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#1 Gazboatman

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Posted 05 March 2012 - 08:18 PM

Ok I'm about to plum my stove in and connect two radiators, I'm not 100% sure what I'm doing, my old stove had the inlet and outlet fittings situated at the bottom end of the boiler, but my new one has the outlet at the bottom and the inlet quite high up on the back. Like I say I'm not quite sure how it works, I'm planning on going through one rad onto the next one then back to the stove, will I need a pump?

Anyone got any diagrams or can tell me what I need to be doing?

Thanks

ETA.. Oh and there will be an expansion tank in it near the stove.

Edited by Gazboatman, 05 March 2012 - 08:19 PM.

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#2 blackrose

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Posted 05 March 2012 - 10:26 PM

Ok I'm about to plum my stove in and connect two radiators, I'm not 100% sure what I'm doing, my old stove had the inlet and outlet fittings situated at the bottom end of the boiler, but my new one has the outlet at the bottom and the inlet quite high up on the back. Like I say I'm not quite sure how it works, I'm planning on going through one rad onto the next one then back to the stove, will I need a pump?

Anyone got any diagrams or can tell me what I need to be doing?

Thanks

ETA.. Oh and there will be an expansion tank in it near the stove.


Surely the outlet of a backboiler is the high one at the top (hot water rises) and the inlet is at the bottom?

Also, the design of your central heating system will very much depend on whether you have a pump, so this is something you have to think about and decide. Either that or design the system and then that will determine whether you need a pump.
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#3 mrsmelly

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Posted 05 March 2012 - 10:35 PM

Ok I'm about to plum my stove in and connect two radiators, I'm not 100% sure what I'm doing, my old stove had the inlet and outlet fittings situated at the bottom end of the boiler, but my new one has the outlet at the bottom and the inlet quite high up on the back. Like I say I'm not quite sure how it works, I'm planning on going through one rad onto the next one then back to the stove, will I need a pump?

Anyone got any diagrams or can tell me what I need to be doing?

Thanks

ETA.. Oh and there will be an expansion tank in it near the stove.


When I fitted one system on one of my boats I used the thermosyphon system, it worked very well and no lectrickery. Its simple to do and I could prob draw you a diagram and email you it somehow if you wanted. :cheers:
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REALITY IS AN ILLUSION CAUSED BY LACK OF ALCOHOL.
IT IS NOT POSSIBLE TO CC ON ONE CANAL.

#4 pete.i

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Posted 05 March 2012 - 10:38 PM

Surely the outlet of a backboiler is the high one at the top (hot water rises) and the inlet is at the bottom?


You are right Blackrose and to Gazboatman. There is a diagram and specs somewhere on this forum for a gravity fed central heating system this does not need a pump. Whether this would work for you or not I do not know but it is just about as simple as you can get for a central heating system. Unfortunately I could not find it. The search function on here defeats me and a lot of others, maybe someone can find that for you or you can have a look for it. It's what I was going to do on my boat until I decided to plumb my central heating into my engine cooling system. I am only using two small rads and I am not live aboard so my heating is,generally, just used to keep the chill off when I'm leisure boating and to dry tea towels and such and this, for me, works well.

Pete

Um Mrsmelly got in there first. Thermosyphon/gravity fed are the same thing.

Edited by pete.i, 05 March 2012 - 10:40 PM.

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#5 JDR

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Posted 05 March 2012 - 10:39 PM

You've got a choice- either use a pump or go for a convection/gravity system. Whatever system you use you will need copper pipe for the first metre from the boiler connection at the back of the stove. If you then used copper for the rest of the system it has the advantage of dissipating heat (100w per metre for 28mm is a rough estimate).The expansion tank is normally at the remote end away from the stove.A convection gravity system will have the hot outlet from the boiler (top) rising gradually in height towards the remote end then gravity will assist the return flow to the boiler.It takes more planning to design but is silent in operation and uses no electricity. A pumped system will require a thermostat as there's no point pumping cold water, will use electricity and generate noise from the pump, could potentially cause problems if something goes wrong (you would be advised to build in some form of isolation valves so pump could be swapped without draining system) but will heat boat quicker than gravity.
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#6 system 4-50

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Posted 05 March 2012 - 10:53 PM

I am no expert but I suggest that it would be good to clarify that what you need is a header tank which will take up any water expansion and not a sealed expansion tank of the sort that is normally fitted near a calorifier in case anybody misunderstands the references to an expansion tank.
Tell me if you think I'm wrong.
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#7 JDR

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Posted 05 March 2012 - 11:16 PM

I am no expert but I suggest that it would be good to clarify that what you need is a header tank which will take up any water expansion and not a sealed expansion tank of the sort that is normally fitted near a calorifier in case anybody misunderstands the references to an expansion tank.
Tell me if you think I'm wrong.

Good point well made.Another advantage of a thermosyphon/gravity system is that the system is not sealed/pressurised so you could use anything that holds water as a header tank (with a hole in the top as a vent and an overflow pipe if you do ever put too much fuel on).
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#8 Gazboatman

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Posted 05 March 2012 - 11:30 PM

Thanks all.

Great site this!

:cheers:
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#9 Gazboatman

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Posted 06 March 2012 - 05:51 PM

Ok I think I have the gist of it now, well I have if I were just having the one rad. I think I found the other thread on this subject but sadly all the diagrams are no longer available to view. I have drawn two diagrams as Im not completely sure how it works when you have two rads running.

Posted Image

Posted Image

Anyone know which of these two is the correct way to do it?

Also does the return pipe have to be on a slope back down to the boiler?

Edited by Gazboatman, 06 March 2012 - 05:54 PM.

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#10 JDR

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Posted 06 March 2012 - 06:57 PM

First diagram is almost there: rather than connecting directly to rads you could tee off to 15mm pipe to connect either top right on outlet to bottom left on return.I have also seen rads with both top connections to outlet and both bottom connections teed off to return.Extend the pipework past the last rad so you can shut off rads until water is flowing.Return feed on gravity system need to slope-it can reach the boiler beneath the height of the bottom connection and still work.Go for 28mm for main pipes if possible.Remember to take the slope of the boat with a full and empty water tank into consideration.Extend return feed beyond stove to make draining system easier.

Edited by JDR, 06 March 2012 - 07:04 PM.

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#11 mrsmelly

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Posted 06 March 2012 - 07:07 PM

Ok I think I have the gist of it now, well I have if I were just having the one rad. I think I found the other thread on this subject but sadly all the diagrams are no longer available to view. I have drawn two diagrams as Im not completely sure how it works when you have two rads running.

Posted Image

Posted Image

Anyone know which of these two is the correct way to do it?

Also does the return pipe have to be on a slope back down to the boiler?


The first one is close but not correct.If you do it that way it will not work. what you do is a loop of 22/28 mill copper pipe from the boiler to the furthest point you want to go and back to the bottom of the boiler, you need a steady continuous uphill slant with the top pipe. You then tee off inside the loop to the top and bottom of the rads allowing the hot water to circulate and drop through the rads. This method works absolutely spot on. The bottom pipe of the loop is generaly straightish but is not too critical as the colder water is actualy sucked in to the bottom of the boiler again. At the far end of the loop tee off to a vented header tank for expanding water. I used a plastic buiscit barrel with lid for that job, I think it cost me 3 quid and looked good painted :cheers:

Edited by mrsmelly, 06 March 2012 - 07:08 PM.

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REALITY IS AN ILLUSION CAUSED BY LACK OF ALCOHOL.
IT IS NOT POSSIBLE TO CC ON ONE CANAL.

#12 JDR

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Posted 06 March 2012 - 07:20 PM

I used compression fittings for most of the system but for the header tank connection used some heatproof rubber designed for use on skin tank and good quality hoseclips.Bit of a bodge but it cost nothing and doesn't leak.
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#13 system 4-50

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Posted 06 March 2012 - 08:44 PM

I have a faint memory that there should ideally be a thermostat on the hot out from the stove near the stove to prevent circulation until the water is hot enough. 50 degrees? If the system circulates for any length of time with cool not hot water in it then corrosion is encouraged particularly in the stove.
Does this sound familiar to anyone?
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#14 Gazboatman

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Posted 06 March 2012 - 09:02 PM

I have a faint memory that there should ideally be a thermostat on the hot out from the stove near the stove to prevent circulation until the water is hot enough. 50 degrees? If the system circulates for any length of time with cool not hot water in it then corrosion is encouraged particularly in the stove.
Does this sound familiar to anyone?

Right I think I've got it..

Posted Image
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#15 mrsmelly

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Posted 06 March 2012 - 09:06 PM

Right I think I've got it..

Posted Image


Yup thats it.....just make sure you have a nice steady rise on the top pipe of the loop. You dont need a thermostat. Put anti freeze in with the circ water and make sure you pre mix it before filling the system. :cheers:
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REALITY IS AN ILLUSION CAUSED BY LACK OF ALCOHOL.
IT IS NOT POSSIBLE TO CC ON ONE CANAL.

#16 Gazboatman

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Posted 06 March 2012 - 09:13 PM

Yup thats it.....just make sure you have a nice steady rise on the top pipe of the loop. You dont need a thermostat. Put anti freeze in with the circ water and make sure you pre mix it before filling the system. :cheers:

Great stuff, so just do something like the diagram and allow for when the water tank is empty. Also is it possible to have four T junctions on one rad, two feeding the top and two at the bottom, or will that not work at all?
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#17 mrsmelly

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Posted 06 March 2012 - 09:19 PM

Great stuff, so just do something like the diagram and allow for when the water tank is empty. Also is it possible to have four T junctions on one rad, two feeding the top and two at the bottom, or will that not work at all?


You could double up on the tees but no need to it will work well. Instead of the sort of sharp raise on your drawing at the start of the top pipe try to do it in a gentle regular line it looks slightly weird but the results are better. The header tank only needs to be wet in the bottom its just for excess water to go into when the temperature rises. :cheers:
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REALITY IS AN ILLUSION CAUSED BY LACK OF ALCOHOL.
IT IS NOT POSSIBLE TO CC ON ONE CANAL.

#18 Gazboatman

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Posted 06 March 2012 - 09:21 PM

You could double up on the tees but no need to it will work well. Instead of the sort of sharp raise on your drawing at the start of the top pipe try to do it in a gentle regular line it looks slightly weird but the results are better. The header tank only needs to be wet in the bottom its just for excess water to go into when the temperature rises. :cheers:

Ok thanks alot, and thanks to everyone else who helped.

:cheers:

Edited by Gazboatman, 06 March 2012 - 09:33 PM.

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#19 JDR

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Posted 06 March 2012 - 09:31 PM

The only other tweek I can think of is to get a bit more of an angle on the return.If its parallel to floor/gunwales then it will have to go uphill to return to boiler, most boats are stern down.May be worth having return teed off at 90 degrees to boiler return.Might need to experiment as you go but looks good.
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#20 Gazboatman

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Posted 06 March 2012 - 09:48 PM

The only other tweek I can think of is to get a bit more of an angle on the return.If its parallel to floor/gunwales then it will have to go uphill to return to boiler, most boats are stern down.May be worth having return teed off at 90 degrees to boiler return.Might need to experiment as you go but looks good.

I think Ishould be ok with that as the stern is to the right of the stove in my diagram. There is a water boiler situated there. That will along the same principles, right?
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