Back boiler Failure

[DShK]

I am unable to find somewhere that sells 28x28x1/2" that isn't online only. Which stands no chance of coming anytime soon due to strikes

[magnetman]

scrap yard?

[BEngo]

Q1 yes, exactly what I had in mind.

 

Q2 That would be perfick.  If you cannot find the right Tee use a 28x28x28 Tee with a short piece of pipe (which you have 🙂)  to  a 28 x 1/2 BSP Female which you can screw the Toolstation item into.

 

N

[Tracy D'arth]

BEngo is partially correct.  The single pipe system of connecting radiators is a bit old fashioned and inefficient. It has the advantage here that the calorifier has priority and will heat quicker than if you re-pipe the flows of the rads to the flow pipe. I would be happy leaving the pipework as it is.

 

Similarly in a domestic situation with a large boiler BEngo is correct about the expansion and vent pipes. But on a boat with a small boiler most are done with a single combined fill and vent pipe connected only to the base of the tank. Yours is slightly better having an over tank vent but it is not essential.

The advantage of a single bottom connection is that any venting steam discharges under water and condenses straight away instead of steaming your boat out.

I would be happy to leave yours as it is or remove the over tank vent pipe. I have installed dozens of boat systems this way.

 

Now to get to the root of your problem.

 

Have you put a small spirit level on the flow pipe all the way along between boiler and calorifier top connection/vent?

 

If you do, I am sure you will find that the attitude of the hull in the water is removing any positive rise in that pipe. In other words you have an air lock in the flow pipe somewhere.  Test the rise of the pipe, fix any high unvented parts, then load the bow to get more slope on the pipe. I bet it will work then.

 

It makes little difference whether the pipe rises steadily or goes up high first, its the difference in height between flow and return pipes that determines the gravity flow rate counterbalancing the pipe resistance. What is vital is that it does not have any high part that holds air preventing the gravity flow.

[frahkn]

Well clearly you are correct about being up late (other thread)!

 

You wouldn't catch me up at 03.24 in the morning.

 

Keep well, or as near as possible.

[Tracy D'arth]

14 minutes ago, frahkn said:

Well clearly you are correct about being up late (other thread)!

 

You wouldn't catch me up at 03.24 in the morning.

 

Keep well, or as near as possible.

I am hopefull for tonight, whats  left of it. Half a bottle of Nitenurse and I am a but drowzy, I'll give it a try.

You are up too? 

[Jen-in-Wellies]

4 hours ago, Tracy D'arth said:

Have you put a small spirit level on the flow pipe all the way along between boiler and calorifier top connection/vent?

One if the very few occasions when a spirit level is of use on a boat.

[frahkn]

7 hours ago, Tracy D'arth said:

I am hopefull for tonight, whats  left of it. Half a bottle of Nitenurse and I am a but drowzy, I'll give it a try.

You are up too? 

Yep!

 

I know I can't sleep so I don't rush to bed.

[DShK]

9 hours ago, Tracy D'arth said:

BEngo is partially correct.  The single pipe system of connecting radiators is a bit old fashioned and inefficient. It has the advantage here that the calorifier has priority and will heat quicker than if you re-pipe the flows of the rads to the flow pipe. I would be happy leaving the pipework as it is.

 

Similarly in a domestic situation with a large boiler BEngo is correct about the expansion and vent pipes. But on a boat with a small boiler most are done with a single combined fill and vent pipe connected only to the base of the tank. Yours is slightly better having an over tank vent but it is not essential.

The advantage of a single bottom connection is that any venting steam discharges under water and condenses straight away instead of steaming your boat out.

I would be happy to leave yours as it is or remove the over tank vent pipe. I have installed dozens of boat systems this way.

 

Now to get to the root of your problem.

 

Have you put a small spirit level on the flow pipe all the way along between boiler and calorifier top connection/vent?

 

If you do, I am sure you will find that the attitude of the hull in the water is removing any positive rise in that pipe. In other words you have an air lock in the flow pipe somewhere.  Test the rise of the pipe, fix any high unvented parts, then load the bow to get more slope on the pipe. I bet it will work then.

 

It makes little difference whether the pipe rises steadily or goes up high first, its the difference in height between flow and return pipes that determines the gravity flow rate counterbalancing the pipe resistance. What is vital is that it does not have any high part that holds air preventing the gravity flow.

 

Good to hear another opinion, thank you. I did wonder about the radiator part - I am actually more keen for the water to be hot than the radiators super hot. Although saying that, the one in the bathroom (first one) could do with getting toasty - my engine room is so cold that my washing machine piping has frozen. Need to avoid that happening!

 

Unfortunately I can't load up my bow at the moment, I am thoroughly frozen in. The ice is so thick I can stand on it. I will buy a small bubble level. If this is the issue, is it worth fitting, in your opinion, a couple bleed valves as BEngo suggested? One at either end of the top pipe maybe?

 

My worry about it being the slope is that I have already loaded my bow up a fair amount. It was commented by my surveyor that my bow drainage holes are quite close to the waterline as it was. Is the only real solution here increasing the slope on the top pipe? Someone here mentioned that it was the initial rise out of the boiler, rather than the slope, which is most important? So is my main goal here just initially getting this airlock out and then it should be good?

 

Thanks!

Edited December 17, 2022 by DShK

[DShK]

I 

 

I wonder if there could be an airlock in either of these places? I think Tony mentioned the top one and the one near the stove. So not sure about the bottom one. Worth putting bleed valves here?

Edited December 17, 2022 by DShK

[Tracy D'arth]

Its only worth cutting the pipe and fitting air vents if there is an air lock at that point. If you check the pipe for fall all along and after tees like that one to the top connection of the calorifier you will find out where there is a high point holding air.

Remember that the same applies to the return pipe, it must not have high points that cannot be vented though problems here are less likely as it will vent at both ends and at every radiator tee.

You have bled the radiators I suppose?  Any valves on the radiator connections?

If you cannot achieve a rise from the boiler to the top calorifier connection consider lowering the boiler and the pipe at that end or raising the calorifier, neither easy.

Taking  the legs off the boiler may be easier.

Edited December 17, 2022 by Tracy D'arth

[Tony Brooks]

If the top pipe, including the white one is not sloping upwards then yes, there might be an airlock in that top elbow. In some diagrams the short horizontal section seems to slop down, away from the upright to the calorifier. Another think that will tend to trap air is what looks like a reduction in diameter between the 28mm and the white pipe. There will be a "step" in the top of the run that may trap air, but a sthe set of the 28mm pipe can still vent i am not sure how much effect this would have, I suspect little or none.

 

I think that if it was mine I would change the bend at the top of the vertical section for a compression T and fit a bleed point in the top of the T. It could well be unnecessary but it would be nice to have. Thinking more, you could use the top of the T to connect  the vent pipe so it would not need a bleed point.

[DShK]

So I just used my phone as a bubble level (I am trying to avoid more trips back and forth to screwfix, it's a bit of a drive!) And I don't know how well it is calibrated, but it does seem pretty flat. Given the overall rise is only 6.5cm this makes sense, I think it would be super sensitive to the boat trim. My logic is that the bit circled at the top of the image above is the problem. It rises perpendicular to the boat (and thus not effected by the trim), and visibly rises, so this must be the high point. 

 

There is a valve on both the inlet and outlet on the radiator. They are open. When I have filled the system, my method has been to open the radiator bleed point until water comes out, to avoid air getting trapped.

 

The white pipe is 22mm it seems. I am trying to avoid replacing all of the white

 

I am thinking I will fit a Tee and bleed point there as you suggest Tony. And see if that solves the issue. I am not sure how well a Tee will handle the fact that the joint won't be quite a 90 degree angle...

Edited December 17, 2022 by DShK

[rusty69]

Have you tried simply isolating the rads to aid with circulation/purging air from the rest of the circuit?

[DShK]

4 minutes ago, rusty69 said:

Have you tried simply isolating the rads to aid with circulation/purging air from the rest of the circuit?

I have not. I will give that a go!

 

Hmm, annoyingly I can't find a way to adapt a 28mm pipe to an air vent. The only adaptor I can find to BSP is to 1". And I can't find a 1" air vent. Perhaps I should just fit a stop-end? Not as easy to bleed but I hope I'm not doing it that often...

[rusty69]

14 minutes ago, DShK said:

I have not. I will give that a go!

 

Hmm, annoyingly I can't find a way to adapt a 28mm pipe to an air vent. The only adaptor I can find to BSP is to 1". And I can't find a 1" air vent. Perhaps I should just fit a stop-end? Not as easy to bleed but I hope I'm not doing it that often...

Unless you are used to plumbing sizes, it can be a right pain to get the right part to fit, but there is always a way. Often that way involves going to a decent plumbers merchant with part in hand and telling them what you are trying to achieve.

 

I hate plumbing, but would something like this work (please check before buying):

 

https://www.screwfix.com/p/pegler-px50c-brass-compression-reducing-tee-28-x-28-x-15mm/2223g

 

and

 

https://www.screwfix.com/p/compression-manual-air-vent-brass-2-pack/7341v

[Tracy D'arth]

16 minutes ago, DShK said:

I have not. I will give that a go!

 

Hmm, annoyingly I can't find a way to adapt a 28mm pipe to an air vent. The only adaptor I can find to BSP is to 1". And I can't find a 1" air vent. Perhaps I should just fit a stop-end? Not as easy to bleed but I hope I'm not doing it that often...

Cut it and insert a 28mm compression coupler,  at the high point. ( like you used over the boiler ) Slackening a nut will vent it just as easily as a vent fitting.

1 minute ago, Tracy D'arth said:

Cut it and insert a 28mm compression coupler,  at the high point. ( like you used over the boiler ) Slackening a nut will vent it just as easily as a vent fitting.

Brass Compression 28 28 1/2"BSP FI tee.

https://www.plumbers-mate-sales.co.uk/brass-28mm-x-28mm-x-12-fi-compression-tee---24542800-6888-p.asp   but the price is terrible and you need a rad vent plug.

[Tracy D'arth]

5 minutes ago, Tracy D'arth said:

Cut it and insert a 28mm compression coupler,  at the high point. ( like you used over the boiler ) Slackening a nut will vent it just as easily as a vent fitting.

Brass Compression 28 28 1/2"BSP FI tee.

https://www.plumbers-mate-sales.co.uk/brass-28mm-x-28mm-x-12-fi-compression-tee---24542800-6888-p.asp   but the price is terrible and you need a rad vent plug.

And I can't believe the price of this, has to be wrong or extortion. https://www.wolseley.co.uk/product/kuterlite-k930-female-iron-reduced-branch-tee-28mm-x-28mm-x-1-2/

1 minute ago, Tracy D'arth said:

And I can't believe the price of this, has to be wrong or extortion. https://www.wolseley.co.uk/product/kuterlite-k930-female-iron-reduced-branch-tee-28mm-x-28mm-x-1-2/

This is better but not cheap https://plumbco-online.co.uk/bsp-f-branch-tee-uk-compression-28mm-x-28mm-x-12

[DShK]

I turned the rads off and turned the stove up for a moment. Got some gurgling sounds along with the knocking. Knocking/boiling continues. I assume this was steam escaping.

 

Rusty - thanks! Unfortunately I don't think that will work. The 90 degree angle needs to be both 28mm,  as it would be in place of an elbow joint. and then the opposing side needs to be the vent. Hope that makes sense. This is how I was imagining it anyway - perhaps this is not what Tony meant.

 

Tracy - Interesting to know just a coupler would work. I am wondering if it would solve the issue though, technically the high point (seems like it would be) the top of the elbow, which is why a tee sounded like a good idea. I guess an elbow compression fitting might work? Trying to avoid buying online as with strikes I won't get anything anytime soon. 

 

A little worried that if I cut that elbow out, that I won't have enough pipe left to fit a compression fitting. Then there isnt enough horizontal space to add pipe in with a coupler....

Edited December 17, 2022 by DShK

[Tracy D'arth]

Time to get bodging I think.  Get a short brass wood screw and some sealant, anything, silicone, polyurethane.  Wrap the screw thread in PTFE tape if you have some, thin string if you haven't, build it up till its as big as the screw head.  Coat the whole with sealant.

 

Drill a small hole ( smaller than the screw ) in the pipe or elbow at the highest point where you think the air is and screw the screw in just enough till the leak stops.  Dry it all off, the heat will do that, and build up sealant around the screw.

 

Not elegant but it will work. In the old days we would do this without the sealant and solder the screw in but that would involve you draining down.

 

If anyone sees it don't tell them I said to do it.

 

[DShK]

6 minutes ago, Tracy D'arth said:

Time to get bodging I think.  Get a short brass wood screw and some sealant, anything, silicone, polyurethane.  Wrap the screw thread in PTFE tape if you have some, thin string if you haven't, build it up till its as big as the screw head.  Coat the whole with sealant.

 

Drill a small hole ( smaller than the screw ) in the pipe or elbow at the highest point where you think the air is and screw the screw in just enough till the leak stops.  Dry it all off, the heat will do that, and build up sealant around the screw.

 

Not elegant but it will work. In the old days we would do this without the sealant and solder the screw in but that would involve you draining down.

 

If anyone sees it don't tell them I said to do it.

 

 

Lol. Okay, I will do this. Need to go buy some PTFE tape and better sealant as one of the joints I reconnected is wheeping. I need to drain the system down to fix this, plus the system is filled with cleaner which needs to be flushed. So I'll drill the hole when the system is empty, seems less scary! Will let you know how it goes, thanks.

[Alan de Enfield]

1 hour ago, DShK said:

Given the overall rise is only 6.5cm this makes sense, I think it would be super sensitive to the boat trim.

 

 

You might find that your radiators get hot when you have a full water tank, (bow down) and they don't work so well if the tank is empty (bow up)

 

It sound as if the whole install is pretty marginal  as to heating or not. 2 1/2" rise along the length of the boat is not a lot - a couple of people in the back-end could make the difference between working or not.

[DShK]

3 minutes ago, Alan de Enfield said:

 

 

You might find that your radiators get hot when you have a full water tank, (bow down) and they don't work so well if the tank is empty (bow up)

 

It sound as if the whole install is pretty marginal  as to heating or not. 2 1/2" rise along the length of the boat is not a lot - a couple of people in the back-end could make the difference between working or not.

 

Indeed. This was something I was trying to figure out when it was clear it wasn't working at all. I definitely think I have an airlock which needs to be solved first. Then I need this ice to melt so I can continue testing how sensitive it is to how full my water tank is!

[MtB]

15 minutes ago, Tracy D'arth said:

Time to get bodging I think.  Get a short brass wood screw and some sealant, anything, silicone, polyurethane.  Wrap the screw thread in PTFE tape if you have some, thin string if you haven't, build it up till its as big as the screw head.  Coat the whole with sealant.

 

Drill a small hole ( smaller than the screw ) in the pipe or elbow at the highest point where you think the air is and screw the screw in just enough till the leak stops.  Dry it all off, the heat will do that, and build up sealant around the screw.

 

Not elegant but it will work. In the old days we would do this without the sealant and solder the screw in but that would involve you draining down.

 

If anyone sees it don't tell them I said to do it.

 

 

Before doing this, there is another technique the OP might be able to try. Potentially quite messy but I've used it to clear air locks successfully on gravity systems with missing vents in important positions.

 

Securely attach a hose pipe to the low point system drain cock and attach the other end to a nice fast-flowing mains water tap. Open the drain cock then open the mains water tap for as long as you dare. The fast flow into the drain cock, through the system and out into the header tank 'sometimes' disturbs and shifts enough air to get the system circulating. Then any remaining air tends to dissolve into the passing water.

 

But not always!

[DShK]

3 minutes ago, MtB said:

 

Before doing this, there is another technique the OP might be able to try. Potentially quite messy but I've used it to clear air locks successfully on gravity systems with missing vents in important positions.

 

Securely attach a hose pipe to the low point system drain cock and attach the other end to a nice fast-flowing mains water tap. Open the drain cock then open the mains water tap for as long as you dare. The fast flow into the drain cock, through the system and out into the header tank 'sometimes' disturbs and shifts enough air to get the system circulating. Then any remaining air tends to dissolve into the passing water.

 

But not always!

 

Ooer.. I will have to see if I have a long enough hose for that (I have to use a water tap quite far from me as my marina hasn't fixed my broken one for months...) and if I can figure a way to turn the water off quickly without spraying water all over the inside of my boat!

 

I will see which one of these worries me less when decision time comes!