Truma Ultraheat

Hi All,
I have been waiting for the temprature to drop far enough for me to check the information given to me by Truma, namely that they set the thermostat on the Ultraheat (electric)room heater, mounted behind the gas heater, at +5 degrees. This morning at 0700 the outside temprature was +4.5 degrees so I went out to check, the the Ultraheat themostat had been set at minimum (right down on the stop) and 500 watts overnight.
On checking, the heater was very warm, either on or had not long gone off, and the inside temprature was 11.2 degrees, 1/2 hour later the heater had cooled and the inside temprature was down to 9.5degrees. This confirmed to me that the information given by Truma was correct and a local heating engineer has advised me that most themostats allow the tamprature to rise by 5 degrees before switching off again, so I am completely happy with my antifrost measures.


Brian2

Brian,

What you are looking at is "Control Span".

Without it being there the controller would switch the heater on and off every time the temperature changed by the minimum temperature range that it could measure. (As this is probably 0.1 degrees you can imagine the wear and tear on the switching mechanism!)

A five degree span sounds perfect, bearing in mind all the stuff that has to heat up and then cool down before the controller switches the heater on or off.

Best regards,

Ian

Hi Dutto,
Thanks for your usual very technical explaination, however my comments were intended to advise anyone using the ultraheat to prevent freezing, that the heater will come on correctly when the temprature control is set on its very lowest setting, Right down on the stop

murph wrote: Hi Dutto,
Thanks for your usual very technical explaination, however my comments were intended to advise anyone using the ultraheat to prevent freezing, that the heater will come on correctly when the temprature control is set on its very lowest setting, Right down on the stop

looks like you might need it ON again Murph, looking at the forcast from tomorrow onwards

Boaby

Hi Boaby,
It stays on permenantly day and night at this time of the year, as the only current it uses when the temprature is above +5, degrees is what is required to run 2 LEDs, one in the on/off switch in the wardrobe, and one in the control unit. Virtually nil when temprature is above the activation temprature, now proved to be +5 degrees.

Brian2

PS We are warmer than most as we have the sea all round, 1/4 mile to the west and 1 mile to the east and are only about 100ft above sea level.

Its something called hysteresis, the difference between the on & off. See http://en.wikipedia.org/wiki/Hysteresis

My better half goes totally hysteresis if she gets too cold, but it's the same if I make a mess so not necessarily a direct result of temperature drop.

ubuntu1 wrote:Its something called hysteresis, the difference between the on & off. See http://en.wikipedia.org/wiki/Hysteresis

Go on then, now explain "Derivative" and then I'll tell you how an instrument technician from Louisiana explained it to me !!


Ian

murph wrote: Hi Boaby,
It stays on permenantly day and night at this time of the year, as the only current it uses when the temprature is above +5, degrees is what is required to run 2 LEDs, one in the on/off switch in the wardrobe, and one in the control unit. Virtually nil when temprature is above the activation temprature, now proved to be +5 degrees.

Brian2

PS We are warmer than most as we have the sea all round, 1/4 mile to the west and 1 mile to the east and are only about 100ft above sea level.

Hi Brian2
When I lived on Bute, on the west coast of Scotland, the warmer waters coming up from the south kept the area frost free, I live around a mile from the coast here,as the gulls fly, its drier here, but very cold, seas freezing.
My trauma is ticking over at the moment, with a wee oil filled heater up the front if needed.
How are you with the floods? most of it is to the north of Brid.
keep try take care.

boaby

Hi Ubuntu,
Are you taking a leaf out of Duttos book, this is the sort of thing that he comes up with.


Brian2

Just so I am sure I understand you correctly Bryan2 when you say you set your ultraheater thermostat at minimum (right down on the stop) do you literally mean below setting 1. I ask because my unit does not seen to turn on at that low setting even when outside temperature is below + 5 degrees. I can however hear a click when the dial is turned up to setting 3 and subsequently feel the element is giving out heat.

Hi Wearsider,
Yes mine is right down on the stop, the only difference between my setup and standard AS arrangement is that I have fitted a remote sensor which overides the sensor in the Truma control, this is mounted on the side of the drivers seat, consequently this controls the temprature near the floor in the cab. It sounds as if yours is different and you will have to find your own setting.
Just been out to the MH and at the moment the temprature outside is +1.2degrees the temp inside is +9.2 and I can feel heat from the heater, so I am happy.


Brian2

My set up Brian2 is the Auto-Sleepers standard arrangement so it is not surprising its dial operates at slightly different values from your enhanced system. Anyway the general principle is the same and the guidance you have provided is most helpful

Hi Wearsider,
It has just occured to me overnight, what was the temprature inside your MH at the time you checked the control, if it was above +5 degrees this would affect the point at which the thermostat operates. See my comment on my very first post on this thread.


Brian2

Dutto wrote:
Go on then, now explain "Derivative" and then I'll tell you how an instrument technician from Louisiana explained it to me !!

Explain Derivative, is that a challenge?

There is more than one type of temperature control.

ON-OFF Control
The crudest form of control (thermostat). The heater is always at full power or off leading to large voltage swings around the setpoint (like the 5 degrees C mentioned). Better control needs some form of temperature controller.

Proportional Control
The heater is driven at a level proportional to the error in temperature (how far away from the setpoint it is), e.g. the temperature drops by one degree and the heater is driven at say 20% to bring the temperature back to setpoint (e.g. a 1000w heater driven at 200w).

The derivative
Is not a control type in itself. It is a measure of rate of change of temperature used to modify how “hard” the heater is driven. The controller knows not only the error but how fast the error is increasing or decreasing and this is used to improve the control accuracy.

If the temperature in the proportional example above drops by one degree very slowly – say over half an hour - the rate of change is slow and the derivative term has little effect.

If the temperature drops very quickly – say in a few seconds because someone has opened a window- the rate of change is fast and the derivative term is added to the proportional control. The heater is driven at say 800w and then cuts back as the temperature begins to rise again.

Well you did ask!

Brod.

Hi Brod,
No I didnt ask.

Brian2

Hi Brian.

murph wrote:
No I didnt ask.

Wasn't you it was me old sparing partner "Dutto"

Dutto wrote:
Go on then, now explain "Derivative" and then I'll tell you how an instrument technician from Louisiana explained it to me !!

I was sort of fishing - expecting a bite later

Interesting stuff though init! (best not reply - swearing not allowed)!

Brod.

Oi you lot, cut it out!

I took early retirement this year after over 30 years in the controls business to get away from all this stuff about PID temperature controllers, HART protocols, RS485 MODBUS networks, etc, etc

Biggest problem wasn't getting the oldies like me up to scratch, it was trying to get some of the young 'uns to grasp the concepts!

I took the line that if the person (so-called 'engineer') you were trying to sell the controller/system to knew more about the process than you, go ahead; if not, steer well clear!

Thank you for your further thoughts Brian2. I will keep experimenting with my setting and advise the outcome in due course.

Hi Wearsider,
Early this morning with temprature inside the van 5.5degreesC, on turning the control a very slight movement was required to get the thermostat to click on, later this morning with temprature at 8.5 it was necessary to turn it up to 1 before the thermostat clicked on. the reason I fitted the remote sensor was because with the origional sensor in the control panel on the side of the wardrobe, almost above the heater, it didnt work properly at keeping the front of the van warm.

Brian2

5.5 degress that is summer, 8.5 that is tropical. Up here it is 0 degrees and I am sat in the garden in my shorts and vest top reading my instruction manual on how to get the air conditioning working

Thanks for the latest update Brian2. My on off control and thermostat is above the Sargent display on upper rear sidewall which houses the microwave so perhap it is not as "warm" a position as your original wardrobe location or as "cool" as your current cab one. The current internal temperature is 4.7 degrees centigrade and I can hear the heater click on at 2 so there really is not a great deal in it.

Hi wearsider,
Of course warm air rises, so any highup site will be warmer than my near the floor sensor, added and sited there for that reason in the coolest part of the van.
But now that you have got yours sussed you know what you are doing with it.

Brian2

PS Just occured to me, my digital thermometer is mounted under the cupboards near head hight, so the sensor will be oporating at slightly lower temprature than the thermometer reads.

The Truma Ultraheat heating thermostat in our Nuevo is located in the kitchen area near the habitation door.... have ours currently set at 1.5 on the 500w dial setting and just been out to check it a short while ago and interior temp is reading +10 with external temp reading of +2 (feels much colder out doors though) bottom of airing cupboard where water pump is situated is warm so the heaters doing it's job, might even be able to crank it down to 1 to just ensure protection from any frost. What would be the ideal temp reading for the inside of the van during freezing spells?

CC

CruizingComet wrote:....... What would be the ideal temp reading for the inside of the van during freezing spells?

CC

CC,

Plus one degree anywhere that there is a water pipe, pump, tank, 'U' bend or fitting will prevent freezing.

However, although many people worry (justifiably) about low temperatures, once the water systems are drained down the real danger is humidity.

If the internal temperature is allowed to fall below the dew point and moisture condenses out of the air on to cold surfaces or into the upholstery it can cause mould in a remarkably short time. It rapidly rots and stains fabrics and the "musty" smell will hang around for months.

The irony of really cold weather is that the humidity drops like a stone! (it appears as what we call "hoare frost" and in St Petersburg, Russia they reckon that in a cold snap you can hear a "tinkling" sound as the ice crystals form and fall out of the air.)

My advice therefore is to drain everything down and then just make sure that there is good ventilation and a small amount of heat at all times.

Best regards,

Ian