No hot water from calorifier

[Karen Lea Rainey]

Hi All,

I,m pretty sure I've got an air lock in the coils inside my calorifier,

It's an Isuzu  engine with just the skin tank and calorifier connected, the boat is new to me but the calorifier was newly installed and not commissioned prior to me purchasing the boat.

It is a 55ltr upright sure cal unit. When I run the engine at about 8-900 rpm (just above tickover) I would have expected to have generated at least some Luke warm water through the hot taps.

There is no bleed point on the calorifier pipes leading to the engine, there is however a T piece bleed point on the pipe from the skin tank,  

The skin tank gets pretty warm after 20 mins or so so I know the circulation is good for water cooling of the engine, you can feel the lower pipe entering into the calorifier  getting warm but the pipe 3 inches or so above it is nearly cold, hence I dont think the water is circulating in the internal coil.

I have blipped the engine to around 3000 rpm  for a full minute hoping that the higher pumping pressure will force any air round the system and clear the air lock from the coils but it hasn't worked.

There is no ( open valve/close valve) tap upon exiting the calorifier before the sink taps and I do have a full flow of water at the hot tap, it's  just not warm.

 

Q. Can I just remove the higher hose pipe coming from the calorifier to where it enters the top of the engine and put a water hose in the heater pipe hence forcing any water around the engine, clearing the air lock and allowing the air to escape through the expansion tank with the cap removed.

Ps there appears to be plenty of water in the engine with the expansion tank showing almost full which is also the highest point of the engine and pipeworks.

[BEngo]

First of all:  the hot pipe from the engine should go into the top of the calorifier.  That way the hottest water in the cauliflower gets the most heating from the engine.

Your suggestion of a hose is fine.  You may be able to achieve the same effect by loosening the heating pipe where it goes into the calorifier with the engine hot and running at day 2000 rpm.  Tighten it up when any hissing and bubbling stops.  If that doesn't work repeat at any other joints on the heating loop.

 

N

[Iain_S]

7 hours ago, BEngo said:

First of all:  the hot pipe from the engine should go into the top of the calorifier.  That way the hottest water in the cauliflower gets the most heating from the engine.

Your suggestion of a hose is fine.  You may be able to achieve the same effect by loosening the heating pipe where it goes into the calorifier with the engine hot and running at day 2000 rpm.  Tighten it up when any hissing and bubbling stops.  If that doesn't work repeat at any other joints on the heating loop.

 

N

Some people do it that way round to prevent thermosyphoning with a hot calorifier and a cold engine, on the grounds that the pump will easily push the water through the coil "the wrong way" when the engne is running. Might also make it easier to bleed by loosening connection to top coil hose. Better, IMO, to connect as you suggest, though, and defeat the reverse thermosyphon effect by pipe routing.

[Boater Sam]

13 hours ago, BEngo said:

First of all:  the hot pipe from the engine should go into the top of the calorifier.  That way the hottest water in the cauliflower gets the most heating from the engine.

Your suggestion of a hose is fine.  You may be able to achieve the same effect by loosening the heating pipe where it goes into the calorifier with the engine hot and running at day 2000 rpm.  Tighten it up when any hissing and bubbling stops.  If that doesn't work repeat at any other joints on the heating loop.

 

N

Based on a lifetime of designing heating systems, I have to disagree.

The greatest rate of heat transfer is by feeding the hot water into the coolest area i.e. the bottom connection, This is a pumped circuit not thermosyphon. This will be approximately 6% more efficient at transferring the heat into the calorifier.

 

Plus the air in the coil will  be expelled upwards, much better than trying to force it down through water. 

There should be a vent or open expansion tank on the top coil connection to get rid of the air.

 

The other way round is a prerequisite in a thermosyphon i.e. not pumped system.

 

If it is piped this correct way with no air vent or tank it is in need of venting by cracking open the top union to release the air.

 

[Onewheeler]

If the plumbing is as I imagine and the engine thermostat is knackered in the open position (or missing) the skin tank might be sufficient a short circuit across the calorifier coil to prevent an airlock clearing. Even so I'd be surprised if running the engine balls-out didn't generate enough head to blow it through.

 

Martin/

[ditchcrawler]

7 hours ago, Onewheeler said:

If the plumbing is as I imagine and the engine thermostat is knackered in the open position (or missing) the skin tank might be sufficient a short circuit across the calorifier coil to prevent an airlock clearing. Even so I'd be surprised if running the engine balls-out didn't generate enough head to blow it through.

 

Martin/

My calorifier is several meters (pipe run) from the engine and higher. I put it in with a bleed valve at the highest point but it has proved to be unkneeded, as any air shifts itself somehow.