the end inserts to make sure they don't pull apart when hot and soft. I also have 6 psi water not 35 psi that most RV pumps are set to. Had to replace a short length of pipe a few days ago, leaking at a push fit. I also replaced a plastic end fitting to hot water tank yesterday - vibration and movement finally split it. 12 months and 15,000 km as the crow flies from home and I had a spare! Don't forget the isolating valves for when things leak.

 

[SkiFreak]

My system is way more complicated than gait's as I use solenoid valves and all stainless fittings. Don't know if I would go down the same route if I was starting again, but it's what I have now and I won't be changing it.
You should have a look at westyss' build thread as he has what I consider to be a very simple yet robust setup.
A simple ball valve in the cabin controls the heating. Definitely an excellent example of the KISS principle. Note the bleed valve that he has incorporated too.

I agree with gait's comments regarding pipework. Rubber pipe is much better in an automotive scenario as it handles vibration very well. I have gone with heavy duty heater hose, opposed to the normal radiator style hose. I have also used super clamps as these have a much better clamping force than normal hose clamps. If you are going to use hose clamps, use good stainless ones. In a hydronic setup there are lots of joins. You need to do whatever you can to negate the possibility of leaks.

If you have an open system you do not need an additional reservoir. This is only needed if you plan on having a closed loop for the Webasto heater. The sole purpose of the reservoir is to add coolant volume to the system.

 

[Tony LEE]

Just one extra point that might be worth noting.

The temperature of the hot water in the calorifier can reach 80C and that is hotter than most RV or domestic 'plastic' pipe systems can handle for any decent length of time (not talking about the coolant circuit, but the fresh water outlet). I used heater hose between the hot outlet and the tempering valve that reduces the water temperature to a safe level. Even then, need to take account of the higher pressures found in a typical RV fresh water system compared to typical engine coolant system pressures. (if the tempering valve is mounted direct on the calorifier then there is no problem)

I have the surge tank cap and the engine radiator cap at the same level so there isn't any great problem with removing a cap only to find the tank or the radiator full to the brim. Came unstuck recently when a manufacturing defect on the neck of the surge tank filler neck resulted in a small pin hole. Didn't matter too much if the system was isolated from the engine, but when I used the engine to heat the calorifier, the pinhole allowed the surge tank to keep depressurising so the surge tank ended up completely full and coolant sprayed out the pin hole instead of just a bit of vapour. Made quite a mess before I realised it.

-------------------
I considered using solenoid valves but the ones I could find had coil currents of up to half an amp and that seemed a bit of a waste of battery capacity. Normally, hot water needs are supplied by the engine if we travel a bit each day so all the valves are left in the same position except if we are parked up and need heating, I isolate one leg of the engine system to save wasting heat keeping the engine hot all night. Real cold mornings, can use the system to preheat the engine for easier starts.

 

[SkiFreak]

I considered using solenoid valves but the ones I could find had coil currents of up to half an amp and that seemed a bit of a waste of battery capacity.

For a 3/4" valve the solenoid can draw over 2 amps!
There is a simple solution to this issue however. Don't use standard solenoids, use latching solenoids instead. That is what I have used in my system.
With a latching solenoid, changing the state of the valve only requires a 300ms pulse. After that there is absolutely no additional power usage.