Converting to thermosyphon

[Bewildered]

Hopefully I will be able to post the images, drew them on word but could not convert them so took photos of the screen.

Ok so I have a 70' boat bought last October, had problems with the heating, system was dry, when topped up pump wouldn't run. Replaced 12v pump, still wouldn't work so eventually stuck in a 230v pump, seems to work ok but obviously uses power. I don't want to run the pump all night so I want to change it to thermosyphon.

The existing layout is like so

 

From the left of the drawing the pump is under the front steps around 2'6" from the side of the boat there is a further 10' to the stove, the first radiator is 10' from the stove then there is 25' between rads 1&2, 8' between rads 2&3, then around 4' to the back of the boat, then around 6' across the width of the boat, 9' more to the calorifier then 10' to the bathroom rad, then of course the full run back to the pump.

The header tank is on the cruiser stern about 6" below roof level. I assume the header tank is on the flow pipe and not the return but I haven't as yet been bothered to pull the washing machine out to check.

The pipe runs from the boiler to floor level all around the boat

 

What I would like to do is this

 

Take the feed pipe diagonally up to just below the gunnels then run under the gunnels (feeding each rad from the top) and dropping down to pick up the original feed pipe after the 3rd rad.

From the stove to the gunnels would be a run of about 10' rising around a foot.

Join the return pipe to bypass the pump.

I was thinking of having the return valve on the first rad set about a 1/4 open the second rad about 1/2 the 3rd rad about 3/4 and the bathroom rad both fully open

The boat is plumbed in large bore plastic, 32mm possibly?

There is a valve at the calorifier to turn it off in the Summer so the engine doesn't heat the rads

As far as I can tell, if the feed pipe rises the hot water will flow and draw the cold in to the bottom.

 

Ok so questions.

1. Will this thermosyphon over this distance?

2. After the run along the gunnels will the hot then travel at floor level to the last radiator?

3. Should the return be taken directly back to the stove? I was thinking leave it and join it at the pump in case I need to re plumb it in

4. Can I join at the pump with a full bore valve so that the pump can be included just by shutting the valve off?

5. I assume the header tank will stay as part of a thermosyphon system?

6. Is my assumption about setting the return valves correct? ( the bathroom rad does not have a thermostatic valve; the valves will be permanently set to open fully)

 

I'm sure there will be more question arise as this thread progresses

I thank you in advance for your pearls of wisdom

Edited September 4, 2016 by Bewildered

[Bewildered]

Forgot to mention there is also a safety valve on the flow pipe behind the stove

[bigste]

Nothing to do with heating but the images are fine. Next time you save it in word or publisher etc, give it a name, like HEATING then underneath the name it will let you change the file type, choose JPEG.

[Scholar Gypsy]

I think that the feed pipe would need to run uphill throughout its length.

 

Your current proposal has it rising for a bit (the diagonal section) and then falling gently to the back of the boat (assuming that, as is normally the case, the gunnels slope with the bows higher than the stern - what is that drop?). So your front radiator should work, but not the rest.

[alan_fincher]

I would be very surprised if it will work well without a pump.

 

Although there have been some very differing views on similar topics both on here, and elsewhere, my own personal view is that you will always struggle to make a system thermosyphon unless the stove is lower than what it is feeding, and the pipes largely run uphill away from it, and downhill back to it.

 

With the stove at the front, and particularly with that pipe run actually travelling across the back of the boat and up the other side, I think you are only going to succeed with a pump present in the system. (I am assuming the bow of your boat sits higher in the water than the stern - true in most cases).

 

I'd be very happy to be proved wrong though, and would be very interested to hear if you do make it work on gravity alone.

[FadeToScarlet]

You might need to change the size of the rads to make it work. Mine has the slimmer, narrow kind, to fit under the pipework nearest the stove and enable the hot pipe to rise throughout.

 

It's only on a very gentle gradient- about a 1' rise over 50' as the boat slopes upwards.

 

You might also need to replace the pipe, 28mm is best although I have installed a thermosyphoning system on a boat with 22mm pipe which works well.

[Bewildered]

The consensus so far seems to be that it won't work unless all the feed is up hill.

 

I was under the impression that as long as the initial output feed rose upwards the hot water would rise along this length drawing/syphoning cold to fill the void left by the departing hot water. And as the cold is drawn it also pulls the hot in behind it helping the flow. So as long as there is a reasonable rise and length to the outgoing hot pipe it should start this process for the whole system, cold being drawn along the length of the system to replenish the evacuating hot. Or am I completely misunderstanding how this works?

Edited September 5, 2016 by Bewildered

[RLWP]

If you don't want to run the pump all night, fit a timer

 

Richard

[Bewildered]

If you don't want to run the pump all night, fit a timer

 

Richard

I also don't want to blow the boiler but I do want to be able to keep the fire in over night.

I did toy with the idea of a pipe thermostat, and fitting a cheap 300w plug in inverter to power the 230v pump, with the thermostat cutting the 12v supply to the inverter.

[RLWP]

I also don't want to blow the boiler but I do want to be able to keep the fire in over night.

I did toy with the idea of a pipe thermostat, and fitting a cheap 300w plug in inverter to power the 230v pump, with the thermostat cutting the 12v supply to the inverter.

 

Sorry, how will you 'blow the boiler'?

 

Richard

[Bewildered]

Sorry, how will you 'blow the boiler'?

 

Richard

I would of thought that the back boiler on the stove would overheat if the hot water was not circulating and cold feeding into it.

I would like to keep the fire burning overnight, at present this means leaving the pump running and draining the batteries

[DHutch]

What might happen, with the stove running but the pump not, is you boil the water in the back boilers. Initially this will emit steam which will then move out and cool and water will refill the void, but it time you might boil the area dry, and then overheat the back boiler.

 

One option is to ensure the nearest radiator, or two, will work by convection/thermosyphon allowing the stove to remain lit safely, and put out some heat, without pump (and hence all rads) working.

 

Without knowing the pipe runs and layout more accurately its hard to say how suitable the boat is for making them all run via thermosyphon, but as said to get it work you do need large bore pipes, basically a rise all the way, and the ability to bleed it perfectly with gravity alone.

 

 

Daniel

[Bewildered]

Having looked into this I think I will give up on the idea; the boat would need a total refit to make it work.

I did toy with the idea of disconnecting the calorifier and bathroom rad and only having rads on one side of the boat but unfortunaly the header tank is on the wrong side also. The pipe that feeds the header drops down to floor level to cross the boat. I can't fit a new header the on same side as the electrical cupboard is in the way.

Perhaps in a few years time I may do a full refit

[PeterDHS]

Nothing to do with heating but the images are fine. Next time you save it in word or publisher etc, give it a name, like HEATING then underneath the name it will let you change the file type, choose JPEG.

or download free software called Cute.pdf. This converts anything you can see as a printable image to a pdf.......including Autocad and other drawing software which tries to exclude recipients who have not coughed up several grand for the privelege.

[FadeToScarlet]

A better 12v pump might help. Although the Bolin type are I believe no longer made, there are others (Solar Projects springs to mind) that draw fractions of an amp when running.

[DHutch]

or download free software called Cute.pdf. This converts anything you can see as a printable image to a pdf.

 

MS Office (word etc) has offered 'save as pdf' for many years, which achieves the same.

 

Windows also bundles a 'snipping tool' which will take a 'picture' of an area of the screen and save it as a .png or .jpg which will upload direct to a post. Older versions of windows can achieve the same by pressing 'print screen' pasting it into Paint, and cropping as desired.

 

 

Daniel

 

 

 

 

 

 

 

 

Having looked into this I think I will give up on the idea; the boat would need a total refit to make it work.

I did toy with the idea of disconnecting the calorifier and bathroom rad and only having rads on one side of the boat but unfortunaly the header tank is on the wrong side also. The pipe that feeds the header drops down to floor level to cross the boat. I can't fit a new header the on same side as the electrical cupboard is in the way.

Perhaps in a few years time I may do a full refit

 

It might well be a serious chunk of work to get all rads to work without a pump, but if you have a couple or even one that could be made to work this will move the water around and prevent it boiling in the back of the stove, the rest could then work using a pump as and when needed.

 

 

Daniel

[WotEver]

 

Older versions of windows can achieve the same by pressing 'print screen' pasting it into Paint, and cropping as desired.

 

Or Ctrl+PrintScreen to capture just the active window (not a lot of people know that, it seems).

 

Tony

[DHutch]

 

Or Ctrl+PrintScreen to capture just the active window (not a lot of people know that, it seems).

 

Tony

Indeed. Extra useful if on twin screen. Windows 7 onwards, snipping tool all the way.

 

 

Daniel

[Bewildered]

Can anyone recommend a good marine plumber/heating engineer in the midlands area?

 

After fitting the battery monitor I now know that the mains pump draws about 5amps and the inverter draws 1/2 an amp so in order to keep the fire in all night I'm drawing 5.5 - 5.7 amps all night long. I need to go back to a 12v pump that is only drawing 1-1.5 amps.

 

As I've already tried a 12v pump without success I want someone who knows what they are doing to fit it and prime it. I think this was the original problem, 12v pumps don't self prime, just how do you prime them and how do you know if the water is circulating?

 

I also want to know if I can have at least part of my system thermosyphon in case of pump failure.

 

We are currently lurking around on the Staffordshire & Worcestershire canal at Coven because we are trying to get a dog from the local rescue centre.

Edited September 19, 2016 by Bewildered

[ditchcrawler]

Can anyone recommend a good marine plumber/heating engineer in the midlands area?

 

After fitting the battery monitor I now know that the mains pump draws about 5amps and the inverter draws 1/2 an amp so in order to keep the fire in all night I'm drawing 5.5 - 5.7 amps all night long. I need to go back to a 12v pump that is only drawing 1-1.5 amps.

 

Have you looked at these, other makes available http://www.anchorpumps.com/lowara-ecocirc-25-6-130-energy-efficient-domestic-heating-circulator-pump-240v-replaces-grundfos-ups-25-60-130-605008350-130?gclid=CKnpwM2znM8CFfQW0wodHeEJYA

[Bewildered]

Have you looked at these, other makes available http://www.anchorpumps.com/lowara-ecocirc-25-6-130-energy-efficient-domestic-heating-circulator-pump-240v-replaces-grundfos-ups-25-60-130-605008350-130?gclid=CKnpwM2znM8CFfQW0wodHeEJYA

Interesting, that could well be the solution.

According to the specs full load current is 0.47amps; am I right in assuming that it will only draw 0.47 amps from the batteries via the inverter? As far as I can remember the current drawn stays the same, only the voltage and wattage change.

If this is right then the 1/2amp the inverter uses,just by being switched on, plus the 0.47 or less from the pump means it should run at under an amp and be more efficient than a lot of 12v pumps.

[ditchcrawler]

No its the 240 volt current they give. so about 4.5 amps at 12 volts

[Bewildered]

Not a great deal better than the one I'm using then, 4.5amps plus the 0.5amps the inverter uses is still 5amps all night long.

It's been about 30 years since I used ohms law but I worked it out as 240v x 0.47amps = 112.8watts, 112.8w/12v = 9.4amps or am I missing something about the conversion to 12v?

[RLWP]

Why are you running a pump at night?

 

Richard

[Bewildered]

Why are you running a pump at night?

Richard

It's the central heating circulation pump. I want to be able to keep the stove alight overnight during the winter. I don't want to turn off the pump and have the water boil and blow up the stove.