Camper heating

[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-...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.

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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.

[Tony LEE]

Yes, always a technical solution possible, but at a dollar cost and an increased risk of failure with often no way of fixing it in the field. Also being a self-funded retiree with no more easy access to sophisticated components at the "right price", I tend to go with the low-tech solutions wherever possible. I also don't use car heater valves either simply because a standard manual ball valve does the job with the way I have it set up AND it is a hell of a lot easier to install. For instance, I can leave the engine coolant line valve always just cracked enough so the calorifier is hot enough for the evening shower after a couple of hours driving, yet there isn't a huge waste of money in also heating the engine at night when we really just need house heating and it serves to reduce short cycling AND the engine appreciates the warm start next morning. Similarly, the three fan heaters balancing valves and their main isolating valve are left in the same position even when we just need water heating - just don't energise the fans. The fans are also controlled by a wall thermostat leaving the webasto to do whatever it wants. If the engine is supplying the heat, I can leave the fans running so the house is nice and warm when we stop to set up camp. If I really want to alter the flows to achieve a certain effect when setting off for the day, the access door to my plant room is right next to the drivers cab door. Wet clothes hanging in the bathroom and want them dry after the day's travel? Just run the bathroom fan and direct engine coolant through that heater.
Works because this vehicle is solely a winter desert vehicle and when the temperatures rise, we just go somewhere more pleasant for a few months.

BTW Rarely run the heater all night. Electric blankets are quieter and cosier and don't hammer the batteries much more than the heater and fans would.

Just remembered that another reason for not using electric valves was they didn't seem suitable for low pressure-drop circuits because they were diaphragm valves with fairly high minimum pressure drop requirements.

[SkiFreak]

I hear everything you are saying and agree that the KISS principle has many merits. It sounds like you have a very simple, yet workable solution.
As I said... if I were designing my system again I doubt that I would go down the same route I have gone.
Having said that, I think that what I have now is very robust and should see many years of service without any major issues.

[Tony LEE]

I have to remove the header tank to fix a tiny leak so will have to remove all the junk stored on top. Then I'll take a photo after I use Brasso to polish up all the brassware.

Those intending to use a calorifier should do their homework. Some of them are well insulated and some are extremely deficient. There is a test report - bit old now perhaps - available on the internet and the performance varies hugely. Mine is one of the latter and the next job is to bury it in extra insulation - and yes, all the pipes are turned downwards and the elbows insulated to reduce thermal syphoning.

[whatcharterboat]

Yeah, Hi Tony....just on your comment about calorifier insulation....just thought I would add that some calorifiers are also designed with the insulation thicker at the top than at the bottom....in other words they are specifically designed to be mounted only one way and if design of the camper requires the calorifier to hang from under the floor or be wall mounted then insulation efficiency will be compromised.

Regards John.

[gait]

FWIW the car heater valves I used (like the ones in the eBay link) are simple ball valves. Just had the tails that the heater hose fits. I haven't added the choke type push/pull cables (can never remember the techie name for them) to operate as they are easily accessible. In operation I open/close the engine connection and open/close water heater connection - something I read somewhere and in cold weather it made sense to push all the engine heated water to where its needed.