Truma Temp Sensor Position

[David_374242465]

In my Bailey Senator 5 (2007) the remote 2 wire Temp sensor for 240v Elec Element use is mounted about 2cm above floor level, near the partition door for the rear bed area.

Is this the ideal position ? I would have thought that a higher position, perhaps near entrance door, would have been much more sensible in sensing the temperature of the living area!

Is this position the same in later models of my van, or in other makes of caravan ?

Moving the sensor is a straightforward job, as the wiring to the unit is a couple of mtrs longer than necessary. (Coiled and tied back behind heater.)

Advice from others with this system would be greatly appreciated.

 

[Damian]

The sensor is in the right position.

It needs to be at floor level, or as close as possible.

Mounting as you have suggested will take it to a high level where the hot air rises to and it will shut down the heater long before the rest of the van has warmed.

 

[xtrailman]

The recommended height for a room thermostat is around 5 to six feet. Have you ever seen a central heating stat at floor level?

In my 2004 senator the sensor works fine, mounted at locker height adjacent the front mains light, you could argue that it is not ideally placed, maybe nearer the door perhaps?

The ONLY reason why sensors are fitted, "out of place" in my opinion, is due to cost savings, labour and materials.

 

[David_374242465]

Thanks fo replies. Two opposite views there....

While understanding Damian's point, I must disagree that floor level is best. In use, I am finding that the living area gets far too warm before the Temp sensor kicks in to switch the heater elements off.

I would have thought that somewhere around waist level within the living / sitting area (around 2mtrs from the heater in my case) would be a reasonable compromise, but I guess each would have their own preference on this point.

As the cable length is fairly long, I reckon I could experiment with different positions.

Anyone out there, with different caravan model, found ideal operation with this system ?

The temperature can of course be crudely controlled by careful setting of the wall controller Thermostat setting, but the this really makes the remote sensor rather redundent....

 

[gary]

Ahh! but we are not talking of 'room' thermostats, these are fitted in caravans and the circumstances it works in are different.

The actual sensor in a household room stat in any situation would be best placed near the floor, that is so it can read and react to the lowest temperature, putting it at shoulder hight then is a compromise to make it easy for you to read/adjust and keep the box out of harms way.

In a house though the movement of air is totally different to that in a caravan, in a caravan, the area/volume is comparatively tiny and the air changes therefore far greater. So while the house stat can work happily lagging behind at shoulder height, in a van it cannot as it needs to react far quicker to temperature change.

At or just above floor level is best then, problem is where, answer to that is where it is not affected by other than the actual lowest temperature.

My experience says the very best place is attached to the gas fires temperature sensor, this ensures the air flow over it is what either source of heating is pulling in to reheat.

Proof really is, no one ever complains about the gas fires temperature control and that's been sited here since the mid 70's, simply, it works!!

I might add though, I'm talking about my sensor, there are copies though and I can't speak for those, but I do understand they don't react as quick and therefore work as well?!

Note, there are other related problems, mainly the relays that switch the elements on and off, they slowly burn out before finally packing up. The problem here is, they also slowly reduce the current to the elements and therefore the heat produced so your not getting the full benefit.

 

[David_374242465]

OK Gary. Learning fast here....

Point taken on relay failure problems. Mine seem to be ok at moment, but will keep an eye on this. (retired Elec Eng, so no prob in replacing relays if need arises.)

Many thanks.

 

[xtrailman]

Heating a caravan is no different to heating a room at home, my lounge has regular air changes from the kitchen hall and front door via a entrance lobby, as the caravan door is not normally left open if you require heat control, at night for instance i see no difference.

This is a direct quote from the installation manual for my Vaillant VRT 360.

"Install the room stat so that it can properly measure the room temperature (avoid heat traps, cold walls etc)

The best place to install it is in the main living area on a interior wall at a height of AROUND 1.5M.

Choose a location where the room thermostat is not affected by draughts from doors or windows, or by heat sources such as radiators"

If the best position was the floor, then the unit would have a optional remote sensor.

Also reducing the hysteresis has the drawback of cycling the heating contacts too much, contributing to the contacts burning out, through excessive switching.

 

[SBS]

Ray

That may well work very well for your home but how many direct air vents are installed in your home compared to the cubic volume? Have a look at the vents in a typical caravan.

I have fitted an Arc Systems sensor to the gas thermostat and it transformed the heating in our Eccles Onyx. Prior to fitting, the heater would switch off and remain off for far too long as the dial was kept warm by the heat retained in the wardrobe.

Gary's advice works.

Mike

 

[xtrailman]

sbs

Isn't the gas thermostat mounted on the gas fire?

If so, that's completely different to the electric element control, my standard fit remote sensor works for me, fitted by bailey.

If i was unhappy with it i would relocate it, to a cold draughty floor? never.

Read my post above, advise from experts in heating, not me, although i have my own idea's, having in the past spent a LOT of time experimenting with various types a sensors, used primarily in industry, in my last house the room sensor ended up in the ceiling!

 

[gary]

Quote: "Choose a location where the room thermostat is not affected by draughts from doors or windows, or by heat sources such as radiators"

I agree with that, infact that's a large part of why I say fit it too the gas sensor, because it's always then free from those very variables and others?.

I would also say I'm wrong about being best near the floor in homes.

Draughts travel freely along the edge of room walls and is actually responsible for those black soot like marks along the edge of carpets...and not the other half?!

As you have found though, fitted to the gas sensor is not the only place in a caravan, but then again, I know from many customers that my sensor always works perfectly here?

The system is designed to switch back on with a two degree temperature drop, I don't then see how better temperature sensing can affect this, either the temperature drops 2degs or it does not.

Further, if the relays fitted are not capable of switching the relative low current without burning out prematurely, then it's not because they cycle more often than the system demands, it's because their not suitable, as infact is the case!

 

[gary]

David, don't take the clicking of the relays as a sign all is ok, I'm sure you know, you'll need to check the current draw is above 8A on 2000w.

Another fairly common fault is one or more relays can weld their contacts shut, this then requires the mains supply switching off to kill the otherwise permanent heating!

 

[dougie_374468830]

relays may be easy to change but the circuit board can be a right sod to get out and even worse to replace

 

[ProfJohnL]

Caravans are very different to domestic and industrial buildings. They have very little thermal mass and are relatively well insulated, thus a little heat can make a big difference, but equally take the heat source away and the temperature will drop quite quickly due to the large amounts of ventilation.

I have experimented with heating in caravans at 0C external ambient temperatures, and using a standard gas heaters with and without a fans running.

Without a fan running to mix the air, it is quite possible to get a foot temperature of 4C and roof temperature of 25C.

Adding a fan with properly balanced outlets it is possible to reduce the stratification to 17C at foot level and 22C at roof level. The majority of fans though modulate their speed according to the temperature of the air from the heat exchanger, so when the heater turns down or off, so does the fan.

It is the foot level changes that are quite dramatic, and it is well established that if you feet and legs are cold, you feel cold, even if your head and shoulders are actually at a reasonable temperature.

If the heating is electric, then the thermostat usually has the heater either on or off. What was surprising during the experiments was to find that when the heater was turned off, how rapidly the foot temperature fell away, so whilst the chest temperature may fall from 20to 17C, the foot temperature fell from 17 to 10C in a very few minutes.

So whilst the higher level temperatures only change a bit, the foot level temperatures vary a lot.

This will lead to the situation where a high level thermostat will remain satisfied whilst the occupant's feet begin to feel really cold making them feel cold all over and thus dissatisfied with the operation of the thermostat.

By comparison, in a house, the thermal mass is much greater, and this moderates temperature changes, and with less air change per unit volume, the foot level temperatures don't change as much or as rapidly. There is convection from heat stored in the fabric of the building, and even some long wave length infra red radiations from floors and walls and furniture. (This is more noticeable in buildings with concrete floors) This all helps to maintain a more consistent and even temperature distribution floor to ceiling.

 

[David_374242465]

Right folks. Think I have enough info now to be totally confused!!!!

I think the problem I have is in part, due to my layout. The Truma heater, has the remote sensor at floor level, further away from the sitting area and only 1 ft to side of heater. (Sensor is actually within a few inches of the fixed end bed area partition door.)

The sitting area (front) is approx 7ft+ away from heater, and although I use the fan and I have two air outlets right under the seating area, I am finding front gets to higher than ideal temperature (medium fan speed), while rear area near floor sensor, remains cold.

OK, perhaps I need to keep fan speed down a bit, to allow more direct heat from heater, but I still think the position of the sensor is wrong, in relation to the normal seating area.

Sensor at floor level, nearer the sitting area but away from draughts or air outlets, seems to be where I am heading.

Won't be away with van for anouther couple of months, but will try a few sensor positions out and report back in regard to my findings.

BTW. One of my gripes in regard to heater operation, is that the area around and above (drawer in my layout), gets extremely hot, over +45degC, with room at a comfortable +22degC, and is one reason I like to use the fan at a fairly high speed, to minimise this heat build-up problem. Bailey have achknowledged this as a problem, and have already replaced a badly distorted (ruined!!) drawer for me under warranty. The replacement drawer has an additional metalized reflective base. Say's it all I think. (No, there was no air leaks or faults in the installation!!!!)

But that is a topic I posted over a year ago now.

Thanks for all the help.

 

[Damian]

Have you tried adjusting the air flow to the outlets by reducing the amount to the front and increasing the flow to the back?

 

[xtrailman]

David

I suspect your sensor is never reaching the cut off temperature.

Have you tried adjusting the diverter at the rear of the fire, to put more bias to the rear of the caravan?

Also try using gas and electric together, assuming your system allows this, but with the fan in auto.

 

[David_374242465]

Damian & Ray.

The rear air outlets are on the other side of the partition door, and to have greatest effect, this door would obviously require to be left open. I have tried adjusting the air diverter valve, and this does what it is meant to do in regard to changing flow between front and rear.

Leaving the door open would probably overcome the sensor problem to some extent, but I prefer that this rear area is kept rather cooler than the front sitting area.

Basically what I want is for the sensor to control the sitting area temperature at around +20 to +24degc, while leaving the rear area a few degrees lower, ideally with the partition door closed.

Maybe I am expecting too much of what is basically a simple heating system, but moving the sensor forward, was I had thought a possible way of improvement.

Ah well!!!! Will try some sensor positions, next time out.

Cheers guys,

 

[xtrailman]

Have you tried adjusting the air flow to the outlets by reducing the amount to the front and increasing the flow to the back?

sorry damien, i missed your post, didn't mean to repeat your suggestion.