A few back boiler questions...

[kayDee]

Hi all...

We're going to go down the back boiler route to heat our back cabin. What I'd really appreciate knowing is:

 

Can I run 2 x 15mm copper pipes from the back boiler directly to the radiator with a pump in series with one of the pipes?

How do you get water into the system?

Does it need some kind of header tank or something? What can I use?

Can anyone recommend a pump? Do they do a 12V one that can handle hot water?

The stove is back to back with one of our galley cupboards - can the pump live in the back of the cupboard?

Will a pump handle pumping the water about 50' to the back cabin?

Can more than one radiator be added? To add it, do you just put it in series with the pipe coming from the pump?

Do the pipes need to be lagged? Will the heat get through okay?

Sorry about all this... We need to arrange some heating fast so we can get my daughter onboard asap!

Any help is REALLY appreciated with this - we're okay at DIY and running the pipes etc - just need to know what the basics are and safety issues etc!

I will try and make this my last thread about heating - I feel bad for going on and on and on and on about it! I think the diesel heating route isn't practical at all.

Thank you!

Kay

x

[denboy]

Hi all...

We're going to go down the back boiler route to heat our back cabin. What I'd really appreciate knowing is:

 

Can I run 2 x 15mm copper pipes from the back boiler directly to the radiator with a pump in series with one of the pipes?

 

yes

How do you get water into the system?

Does it need some kind of header tank or something? What can I use?

yes to fill the system an plastic expansion tank from a car or truck will do

 

Can anyone recommend a pump? Do they do a 12V one that can handle hot water?

jabsco one from garry http://www.jabsco.com/products/marine/circ..._2558/index.htm not the cheapest but reliable

The stove is back to back with one of our galley cupboards - can the pump live in the back of the cupboard?

yes the above pump is so silent

Will a pump handle pumping the water about 50' to the back cabin?

yes you put it on the return pipe

Can more than one radiator be added? To add it, do you just put it in series with the pipe coming from the pump?

Do the pipes need to be lagged? Will the heat get through okay?

no lagging required

Sorry about all this... We need to arrange some heating fast so we can get my daughter onboard asap!

Any help is REALLY appreciated with this - we're okay at DIY and running the pipes etc - just need to know what the basics are and safety issues etc!

I will try and make this my last thread about heating - I feel bad for going on and on and on and on about it! I think the diesel heating route isn't practical at all.

Thank you!

Kay

x

[sociable_hermit]

Mine has a header tank at the top of the steps by the rear doors - the overflow is piped into the bilge. The header is a good 6" above the radiator. The bottom pipe from the radiator drops about 5" en route to the back boiler, but the boat is stern-heavy so the actual drop is nearer 4". This is more than sufficient and the rad stays nice and warm.

 

Gravity and convection are your friends - don't use a pump unless you have to.

[denboy]

Mine has a header tank at the top of the steps by the rear doors - the overflow is piped into the bilge. The header is a good 6" above the radiator. The bottom pipe from the radiator drops about 5" en route to the back boiler, but the boat is stern-heavy so the actual drop is nearer 4". This is more than sufficient and the rad stays nice and warm.

 

Gravity and convection are your friends - don't use a pump unless you have to.

you wont get a gravity system to work through 15 mm pipe though

[kayDee]

Thanks for that people. I mentioned the pump so I wouldn't have to run the pipes on an angle all the way to the radiator. Does anyone have some photos of how they've connected up their systems so we can get an idea? I'm just not sure how the header tank thing connects into the system with it being a plastic container? Sorry for the questions - this will be very basic to some people but its hard to picture how things are connected up - we'd probably mange it with a few photos. Does it matter where the header tank is on the system? Can it be at the stove end?

Thank you...

Kay

x

[Chris Pink]

Thanks for that people. I mentioned the pump so I wouldn't have to run the pipes on an angle all the way to the radiator. Does anyone have some photos of how they've connected up their systems so we can get an idea? I'm just not sure how the header tank thing connects into the system with it being a plastic container? Sorry for the questions - this will be very basic to some people but its hard to picture how things are connected up - we'd probably mange it with a few photos. Does it matter where the header tank is on the system? Can it be at the stove end?

Thank you...

Kay

x

 

Mr Hermit has it about right, use as much gravity as you can, a pump will annoy on a quiet evening.

 

28mm copper pipe with a gradual rise to the radiator and a gradual fall back (not that difficult to arrange on a boat) with a 15mm spur to the header tank at the furthest point of the system. You can run the system pressurised (header cap on) or un-pressurised (header cap off) to give you a bit more control.

[saltysplash]

Mine has a header tank at the top of the steps by the rear doors - the overflow is piped into the bilge. The header is a good 6" above the radiator. The bottom pipe from the radiator drops about 5" en route to the back boiler, but the boat is stern-heavy so the actual drop is nearer 4". This is more than sufficient and the rad stays nice and warm.

 

Gravity and convection are your friends - don't use a pump unless you have to.

 

 

Hear Him

[Proper Job]

Your best bet is to use 22mm pipe and have a thermal system.

 

I had one on a 50'er and it worked really well with two rad's. Keep the pipework unlagged as they act as skirting heaters throughout the length of the boat. As sociable hermit say, header tank as high as possible (open vented) as far away as possible from the heat source.

 

The new boat doesn't have a back boiler in the stove and the back of the boat is a bit chilly in the mornings

 

I am seriously thinking about a conversion or trading it in.

[Justme]

You can run the system pressurised (header cap on) or un-pressurised (header cap off) to give you a bit more control.

 

Before you take this advice you should seek the advice of a professional. My understanding is that you should never run a solid fuel boiler with a pressurerised system as the heat source is uncontrolable (IE you cant turn it off instantly like you can with gas & oil) so you could be creating a large pressure bomb.

 

 

 

Justme

[Proper Job]

Before you take this advice you should seek the advice of a professional. My understanding is that you should never run a solid fuel boiler with a pressurerised system as the heat source is uncontrolable (IE you cant turn it off instantly like you can with gas & oil) so you could be creating a large pressure bomb.

 

 

 

Justme

I've only ever run 'open vented' and a sight glass (clear plastic tube) to ensure that it always has water in the header tank

[kayDee]

If I go for the convection / gravity idea (open vented), how much of a gentle incline are we talking on the pipes? Is 22mm okay or is bigger better (pardon the wording!) ?

Can you fit pipes bigger than 15mm into radiators or do you need to fit reducers at the radiator end? Does the header tank spur off the return pipe from the radiator?

I'm wondering about this incline up to the radiator because the pipe run is quite long - what looks like a gentle incline could be quite a height at the radiator end!

If I want just one radiator; is it a case of one pipe from the stove into one side of the radiator and the other pipe from the stove into the other end of the radiator? Simple as that?

Thanks

Kay

x

 

Will air just work its way up to the highest point - the vented header tank?

[sociable_hermit]

Yes, the pipe to the header tank comes off the top of the radiator at the other end to the stove connections. So it connects to the highest point in the rest of the system and the tank itself is the highest point of all. Any air should make its way up to the header tank (though note use of the word 'should'). My header tank is metal and appears to be some sort of Army water container - complete with a 1p coin braized on the front to repair a hole! It has a car-style sprung radiator cap with an open vent pipe beneath, which has been plumbed down to the bilge just in case it should ever overflow. Because it's so much higher than the rad it only needs to be half full and I've never seen it boil up.

 

Rather than all of the pipes being angled, mine has two braided hoses that curve up in a lazy 'S' to the radiator (i.e. a double curve, but it doesn't curve back on itself). The fixed pipes and the rad are simply angled enough to compensate for the angle the boat sits at. A gradual angle probably works better in theory, but in practice this arrangement appears to work just fine. It also looks neat. Someone (not me!) obviously spent a lot of time getting this right.

 

The only thing I wish it had is a drain tap between the lower braided hose and the bottom of the radiator, so I could drain and flush through the radiator in a controllable manner! This wouldn't drain the system completely, as the bottom of the back boiler is lower down, but it would be just the right height to get a decent sized container underneath

 

Edited to say: some sort of sight glass on the header tank would be useful, too.

Edited October 21, 2008 by sociable_hermit

[kayDee]

Hi...

Is this about right then people?

Kay

x

[blackrose]

If I go for the convection / gravity idea (open vented), how much of a gentle incline are we talking on the pipes? Is 22mm okay or is bigger better (pardon the wording!) ?

Can you fit pipes bigger than 15mm into radiators or do you need to fit reducers at the radiator end? Does the header tank spur off the return pipe from the radiator?

I'm wondering about this incline up to the radiator because the pipe run is quite long - what looks like a gentle incline could be quite a height at the radiator end!

If I want just one radiator; is it a case of one pipe from the stove into one side of the radiator and the other pipe from the stove into the other end of the radiator? Simple as that?

Thanks

Kay

x

 

Will air just work its way up to the highest point - the vented header tank?

 

The top run doesn't have to incline all the way to the last rad because as soon as the water leaves the backboiler it will be cooling. So have a short steep incline from the backboiler and then a gentle incline to the first rad. Then you can just have it level or a very gentle decline to the last rad. The run should go around the last rad and ideally it should decline all the way back without any incline to get it back into the backboiler. This can be difficult on a long run so you may have to use longer, low height rads.

 

Where you have to take the main run through 90 degrees try to use 2 x 135 degree bends instead - think about making it easier for the water to run around the system. That's why you will need to use 22mm or even 28mm pipe if you can.

 

I tried T-ing the header tank off the return run (using black car heater hose), but the system made too much noise and I ended up changing it so it comes off the top run at the highest point. The benefit of that is that it's self bleeding too, but I had to vent the header tank out the side of the boat because I think it was making the boat too humid.

 

Don't forget about a tap at the bottom of the main run so you can drain the system if you need to.

 

I know you want to do install your system quick, but a thermocycling system will probably need to be more carefully thought out than a pumped system, so take your time.

 

Here are a couple of pictures which might help.

 

Header tank (will eventally be in a cupboard)

 

Connection to header tank

 

Last rad

 

Hi...

Is this about right then people?

Kay

x

 

No, the top run needs to go to the top of the rads and run at that height. The header tank can come off of the rad as in your picture or off the main run - whichever is highest

Edited October 21, 2008 by blackrose

[sociable_hermit]

If it's only one radiator you can put the pipes to/from the back boiler top and bottom of the rad at the same end, and the pipe from the header to the top at the other end. Still seems to work. It's a lot simpler than the multi-radiator systems shown in the photos!

[kayDee]

If it's only one radiator you can put the pipes to/from the back boiler top and bottom of the rad at the same end, and the pipe from the header to the top at the other end. Still seems to work. It's a lot simpler than the multi-radiator systems shown in the photos!

 

Thanks for the reply. Won't it create too much of an incline to feed the radiator from the top? Or does it not work like that?

Kay

x

[sociable_hermit]

That's not an issue - in fact it's got to have the height difference in order for the water to circulate.

 

I think the key things are that:

1. the lower pipe from the rad to the back boiler is lowest in the system, without dipping below the level of the back boiler itself,

2. the higher pipe runs at a height which is higher than the back boiler (and the lower pipe) but lower than the top of the radiator, and

3. the header tank is the highest point in the whole system.

 

The header tank keeps the whole lot full of water - it shouldn't contain any air. Convection causes hot water to rise in the back boiler and make its way along the upper pipe and into the radiator. As the radiator emits heat the water cools and sinks to the bottom, flowing back towards the back boiler along the lower pipe. Whereupon it gets heated up again and starts the cycle once more.

 

It would be worth getting a second opinion on these points, though! Memory fade...

 

Personally given the distance you're covering I'd put the pipes in relatively straight, with heatproof flexible hoses up onto the radiator. Shallow angles are very hard to get right, both in terms of positioning and jointing!

Edited October 21, 2008 by sociable_hermit

[LEO]

Hi,

 

I would have connected the feed from the expansion tank into the return pipe to the boiler, The way you have shown it will result in water in the expansion tank becoming hot. Air could then be bled from the radiator by a normal bleed screw. Not sure what others think.

 

Hope this helps, - the original 'avatar' still looks good.

 

Albi.

[sociable_hermit]

I would have connected the feed from the expansion tank into the return pipe to the boiler

 

I think, if I'm imagining that correctly, it would prevent any air from finding its way back to the header tank and thence to atmosphere, as it would get stuck in the top of the radiator.

 

The header tank can get hot - it depends on the distance between the header and the radiator. One advantage of plumbing both pipes to/from the back boiler in at the same end of the radiator is that the opposite top corner will be slightly cooler, if this is where the pipe from the header tank is attached. If the pipe to the header is copper this will all act as a heatsink to a certain extent, too. The height and capacity of the tank itself is also an issue - if it's only 1/4 full when cold, and a long way up from the radiator, it's less likely to boil up and/or overflow when the system gets hot.

[LEO]

Hi,

 

As stated, air can be removed from the rad. by a bleed screw.

 

Albi.

[bottle]

I agree with Leo.

 

Just think about the initial filling, if the water is flowing into the system at the top, how is the air going to get out.

 

When the system is up and running there may be a need to bleed as the gasses build up but this would reduce in time.

 

I await the experts.

[Chris Pink]

Before you take this advice you should seek the advice of a professional.

 

 

My understanding is that you should never run a solid fuel boiler with a pressurerised system as the heat source is uncontrolable (IE you cant turn it off instantly like you can with gas & oil) so you could be creating a large pressure bomb.

 

 

 

Justme

 

Yep, did that, the 'advice of a professional bit', and I have a header tank with a pressure relief cap (as far as i know all expansion tanks sold for the purpose have such a cap). When the fire is hot the system works better - it's quieter and the radiator gets hotter. But when the fire is ticking over i prefer to run it open even though it's a bit bit noisier it seems to flow easier.

 

Won't it create too much of an incline to feed the radiator from the top?

 

What works for me is to take the initial outlet up from the fire at 45° and then start the gentle rise. 28mm is recommended diameter of pipe. The return goes down so that the lowest point of the system is at the bottom of the stove.

 

I had another system done once with 22mm pipe and the header tank coming off the bottom pipe. Didn't work although it may not have been those factors as no 2 systems are alike.

[Justme]

Dint consider that you used a car type header tank & not a domestic pressure tank. I guess that would be the best of both worlds.

 

Justme

[blackrose]

I think there's some confusion here between pressurised systems (of which I have no knowledge but personally wouldn't fit to a solid fuel stove backboiler), and an open unpressurised system such as mine. With the latter there is no need for any bleed nipple or pressure release valve as long as the header tank is Td off from the highest point of the top run. It will then self-bleed.

[LEO]

Hi,

 

I tend to agree with the comments about not fitting pressurised hot water systems. I suggested connecting the expansion tank to the lower pipe as I have found that connecting said tank to the highest point leads to one having an expansion tankful of hot water - a steaming extravagance.

 

Once the air has been drained out of the radiator no further bleeding should be needed and hopefully water in the expansion tank will remain cool.

 

I have the former arrangement (connecting the expansion pipe to the highest point) and it is quite useful having the warm/hot expansion tank in the engine room as it acts as a small rad when the heating/hot water circulating pipes are being run as a pumped or gravity system.

 

ATB.

 

Albion.

Edited October 22, 2008 by LEO