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1hilperton
1hilperton

Posted: Fri Mar 19, 2010 9:03pm

Post Subject: Heating system

Tony thanks for your answer more info the system is fitted with a pressure relief valve also an air accumulator the relief valve vents overboard the pump runs continuly and the rads never seem to reach a very high temperture infact not a very good system as with many boat fitters they do not seem to hang around too long so joy there

Tony-B
Tony-B

Posted: Sat Mar 20, 2010 8:46am

Post Subject: Heating system

Right, but I still have no idea what prompts you to ask. The problem is that when you pressurise the system by adding water some water will be forced into the air accumulator which will lower the expansion volume UNLESS the air pressure in the expansion accumulator is higher than the water pressure. At this time I should point out that boat systems normally contain a 20% to 50% antifreeze mixture that needs changing every 2 or 5 years depending upon antifreeze type. So filling with water dilutes the antifreeze. Unless the pump is making loud gurgling noises indicating it is running with lots of air in it I would wait until it is time to change the antifreeze. At that time drain the system so there is no pressure in it and then pressurise the accumulator to a little above 1 bar (15psi). The one bar comes form domestic combi-boiler practise and I have no idea if its absolutely correct, but its the best I can do and it should work. Using a pump on the filling pipe fill the system with a 50% antifreeze mixture and pressurise it. Bleed the system, repressuirising it as required with the mixture. When the system is bled set the pressure to 1 bar. If you do not use antifreeze your system will be subject to corrosion and frost damage. This will make no difference to the rads because their low temperature indicates the rads are dumping more heat then the stove can produce in the time the water is inside it. As long as you are running the stove at a high enough setting the first thing to try is to slow the water flow rate. Either by adjusting the pump p speed or volume if it has such a facility and if not by closing all the lock shield valves (the ones that you can not easily turn) on the rads and opening them about 1/4 turn. Count how many turns closed them so you can always set them back again if it makes no difference. Then, if the temperature rises you can gradually open them a bit more to get the radiator hotter. You may find that fitting a pipe thermostat close to the stove on the TOP pipe will allow the water in the boiler to heat up before it is passed to the rads. This may or may not improve the radiator temperature. It is VITAL that you leave the present pump switch in parallel with the thermostat so you can override the stat if it fails. Tony Brooks PS Do not go squirting neat antifreeze into a radiator bleed valve. Hot neat antifreeze is denser than cold water so it may well refuse to rise into the radiators and thus prevent them getting warm.

micktuner
micktuner

Posted: Sun Mar 21, 2010 12:28pm

Post Subject: Heating system

this may help on my brothers boat he had the same problem it turned out to be a air lock in the rads so try bleeding them also what we found with a pressure system the hotter it got the more water it dumped over the side so we turned it into a basic system with a normal header tank and since have had no problems

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