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Split Calorifier


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6 hours ago, The Happy Nomad said:

 

So when we have a leaky radiator valve at home and we get the green staining on the copper pipe its not actually caused by the water/leak.

 

Really?

The water from the leak accelerates the corrosion from the residual flux, or the flux accelerates the corrosion from the water, depending on how you look at things. Moisture in the air will work with the flux too, given enough time. Plumbing fluxes are much more aggressive than the ones used in soldering electronics together.

 

9 hours ago, George and Dragon said:

Other threads have mentioned leaking PR valves but I don't actually know what that looks like. There's a valve kind of thing on the top of the calorifier, is that it? And the red knob?

I'm going to struggle to identify which of the various pipes is what - there must be heating coils from the engine and Webasto as well as the cold in and hot out (my guess is the hot out is from the top!) and I have no idea how to tell the difference between an accumulator and an expansion vessel.

As others have said; yes the red knob is on the PRV and is used to deliberately open it to clear any scale on the valve seat that is making it drip. Tracing the overflow pipe from the PRV is probably your first priority, as if this goes in to the bilge, rather than overboard via a skin fitting, then a leaking PRV could be the source of your cabin bilge water and will save you having to buy a new cauliflower. A new PRV is cheap in comparison.

Next thing to do is turn the pump on and locate where the bilge water is coming from, a bilge PRV overflow, or the calorifier itself. A split cauliflower will have water coming out somewhere, but it may travel a long way under the insulation from the actual split before coming to the surface..

Accumulators and expansion vessels are physically identical. The difference lies in their location and the pressure they are set at. The accumulator is set at the pump cut in (low) pressure and fills with water as the pump brings the system up to pressure. As water is drawn off, this is let out in to the system, delaying when the pressure falls to the pump cut in pressure. It reduces the number of times the pump cuts in and out. It is located usually in the cold water line, somewhere downstream of the pump.

The expansion vessel is located in the hot water system somewhere downstream of the non return valve from the cold water side. If there is no non-return valve, then the accumulator also acts as an expansion vessel. It is set at the higher pump cut out pressure. Without an expansion pressure, when hot water expands as it is heated the pressure in the system spikes upwards rapidly till the PRV opens. If the PRV sticks closed, then the pressure can get high enough to split a calorifier. The expansion vessel allows somewhere for the expanding volume of water to go, keeping the pressure reasonable. Without it, even if the PRV works properly, the changing pressure as the water heats and cools will fatigue the copper of the calorifier and the solder holding it together at the seams and will shorten its life.

When I built my boat I didn't include an expansion vessel and my cauliflower failed at a joint within five years. Others have reported similar experiences. Despite this, expansion vessels are not always fitted on boat hot water systems.

I can see one expansion vessel, or accumulator in your pic. Find the water in feed to the calorifier, probably the lowest 15mm pipe connection. Look for a non return valve in the pipe leading to that. If there is one, then the system should have an expansion vessel too. If fitted, an accumulator could be anywhere in the cold water pipe work, near the pump is common. Similarly, the expansion vessel could be anywhere in the hot water system. Neither has to be actually near the cauliflower. If you don't have an expansion vessel and the calorifier does turn out to have split, I'd strongly recommend fitting one when the cauliflower is replaced.

Jen

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9 hours ago, David Mack said:

They are basically the same. It's where they are positioned that distinguishes between them. The accumulator is tee'd off the outlet pipe from the water pump (i.e. cold water) - usually, but not always, close to the water pump. The expansion vessel is located on the hot pipework, usually close to the calorifier.

 

So the grey/pale blue thing is an expansion vessel. Thanks

 

9 hours ago, matty40s said:

I don't think the steps are particularly well fixed looking at the cracked tiles at the bottom end..:ninja:

 

Numerous cracked tiles there and in the bathroom. I've sheared the head off a couple of the screws fixing the steps in position already, and I haven't yet found out how they fixed them at the bulkhead. The joys...

 

Once they're out I'll also have access the the bottom of the electrics cupboard which I do have a small level of understanding.

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49 minutes ago, George and Dragon said:

So the grey/pale blue thing is an expansion vessel. Thanks

The only way to be sure is to follow the pipe back from the grey/pale blue thing and find if it is connected to the hot, or cold water side of the plumbing. Note @David Mack says "usually", not "always" close to the calorifier.

Jen

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1 hour ago, Jen-in-Wellies said:

As others have said; yes the red knob is on the PRV and is used to deliberately open it to clear any scale on the valve seat that is making it drip. Tracing the overflow pipe from the PRV is probably your first priority, as if this goes in to the bilge, rather than overboard via a skin fitting, then a leaking PRV could be the source of your cabin bilge water and will save you having to buy a new cauliflower. A new PRV is cheap in comparison.

Probably through the bulkhead into the engine bilge. 

 

1 hour ago, Jen-in-Wellies said:

Accumulators and expansion vessels are physically identical. The difference lies in their location and the pressure they are set at. The accumulator is set at the pump cut in (low) pressure and fills with water as the pump brings the system up to pressure. As water is drawn off, this is let out in to the system, delaying when the pressure falls to the pump cut in pressure. It reduces the number of times the pump cuts in and out. It is located usually in the cold water line, somewhere downstream of the pump.

I'm pretty sure there is one installed, the water pump doesn't come on immediately a tap is opened and continues running for a few seconds afterwards. 

 

Although:

1 hour ago, Jen-in-Wellies said:

The expansion vessel is located in the hot water system somewhere downstream of the non return valve from the cold water side. If there is no non-return valve, then the accumulator also acts as an expansion vessel. It is set at the higher pump cut out pressure. Without an expansion pressure, when hot water expands as it is heated the pressure in the system spikes upwards rapidly till the PRV opens. If the PRV sticks closed, then the pressure can get high enough to split a calorifier. The expansion vessel allows somewhere for the expanding volume of water to go, keeping the pressure reasonable. Without it, even if the PRV works properly, the changing pressure as the water heats and cools will fatigue the copper of the calorifier and the solder holding it together at the seams and will shorten its life.

Excellent explanation. Do/did you do this for a living?

 

1 hour ago, Jen-in-Wellies said:

I can see one expansion vessel, or accumulator in your pic. Find the water in feed to the calorifier, probably the lowest 15mm pipe connection. Look for a non return valve in the pipe leading to that. If there is one, then the system should have an expansion vessel too. If fitted, an accumulator could be anywhere in the cold water pipe work, near the pump is common. Similarly, the expansion vessel could be anywhere in the hot water system. Neither has to be actually near the cauliflower. If you don't have an expansion vessel and the calorifier does turn out to have split, I'd strongly recommend fitting one when the cauliflower is replaced.

So I really must get those steps out of the way

 

7 minutes ago, Jen-in-Wellies said:

The only way to be sure is to follow the pipe back from the grey/pale blue thing and find if it is connected to the hot, or cold water side of the plumbing. Note @David Mack says "usually", not "always" close to the calorifier.

OK

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Got the steps out today. Had a good clean up. Rather surprised to find a disposable nappy at the bottom of the cauliflower cupboard.

 

I turned water on so I could use the toilet and wash my hands. Immediate evidence of moisture at the biggest split in the insulation. 

 

I haven't yet found a separate accumulator but then I haven't had chance to look properly. Would it be a similar size as the expansion vessel?

 

[I should point out that 0632 dialling codes changed to 0191x in 1995 unlike many others that gained a 1 after the leading 0]

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21 minutes ago, George and Dragon said:

I turned water on so I could use the toilet and wash my hands. Immediate evidence of moisture at the biggest split in the insulation. 

Oh well. Split cauliflower then.

21 minutes ago, George and Dragon said:

I haven't yet found a separate accumulator but then I haven't had chance to look properly. Would it be a similar size as the expansion vessel?

Probably similar. It is a boat, so anything is possible!

21 minutes ago, George and Dragon said:

[I should point out that 0632 dialling codes changed to 0191x in 1995 unlike many others that gained a 1 after the leading 0]

Explanation. Like 555 codes in American movies.

Edited by Jen-in-Wellies
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