Jump to content

Running pressurised pipes under the gunwales


Featured Posts

Is it problematic to run pressurised pipework for central heating and hot/cold water at gunwale height? There is a chance I will not be able to have pipe fitted behind the lower walls for various reasons. there will be a chine on our Widebeam, which most people box in with pipes running along the slope, but we intend to leave the chine open. 

 

I thought it might be an idea to run two pipes along one side under the gunwales to feed to radiators from a Webasto. The other side would carry the hot and cold water (I'm guessing a jabsco pump is okay with that much of a lift directly after the outlet?)

 

I would probably fit some old fashioned style radiators upside down to avoid pipe having to trail down the wall. I can't think of a reason why radiators wouldn't work this way, particularly with a Webasto system pressurised to 1bar. 

Link to comment
Share on other sites

3 minutes ago, Poppin said:

I would probably fit some old fashioned style radiators upside down to avoid pipe having to trail down the wall. I can't think of a reason why radiators wouldn't work this way, particularly with a Webasto system pressurised to 1bar. 

You could run the hit water from the boiler directly into the top of the radiator, but you would still want to take the return water back to the boiler from the bottom of the radiator. So you need a vertical pipe down the wall at one end.

Link to comment
Share on other sites

Radiators won’t work if fed from the top. The hot water will flow along the top of the radiator whilst the bottom (and middle) remain cold. Hot water being lighter than cold!
 

The only issue with having fresh water pipes at gunnel level is that they will be more prone to freezing in winter (if the boat is left unheated) because pipes below the water line are kept relatively warm by the canal/river water.

Link to comment
Share on other sites

1 hour ago, nicknorman said:

Radiators won’t work if fed from the top. The hot water will flow along the top of the radiator whilst the bottom (and middle) remain cold. Hot water being lighter than cold!
 

The only issue with having fresh water pipes at gunnel level is that they will be more prone to freezing in winter (if the boat is left unheated) because pipes below the water line are kept relatively warm by the canal/river water.


so it’s the heat that causes the water to travel up the radiator? I thought it was just pushed through with the pump and there were internal pipes inside the rad. I guess not! 
 

so then there would be no issue if the pipe ran down from above at each radiator and entered the radiator at the bottom. This section of pipe could be pretty copper or chrome as opposed to cheaper plastic hidden under gunwale

Link to comment
Share on other sites

3 hours ago, nicknorman said:

Radiators won’t work if fed from the top.

 

 

This is news to me! Obviously nobody has told the radiators in the thousands of solid fuel natural convection heating systems in boats and houses across they UK working perfectly well with the flow pipe connected into the top. 

 

But more seriously, this does depend on the return connection being connected into the bottom of the rad, so the stratification in a convection system can occur. But it can also apply to pumped systems too. Consider the many poorly natural convection systems that barely worked until a pump was added to assist.

 

And in the OP's case the pipes could run at gunwale level then both the flow and return connections to each rad drop vertically to valves in the bottom....

 

 

Which on reflection is exactly how I arranged the pipes when I designed the rad system connected to the Whispergen. It works fine.

  • Greenie 1
Link to comment
Share on other sites

Although I would prefer not to do the CH that way, I am with Mike. Thousands of NBs with gravity circulated central heating system are done that way.

 

At least all your pipes will be easily accessed for service/repair issues.

Link to comment
Share on other sites

4 hours ago, MtB said:

 

 

This is news to me! Obviously nobody has told the radiators in the thousands of solid fuel natural convection heating systems in boats and houses across they UK working perfectly well with the flow pipe connected into the top. 

 

But more seriously, this does depend on the return connection being connected into the bottom of the rad, so the stratification in a convection system can occur. But it can also apply to pumped systems too. Consider the many poorly natural convection systems that barely worked until a pump was added to assist.

 

And in the OP's case the pipes could run at gunwale level then both the flow and return connections to each rad drop vertically to valves in the bottom....

 

 

Which on reflection is exactly how I arranged the pipes when I designed the rad system connected to the Whispergen. It works fine.

Alright mr. pedant! but I think the text after the sentence you’ve quoted, and the context of the thread, made it clear I was talking about radiators with both connections at the top.

Link to comment
Share on other sites

6 hours ago, blackrose said:

How are you going to bleed radiators if they are upside down and the bleed valve is at the bottom? 

If the flow is connected to the top of the radiator and the feed pipes are above the radiator, then the radiator itself won't need bleeding, but bleed valves will be needed at the highest point on the flow and return pipes.

Link to comment
Share on other sites

Yes I wasn't sure exactly where the flow/return pipes were going to be in relation to the rads. 

9 hours ago, Poppin said:

 There is a chance I will not be able to have pipe fitted behind the lower walls for various reasons. 

 

You wouldn't normally have pipes running behind panelling on a boat anyway. Boxed in is fine but you must be able to access them. 

Link to comment
Share on other sites

30 minutes ago, nicknorman said:

Alright mr. pedant! but I think the text after the sentence you’ve quoted, and the context of the thread, made it clear I was talking about radiators with both connections at the top.

 

 

And equally I grant that the OP implies he intends to connect both the flow and the return pipes into the top in his last para, but the open goal you presented was too tempting to ignore :giggles:

 

So in summary I think (know, rather) the OP's exact proposal won't work but if either the flow or the return is dropped vertically down and connected into the bottom of the rad (as the OP asserts he does not want), will work. Which to select is a subject that can result in debate.

 

Link to comment
Share on other sites

27 minutes ago, David Mack said:

If the flow is connected to the top of the radiator and the feed pipes are above the radiator, then the radiator itself won't need bleeding, but bleed valves will be needed at the highest point on the flow and return pipes.


how about a bottle vent at a high point near the webasto?

 

19 minutes ago, blackrose said:

Yes I wasn't sure exactly where the flow/return pipes were going to be in relation to the rads. 

 

You wouldn't normally have pipes running behind panelling on a boat anyway. Boxed in is fine but you must be able to access them. 

 

i have seen pipes running behind panelling (central heating, water) on pretty much every livaboard boat I’ve been on. And two that I have owned myself. It is annoying for access but unless you drill through one I would think damage is unlikely. 

Link to comment
Share on other sites

1 minute ago, nicknorman said:

Hot in at the top, cold out at the bottom. Same as for a skin tank. Is there another (sensible) way of doing it?

 

Yes. Hot in at the bottom, slightly cooler out at the top. Both work fine once a pump is involved! 

 

But there will be those who insist hot in at the bottom is best because "hot water rises"... and there is no arguing with them as they just don't and won't understand. 

Link to comment
Share on other sites

7 hours ago, blackrose said:

How are you going to bleed radiators if they are upside down and the bleed valve is at the bottom? 

Surly they will self bleed through the return pipe at the top, its been pointed out the feed needs to go at the bottom

 

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
  • 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.