# Most economical way to run the hot water system in motorhome



## darach (Dec 15, 2006)

Has anyone worked out the best way of running your hot water system during a long trip, we are new to motorhoming and have been turning the hot water boiler on when parked up each night and turning off in the morning before travelling on. At home in your house you would never dream of doing this as it is so much cheaper to leave it on 24 hrs a day. Any information would be grateful, we do have special safety valves fitted to our cylinders, so the gas can be kept on while driving. (secumotion regulator system).
Thanks
Derek


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## teemyob (Nov 22, 2005)

*Water*

Hello,

A calorifier is the cheapest way. Engine heats water when on move. You can then use the immersion when on hook-up.

However. the cost of fitting will take some time to recoup.

Trev.


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## vicdicdoc (May 14, 2005)

Depends on your hot water needs . . for small quantity we boil the kettle for showers / washing up we put the [Truma] water heater on but always turn it off once its warmed up [usually after 30 mins] . . . no point keeping water hot if you don't have a need for it, it only wastes gas.


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## Rapide561 (Oct 1, 2005)

*Water heeating*

Hi

My water heater is powered by gas and/or electric. When stationary, I leave the water heater on constant, thermostat set at 60 degrees C.

Russell


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## erneboy (Feb 8, 2007)

Derek, I think it will depend on which system you have. My mh is similar to yours. I have Eberspacher heating, I tend to leave it on most of the day as once it has warmed a tank (which takes about 15 minutes) it keeps it hot by running for around 5 minutes every two or three hours. I turn mine off at night and still have a fair amount of warm water in the morning, to shower I run it again and it heats the warm water up to full temperature in a few minutes. By the way I replaced my cooker, did you get yours fixed, Regards Alan.


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## DABurleigh (May 9, 2005)

Derek,

"Has anyone worked out the best way of running your hot water system during a long trip"

Define "best". Most convenient? Cheapest?

"turning the hot water boiler on when parked up each night and turning off in the morning before travelling on. At home in your house you would never dream of doing this as it is so much cheaper to leave it on 24 hrs a day."

No. It is cheapest when you heat it when you need it.

Dave


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## darach (Dec 15, 2006)

Thanks everyone
My system is gas and electric, the system that Trev recommends sounds good but we have a new van and dont want to modify.
Definitely when parked up we would leave the water heater on, what I would like to know is there any disadvantages of leaving it on when travelling?
I have metered the hot water system in the house at home which is easy to check and definitely cheaper to leave on 24 hrs a day than heating when needed.
Hi Alan
My system is an Alde, but both vans have the same type insulation I'm sure.
I have jsut replied on your other thread regarding the oven problem. hope yours is now trouble free.

Thanks again 
Derek


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## aultymer (Jun 20, 2006)

Ours is on 365 days/ year (gas only). It is so good if you are working on the van or filling fuel to be able to just turn the tap and get hot water. This is one of the bits of motorhomeing I regard as a little luxury. If you use it for filling kettle you get preheated water and quicker cuppa!
We are also too disorganised to remember to switch it on 20 mins before taking a shower. It does not need to be at a high setting - just available.

Don't care what anyone else does/or economics, it's just nice to have.


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## Rapide561 (Oct 1, 2005)

*Water*

Hello

I totally agree with you Aulytimer. Constant hot water. Now, that was a sit-com years ago with someone called Prunella........ and also whats her name from Corrie?

Russell


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## SpeedyDux (Jul 13, 2007)

*Re: Water*



teemyob said:


> Hello,
> 
> A calorifier is the cheapest way. Engine heats water when on move. You can then use the immersion when on hook-up.
> 
> ...


I couldn't agree more, Trev.

There's that great big inefficient internal combustion engine up the pointy end chucking out waste heat. The engine heats water then sends it round the radiator and heater system. Instead of warming the atmosphere via the radiator, some of that engine waste energy could easily be used to heat massive amounts of fresh water for washing and showering. A bit of extra plumbing and a calorifier shouldn't cost much. Does the Alde system already do this?

At present you are still buying expensive energy twice. Diesel etc. for the engine and its water cooling system, and gas /diesel / electicity for heating fresh water. That makes no sense.

MH manufacturers / converters need to think harder about OVERALL energy efficiency of motorhomes. It isn't rocket science. Just mental laziness on their part, in my humble inexpert opinion. Oh yes, I'm sure there must be _hundreds _of excuses why it can't be done. :roll:

SD


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## Boff (May 10, 2005)

Hi!



darach said:


> I have metered the hot water system in the house at home which is easy to check and definitely cheaper to leave on 24 hrs a day than heating when needed.


That could only be if you have electric water heating at home AND lower rates per kWh during the night. However, in your van it makes no difference whether you use the gas during day or night. Pricewise, that is. Means that the most cost-effective way is as simple as this: The less water you heat up, the less you pay.

So whenever hot water is not needed, switch off the boiler. When only needed for washing up, switch off just before you start, so the boiler will not attempt to re-heat in between. And for the morning shower we have a simple rule: The first one who goes to the loo in the morning switches on the boiler.

There is one exception, however: If it is likely that temperature drops below the threshold of the boiler's safety valve, which is about +5 degrees C, then better leave it on. Because if the boiler dumps its contents on the road, that is really a waste of energy.

Best Regards,
Gerhard


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## erneboy (Feb 8, 2007)

Derek, our warm water is warmed by the engine when driving, it does not usually get very warm (no doubt a very long run would be required for that to happen) but it does take the cold edge off the water so that it heats very quickly when we switch the heater on. Yours may also be connected. The piping to your heater and the model identification may help you figure out if it is. Regards Alan.


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## Roger7webster (Oct 10, 2006)

The Trauma electric/gas water heater fitted to many uk manufactured motor homes is not insulated and is therefore very inefficient when compared to your average house domestic hot water cylinder. Another example of the poor manufacturing standards in the industry 
Regards 
Roger


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## Rapide561 (Oct 1, 2005)

*Truma boiler*



Roger7webster said:


> The Trauma electric/gas water heater fitted to many uk manufactured motor homes is not insulated and is therefore very inefficient when compared to your average house domestic hot water cylinder. Another example of the poor manufacturing standards in the industry
> Regards
> Roger


Are these boilers not insulated? I think that the ater stay hot for a long time after the power is dosconnected, bearing in mind we are talking about 10 - 12 litres only in volume.

Russell


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## Jezport (Jun 19, 2008)

Roger7webster said:


> The Trauma electric/gas water heater fitted to many uk manufactured motor homes is not insulated and is therefore very inefficient when compared to your average house domestic hot water cylinder. Another example of the poor manufacturing standards in the industry
> Regards
> Roger


My Truma stays hot when switched off for quite a time


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## Roger7webster (Oct 10, 2006)

I have had the top off mine and fitted 25mm polystyrene sheet and wrapped it all in an insulating blanket, not a perfect solution but it helps. 
The water may tend to stay warm for a period if your heater is fitted in a seat locker or wardrobe. Definitely no insulation fitted to my 2006 Ace. 
Regards 
Roger


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## Rapide561 (Oct 1, 2005)

*Boiler*

Hi

I suppose the only way to decide which is the most economical method, would be to conduct an experiment.

1) Weigh the gas cylinder and use gas only to heat hot water for a 24 hour period. Re weigh the gas cylinder at the end of the 24 hour period.

2) Weigh the gas cylinder and use gas only to heat water for another 24 hour period. Water use would need to be exactly the same as (1) above. At the end of 24 hours reweigh the cylinder.

Obviously, no other gas applicances could be used in the 24 hour test period.

Russell


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## Boff (May 10, 2005)

Roger7webster said:


> The Trauma electric/gas water heater fitted to many uk manufactured motor homes is not insulated...


Well, mine is.

And rather well-insulated it is. I know it because I have already taken it apart once. :wink:



Rapide561 said:


> I suppose the only way to decide which is the most economical method, would be to conduct an experiment.


In this case, simple applied physics would do the trick, too: :wink:

Given a boiler with a certain content and a certain amount of insulation. Then the loss of heat is determined solely by the temperature difference between water content and the outside air. If both have the same temperature, then there is no heat exchange at all, and the more the water is heated up compared to outside, the more heat loss occurs.

The most trivial consequence is of course, that if the boiler is switched off all the time there will be no heat loss at all. :wink:

The other extreme, boiler switched on all the time, will mean that the temperature difference is always maximal. _So heat losses are also maximal._

And as, other than in a house, there is no price difference depending on time of consumption, it is always more economic to keep heating periods as short as possible.

Best Regards,
Gerhard


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## aultymer (Jun 20, 2006)

> it is always more economic to keep heating periods as short as possible.


With a well insulated boiler this may occur by keeping the heating on all the time so that the boiler does not have to be heated from cold every time you want hot water.(choose your temperature setting carefully)
We keep it on for the sheer convenience of having hot water if we need it. If we could not do this we would make do with a tent and save lots of money.


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## 92859 (May 1, 2005)

*water heating*

Greetings,

We only put the boiler on when we need hot water for a shower or washing first thing in the morning, for washing the pots, quick hand and face wash we just boil the kettle, don't forget that every time you run the hot water you can waste up to a litre and a half of water before the hot comes out.

On our old boat we had a calorifier that used the engine coolant to heat the water up. This is something that could still be achieved utilising the engine coolant from the motorhome, we already have a heater matrix in the rear of the van so it is possible that we could rig up a simple calorifier, mind you, I am not so handy nowadays.


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## relay (May 9, 2005)

*Re: water heating*



Humber-Traveller said:


> Greetings,
> don't forget that every time you run the hot water you can waste up to a litre and a half of water before the hot comes out.


Good point, but it does depend on how hot the water is & how much you need. If ours is on the hottest setting, I find that for washing, the amount of cold/cool that comes out just about balances the amount of hot I need to fill the basin. If it's just for a quick wash of the hands then it's a bit more wasteful.

-H


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## aultymer (Jun 20, 2006)

Hi H-T,
I have looked at this as well, having spent many years in the yachty industry.

On a boat, especially a canal boat, weight is not a consideration. Calorifiers are not lightweight! They also work best if you can have a large tank to store the heated water. Calorifier, tank and the water in them represent more than some vans have as a payload bearing in mind you still need a boiler for the times you have not been driving.
Last year in the river Charante we clocked up 10 hours of engine time just heating water for 5 showers on the days we didn't move the boat!! (no boiler).


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## 116630 (Sep 14, 2008)

*cheap hot water*

Hi
I have fitted a teal unit (you can find them on ebay) and fitted it in a locker. There a few different models and as my motorhome is not new I have one that connects into the pipes to the heater. this gives me 2 gall (9ltr approx) of free hot water. For a new mh I would suggest the 12v version fitted in a locker making sure you can get water in and out (remove bowl) and away you go.


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## 106916 (Sep 8, 2007)

DABurleigh said:


> Derek,
> 
> "Has anyone worked out the best way of running your hot water system during a long trip"
> 
> ...


you are right Dave, I think the previous poster WAS confusing "cheapest" with "most convenient".

Vidura


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