Back Boiler system

[Boatman Al]

Hi,

 

So ive been looking into installing a diesel heater, but as a liveaboard im now under the impression that they can be very costly to run, maintain, service etc. Especially with fuel prices rocketing. So im now wondering how easy a task it would be, and how cheaper it might be to install one radiator at the back of the boat, attached to the stove that is closer to the bow.

 

Do some stoves already have a back boiler built in? The owner of the boat ive just bought claims the stove onboard has one that has been sealed up with putty?? I definately did spot a sealed pipe hole on the back.

 

Can i buy any old back boiler from a chandlers and fit it to any stove? The stove onboard doesn't seem to be any obvious model or brand.

[Grace and Favour]

Hi,

 

So ive been looking into installing a diesel heater, but as a liveaboard im now under the impression that they can be very costly to run, maintain, service etc. Especially with fuel prices rocketing. So im now wondering how easy a task it would be, and how cheaper it might be to install one radiator at the back of the boat, attached to the stove that is closer to the bow.

 

Do some stoves already have a back boiler built in? The owner of the boat ive just bought claims the stove onboard has one that has been sealed up with putty?? I definately did spot a sealed pipe hole on the back.

 

Can i buy any old back boiler from a chandlers and fit it to any stove? The stove onboard doesn't seem to be any obvious model or brand.

 

Back boilers are specific to each stove. . . .

 

 

You'll need to identify the stove - - - can you post a photo on here and doubtless someone will know what it is:

 

 

HOWEVER - depending upon the age and condition of the stove - (and why the 'sealed hole at the back was sealed in the first place!) - I would suggest if at all possible, bet a new stove and back boiler - - it'll still be cheaper than fitting a diesel stove!

[Boatman Al]

As far as im aware the stoves outlets were sealed when the owner ripped out the radiators as he didnt want them in. Ive been reading about gravity fed systems and ive found these alde finrad convector rads. does a gravity fed system need a header tank? as the side of the boat that the system will run on doesnt have n available place for it.

[Higgs]

As far as im aware the stoves outlets were sealed when the owner ripped out the radiators as he didnt want them in. Ive been reading about gravity fed systems and ive found these alde finrad convector rads. does a gravity fed system need a header tank? as the side of the boat that the system will run on doesnt have n available place for it.

 

 

Hi Al,

 

Got your PM. Wondered where you'd gone. See you've got another boat.

 

If you need some help with backboiler stuff, PM me and I'll drop by. Higgs

[Smelly]

You will need to ake provision for expansion of the coolant. If space is an issue you could seal the system and use and expansion vessel however when it fails there will be a mess... A header tank is the ideal; it needs to hold at least 4% of the coolant capacity.

[Chertsey]

I've a feeling that if the stove has been used for a while with the back boiler dry, the back boiler is likely to be knackered.

[Davo_Willow]

Hi,

 

So ive been looking into installing a diesel heater, but as a liveaboard im now under the impression that they can be very costly to run, maintain, service etc. Especially with fuel prices rocketing. So im now wondering how easy a task it would be, and how cheaper it might be to install one radiator at the back of the boat, attached to the stove that is closer to the bow.

 

Do some stoves already have a back boiler built in? The owner of the boat ive just bought claims the stove onboard has one that has been sealed up with putty?? I definately did spot a sealed pipe hole on the back.

 

Can i buy any old back boiler from a chandlers and fit it to any stove? The stove onboard doesn't seem to be any obvious model or brand.

 

I am interested in any responses to this. I have a Morso squirrel with back boiler fitted but pipes are not connected. I also have a central heating pump installed in the engine bay but not connected to anything. What should I do?

 

If someone could post a diagram it would be appreciated!

 

Davo

[Boatman Al]

I think ive figured the bulk of this problem out. my remaining questions are:

 

1. I have nowhere suitable on the side of the boat where rads and stove are to box or put a header tank, unless it was a rather thin tank that wouldnt affect passage down the corridor. What kind of tank is required? how small can i get away with? plastic or metal? where from?

 

2. where do you get good suitable rads from? i cant find any online apart from old house ones.

 

3. could you put finrads into the piping aswell as rad?

[Manxcat]

2. Where do you get suitable rads from....

 

Are these any use to you?

[Smelly]

Post a photo of your stove and someone will probably be able to ID it.

 

As a liveaboard I'd suggest you look to a thermosyphoning setup; you'll come to a time when your batteries are at the end of their life and you'll resent the wattage a pump is consuming.

[steve hayes]

As a liveaboard I'd suggest you look to a thermosyphoning setup; you'll come to a time when your batteries are at the end of their life and you'll resent the wattage a pump is consuming.

 

I agree with Smelly, had a squirrel with a back boiler and rads plumbed in 28mm copper pipe that ran from the front of a 55ft boat all the way to the back cabin. Rads were in the bathroom and back cabin. A gentle rise from the back of the squirrel up to the top of the radiator level provided plenty of circulation and heat in the back cabin. We had an expansion tank in the engine room, but it was in the corridor, we were going to move it to the other side of the corridor fed from the lower pipe with the run under the floor, but we sold the boat before I tried this out.

 

The only issue we had was if the stove was got going too quickly the water coughed and banged as the circulation hadn't got going properly.

[geehils]

My boat had a Morso Squirrel with backboiler and circulating pump.

 

It was a complete waste of time, I had the whole lot taken out and now just use the stove to heat conventionally or the Mikuni diesel heater to provide heat via the radiators.

 

The backboiler would never get the radiators anything other than lukewarm and that took hours. You also had to have the pump on 24/7 otherwise water would boil in the backburner and then at regular intervals steam would blast out through the header tank liberally covering the engine room in a nice water/antifreeze mix.

 

Seemed like a good idea, but was very dissapointing and since taking it out the stove burns hotter and doesn't tend to go out.

 

Before taking it out I talked to several engineers to try and fix it, but couldn't find anyone that had anything good to say about these.

 

That's my experience, so I'd check it out carefully before going this route.

[bizzard]

Why bother with the expense of radiators when a nice simple out and back 28mm polished copper pipe would thermo-syphon better and be amply warm enough.

[Chertsey]

Why bother with the expense of radiators when a nice simple out and back 28mm polished copper pipe would thermo-syphon better and be amply warm enough.

That's what we've got on Bakewell (72'), well, OK, not polished. It runs from the Squirrel via a calorifier to a small radiator in the back cabin which just gets warm enough to fend off the damp, but the rest of the boat is very adequately heated and we get hot water as well.

[Higgs]

My boat had a Morso Squirrel with backboiler and circulating pump.

 

It was a complete waste of time, I had the whole lot taken out and now just use the stove to heat conventionally or the Mikuni diesel heater to provide heat via the radiators.

 

The backboiler would never get the radiators anything other than lukewarm and that took hours. You also had to have the pump on 24/7 otherwise water would boil in the backburner and then at regular intervals steam would blast out through the header tank liberally covering the engine room in a nice water/antifreeze mix.

 

Seemed like a good idea, but was very dissapointing and since taking it out the stove burns hotter and doesn't tend to go out.

 

Before taking it out I talked to several engineers to try and fix it, but couldn't find anyone that had anything good to say about these.

 

That's my experience, so I'd check it out carefully before going this route.

 

 

Backboiler systems work well. No need for pump or anything that restricts the flow down from the 28mm circuit. Rads are fitted with 'T' junctions to 15mm. But, there should be a continuous 28mm circuit from and to boiler. Even with rads shut off, the 28mm loop has free flow.

 

I associate boiling with air in the system. Water leaves the top of the boiler at around 50c and shouldn't be in there long enough to boil. It returns at about 25c. Rads about 30c.

Edited May 15, 2012 by Higgs

[geehils]

Backboiler systems work well. No need for pump or anything that restricts the flow down from the 28mm circuit. Rads are fitted with 'T' junctions to 15mm. But, there should be a continuous 28mm circuit from and to boiler. Even with rads shut off, the 28mm loop has free flow.

 

I associate boiling with air in the system. Water leaves the top of the boiler at around 50c and shouldn't be in there long enough to boil. It returns at about 25c. Rads about 30c.

 

The system was regularly bled to make sure that no air locks occurred, yet without the circulating pump on all the time I could guarantee it would boil. For whatever reason the system in my boat just didn't work, I wish it had.

[canals are us?]

You will more than likely find the backboiler is knackered due to being used with no water inside. If I was you I would invest in a new one. If you post a photo of the stove we may be able to identify the stove.

 

If it was me though I would install a new stove with new boiler. On the squirrel, villager puffin etc these small 8-9000btu boilers are actually intended to heat a homes domestic hot water cylinder.

In the case of narrowboats they are used to heat rads or rad & calorifier. These small boilers are fitted as a clip in and can be replaced without having to replace the stove, providing the boiler is still made.

The boilers that are built into the stove are called wraparound or factory fitted and would be way too big for a narrowboat.

Yes I would definately fit a small expansion tank. You could visit a scrapyard and buy a cars expansion tank and just drill a hole in the cap so it doesn't pressurise.

There are many outlets selling radiators. Plumb centre being the largest. As you will be doing a gravity system you want to buy rads with the 4 tappings. I like stelrad as a make.

 

The boilers come in steel or stainless steel. Stainless steel being better as they last longer but dearer.

When I buy a narrowboat I would eventually replace the inherited stove for a woodwarm fireview 4.5kw.

 

 

Geehills.

 

I think backboilers are great.

 

We have solid fuel boiler stove heating our present house and had another which heated 12 rads.

 

It sounds very much like your morso back boiler system wasnt fitted correctly. It should not boil. The flow pipe should always rise, one to create gravity circulation and two to vent air out the boiler.

 

Or another possibility to many rads, or too big. As a quide an 8,000btu squirrel boiler will only heat two 600mm X 1100 single rads.

There was a diagram on here somewhere on gravity circuit design.

 

James

Edited May 15, 2012 by canals are us?