Plumbing / Heating

[volmaakt]

Hello. I have been reading through as many of the posts regarding back boiler heating systems as I can before I set up my system. I have a barge and my stove is In the centre. I need to run radiators fore and aft. I think I have managed to figure how to get this gravity fed but I have a few of questions. Is there a minimum height for the header tank above the rest of the system? Can an in-line pump be used to get the system circulating quicker and then switched off without impeding the system? Would the system work going in two directions from the back boiler? Is there any leeway on one of the returns travelling slightly uphill for the last couple of meters (I thought with the water circulating it might pull the colder water into the boiler)? This is a solid fuel system and only radiators. Thank you.

[Tracy D'arth]

In your order.

 

1. No, as long as its higher at the base than the highest point on the system.
2. No, it will restrict the gravity flow and is totally unnecessary anyway.
3. Yes, but think about venting the circuit that does not have the header tank.
4. Yes, providing the rise on the return is a lot less than the rise on the flow, you could run the return flat on the floor with a direct rise to the boiler return.

As with all gravity systems us slow bends in pipe rather than elbows to minimise resistance to flow.  Get the flow pipe up as high as is practicable.

[volmaakt]

Thank you for your reply. What would be the best way to vent the other run, would it need another header tank? Most of the diagrams I have seen for open vented systems seem to show ,basically, a pipe hanging over an open bucket. Is there a proper component for this or is it something people fashion?

[Tracy D'arth]

You can fit a screw down vent like a radiator bleed plug at the high point, one the water has lost its dissolved air it will stay air free,  avoid auto air vents, vibration makes them weep.

If you use plastic pipes, fix them to rise on top of a batten to prevent all the sags when hot.

 

Expansion tanks can be bought but its easy to use a heavy gauge plastic container, like oil drum, with a Hep2o tank connector in the bottom, no over vent pipe required. Should be approx minimum 2 litres volume for each kilowatt of boiler output.  No more than 1/4 filled when cold. So a 10 litre one for say a Squirrel stove.

Make sure it will stand boiling water without collapsing.

If you have a tame fabricator a nice stainless steel one is lovely. Put a loose lid on, not sealed, to reduce evaporation and check water level twice in the heating season. Antifreeze with corrosion inhibitor included at min 30% concentration will stop the radiators rusting.

 

Edited August 31, 2020 by Tracy D'arth

[ditchcrawler]

28 minutes ago, volmaakt said:

  Is there a proper component for this or is it something people fashion?

Most things on boats you just fashon

[volmaakt]

Oh don’t I know it. But I have just been explaining to my 10 year old why we need an expansion tank including TD’s explanation of a steam flash explosion and he really wants me to buy something “proper” not make it myself... no faith at all.

Does the tank need a feed down into the return or just from the feed?

Any recommendations for radiators?

Edited August 31, 2020 by volmaakt

[Tracy D'arth]

6 minutes ago, volmaakt said:

Oh don’t I know it. But I have just been explaining to my 10 year old why we need an expansion tank including TD’s explanation of a steam flash explosion and he really wants me to buy something “proper” not make it myself... no faith at all.

Does the tank need a feed down into the return or just from the feed?

Any recommendations for radiators?

Tank connects to the high point only and vents the flow. It is not necessary to have bottom expansion and over top vent on a small boat system on gravity.

you want radiators that have all 4 corners threaded so you can put the flow down from under the gunwale into a top tapping with a valve if you wish and the return into a diagonally opposite bottom tapping with a lock shield valve if you wish for balancing heat output, but not vital. Many have no valves but then it gets a bit warm when you just want hot water from the calorifier in summer!

[Bee]

Very much a case for keep it simple. Hot pipe rises all the way to (probably) the back of the boat, this can be awkward as the boat is usually ballasted lower at the back. Expansion pipe with tank perched on top taken FROM the highest point of the pipe run, return pipe falls all the way to the back boiler. I have always used 1" dia pipe. It can look a bit amateurish but when you get back to the boat in February, its freezing and the battery is flat it is great to be able to light the fire with no fear of the pump not working. Also use antifreeze as if it freezes somewhere it won't circulate and the boiler makes funny noises and then goes bang.

[Tracy D'arth]

8 minutes ago, Bee said:

Very much a case for keep it simple. Hot pipe rises all the way to (probably) the back of the boat, this can be awkward as the boat is usually ballasted lower at the back. Expansion pipe with tank perched on top taken FROM the highest point of the pipe run, return pipe falls all the way to the back boiler. I have always used 1" dia pipe. It can look a bit amateurish but when you get back to the boat in February, its freezing and the battery is flat it is great to be able to light the fire with no fear of the pump not working. Also use antifreeze as if it freezes somewhere it won't circulate and the boiler makes funny noises and then goes bang.

I have done many systems with 5 kw boilers using only 22mm main and 15mm pipes to radiators without problems but you have to get the rises and falls dead on and no dips and few elbows, but then I have been doing it for 50+ years!  Depends on boat size and layout. If you have 2 circuits with the boiler between them you should be fine with 22mm.

[volmaakt]

Just running radiators off the stove. Have an instant gas heater for water. My plan is for the expansion tank to be at the front end of the boat (bathroom). I had planned it to be after the two radiators on the fore run and fed into the return. This is the highest point on both the fore and aft run. Can the tank be in a room or should it be behind/under something?

Was planning on using 28mm copper for the first 150 cm and then dropping down to 22mm hep.

[Tracy D'arth]

2 minutes ago, volmaakt said:

Just running radiators off the stove. Have an instant gas heater for water. My plan is for the expansion tank to be at the front end of the boat (bathroom). I had planned it to be after the two radiators on the fore run and fed into the return. This is the highest point on both the fore and aft run. Can the tank be in a room or should it be behind/under something?

No tank is in the flow, top pipe to vent, not the return. Put it where you like, get inventive and make a feature of it!  Lav cistern? imitation fish tank?

[ditchcrawler]

3 minutes ago, Tracy D'arth said:

  imitation fish tank?

Tropical ?

[Tracy D'arth]

1 minute ago, ditchcrawler said:

Tropical ?

Sharks, I did say inventive.

11 minutes ago, volmaakt said:

Just running radiators off the stove. Have an instant gas heater for water. My plan is for the expansion tank to be at the front end of the boat (bathroom). I had planned it to be after the two radiators on the fore run and fed into the return. This is the highest point on both the fore and aft run. Can the tank be in a room or should it be behind/under something?

Was planning on using 28mm copper for the first 150 cm and then dropping down to 22mm hep.

Agreed. I would use copper for the first metre at least, plastic gets terribly soft when hot and its hard to support it behind the boiler.

[volmaakt]

I’ve got an old Demi-john, could add coloured water and watch it swirl while on the loo...

Thanks for your help, I’m sure I will have more questions when I start. Oh, one more, might be stupid. Can you use a back boiler stove as just a stove before connecting all the pipe work etc.?

[Tracy D'arth]

35 minutes ago, volmaakt said:

I’ve got an old Demi-john, could add coloured water and watch it swirl while on the loo...

Thanks for your help, I’m sure I will have more questions when I start. Oh, one more, might be stupid. Can you use a back boiler stove as just a stove before connecting all the pipe work etc.?

Not a good idea, the back boiler will get very hot, and damaged,  its thinner than the cast stove and some are/were glass lined. You risk wrecking it.  Can you fit the back boiler later?

You can with a Morso Squirrel but its a faff.

[volmaakt]

It is built into the stove. I suppose I had better get a move on with the radiators etc. then, starting to get a tad chilly up here in Scotland

[David Mack]

On 31/08/2020 at 20:42, volmaakt said:

My plan is for the expansion tank to be at the front end of the boat (bathroom). I had planned it to be after the two radiators on the fore run and fed into the return. This is the highest point on both the fore and aft run.

 

You could take the hot pipe from the boiler into the aft end top tapping of the foremost radiator, and run the feed/expansion pipe out of the forward top tapping. Return pipe can use either of the bottom tappings.

[volmaakt]

I was planning on one circuit to go fore, top tapping for feed and bottom tapping for return and the same to go aft. There are four tappings at the back of the stove. The fore run is to have the header tank and the aft run to have a pipe venting outside, this will be off the feed and will vent higher than the header tank. I have tried to add a picture of the inside of my proposed header tank. If I have then the rest of my message may make sense if not then never mind. At the top left of the picture is an overflow pipe which I was planning on running into the return run back to the stove, bottom right of the picture is where I am planning to feed into the tank from the highest point of my feed from the stove, this is two inches from the bottom of the tank. I wanted to use these points because they are existing, welded fittings from my tanks previous life as a urn. I figured this was preferable to blanking them off and then having to cut new holes into the tank. Does this look feasible?

[Tony Brooks]

6 minutes ago, volmaakt said:

I was planning on one circuit to go fore, top tapping for feed and bottom tapping for return and the same to go aft. There are four tappings at the back of the stove. The fore run is to have the header tank and the aft run to have a pipe venting outside, this will be off the feed and will vent higher than the header tank. I have tried to add a picture of the inside of my proposed header tank. If I have then the rest of my message may make sense if not then never mind. At the top left of the picture is an overflow pipe which I was planning on running into the return run back to the stove, bottom right of the picture is where I am planning to feed into the tank from the highest point of my feed from the stove, this is two inches from the bottom of the tank. I wanted to use these points because they are existing, welded fittings from my tanks previous life as a urn. I figured this was preferable to blanking them off and then having to cut new holes into the tank. Does this look feasible?

 

 

I am not clear on this. The tank is both an expansion tank and reservoir so if the level rises to above the "overflow" level the whole system will be full of water so where is the excess going to go. If you want an overflow it needs to exit the tank and just go into the bilge / outside air.  Personally I would fill into the lowest point in the system and vent from a high point so air is forced upwards as you fill the system. Your "overflow" may well make a good vent.

[Tracy D'arth]

10 minutes ago, Tony Brooks said:

 

I am not clear on this. The tank is both an expansion tank and reservoir so if the level rises to above the "overflow" level the whole system will be full of water so where is the excess going to go. If you want an overflow it needs to exit the tank and just go into the bilge / outside air.  Personally I would fill into the lowest point in the system and vent from a high point so air is forced upwards as you fill the system. Your "overflow" may well make a good vent.

That is OK on gravity, if there was a pump in the system he would get pumping over in the tank.

[volmaakt]

Yes, hadn’t quite thought that one though properly, thank you. So if I used the two existing points would I run the right hand side of the picture point down into the return to the stove and have the other pipe as a vent from the highest point of the feed? A concern is that this pipe is only 10mm, is this enough to vent if I ran 15 or 22 up to it

This is a gravity system and just radiators.

[Tracy D'arth]

All completely unnecessary on a gravity system. Simply take the bottom of the tank to the high point of the system with 15mm pipe, it will function as the fill, expansion and vent combined. In the unlikely event that you boil the system it will be fine, thousands of others are the same. Put a loose lid on the tank to stop any splash just in case.

[volmaakt]

Thanks. I have a lid for the tank. Would the point on the right of the picture serve for this even if it is a couple of inches off the bottom of the tank assuming the water level would be kept above this? Should I just leave the other pipe in the tank be?

[Tracy D'arth]

2 hours ago, volmaakt said:

Thanks. I have a lid for the tank. Would the point on the right of the picture serve for this even if it is a couple of inches off the bottom of the tank assuming the water level would be kept above this? Should I just leave the other pipe in the tank be?

Fine, just seal the vertical pipe off.

[volmaakt]

Thank you for all your help.