Back boiler - more trouble than it's worth?

[tjh82]

Hey

 

New to boating and new to the forum so apologies if this has already been discussed a million times, but....

 

I'm currently renovating a 56ft narrowboat and one of the jobs on the list (it's a big list) is replace the stove.

 

It was mentioned when I'm doing this I might want to add a back boiler.

 

Thought this sounded like a good idea, free heat and all that.

 

But then I was told they are loads of faff, unreliable and not to bother.

 

The stove (will be) about halfway down the boat and was thinking of a gravity fed system running to a radiator at the bow end where the bedroom will be.

 

Looking at the Morso Squirrel, so just weighing up if I'll bother with a back boiler too.

 

Any experience, tips or advice much appreciated.

 

Cheers

[Grace and Favour]

There are many boats that have a stove with a back boiler, and they work perfectly well.

 

Fitted properly - there's no reason why it should not be as effective and reliable as any other back boiler.

 

 

However, it is not, of course, 'free heat'. - whatever heat is transported to your bedroom/wherever has to be provided by the stove, so if your radiator is using 1Kw of heat, then that's 1Kw less in your saloon.

 

In saying that, a correctly used 5Kw Squirrel is more than capable of keeping a narrowboat warm.

[bottle]

tjh82

 

Welcome to the forum.

 

I will not say don't just relate our set up, Morso 1430 at very front of boat, bedroom at the rear, 60' boat and temperature gradient throughout the boat is correct for us.

 

We like a cool bedroom but not cold, well not quite, I like cold, other half likes cool.

[cheshire~rose]

We used to have a back boiler. Our boat is 50' and we have a tiny Villager Puffin stove. There are 2 radiators, one half way along the boat and one at the back in the bedroom. They are run with an electric pump that is housed in the bedroom.

 

We could not leave the radiators on overnight due to the noise of the pump. The pump also draws power from the batteries. I appreciate many systems are gravity fed and if ours was this would overcome that problem.

 

Our back boiler corroded through around 3 years ago. We do not miss it at all. We do have an ecofan.

 

Now we are faced with knowing at some point we must get around spending money we wuld rather not to replace the boiler which we do not miss! I did think about getting it taken out but I suspect dismanting a 10 year old stove will not be a trouble free job and is likely to involve bits getting broken because they are seized up. If we dismantle the stove then we might as well fit a new boiler because in years to come when we try and sell the boat someone will wonder what the radiators are for!

 

If I was starting over again I would not bother with a back boiler!

Edited June 9, 2014 by cheshire~rose

[John V]

I know mine is a very fat boat but my back boiler is brilliant it's in a Rayburn Royal stove and it heats the wheelhouse. both bedrooms, towel rail in the bathroom and two hot water tanks, the pump is a normal 240v central heating pump running on a very small pure sine wave inverter and it's virtually silent

[peterboat]

Wouldnt be without my backboiler it heats water and warms all the boat up but it is a fat bottomed boat and a 10kw stove so have to get rid of some of that heat

 

Peter

[Beaker]

Our Willow stove has a back boiler feeding a radiator in the bathroom, which is handy for drying towels, damp coats etc.

 

As far as heating the rest of the boat though, we find the bedroom is plenty warm enough without additional heating, enough heat percolates through from the saloon (with or without the help of the ecofan, the jury's still out on that one).

 

ETA The bedroom also gets some heat from the top of the Alde boiler via the calorifier when we've either had the immersion on or been running the engine. We don't use the gas central heating, probably never will.

Edited June 9, 2014 by Beaker

[tjh82]

Thanks a lot for all the advice and stories...seems a pretty even split!

[canals are us?]

In winter I really like my back boiler and stove (woodwarm fireview 4.5kw) It has a 2.3kw 8,000btu back boiler and heats either 2 rads on my 50ft trad narrowboat or the calorifier.

I turn the gravity rads off and switch the pump on to heat the 55litre calorifier. To heat my calorifier it takes around 2 hours from cold/lighting the fire, once it's heated I turn the pump off and turn the rads back on.

If I wasn't heating the calorifier I wouldn't bother with the backboiler, but needed the rads to dissipate the heat when the calorifier is up to temperature.

I found before installing the back boiler the heat output was more but as my stove is at the front the rads help even out the temps along the boat.

 

James

[blackrose]

If your stove is about halfway down a 56ft boat then I'd say don't bother with a backboiler. However that also depends on how open plan the boat is and how easily heat can convect through the boat.

Edited June 11, 2014 by blackrose

[Ian Fossett]

I am afraid back boilers should never ever be fitted into a pressurised system. I know people do, but it breaks every rule in the book and is extremely dangerous. I have been looking for ages for a way of using our stove heat to heat our water. We are very fortunate to be on mains power so we use a 1kw immersion heater for water heating ,we also have a eberspatcher hydronic running on kerosene and a Firfox multifuel stove. I recently discovered the FHT stove designed by a guy named Simon Redferd . It appears to tick all the boxes and can be easily retrofitted into existing systems. Unlike a backboiler it is designed to be fitted into a pressurised system and cannot overheat if the circulation pump fails. Its main design feature is a fan assisted heat exchanger . I would advise all livaboards to check out the FHT stoves website, the stove is not yet on sale but you can express interest in the product by contacting Simon Redferd. http://www.fhtstoves.com/index.html

[Tony Brooks]

First off the link above makes some claims that are not substantiated by experience and practice. Solid fuel stoves with back boilers have been safely used for years on all kinds of boats and homes when COMPETENTLY installed as a non-pressurised gravity system. If they were as unsafe as implied then the BSS would have had something to say about them.

 

I also note that despite showing a narrowboat diagram they give NO electrical consumption figures. It seems to me to require a fan motor running 24/7 and according to the diagrams a 12V pump. I also suspect that it may not adapt too well to a gravity system as the heat exchanger is horizontal and if so that means an electric pump is mandatory.

 

I have had no problems using a gravity system with a vertical twin coil calorifier to get hot water and a pumped system would be even easier.

 

What is the attraction of a sealed system on a boat? It just makes recharging it with antifreeze mixture rather harder than mixing and filling a header tank.

 

I am tempted to report the last post but on balance think it would be good to discuss the proposition.

[Pete & Helen]

We used to have a back boiler. Our boat is 50' and we have a tiny Villager Puffin stove. There are 2 radiators, one half way along the boat and one at the back in the bedroom. They are run with an electric pump that is housed in the bedroom.

 

We could not leave the radiators on overnight due to the noise of the pump. The pump also draws power from the batteries. I appreciate many systems are gravity fed and if ours was this would overcome that problem.

 

Our back boiler corroded through around 3 years ago. We do not miss it at all. We do have an ecofan.

 

Now we are faced with knowing at some point we must get around spending money we wuld rather not to replace the boiler which we do not miss! I did think about getting it taken out but I suspect dismanting a 10 year old stove will not be a trouble free job and is likely to involve bits getting broken because they are seized up. If we dismantle the stove then we might as well fit a new boiler because in years to come when we try and sell the boat someone will wonder what the radiators are for!

 

If I was starting over again I would not bother with a back boiler!

 

Do you just use your stove with no water in the back boiler now? Thought that if you did that it might melt it

[Tony Brooks]

I think many people fill redundant back boilers with dry sand. I think that you could also cap the external stubs and drill a small hole in the boiler if it has not split) to let expanding air escape. Then it would not matter if it did melt.

[Higgs]

There's no need to have a pressurized system. With an expansion tank and without a pressure cap, the water simply expands into the tank. There is also no need of a pump in a properly fiitted system. It's simple and basic, works and is silent. Usually on, no stop, from October to April.

[blackrose]

I agree with Tony and Higgs. I don't think backboilers should be used as part of pressurised systems, simply because they're not normally designed as pressure vessels. Most cheap pressure vessels have some sort of cylindrical shape to them to cope with the internal pressures. Rectangular cubes have to be much more heavily built if used as pressure vessels otherwise they can split along the edges and corners which are weak points. Few solid fuel stove backboilers are built to that sort of specification.

[HappyBunny]

I have a morso squirrel with back boiler, at the front of my 53 foot narrowboat, and a gravity fed system taking pipes down to the bedroom and twin calorifier .... it is marvelous ... takes the chill off the bedroom without getting too hot, keeps the living room sensibly warm and cosy (as opposed to oppressively hot) and plenty of hot water ... the pipes run through the back of my wardrobe and the cupboard where I keep my sheets, so no damp problems there .....and I can dry my woolly socks on the pipes too .... it's all good

[John V]

I think some of the posts concerning "pressurised" systems are misleading and alarmist.

Ashore these stoves with square or rectangular tanks are used in conventional "open systems" but these in fact are pressurised as the header tank is normally in the loft and the stove 20' or more below.

A properly designed pressurised system on a boat with a correctly sized accumulator tank and the correct pressure emergency relief valve will not expose the boiler to any higher stresses than those for which it was designed.

[smileypete]

A properly designed pressurised system on a boat with a correctly sized accumulator tank and the correct pressure emergency relief valve will not expose the boiler to any higher stresses than those for which it was designed.

 

In one word: No.

 

cheers, Pete.

~smpt~

[b0atman]

I have still to convert my poor radiator system to a proper gravity fed system.

Why oh why are builders now doing installations like household plumbing with pumps for circulation ?

KISS

[Ian Fossett]

UK building regs state that it is permisable to fit a solid fuel stove to a pressurised system provided it is approved by the manufacturer .The problem is you wont find a stove manufacturer or calorifier manufacturer who does. The reason is its very dangerous even more so on a boat . However there is hope on the horizon but its not currently available but hopefully will be soon http://www.fhtstoves.com/ . The designer is a guy called Simon Redford. The FHT stove is 100% safe in the event of pump failure, and is designed to be integrated into a pressurised system. It seems to tick all the boxes as far as boat installation is concerned.

[Beaker]

That's the second time you've posted that link, are you sure you've no connection?

[Ian Fossett]

Wish I did will be worth a fortune!!

[John V]

UK building regs state that it is permisable to fit a solid fuel stove to a pressurised system provided it is approved by the manufacturer .The problem is you wont find a stove manufacturer or calorifier manufacturer who does. The reason is its very dangerous even more so on a boat . However there is hope on the horizon but its not currently available but hopefully will be soon http://www.fhtstoves.com/ . The designer is a guy called Simon Redford. The FHT stove is 100% safe in the event of pump failure, and is designed to be integrated into a pressurised system. It seems to tick all the boxes as far as boat installation is concerned.

 

so you are basicly saying that every hotwater system using a calorifier from an engine cooling system is dangerous....I don't think so (they're presurised to a higher BAR than a central heating system)

 

edit to add my central heating system has a pressure relief valve set at 1 Bar I have just been to check my engine filler cap and that is 20psi approx 1.3 Bar

Edited July 1, 2014 by John V

[blackrose]

 

so you are basicly saying that every hotwater system using a calorifier from an engine cooling system is dangerous....I don't think so (they're presurised to a higher BAR than a central heating system)

 

edit to add my central heating system has a pressure relief valve set at 1 Bar I have just been to check my engine filler cap and that is 20psi approx 1.3 Bar

Calorifiers are pressure vessels made of non-corrosive materials that hopefully have been tested to pressures well above 1.3 bar. The difference is that you have no knowledge that your corrosion prone backboiler has been tested to such pressures, so how do you know it's not going to crack or burst below the set pressure of your PRV?

Edited July 1, 2014 by blackrose