Radiator circuit install

[Black Ibis]

I'm going to be installing radiators running off the backboiler of a stove in a boat, and was wondering what people thought of the following layout:

 

 

 

The arrangements are:

 

-Stove with backboiler

 

-22mm copper pipe to Bolin circulation pump under gunwale

 

-Tee off 15mm for small rad in bathroom

 

-Duck under floor of bathroom (one unbroken length of 22mm speedfit) from right hand side of boat to left hand side under gunwale

 

-Tee off 15mm for two other radiators

 

-Header tank (Open? Or pressurised?)

 

-22mm return (also going under bathroom floor back to the right hand side) back to backboiler.

 

 

Do you think the diving under the floor to change sides will be OK? It's possible to keep it all on the right hand side, but changing to the left part way through does make more sense with my planned layout. I guess that would rule out any thermosiphoning at all, but then, so would running it under the gunwale and teeing off for the rads. It does rely completely on the circulation pump, which I guess could be a liability; it might be worth carrying a spare to ensure I can always run the heating.

 

I'm also not sure that it's best to tee off for the rads rather than having the pipe run all the way through, but I suppose this way, all get equally hot, rather than the last one receiving almost cold water.

 

The Bolin will be switched on by a thermostat on the pipe from the back boiler.

 

Edit to add: there's a good 50' between the stove and the furthest radiator, it's a BIG boat!

Edited February 5, 2013 by Black Ibis

[Robbo]

The pump should be on the cold side.

[FadeToScarlet]

The pump should be on the cold side.

 

Interesting, the specs for the pump say it can be installed anywhere in the system.

 

It's not a problem to have it on the cold side, though.

[Robbo]

Interesting, the specs for the pump say it can be installed anywhere in the system.

 

It's not a problem to have it on the cold side, though.

 

The water isn't as hot on that side so the pump should last longer. And as its lower in height it will always be primed than having it on the hot side from the stove.

Edited February 5, 2013 by Robbo

[FadeToScarlet]

The water isn't as hot on that side so the pump should last longer. And as its lower in height it will always be primed than having it on the hot side from the stove.

 

Thanks, that makes sense.

[nb Innisfree]

How about a heat sink in case the pump fails and or the boiler runs away, also there is no vent.

 

Edited to make sense.

Edited February 5, 2013 by nb Innisfree

[FadeToScarlet]

How about a heat sink in case thepump fails and or the boiker runs away, also there is vent.

 

What sort of heat sink?

 

If I ran a copper pipe down and attached it to the baseplate, for example?

[nb Innisfree]

What sort of heat sink?

 

If I ran a copper pipe down and attached it to the baseplate, for example?

 

It has to be independant of pump so wouldn't work. Perhaps a rad on thermo syphon as near to boiler as poss.

 

Or maybe the header tank near to and above the boiler, make it big enough to dissipate heat.

Edited February 5, 2013 by nb Innisfree

[Robbo]

What sort of heat sink?

 

If I ran a copper pipe down and attached it to the baseplate, for example?

 

A radiator makes a good heat sink!

[nb Innisfree]

Edited.

Edited February 5, 2013 by nb Innisfree

[FadeToScarlet]

It has to be independant of pump so wouldn't work. Perhaps a rad on thermo syphon as near to boiler as poss.

 

Or maybe the header tank near to and above the boiler, make it big enough to dissipate heat.

 

Ok, that makes sense.

 

If I run the 22mm hot under the gunwale, and the cold return along the floor, I can tee a rad into that, and it ought to thermo siphon, especially if the pipe between back boiler and rad rises up.

 

Edit: stupid question, what do you mean by a vent? If the header tank is open to the atmosphere at the top?

 

Thinking about thermo siphoning, I could tee off the back of the stove, and have a thermosiphoning radiator - with the angled pipes out of the way behind the kitchen units - right at the front of the boat, to the left of the stove, and a separate circuit to the right with the Bolin pumping around.

 

I think that's what Blackrose has on his boat, will do a search to see if it is.

Edited February 5, 2013 by FadeToScarlet

[nb Innisfree]

Ok, that makes sense.

 

If I run the 22mm hot under the gunwale, and the cold return along the floor, I can tee a rad into that, and it ought to thermo siphon, especially if the pipe between back boiler and rad rises up.

 

Edit: stupid question, what do you mean by a vent? If the header tank is open to the atmosphere at the top?

 

Thinking about thermo siphoning, I could tee off the back of the stove, and have a thermosiphoning radiator - with the angled pipes out of the way behind the kitchen units - right at the front of the boat, to the left of the stove, and a separate circuit to the right with the Bolin pumping around.

 

I think that's what Blackrose has on his boat, will do a search to see if it is.

 

Yes a header tank would act as a vent if it was on a clear run from the boiler especially if it was near to it.

 

I questioned the vent because the header tank looked a bit remote and possible on small pipes.

 

ETA: I would connect the bottom of header tank to the return and the flow into the top to act as a vent in case of boiler runaway, in that setup pump would need to be on the return to stop water circulating through header tank.

Edited February 5, 2013 by nb Innisfree

[FadeToScarlet]

Yes a header tank would act as a vent if it was on a clear run from the boiler especially if it was near to it.

I questioned the vent because the header tank looked a bit remote and possible on small pipes.

 

Gotcha. Could be on the lookout for a slim but high volume header tank to put in the saloon on the wall, then, so it's close to the fire- and large, too, to act as a heatsink.

 

Maybe with a nice copper front panel to polish!

 

Might a second header tank, on the other side of the dip under the floor, might be useful?

[nb Innisfree]

Gotcha. Could be on the lookout for a slim but high volume header tank to put in the saloon on the wall, then, so it's close to the fire- and large, too, to act as a heatsink.

 

Maybe with a nice copper front panel to polish!

 

Might a second header tank, on the other side of the dip under the floor, might be useful?

 

I've added an edit to my post. One header tank will do provided it's big enough to contain any expansion if water boil, if its in the lounge I would fit a watertight lid and vent it outside just in case, you don't want overflow all over the floor!

 

ETA: on the other side an automatic airvent would prevent any airlocks.

Edited February 5, 2013 by nb Innisfree

[rjasmith]

Maybe with a nice copper front panel to polish!

 

How about looking in eBay for an old copper, water type fire extinguisher? Just needs the innards removing (remove cap and take them out), drill hole in bottom and fit a compression tank connector for the feed pipe (may need soldering to get a good seal), use the fire hose outlet as an upper tank air vent and refit the cap as an inspection/top up facility.

 

Plenty of bling about it to keep polished!

 

I took a separate 22mm vent pipe up to a roof outlet for safety vent purposes as the fire extinguisher hose outlet is too small for this. (A dummy mushroom vent sits over this to stop anyone on the roof getting a surprise turkish bath in the event of an overboil!) I also fitted a piece of polycarbonate tube between fire hose and bottom connection to make a sight glass for checking the level.

 

Richard

Edited February 6, 2013 by rjasmith

[n.b.Goldie]

Why bother with a pump? Thermosyphon on 22mm pipe will work well, be totally silent and will not require electricity.

Just make sure the hot from the boiler runs high, perhaps under the gunnell and the cold (return) runs no higher than the input to the boiler.

I have used this system on my previous boat and it worked brilliantly. As long as there was heat in the (squirrell) Stove we had central heating.

RegardsDitchdabbler

[FadeToScarlet]

Why bother with a pump? Thermosyphon on 22mm pipe will work well, be totally silent and will not require electricity.

Just make sure the hot from the boiler runs high, perhaps under the gunnell and the cold (return) runs no higher than the input to the boiler.

I have used this system on my previous boat and it worked brilliantly. As long as there was heat in the (squirrell) Stove we had central heating.

RegardsDitchdabbler

 

The reason we are using a pump is that a) the boat is 72ft long we want to use the wall space for bookshelves, not have all the walls on one side taken up with gigantic pipework. Our current boat has one rad thermosyphoning off the backboiler and that works fine, but it's only a little boat and even then the bedroom only gets properly warm when the stove is on full blast.

[smileypete]

I'm going to be installing radiators running off the backboiler of a stove in a boat, and was wondering what people thought of the following layout:

First off, running a pressurised system on a SF stove is a definite no-no.

 

Might be worth having a big radiator in the saloon to give more choice on where the backboiler heat goes. If so, it might as well be gravity fed and save the problem of pump failure as long as the rad and pipework is big enough.

 

With gravity, hot water from the back boiler needs to be able to rise as much as poss and find a radiator. If the system starts to boil, the steam will head towards the header tank vent, make sure it doesn't oppose the thermosyphon in doing so, if it helps the thermosyphon all the better.

 

With pumped or gravity, any dissolved air coming out of the water needs to be able to rise and find a radiator, a header tank vent, or a bleed valve, and not get stuck in an inverted U of pipe.

 

Could be useful to find someone with a good working system and see what's involved. Also look into what's involved for domestic gravity and pumped systems.

 

cheers, Pete.

~smpt~

Edited February 6, 2013 by smileypete

[Ian Mac]

Now then this is a job I've always fancied having a go at. My old gaffer designed and fitted a Solid fuel central heating system in a bungalow, that's not that clever, doing it without a pump is. The art is fitting the biggest pipe that the boiler has as a outlet for, preferably to the top of the boiler so the pipe rises directly upwards, one can up the size but the initial throttling matters. If the connection comes out the back you have to use a large slow sweep, the slower the better. The large pipe should go as high as it possibly can, then still rising on maybe a 1 in 100 climb, with the boat in its most nose light mode, assuming you are running the pipe towards the back. This is a good reason for having the fire at the back of the boat, but I know most are at the front!

The size of the near horizontal pipe should be such that its volume is slightly less than that of the vertical pipe. The junction between the vertical and the near horizontal should be made with a large radius swept T the upright should either continue up and be an open vented or have a safety valve fitted, both must be external to the cabin. The radiators then come off the horizontal in small pipes vertically down to the radiator top, from the bottom of the radiator should come a large pipe down to the lower return horizontal, again this should fall from the far radiator all the way back to the fir at about 1 in 100. This return pipe should be the same size as the horizon flow, and should ideally arrive at the boiler return port directly, ie it should not need a vertical piece. If it does then this needs to be the same size as the horizontal return, and the corner piece should be a slow sweep.

Now you can actually work out the sizes given the known stiction of the pipe, you can find this on the interwebbie I'm sure, and its length and the temperatures required in each radiator. On the other hand one just adjusts the return check values appropriately. You also have to get you boiler size right for the required room temperatures.

Also remember when sizing your boiler that the return temp should not fall below 25degrees c otherwise you will get condensation forming inside your boiler and this will rot it for fun.

--

Cheers Ian Mac

[Black Ibis]

With some help from the ever knowledgeable MoominPapa and this thread, our current plan for the heating layout is as this shows. First rad to be thermosyphoning.

 

http://farm9.staticflickr.com/8245/8453180934_93b070ff3a_b.jpg[/img

Edited February 7, 2013 by Black Ibis

[nb Innisfree]

With some help from the ever knowledgeable MoominPapa and this thread, our current plan for the heating layout is as this shows. First rad to be thermosyphoning.

 

http://farm9.staticflickr.com/8245/8453180934_93b070ff3a_b.jpg[/img

 

Pump needs to be the last port of call for water returning to boiler, at the moment it could short circuit through the header tank.

 

ETA: Also the the red overflow pipe into top of tank ought to be larger diam than the one going in to the bottom otherwise in the event of a boilover water will take path of least resistance which could be the blue pipe and result in header tank contents being pushed out.

 

I assume the tank is sealed apart from overflow pipe otherwise it will overflow rather than exit via the higher overflow pipe.

Edited February 7, 2013 by nb Innisfree

[MoominPapa]

With some help from the ever knowledgeable MoominPapa and this thread, our current plan for the heating layout is as this shows. First rad to be thermosyphoning.

 

http://farm9.staticflickr.com/8245/8453180934_93b070ff3a_b.jpg[/img

The pump should be in the pipe to the boiler. so it pumps around all the radiators. Bolin pumps allow free circulation when they're off, so it won't stop the bathroom rad working in thermosyphon when the pump is off. As you've drawn it there's a risk that some of the circulation will just go around the radiators and miss the boiler.

 

 

Also, what does the team think of this to avoid air collecting in the two rads which are fed via under-floor pipes?

 

 

MP.

[Ian Mac]

Two things about your design.

1) larger pipe to vent the system please, boiling water expands the volume by a huge amount it will need a way to escape easily, not by a twisted small pipe, run at least 22mm pipe up, at least, 28mm better. The pressure can rupture small pipes, then you have real problems.

2 Don't forget the 25C rule for returning water. A cold return really does rot boilers It also encourages it to rot from the inside out, so you don't see it happening till its a puddle on the floor! You should have two thermostats, one on the return which inhibits the pump while the water is cold and another which runs it, come what may, because the flow is getting too hot.

--

cheers Ian Mac

[FadeToScarlet]

OK, taking into account (I think) all the contributions so far....

 

 

Edit: Probably also with 28mm up to the roof vent, so it can vent easier from the header tank, giving an easier path for the water than to go to the wrong, cold side.

Edited February 7, 2013 by FadeToScarlet

[MoominPapa]

OK, taking into account (I think) all the contributions so far....

 

 

Edit: Probably also with 28mm up to the roof vent, so it can vent easier from the header tank, giving an easier path for the water than to go to the wrong, cold side.

 

Looks good. You can probably use 22mm all the way from the plastic to rads 2 and 3, to avoid changing sizes again, if that makes life easier. (28mm fittings are eyewateringly expensive)

 

Mp.