bubble stove back boiler

[chevron]

Hi

 

Hope someone can advise or point me in a direction of the information i need. have a bubble stove with a back boiler which supplies a simple large bore copper pipe which runs the length of the boat in a loop back to the boiler on rear of the bubble stove the system was fitted when the boat was new ,It has a water supply with an isolation tap for filling the system and has a Zilmet - 10 Litre Flat Expansion Vessel with a pressure release valve and gauge, the system when the bubble stove is turned up goes to 2.8 bar and then I get a slight drip from the pressure release valve which has 3. bar stamped on it.My questions are once I have bleed the system to get air out of it should the isolation tap be closed so its a closed system relying on the Zilmet - 10 Litre Flat Expansion Vessel is the running pressure of 2.8bar because I am leaving the water pressure supply turned on? what sort of pressure should the Zilmet - 10 Litre Flat Expansion Vessel be set at via a pump? what sort of pressure should the sysytem run at?

 

Many thanks for all the advice I have received on my other questions

Edited October 24, 2015 by chevron

[Tony Brooks]

Personally I would set the pressure to zero and ensure the water level inside is such that the vessel can accept the expansion of the water. I would also unscrew the pressure relief valve. I find sealed pressurised systems with stoves unsettling even if they are an oil fired stove that is thermostatically controlled.

 

Awaits incoming!

[Taslim]

Incoming but not hostile.

 

If, as the OP says, the system only feeds a single 'big radiator' then a preasure system is a waste of parts. I would be very nervous about being around it too.

 

An open system must be safer but fit a relief valve at the hot side boiler output just in case.

[peterboat]

i would have thought the pressure in the pressure vessel would be about 2.5 bars to allow it to expand properly mine has a relief valve on it so any excess pressure is released works well no waste of coolant and no need to top up

[Tony Brooks]

i would have thought the pressure in the pressure vessel would be about 2.5 bars to allow it to expand properly mine has a relief valve on it so any excess pressure is released works well no waste of coolant and no need to top up

 

But the same applies to open heating systems as long as there is enough space in the expansion tank to allow for expansion. At least it was on my Ellis system. I simply do not understand how pressure in a system allows "it to expand properly". Its the volume above the liquid that does that. All the pressure will do is to raise the boiling point.

 

In a domestic combi-system the system is sealed and the air pressure in the "tank" is to force stored liquid into the system to make up for leaks against the head caused by that part of the system above the boiler. There is no need for this if the header tank is at the highest point in the system. In my view there is too much crossing from domestic practice into boat use and simply complicating the systems.

[peterboat]

 

But the same applies to open heating systems as long as there is enough space in the expansion tank to allow for expansion. At least it was on my Ellis system. I simply do not understand how pressure in a system allows "it to expand properly". Its the volume above the liquid that does that. All the pressure will do is to raise the boiling point.

 

In a domestic combi-system the system is sealed and the air pressure in the "tank" is to force stored liquid into the system to make up for leaks against the head caused by that part of the system above the boiler. There is no need for this if the header tank is at the highest point in the system. In my view there is too much crossing from domestic practice into boat use and simply complicating the systems.

the expansion vessel just has a bladder in it if you have no pressure to push it back the weight of the water could do that then it would not work properly

[Tony Brooks]

the expansion vessel just has a bladder in it if you have no pressure to push it back the weight of the water could do that then it would not work properly

 

Except I said I would unscrew the relief valve. That would provide a vented system and gravity will push the water into the system. That is providing the expansion tank has a degree of head relative to the rest of the system. If not then it will be as you say. However I still feel unease at that type of system on a boat and if it were mine it would be converted to a vented system PDQ. Apart form the small (in this case) but potential danger of the system boiling there is also a question about the EASE of adding/ testing antifreeze.