Jump to content

Gravity fed rads.

nbTijan

By nbTijan
in Boat Equipment

 Share

Featured Posts

nbTijan Gongoozler

nbTijan

Posted
Posted

Hi - for reasons which are too complicated and painful to recount! - I now have two new radiators connected to a gravity feed from a back boiler on a small solid fuel stove.

The old radiators - which were in simalar but slightly different positions - used to heat up within an hour or so of the stove being lit... However the new ones struggle to get warm even after two or three hours, and the pipework gives off a lot of clanging and banging and gurgling..!

As the place where the work was done is now 250 miles away from where the boat is I can't really get the guy who did the work to come and ''sort it out'' - hence my post to this forum.

From the diagram - which is how I think the pipework is laid out, some of it being hidden - does it look like the system SHOULD work, but just maybe needs topping up or given more time to bed in... Or does it look as though I should really have a small pump somewhere on the circuit, and if so is there anywhere in particular it should go.

The little header tank is an old, small copper cylinder with a radiator cap on the top. This effectively ''seals'' the system. Should there be some kind of breather pipe fitted as well.

Thanks for taking the time to read through this.

 

29674446.jpg

Link to comment
Share on other sites
WotEver Veteran II

WotEverDonate to Canal World

Posted
Posted (edited)
I'm not certain and can't get to measure it at the moment but I'd guess the main pipes are around 30mm.

In that case, it should work :lol:

 

A pump is always good, but you've got the hot flow running uphill and the cooler return running downhill which is the important bit. I'd suspect an airlock - have you bled the radiators?

 

Tony

 

quick edit for fat fingers

Edited by WotEver
Link to comment
Share on other sites
nbTijan Gongoozler

nbTijan

Posted
  • Author
Posted
As WotEver said sounds like an air lock!

 

Thanks - I did try bleeding the end rad but no air came out... though perhaps I needed to have the stove going for a longer time before I did it, to generate some 'momentum' in the system. I will give that another go next time I'm down on the boat.

Link to comment
Share on other sites
bristol & argo Collaborator

bristol & argo

Posted
Posted
Thanks - I did try bleeding the end rad but no air came out... though perhaps I needed to have the stove going for a longer time before I did it, to generate some 'momentum' in the system. I will give that another go next time I'm down on the boat.

 

Are you sure the rad valves are turned on?

Is the top flow pipe arrangment and slope still the same?

 

clanging and banging is the water boiling in the stove, so that means it has been unable to get moving around the system.

 

Try starting with a smallish fire and feel the pipes to try to follow how the flow gets going - or not as the case may be.

 

Simon.

Link to comment
Share on other sites
nbTijan Gongoozler

nbTijan

Posted
  • Author
Posted
Are you sure the rad valves are turned on?

Is the top flow pipe arrangment and slope still the same?

 

clanging and banging is the water boiling in the stove, so that means it has been unable to get moving around the system.

 

Try starting with a smallish fire and feel the pipes to try to follow how the flow gets going - or not as the case may be.

 

Simon.

 

 

Thanks - I'll try that... Rad valves have been open. (I'm going to offline till this evening). Thanks everyone for their thoughts.

Link to comment
Share on other sites
nb Innisfree Veteran II

nb InnisfreeDonate to Canal World

Posted
Posted (edited)
Hi - for reasons which are too complicated and painful to recount! - I now have two new radiators connected to a gravity feed from a back boiler on a small solid fuel stove.

The old radiators - which were in simalar but slightly different positions - used to heat up within an hour or so of the stove being lit... However the new ones struggle to get warm even after two or three hours, and the pipework gives off a lot of clanging and banging and gurgling..!

As the place where the work was done is now 250 miles away from where the boat is I can't really get the guy who did the work to come and ''sort it out'' - hence my post to this forum.

From the diagram - which is how I think the pipework is laid out, some of it being hidden - does it look like the system SHOULD work, but just maybe needs topping up or given more time to bed in... Or does it look as though I should really have a small pump somewhere on the circuit, and if so is there anywhere in particular it should go.

The little header tank is an old, small copper cylinder with a radiator cap on the top. This effectively ''seals'' the system. Should there be some kind of breather pipe fitted as well.

Thanks for taking the time to read through this.

 

29674446.jpg

 

Seems to me that the header tank isn't vented, that will prevent system from releasing any air locks. have you tried it with rad cap off? Perhaps a small expansion/overflow pipe from tank to the outside?

Edited by nb Innisfree
Link to comment
Share on other sites
nb Innisfree Veteran II

nb InnisfreeDonate to Canal World

Posted
Posted (edited)
I've revised your layout. Contruct the below and it should work fine. :lol:

 

plumbingcircuit2.jpg

 

The problem with you original layout is there is no method of capturing air bubbles in the system due to the expansion tank being connected in the wrong place.

 

Sot on, though make sure header tank is vented and flow pipe slopes upwards to rads, maybe a valve on the return at the end to encourage flow through rads. Or your setup could still work if you vent header tank and highest point on flow, return top of last rad into top of header tank or an automatic air valve (AAV) will work fine, they are cheap, simple and will fit into top of furthest rad

Edited by nb Innisfree
Link to comment
Share on other sites
bristol & argo Collaborator

bristol & argo

Posted
Posted
on a shorter boat the whole boat slopes enough that it doesn't really require a sloped pipe so clipping below the gunnel is fine. It may be more of an issue on a 70 footer however.

 

Its even more of an issue if the heat source is forward of the rads, on Bristol the heatsource was a Rayburn so the cold return was fairly high off the floor too.

 

Anyway, back to refitting nb tijan, the air bubbles will collect in the higher rad, and the sign that the system needs bleeding is when it stops getting hot....

Agreed the reservoir bottle would be better connected to the top right hand end of the higher rad to make it self bleeding, or maybe just fitting an auto air vent would be enough.

 

At least with the current arrangement the steam is contained and only the relatively cool reservoir water would be ejected.

 

 

Simon.

Link to comment
Share on other sites
nbTijan Gongoozler

nbTijan

Posted
  • Author
Posted

Thanks to everyone for all your thoughts and ideas on my heating problem. I'm not able to get down to the boat now till probably just before Christmas or just after New Year, but when I do I'll investigate and explore the ideas you've contributed and post an update here as to progress. Thanks again and I hope you all have an enjoyable Christmas.

Link to comment
Share on other sites
Smelly Veteran

Smelly

Posted
Posted (edited)
How about this, easiest if OP wants minimum disruption.

 

Gravity.jpg

 

or just tee into the riser to the expansion tank from the top rail.... If that section has a valve on it it can be used to prevent the hot water simply trying to rise into the expansion tank. edit... a valve between the riser and the top rail of course...

 

Be careful with auto air vents. They were discussed here a while back and they only seemed to vent at around 8-10 bar which might be a bit much.

Edited by Smelly
Link to comment
Share on other sites
nb Innisfree Veteran II

nb InnisfreeDonate to Canal World

Posted
Posted
or just tee into the riser to the expansion tank from the top rail.... If that section has a valve on it it can be used to prevent the hot water simply trying to rise into the expansion tank. edit... a valve between the riser and the top rail of course...

 

Be careful with auto air vents. They were discussed here a while back and they only seemed to vent at around 8-10 bar which might be a bit much.

 

The AAVs I am referring to are the bottle type which just use a floating ball similar to a diving snorkel. They vent as soon as water level drops due to air trapped. Foolproof really.

Image006-1.jpg

Link to comment
Share on other sites
blackrose Veteran II

blackrose

Posted
Posted (edited)
I've revised your layout. Contruct the below and it should work fine. :lol:

 

plumbingcircuit2.jpg

 

The problem with you original layout is there is no method of capturing air bubbles in the system due to the expansion tank being connected in the wrong place.

 

That's a much better layout for a convection/gravity thermocycling system.

 

On mine the header tank isn't capped. It comes off the top run at the highest point which makes the system self-bleeding. I don't think a pressurised thermocycling system will facilitate flow.

 

Edit: the only thing I'd add is that I'd connect all 4 inlets/outlets of the last rad to the main run rather than just one at the top and one at the bottom. It just seems to me that you'd get more hot water going through the rad and avoid any cold spots - especially if the run to the last rad is more than a few metres.

Edited by blackrose
Link to comment
Share on other sites
bag 'o' bones Rising Star

bag 'o' bones

Posted
Posted

the only reason to pressurise a thermosyphon is if you needed to increase the thermal capacity above 100 centigrade. Hence why car cooling systems - which generally have to operate in a limited amount of space - are pressurised to increase their efficiency.

 

Not sure why you would want to fit such a system on a narrow boat though!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.