Converting to thermosyphon

[Scholar Gypsy]

There are lots of 12v circ pumps that take an amp or less. I've got one of these to push round water from the heat exchanger on the engine.

 

http://www.midlandchandlers.co.uk/store/product/wp-029.aspx

[RLWP]

I don't want to turn off the pump and have the water boil and blow up the stove.

 

Yes, you keep saying this. If you damp the fire down to keep it in overnight, you won't 'blow up the stove'

 

Can someone with more back boiler experience add to this please

 

Richard

[Bewildered]

Yes, you keep saying this. If you damp the fire down to keep it in overnight, you won't 'blow up the stove'

 

Can someone with more back boiler experience add to this please

 

Richard

I see what you are saying but never having owned a stove before I have no idea what temperature the fire will burn at after being damped down and would rather not take the risk until I have a better idea; therefore the wisest course of action would be to minimise the risk and have a low powered pump keep it circulating.

 

There are lots of 12v circ pumps that take an amp or less. I've got one of these to push round water from the heat exchanger on the engine.

 

http://www.midlandchandlers.co.uk/store/product/wp-029.aspx

As I posted previously, we have already tried a 12v pump and it didn't work, we suspected air locks in the system. Hence my request for a recommendation for a good plumber. 12v pumps don't self prime, so how do you prime them after fitting?

I'm after a decent plumber who understands these systems to set it up and test it and show me how to maintain it.

If for example I light the stove but find that the pump is not circulating, what can I do to clear an airlock? Is there anyway to check circulation before lighting the fire? Etc

[RLWP]

I see what you are saying but never having owned a stove before I have no idea what temperature the fire will burn at after being damped down and would rather not take the risk until I have a better idea; therefore the wisest course of action would be to minimise the risk and have a low powered pump keep it circulating.

 

You need some information from back boiler stove users. I know our Franco-Belge stove in a previous house didn't need the pump running

 

Richard

[ditchcrawler]

I see what you are saying but never having owned a stove before I have no idea what temperature the fire will burn at after being damped down and would rather not take the risk until I have a better idea; therefore the wisest course of action would be to minimise the risk and have a low powered pump keep it circulating.

 

As I posted previously, we have already tried a 12v pump and it didn't work, we suspected air locks in the system. Hence my request for a recommendation for a good plumber. 12v pumps don't self prime, so how do you prime them after fitting?

I'm after a decent plumber who understands these systems to set it up and test it and show me how to maintain it.

If for example I light the stove but find that the pump is not circulating, what can I do to clear an airlock? Is there anyway to check circulation before lighting the fire? Etc

Mount the pump low down in the bottom leg. I use a Johnson pump to feed an extra radiator when required and it has to be mounted in the correct orientation its in a vertical pipe at the bottom of the system and is actually in the toilet so the noise is well away from the lounge. I wouldn't want it running beside me. I would also suggest that you have at least one radiator that thermosyphons in case of pump failure.

[Bewildered]

Mount the pump low down in the bottom leg. I use a Johnson pump to feed an extra radiator when required and it has to be mounted in the correct orientation its in a vertical pipe at the bottom of the system and is actually in the toilet so the noise is well away from the lounge. I wouldn't want it running beside me. I would also suggest that you have at least one radiator that thermosyphons in case of pump failure.

What you say makes sense. This boat has been modified since the original build, the stove used to be in the front corner and is now situated about 10feet or so from the the front of the boat, the pump is as far as I can tell is in the original location under the front steps which is at the top of the system. Probably why I get air lock problems.

I don't do plumbing. It is somthing I have never bothered to learn. Yes I could work it out logically but I would rather it be modified and set up correctly by someone who knows exactly what they are doing.

 

All the advice is helpful for me to get a better understanding of what should be done but I'm still not going to do it myself.

 

All I want is a recommendation for a good marine plumber/heating engineer somewhere in the Midlands, preferably near Coven

[Scholar Gypsy]

Plastic plumbing is not that scary, unless you are obsessive about right angles and so on. But this may not be relevant to the point you are making ...

[ditchcrawler]

 

 

All I want is a recommendation for a good marine plumber/heating engineer somewhere in the Midlands, preferably near Coven

I think that may be your problem, probably as hard to find as good electricians, they are out there but thin on the ground.

edit

I bet there are not that many domestic plumbers, I wont say Heating Engineers out there who could plumb a thermosyphoning system these. back boilers are a 1950s thing days

Edited September 20, 2016 by ditchcrawler

[Bewildered]

I think that may be your problem, probably as hard to find as good electricians, they are out there but thin on the ground.

edit

I bet there are not that many domestic plumbers, I wont say Heating Engineers out there who could plumb a thermosyphoning system these. back boilers are a 1950s thing days

As you say they may be thin on the ground but not everyone plumbs their own boats.

I did have a mate who is a good plumber take a look at it when I first got the boat but as you pointed out it is older tech and he admitted he really didn't know much about it.

 

Perhaps rather than add this request to an existing topic, that people may not be looking at, I should start a new one. Someone somewhere must know a good marine plumber that understands theses systems

[Nev]

I'd go to Oxley Marine (or give them a call) just past Autherely junction. A decent set of chaps who know boats and will give you good advice. I have used them on my last boat for a breakdown and once they commit to a job they get it done.

 

FWIW on Percy I have a very effective thermosyphoning system but it is made of large bore copper pipes on a gentle climb from the boiler to the bathroom on one side of the boat, no hot water tank as we have a gas heater . Very industrial looking but to me very attractive (especially after the copper has been polished, yes a shiny boat but inside !) The upper pipe goes from 22mm to 28mm and the return 28 - 22mm but the 22mm is longer on the return. Not sure if this helps the syphoning effect - I'd expect so. It is very effective and no pump so absolute peace and quiet.

 

Good luck, let us now how you get on?

 

Nev NB Percy

 

Edited to say - On our last boat I fitted a pipe stat to the pump with a switch overide to we could damp the fire down for the night and let the pipe stat control the 12v pump to prevent the stove back boiler boiling (my fear not fact) - the pump coming on in the middle of the night still woke me up !!

Edited September 20, 2016 by Nev

[Bewildered]

Finally sorted out the heating, nice and toasty now

 

I ended up fitting a 12v Johnson circulation pump at the other end of the boat under the stern stairs. I removed the 240v pump and joined up the pipes.

It didn't work straight away as I think I still have an air lock between the pump and the last rad on the system in the bathroom, the return pipe from this rad runs at floor level towards the back of the boat and the rises about 2 feet to the back corner where I can't get to it then it drops to floor level as it crosses the boat to the new pump under the stairs. Couldn't get the system circulating as I think there is an air lock in this corner.

The next day I put in a couple of T pieces with a full bore valve joining the flow and return just behind the pump. Was initially air locked but after a while and a lot of pipe shaking it cleared. All rads now working except the bathroom. If I ever manage to get rid of this air lock I should be able to shut off the new valve to complete the circulation circuit.

[adrianh]

Back to post 1, do you mean that you have fitted a domestic heating (230 volt)circulating pump instead of the 12 volt pump?

These have a much higher flow rate than you are going to get from a small DC pump, hence the current consumed.

If so this type of pump is no different in construction to an open impellor 12 volt pump so any pump positioned correctly will pump providing it has enough pressure (called 'head') output capacity.

Apart from the Johnson type and Solar heating pumps available, you can buy industrial type water pumps fitted with 12 volt motors, however these cost a lot more.

Most 12 volt pumps seem to have end inlet and tangential output connections and are always deigned for a positive head of water at the inlet to operate correctly.

As you had problems with air locks at the pump then you need to ensure that the header tank supply and then the vent are connected just upstream of the pump using a swirl chamber (see http://www.plumbcenter.co.uk/product/tower-flue-air-seporator-22mm/)so that the pump will always be filled when not running and will remove 'air' when running. This assumes that you do not have any thing that can let air back into the system ie automatic float type air vent positioned close to the pump suction.

Regarding protecting the back boiler from overheating, do not just rely on damping down - when this goes wrong you will have a boiler/heating system not designed for steam pressure in a dangerous condition! The normal vent system will not remove steam pressure/ water quick enough. Fit a thermostat on the boiler casing to run the pump when the temperature goes above 75 to 80 degrees C. A domestic hot water cylinder stat can be used for this purpose.

If you want more help re pumps PM me

[cereal tiller]

What you say makes sense. This boat has been modified since the original build, the stove used to be in the front corner and is now situated about 10feet or so from the the front of the boat, the pump is as far as I can tell is in the original location under the front steps which is at the top of the system. Probably why I get air lock problems.

I don't do plumbing. It is somthing I have never bothered to learn. Yes I could work it out logically but I would rather it be modified and set up correctly by someone who knows exactly what they are doing.

 

All the advice is helpful for me to get a better understanding of what should be done but I'm still not going to do it myself.

 

All I want is a recommendation for a good marine plumber/heating engineer somewhere in the Midlands, preferably near Coven

Installed a Solar projects pump on a friend's boat yesterday,it draws 14 watts

 

The original pump drew 2 amps. and was permanently on,so 48 AH per 24 hour period

 

The Stove is a Stovax brunel ,the Back boiler feed 3 Rads.one close to the stove which can operate on thermosyphon,the other 2 are 25 feet away

 

The Pump is now switched with a WILLHI 12 volt digital Temp. Controller,start pump at 75 degrees C and stops pump at 65 C

 

Monitored its performance .it runs for 20 Seconds and shuts off for 8 minutes 10 seconds with stove at a "medium" setting

 

Will likely consume 2AH per 24 hour period,bit of an improvement?

 

CT