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06-08-2009, 12:09   #1
gears
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Back boiler and a pressurised water system

I've tried to find this in old posts as I assumed it would have been talk about before, but no luck. So forgive me if it's a repeat post.

Any way my question is that I seen to remember being told that there is a risk in using a back boiler and a pressurised water system because there is essentially no control over the heat out put from the back boiler, just throw another log, shovel of coal or what ever and there's a sudden increase in heat which could result in an explosion (extreme I know) from a pressuriesed system.

Does any one know if there's truth to this?
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06-08-2009, 13:23   #2
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ive put similar questions to plumbers.... usually when condensing boilers are also in the mix.....
one has said that theres no problem using a pressuirised system once the back boiler can take the pressure, which the usually can (3 bar??) ... expansion vessels may be required if stoves are used....

but professional plumbers out there would have more info...
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06-08-2009, 13:28   #3
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I looked into this a few years back with the same concerns you voiced here. Basically I found that it would be a very similar concept to the boiler on a steam train and similarily would need a pressure release valve and possible back-up release valve system. Also all the pipework would have to be a pressurised system. Finally, none of the pipework could be encased in concrete because of the expansion/contraction and there would be continuous noise within and from the system. It would be a costly system to install properly.
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06-08-2009, 13:59   #4
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I looked into this a few years back with the same concerns you voiced here. Basically I found that it would be a very similar concept to the boiler on a steam train and similarily would need a pressure release valve and possible back-up release valve system. Also all the pipework would have to be a pressurised system. Finally, none of the pipework could be encased in concrete because of the expansion/contraction and there would be continuous noise within and from the system. It would be a costly system to install properly.
some plumbers ive spoken too say it would cost in the region of €1500-2000 extra for a basic system in a 2000 sq ft house...
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06-08-2009, 15:33   #5
gears
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I'd still be concerned about the uncontrolled heat source and high water pressure. Relying on pressure release valves doesn't fill me with confidence having a second one as a back up would help.

I would be interesting to hear from any one who has such a system though... Any one out there?
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06-08-2009, 16:42   #6
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I am putting in a Thermal store to store the heat from the stove with back boiler. Basicaly the store (500litres) is vented and backs up the main heating system which is pressurised. Heat is transfered between systems by a heat exchanger in the store so essentially they are seperate systems.

The aditional costs are roughly €650 for the store, €300 for the pumps and gubbins that go with it oh and the labour but as mine is new build the plumber is only charging an aditional €100 for this.

The system can be seen working at Brooks heat merchants. Its a safe efficient system.
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06-08-2009, 17:15   #7
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some plumbers ive spoken too say it would cost in the region of €1500-2000 extra for a basic system in a 2000 sq ft house...
I was given a cost excess of €4,500 for a 2,500 sq ft house...
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06-08-2009, 17:24   #8
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I was given a cost excess of €4,500 for a 2,500 sq ft house...
oil boiler and rad system?
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06-08-2009, 17:29   #9
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oil boiler and rad system?
high pressure back boiler, oil boiler and rad system
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06-08-2009, 17:36   #10
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high pressure back boiler, oil boiler and rad system
are you including the back boiler in the extra?? i wouldnt be...
back boiler and associated work = circa €2000 thus our figures would add up...

im simply talking about the extra to make a system pressurised....
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06-08-2009, 17:40   #11
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are you including the back boiler in the extra?? i wouldnt be...
back boiler and associated work = circa €2000 thus our figures would add up...

im simply talking about the extra to make a system pressurised....
I'm including the cost of the new backboiler less the cost of a standard one and all associated work.
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06-08-2009, 20:11   #12
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Sorry Sydthebeat, I hadn't much time to expand on this earlier. Fundamentally our prices are the same, but my client and I were put off the system by the idea of all the noises the system would make due to the stainless expanding and contracting. The price itself wasn't off putting but it is a leap in any budget. I do think the concept is very good though and way more functional then the conventional back boiler system.

I also find the combined oil and back boiler system has a huge flaw in that the back boiler becomes another radiator heating the chimney brest when the fire is not lighted and the oil boiler is working the system.
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06-08-2009, 21:17   #13
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Why I never put a back boiler on a closed system.

Just musing here:

Closed heating system with back boiler.
Fire going full bore, rads piping hot.
-
Power Cut.
-
How does the excess heat get dissipated under gravity in a closed pumped system?

Last edited by Carlow52; 06-08-2009 at 21:18. Reason: title
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06-08-2009, 23:18   #14
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Just musing here:

Closed heating system with back boiler.
Fire going full bore, rads piping hot.
-
Power Cut.
-
How does the excess heat get dissipated under gravity in a closed pumped system?
expansion vessel...
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06-08-2009, 23:50   #15
Carlow52
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expansion vessel...
Too risky in my view depending on pressure relief valves and expansion vessels to absorb the heat produced by say an 12kW fire with no circulation pump. Radiators at 130-150 degrees C would be profoundly dangerous
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