Back boiler heating

[Sneill]

Hi Guys 

excuse my naivety but I am new to this Malarky!

my mate is in the process of updating his boat and in doing so is replacing the calorifier for one that has an element that can be powered from his solar.

my question is 

if we relocate the position of the calorifier so that it is sited lower than the pipe work coming from the back boiler , can we still use the back boiler if we add a pump to the system ?

 

thanks in advance 

Neill

[Tracy D'arth]

There is a safety risk with relying on a pump with a solid fuel back boiler. I refuse to install any such system.

It is quite simple to get gravity to do the circulation even if the calorifier coil is lower than the back boiler top outlet, its the rise from the boiler and the fall to the return that makes gravity do the work safely.

[MtB]

7 minutes ago, Sneill said:

 

if we relocate the position of the calorifier so that it is sited lower than the pipe work coming from the back boiler , can we still use the back boiler if we add a pump to the system ?

 

Yes it would work but is rather foolish. If the pump fails or its power supply while the stove is alight, the water in the back boiler will probably boil. And paradoxically, boiling is the last thing you ever want a boiler to do. 

[Tony Brooks]

Better still position the calorifier so the boiler water will circulate by gravity/convection, then you don’t use any electricity. Pumped systems on most stoves with back boilers can get very dangerous if they run away - think big bank with loads of steam and rusty boiling water spraying about.

 

He will almost certainly have electricity and charging problems in winter using an immersion heater so the more electricity he can save the better.

[Sneill]

So Tracy 

I understand about the rising pipe work but if the calorifier is lower than the back burner the rising pipe work will eventually have to fall, will this work ?

[Tony Brooks]

2 minutes ago, Sneill said:

So Tracy 

I understand about the rising pipe work but if the calorifier is lower than the back burner the rising pipe work will eventually have to fall, will this work ?

 

Depending upon pipe bore and run probably yes but possibly not as well as it could. It may also depend upon the relative positions and thus pipe layout of the boilers, radiators and calorifier. A diagram may help.

[Jen-in-Wellies]

My boat has a gravity powered back boiler. When I had to replace the (vertical) calorifier, the new one had the gravity coil outlets at a different height from the old. I adjusted the mounting for the calorifier so it met the pipe work, rather than the other way round.

[Tracy D'arth]

22 minutes ago, Sneill said:

So Tracy 

I understand about the rising pipe work but if the calorifier is lower than the back burner the rising pipe work will eventually have to fall, will this work ?

Yes.  Rise as far as practical from the top of the boiler, continue a rise to near the calorifier, put a feed tank on the highest point, drop to the top of the calorifier coil, return falling slightly to the boiler, pop up to the bottom boiler connection.

[Sneill]

Thanks Tracy

the set up as it stands has one radiator to the front of the boat , back boiler central to the boat and a calorifier towards the rear adj to where the feed and vent pipes are .Any chance you could scribble down a drawing of how it should all be plumbed as neither the rad or hot water are very successful atm! 
any help much appreciated

[Tracy D'arth]

I can't draw for toffee,

 

Boiler top up to gunwale, 22mm,  then to calorifier top coil, 22mm,  Fill & expansion tank connects here.  Then to radiator top connection (valve) 15mm.

Rad bottom to boiler bottom 15mm and calorifier bottom to boiler bottom 22mm. Drain cock on lowest point.

 

I am assuming a boat length of around 50 to 60 feet.

[blackrose]

On 28/07/2022 at 16:58, Sneill said:

my mate is in the process of updating his boat and in doing so is replacing the calorifier for one that has an element that can be powered from his solar.

 

Are we talking about regular photovoltaic solar panels or a solar hot water setup? If it's regular solar panels I'm not sure that heating water is the best use for these? 

[Sneill]

Pls see attached scribble ! How much rise should be present in pipe work from boiler ? I assume that the rad was added Recently  as pipework  appears fresh compared to the rest of system . I am sure the problems are due to not enough rise in pipe work? Also is there a technical reason for the pipework arrangement in second photo ? 

Edited August 4, 2022 by Sneill
Spelling

[Alan de Enfield]

31 minutes ago, Sneill said:

.......technical reason for the pew irk arrangement.............

 

????

[Tony Brooks]

1 hour ago, Sneill said:

Pls see attached scribble ! How much rise should be present in pipe work from boiler ? I assume that the rad was added Recently  as pipework  appears fresh compared to the rest of system . I am sure the problems are due to not enough rise in pipe work? Also is there a technical reason for the pipework arrangement in second photo ? 

 

I don't see why you need the pipes that run in parallel with the calorifier, it may even rob the calorifier of flow. Just move the vent and feed to the other side of the calorifier or even connect to the calorifier coil connections.

 

With that arrangement there is a chance that the circulation through the calorifier may be compromised by the trim of the boat (bow up) but as long as the boiler is fairly close to the calorifier I expect it will work.

 

That photo of pipework. On long copper runs that type of configuration can be used to allow for expansion by allowing the two parallel legs to bend slightly, but it looks to me as if it has been done to avoid bending the large pipes and the horizontal displacement is too small to allow a neat 2 elbow dog leg for the alignment.

 

 

 

[Sneill]

Hi Black Rose 

yes normal solar just to help with hot water through the summer months 

Hi Tony 

when  lit the back boiler only manages to “warm “the high pipes , the lower pipes and calorifier do not warm at all?

[Tony Brooks]

17 minutes ago, Sneill said:

Hi Black Rose 

yes normal solar just to help with hot water through the summer months 

Hi Tony 

when  lit the back boiler only manages to “warm “the high pipes , the lower pipes and calorifier do not warm at all?

 

Basically that is as it should be because the calorifier coil (until the calorifier is hot) and the radiators(s) take heat from the circulating liquid and use that heat to warm the air or domestic hot water, BUT I would expect the lower pipes to get warm, but not as hot as the top ones. Has neat antifreeze been added to the system without diluting t to the required strength first? If so that can prevent circulation. It also depends upon the heat output of the boiler. If the heat output of the back boiler is low then the radiator may well get hot at the top and progressively cooler as you move down and similar in the calorifier.

 

I think Blackrose was trying to gently point out that the first priority for the use of solar (which is limited on a narowboat) is to keep the batteries fully charged. Only once that is done each day can you afford to use the then waste solar energy to heat water. More batteries are wrecked, some in as little as week or two, by consistent undercharging. Doing what is proposed means your friend needs to have a reliable way of establishing when his batteries are all but fully charged so he can switch to water heating.

Edited August 4, 2022 by Tony Brooks

[Sneill]

My point being is the calorifier doesn’t get hot 

the only time he successfully heats the water is from the secondary coil running from the engine 

[Tony Brooks]

54 minutes ago, Sneill said:

My point being is the calorifier doesn’t get hot 

the only time he successfully heats the water is from the secondary coil running from the engine 

 

Assuming the calorifier is close to the engine and the radiator is at the front.

 

Well, it looks like the calorifier is linked to the other pipework by 15mm legs so that will tend to restrict the flow, especially a s there seems to be a 22mm bypass.

 

If the boat trims as narrow boats typically do, down by the stern, then if your diagram is anything like to scale there is a long downhill section (top pipe) between stove and calorifier that will do nothing to assist circulation, then similar applies to the calorifier return leg.

 

Because of where you have the vent pipe (lowest point of the top run) there could well be airlocks in it the  calorifier coil. I would try to move the vent to T into the calorifier feed so air can escape. If you have a compression fitting where the calorifier top leg joints the top run try loosening it to see if any air comes out.

[Tracy D'arth]

Get rid of all those elbow, they should be bends.

The bypass after the calorifier is unnecessary. 

 

Take the boiler top pipe as high as possible but maintain a rise to the calorifier ( and the rad) remembering that your boat probably has a rise the opposite way.