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Awhpaul

Can you reverse blown air heating

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We have the truma ultrastore and like most, the blown air heating is pretty poor. The fan works well and circulates well, but so much heat is lost in the ducting... Would it work better if we reverse the fan? Essentially instead of sucking the hot air down the ducts, traveling 3-4 meters is a cold environment and out the vents -> suck in the vents and out over the heater. To me it seems this would producer warmer air.

 

Question is would this cause anything to break? Anyone already tried it?

 

thanks

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18 minutes ago, Awhpaul said:

We have the truma ultrastore and like most, the blown air heating is pretty poor. The fan works well and circulates well, but so much heat is lost in the ducting... Would it work better if we reverse the fan? Essentially instead of sucking the hot air down the ducts, traveling 3-4 meters is a cold environment and out the vents -> suck in the vents and out over the heater. To me it seems this would producer warmer air.

 

Question is would this cause anything to break? Anyone already tried it?

 

thanks

 

The Utra store is already a convector heater so you are getting heat convecting out of the top of it.

 

It doesn't suck air down the ducts it pushes the hot air that originates in the Ultrastore and pushes it out to the events around the caravan.

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Interesting question ! My immediate thought is that you would only have one outlet for warm air instead of three or four which on the face of it would reduce the overall heating capabilities.

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 :welcome: to Caravan Talk Awhpaul.

 

Firstly, I think the Ultrastore is the hot water system … I would guess you are referring to the Ultraheat system?

 

To be honest, I’m not quite sure what you’re thinking of doing, but it doesn’t sound like anything I’ve heard of before.

 

If you’re worried about heat loss, I know that quite a few people have lagged the piping where possible.

 

John

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The whole point of the ducts is to take hot air to where it is needed.

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Start to close the vent near the heater can help balance out the vent further away . The duct pipe is double skinned but wrapping it with insulation can help if it runs outside under the floor .

 

 

 

Dave

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I thought for a moment that this was a question about using the ducted air for a vacuum cleaner. Sorry, just my senile sense of humour. The Truma system provides heat from a gas heat exchanger or (and/or) electric element located behind the heat exchanger. On electric it only does about 1.8KW which depending on the size of caravan/outside temperature/insulation is very little. if this small amount of heat is distributed it sometimes isn't enough. if the air duct goes out under the floor it drops the efficiency even more. On gas, these heaters generate much more heat and are usually adequate. We used to put ours on gas in the winter until the caravan was comfortable and then switch to electric. Get the underfloor duct lagged if its not already done.  

Edited by Ern

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Thanks for the responses... I've tried lagging the ducts and it did help but it still not particularly hot. 

 

I know the heating wouldn't be aswell distrusted but at least it would be hot. Just don't want to break anything 🤔

1 minute ago, Ern said:

I thought for a moment that this was a question about using the ducted air for a vacuum cleaner. Sorry, just my senile sense of humour. The Truma system provided heat from a gas heat exchanger or (and/or) electric element located behind the heat exchanger. On electric it only does about 1.8KW which depending on the size of caravan/outside temperature/insulation is very little. if this small amount of heat is distributed it sometimes isn't enough. if the air duct goes out under the floor it drops the efficiency even more. On gas, these heaters generate much more heat and are usually adequate. We used to put ours on gas in the winter until the caravan was comfortable and then switch to electric. Get the underfloor duct lagged if its not already done.  

You're spot on, on gas it's fine but would like to be able to use the "free" electric on site.

 

The heat out of the face is really hot, just the action of blowing it under the van seems to be costly in regards heat loss.

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2 minutes ago, Awhpaul said:

 

I know the heating wouldn't be at least it would be hot. Just don't want to break anything 🤔

 

If you want hot block all the vents bar those immediately by the heater, then with the fan switched on the gas can go into full wack.

It will be hot, but only stood by the heater and the remaining working vent, it will be freezing elsewhere.

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Never had this issue-only the bathroom in our Verona was a bit cooler and that was sorted as above by adjusting the flaps on the outlets. I think if I am reading your post correctly you stand the risk of overheating the unit and causing it to shut off completely.  Just buy a little electric extra heater for the area you find cold perhaps?

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12 minutes ago, Ern said:

I thought for a moment that this was a question about using the ducted air for a vacuum cleaner. Sorry, just my senile sense of humour. The Truma system provides heat from a gas heat exchanger or (and/or) electric element located behind the heat exchanger. On electric it only does about 1.8KW which depending on the size of caravan/outside temperature/insulation is very little. if this small amount of heat is distributed it sometimes isn't enough. if the air duct goes out under the floor it drops the efficiency even more. On gas, these heaters generate much more heat and are usually adequate. We used to put ours on gas in the winter until the caravan was comfortable and then switch to electric. Get the underfloor duct lagged if its not already done.  

 

The electric has plenty of power for UK winters, it's the lack on insulation on underfloor runs that's the big weakness - our 2001 Bailey Pageant had an underfloor run which I insulated using domestic tank insulation and cable ties - once that was done, the 500w setting was fine down to about +5 C ambient while the 1kw setting was fine below that, certainly down to -12 C we had on one trip - the only time we used the 2kw setting was to get the temperature up from stone cold - we never used gas as we always had a EHU.

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Lag the pipework better and you'll get less heat loss (especially if the pipe travels outside under the floor).  But importantly use the Ultraheat as it is supposed to be in Gary (ArcSytems excellent post #3 here https://www.caravantalk.co.uk/community/topic/82831-swift-challenger-truma-ultraheat/

 

 

Electric is 500 Watt / 1000 Watt / 2000 Watts depending on the switch setting.  Gas produces 3500 Watts (or 6kW in the 5004 variant) so will, naturally get _significantly_ hotter.  

 

Use gas to start off then onto electric?

 

We use a fan heater on a 1kW setting for when we shower and dry off (in the adjacent bedroom) and run the Ultraheat on 1kW while we do that, even after lagging and flap adjustment.  Mind we like a hottish bathroom cf the lounge area as we are normally clothed when lounging.  ;)

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one tip is to put the heating on 30 minutes before sunset, but I have to say that I find the heating okay although we don't go out in the winter. 

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We always found it best to turn the fan off until the main unit is good and hot otherwise the heat exchanger takes ages to get up to temperature. 

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I agree with you, the blown air on the ultraheat is wick.

 

On my last van i lagged the ducting as you have done but also reworked the ducting with very good effect. Also you can change the flow forward to back depending ln your needs. 

 

For example in my van the bathroom was like a furnace and the front lukewarm. I firstly closed the bathroom vent which helped the bathroom but not much at the front. So i looked under the lockers and found that the ducting went straight to the bathroom, with the front T'd off from that. I switched this round so that the air to the front did not have to do a right angle and hey presto an acceptable heating (still not as good as the truma combi/whale heating though)

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My current van with the Truma Combi is cold in the bathroom and near the bed as both these pipes run through underneath.

I have a very small oil filled radiator in the bathroom and this works well.

 

On the Ultraheat, I found it best to use the fan on manual and set it fairly low, this then gives a low but hot flow. 

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