Re: [MH-list] Buying new - Alde hydronic heating systems - well O.T.


Simon Whitehead
 

Before buying my first MH I had a Polar Caravan with wet heating. This caravan was 25 years old and was made in Sweden. The gas heating, made by Primus, worked well and was extremely effective in cold weather. The circulating pump was a small 12 volt unit and is available from Jabsco and, although not cheap, did the job well. The current drawn from the battery was about 3 amps on startup while the glow-plug was running and then dropped to only 0.8 amps for the pump.
The heat exchangers were wonderful; they were aluminium finned units about 4 feet long and there were 4 plus the hot water unit. I think the total circulated water capacity was less than 10 litres so the weight wasn't an issue. The system was totally effective and coupled with the excellent insulation we were lovely and warm when it was cold outside. I do admit that we never tried it when the temperature was below about -3C.

There were many issues with the system that were born out of its extreme age. The pump was not reliable as it was worn out and the gas was lit by a glow plug that, by today's standards, was also unreliable as an igniter. I had to remember to top up the system with antifreeze in winter. The system was not automatic but that, again, was a function of age.

The great thing about a wet system, particularly in a MH, is the ability to mix the heat source with the engine. It offers opportunities for keeping the whole MH warm whilst driving (and providing hot water) and also preheating the engine before moving off at the start of a journey. I also like the idea of mixing the system with the truma air because that gives greater system security.

Simon




On 16 Mar 2004, at 08:17, E.F.Webb wrote:

Re postings by Hilary, John Goodman, Iain Harrison, etc., yes ,
perimeter heating as it was known may well be described as an
obsolete system, having been popular in the 70`s & 80`s on a
commercial [& less so] a domestic basis. It`s odd that it has
resurfaced in a small way now in motorcaravanning, being sold as an
expensive luxury item. Snake oil may yet return to the market square!

For obvious reasons natural convectors are much less efficient than
fan-powered units but that`s not the only cause of their demise.
They became unpopular commercially because nobody could be sure if
letting areas should be measured at the floor or desktop levels &
because of the vulnerability of the casings,apart from the
popularity of office cooling. Element cleaning is also a problem -
dust builds up alarmingly at low levels & return airflow carries it
into the fins - & few "heating engineers" are familiar with the
design requirements. Which is where we came in.

Interestingly one of the better domestic systems used circular-
section hairpin-finned oil cooler element, as intended for Land or
Range Rovers [I forget which] instead of the usual square section.

Ernie Webb





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