Back Boiler

[The Wind Lass]

We have a small boat (40ft) that was fitted with a back boiler (on a multi fuel)  with 4 radiators. We expected to be roasting with this set up....however, the radiators don't heat up but coolant spews from the header tank when the fire is hot. The coolant looks like it hasn't been cut with water, am thinking that could be the problem. All radiators are open. Any thoughts/advice? 

And, yes we keep the pump on when the fire is lit. 

 

[Tonka]

3 minutes ago, The Wind Lass said:

We have a small boat (40ft) that was fitted with a back boiler (on a multi fuel)  with 4 radiators. We expected to be roasting with this set up....however, the radiators don't heat up but coolant spews from the header tank when the fire is hot. The coolant looks like it hasn't been cut with water, am thinking that could be the problem. All radiators are open. Any thoughts/advice? 

And, yes we keep the pump on when the fire is lit. 

 

I assume you have bled the system.

Did you mix the antifreeze with water before filling.

[BEngo]

Coolant from the header tank means the liquid is boiling in the backboiler.  That means the pump is not circulating the liquid fast enough, or the fire is too big for the rads capacity.  If the liquid is neat antifreeze it will be less effective as a coolant, but it should all still work.

 

Have you refilled the header tank?

Do all the radiators get hot all over with the fire lit, going steadily, but not half up the chimney,  and the pump running?

Check that all the radiator valves are wide open. Remove any thermostatic valve heads.

Check there is no air in the rads, using the bleed screws.

 

If these are all OK run the fire  gently, with pump on.  Does that warm the radiators and boat without boiling?

 

If you can give details of the stove, and the sizes of the radiators it will be possible to check whether the boiler is too big for the radiators.

 

N

[Tracy D'arth]

Solid fuel boilers on boats that rely on a pump for circulation are in my opinion dangerous and should not be allowed.

 

If the water is boiling and overflowing you have no circulation. Either an air lock, a blockage or a pump that is not pumping

Could there be a stop valve on the radiator circuit that has been closed? I do not mean the radiator valves.

Has this ever worked since you bought the boat?

When did the problem start and what was changed before it started?

[The Wind Lass]

16 minutes ago, Tracy D'arth said:

Solid fuel boilers on boats that rely on a pump for circulation are in my opinion dangerous and should not be allowed.

 

If the water is boiling and overflowing you have no circulation. Either an air lock, a blockage or a pump that is not pumping

Could there be a stop valve on the radiator circuit that has been closed? I do not mean the radiator valves.

Has this ever worked since you bought the boat?

When did the problem start and what was changed before it started?

We just bought the boat and have not been able to get it to work at all. None of the radiators heat up. Suspiciously there is an on/off button for the boiler but as far as I can tell it only turns the pump off. The pump is new and does run. We bought the boat from a boatyard and they had it working at some point. Surveyor looked at it and didn't note any problems but also didn't run it. I haven't bled it, only noted that the coolant looked neat. Is there a way to disable the back boiler? We really don't need it. 

[Tracy D'arth]

6 minutes ago, The Wind Lass said:

We just bought the boat and have not been able to get it to work at all. None of the radiators heat up. Suspiciously there is an on/off button for the boiler but as far as I can tell it only turns the pump off. The pump is new and does run. We bought the boat from a boatyard and they had it working at some point. Surveyor looked at it and didn't note any problems but also didn't run it. I haven't bled it, only noted that the coolant looked neat. Is there a way to disable the back boiler? We really don't need it. 

Draining the water will stop the boiler working, is there a calorifier too? But running the fire without water in the boiler will wreck the back boiler for good.

 You say the pump runs, in other words it makes a noise? But does it actually move any water?  The pump is new you say, so is it fitted the right way round?

Edited February 2, 2023 by Tracy D'arth

[The Wind Lass]

1 minute ago, Tracy D'arth said:

Draining the water will stop the boiler working, is there a calorifier too? But running the fire without water in the boiler will wreck the back boiler for good.

 You say the pump runs, in other words it makes a noise? But does it actually move any water?

There is a calorifier but the backboiler is not connected to it. Good point about the pump, but at this point I don't think I want to bother to get the system working. But I would like to preserve the rads for another possible use (maybe diesel heat?). I'll check the stove to see if the back boiler is integral, if not, maybe I can remove it? 

[Higgs]

7 minutes ago, The Wind Lass said:

There is a calorifier but the backboiler is not connected to it. Good point about the pump, but at this point I don't think I want to bother to get the system working. But I would like to preserve the rads for another possible use (maybe diesel heat?). I'll check the stove to see if the back boiler is integral, if not, maybe I can remove it? 

 

That has kind of put the kybosh on helping with your initial enquiry. Your rads could be part of the problem. They may just need bleeding.

 

 

Edited February 2, 2023 by Higgs

[Nightwatch]

5 minutes ago, Higgs said:

 

That has kind of put the kybosh on helping with your initial enquiry. Your rads could be part of the problem. They may just need bleeding.

 

 

My first and last thoughts.

[Tony Brooks]

I don't see how anyone can help pinpoint potential problem points, apart from bleeding rads, without actually seeing how the pies are run, and the pump is orientated. Photos or accurate diagrams help us understand. This may be a DIY installation that ha snot given sufficient thought to not creating air locks.

[Tracy D'arth]

12 minutes ago, The Wind Lass said:

There is a calorifier but the backboiler is not connected to it. Good point about the pump, but at this point I don't think I want to bother to get the system working. But I would like to preserve the rads for another possible use (maybe diesel heat?). I'll check the stove to see if the back boiler is integral, if not, maybe I can remove it? 

Highly unlikely, depends on the type of stove.

[The Wind Lass]

5 minutes ago, Higgs said:

 

That has kind of put the kybosh on helping with your initial enquiry. Your rads could be part of the problem. 

 

 

True, and that's a good point about the radiators. I'm going to investigate a bit, but I'm reading about safety issues with the backboilers and so am doubtful about wanting to keep it. But also want to make sure I can remove it completely as it looks like there have been cases of empty/sealed backboilers exploding when there's a fire in the box. 

[Higgs]

3 minutes ago, The Wind Lass said:

True, and that's a good point about the radiators. I'm going to investigate a bit, but I'm reading about safety issues with the backboilers and so am doubtful about wanting to keep it. But also want to make sure I can remove it completely as it looks like there have been cases of empty/sealed backboilers exploding when there's a fire in the box. 

 

If you could post some photos, the people here could help. 

 

 

[Tracy D'arth]

7 minutes ago, The Wind Lass said:

True, and that's a good point about the radiators. I'm going to investigate a bit, but I'm reading about safety issues with the backboilers and so am doubtful about wanting to keep it. But also want to make sure I can remove it completely as it looks like there have been cases of empty/sealed backboilers exploding when there's a fire in the box. 

So you empty it, why seal it? It can't go BANG if its open. The dangers of pumping solid fuel boilers on boats are what happens if the pump fails, or the battery goes flat with a big fire burning?

[Higgs]

25 minutes ago, Tracy D'arth said:

So you empty it, why seal it? It can't go BANG if its open. The dangers of pumping solid fuel boilers on boats are what happens if the pump fails, or the battery goes flat with a big fire burning?

 

Also - depending on where the pump is, the  pumping section (impellor), what have you, could have disintegrated, leaving the motor working but no pumping. 

 

 

Edited February 2, 2023 by Higgs