Back boiler/Hot Water problems

[junior]

I have a solid fuel stove with a back boiler fitted. It is one of my 2 source's of hot water, the other being the engine.

 

At the moment it is not heating my hot water. Since I bought the boat I've always been under the impression that it worked fine as I've always had hot water, however looking back, this could have been heated by the engine and kept warm in the calorifier as I've moved every 24/48hrs. Now I've not run the engine for 3 consecutive days (for the first time since I've had the boat) I've realised something is not right as I have no hot water.

 

I think I have a simple systen with just the back boiler, one radiator and a calorifier. As far as I know there is nothing else in the system apart from a sort of open topped plastic tank in my engine room that is full of anti-freeze that has something to do with the hot water system.

 

Last week I noticed that the water level in the tank in the engine room had dropped a bit so I topped it up with water. I went away for the week and when I came back I lit the stove. About 2 hours later I'm laying in bed and I suddenly hear a gushing water sound, so thinking the boat is sinking I run to the engine room to find the tank spewing water/anti-freeze all round the engine room! Anyway I cleared up and went back to bed.

 

Anyway so today I woke up and realised I had no hot water. After much scratching of head I decided to solve it by putting half a sack of coal on the stove. This didn't work.

 

Up until now I've always kept the one radiator turned off as my (misinformed) logic thought the radiator would steal and waste all the heat/hot water. I decided to turn it on incase by having it off I was actually stopping the heat/hot water getting to the calorifier as the radiator is between the boiler and before the calorifier. Also I felt the copper pipe that comes out of the stove and it was boiling hot all through the kitchen and then it went cold as the radiator. I went and checked the radiator after about 30 mins and only the top quater nearest the inlet pipe was warm, the rest of the radiator was stone cold.

 

Time to work out how to bleed the radiator. I undid the srew on the radiator and air came out for about 15 seconds then I got a trickle of blue water and did up the screw. After a few hours pretty much the whole radiator was hot, however I went into the engine room to find a covering of anti freeze and water all over everything. I went out for a few hours this evening and was looking forward to being able to come home to a shower and doing the washing up.

 

I've just come home to a cold radiator and cold water. I bled the radiator again and had air coming through for about 30 seconds before I got water.

 

Anyone know what's going on?

[alan_fincher]

It would be useful to publish all you can about position of stove, calorifier, radiator, pipes etc within the boat, with some indication about relative heights above a datum.

 

Also what type of stove you have, bore of pipes, etc.

 

I don't think all back-boiler stoves, particularly those with small back boilers, are particularly good at heating water, and if (say) the calorifier is lower than the boiler, (maybe because a boat is bow high, if for no other reason), then gravity may not be working in your favour.

Of course none of this should mean anything spewing out of header tanks - even if inefficient that still shouldn't happen.

 

Pictures or a drawing, maybe?

[matty40s]

you have an airlock., you also probably have it in the calorifier section of your run.

your rad will have more than one adjustable valve, are they all open.

I would doubt that this system has ever been used on your boat given the history, so would look for hidden stop valves as well!!

[smileypete]

If the boat is new to you then it's quite possible the back boiler heating doesn't work all that well at all. It does sound a bit that way.

 

Posting loads of photos of the pipe layout and the stove, rads, calorifer will help others to help you. It might need re-jiging sometime to work better.

 

Is there a pump in the system at all? If not the chances of getting a hot calorifier from the back boiler may be quite slim, in the meantime do leave the rad full on. If the rad is undersized and it still boils whatever you could try covering part of the backboiler interior surface with a piece of firebrick to reduce the backboiler output.

 

cheers, Pete.

~smpt~

[junior]

Thanks for the replies, I've had a very busy few days so not been able to update the post.

 

I still have no hot water though. I did have lukewarm water 2 days ago though so it's trying to heat it I think. I'm afraid I can't post pictures on here of the system and I don't know what half the stuff is that @Alan Fincher said I should post.

 

Here is a description of my system and what I have done so far;

 

I've bled the radiator and I had air coming out for about 3 mins, then blue water. After a while the radiator started to warm up so I thought I'd fixed it. But after a day of having the SFS roaring, only the top half of the radiator is warm and the bottom half stone cold. I tried bleeding it again but no air came out, only blue water.

 

The pipe from the back of the SFS is hot all the way througn the boat to the radiator. At the t-junction where it goes down into the radiator it is hot, along with the top half of the rad. The pipe stays warm along to the calorifier but as it gets closer to the calorifier it cools. The return pipe from the calorifier is stone cold all the way back to the back boiler on the SFS, including the t-junction where it goes up into the radiator, which as I said earlier is cold from halfway down.

[MtB]

Your system is not straightforward or well designed I'd suggest, as you mention the engine expansion tank spraying antifreeze around the engine room when the stove boils. This suggests the SFS is sharing circulating water with the engine cooling system, a definite NO in my personal opinion. I am not expert at designing boat heating and hot water systems so could be wrong on this but I think this would be asking for trouble, and you've got it!

 

It is not possible to advise you meaningfully until you answer the questions others have asked, in particular is there a pump, and what are the relative heights of the SFS, calorifier and radiator. Photos of every inch of the system would be enormous help too. There is a huge spectrum of installation designs and until we can get a grip on what you have, any advice will be just guesswork and may or may not be right.

 

MtB

 

 

 

(Edit for spellin)

Edited November 12, 2013 by Mike the Boilerman

[smileypete]

Bear in mind if antifreeze is used it must be premixed or it'll stratify and you probably won't get any decent gravity circulation.

 

cheers, Pete.

~smpt~

[junior]

Your system is not straightforward or well designed I'd suggest, as you mention the engine expansion tank spraying antifreeze around the engine room when the stove boils. This suggests the SFS is sharing circulating water with the engine cooling system, a definite NO in my personal opinion. I am not expert at designing boat heating and hot water systems so could be wrong on this but I think this would be asking for trouble, and you've got it!

 

It is not possible to advise you meaningfully until you answer the questions others have asked, in particular is there a pump, and what are the relative heights of the SFS, calorifier and radiator. Photos of every inch of the system would be enormous help too. There is a huge spectrum of installation designs and until we can get a grip on what you have, any advice will be just guesswork and may or may not be right.

 

MtB

 

 

 

(Edit for spellin)

Ok I'll try and work out photos.

 

The header tank is not for the engine, it is just for the back boiler system. To be honest I think that I caused the splurge of water over the engine room myself. I noticed that over time the level was dropping so I filled it up. Then I lit the stove and the level started rising......you get the picture.

[MtB]

Ok I'll try and work out photos.

 

The header tank is not for the engine, it is just for the back boiler system. To be honest I think that I caused the splurge of water over the engine room myself. I noticed that over time the level was dropping so I filled it up. Then I lit the stove and the level started rising......you get the picture.

 

Ah ok, this makes things a lot easier.

 

Given the engine heats the water too, I'd suggest you run the engine! It is quite possible that, subject to levels, the hot calorifier is heating the radiator not the SFS.

 

The header tank level rising on lighting the stove indicates a pretty large slug of air in it somewhere. Water expands slightly on heating, air expands massively!

 

MtB