Reasons for hw not coming from engine to calorifier

alisdair4

alisdair4

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Isle of Bute
midnightdrifter.net
On one of my infrequent trips to the boat yesterday, I discovered that, despite the engine being run (under load) for about an hour, hot water was not coming out of the hot tap in the sink. This is very unusual for this boat - the HW normally kicks in after about 15 minutes. Engine is a Beta. Any ideas for the " "obvious fault"?
 
alisdair4 said:
On one of my infrequent trips to the boat yesterday, I discovered that, despite the engine being run (under load) for about an hour, hot water was not coming out of the hot tap in the sink. This is very unusual for this boat - the HW normally kicks in after about 15 minutes. Engine is a Beta. Any ideas for the " "obvious fault"?
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Did you feel the pipes going from the engine to the calorifier and back? These should both be hot after 10 minutes or so. If either of them are cold and the water level in the cooling system (for an indirect system) is correct, then you have blockage or air lock.

If both the pipes are hot then there's something wrong with the domestic hot water system (mixer tap / thermostat problem or something else).

Not a solution but at least you know where to look.

Richard
 
As RichardS says, an air lock seems the most obvious reason. The hoses from the engine to the calorifier can be quite prone to this and it is surprising how a small amount of air can stop the flow of the circulation pump. If there is a small leak somewhere it may not normally be obvious but air can be drawn in when the engine is at rest.

Your post does not say but I assume you mean that cold water flowed from the hot tap? Or no water at all, in which case the cause is completely different.
 
Richard,

thanks - I will check these next week. I ran out of time (and light) at the weekend.

Vyv, Sorry - I should have said, that cold water flows from the hot tap when the engine has been run. Also, the calorifier produces hot water when the 240v is switched on. So, the water pumps for the H&C system seem OK.

An airlock sounds plausible, given the boat has been sitting for a few months and the water tank was almost empty.

Thanks again, both/


vyv_cox said:
As RichardS says, an air lock seems the most obvious reason. The hoses from the engine to the calorifier can be quite prone to this and it is surprising how a small amount of air can stop the flow of the circulation pump. If there is a small leak somewhere it may not normally be obvious but air can be drawn in when the engine is at rest.

Your post does not say but I assume you mean that cold water flowed from the hot tap? Or no water at all, in which case the cause is completely different.
Click to expand...
 
alisdair4 said:
Richard,

thanks - I will check these next week. I ran out of time (and light) at the weekend.

Vyv, Sorry - I should have said, that cold water flows from the hot tap when the engine has been run. Also, the calorifier produces hot water when the 240v is switched on. So, the water pumps for the H&C system seem OK.

An airlock sounds plausible, given the boat has been sitting for a few months and the water tank was almost empty.

Thanks again, both/
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The level in the water tank will have no relevance , at least not if you get normal flow rate from your taps.

It is an airlock in the pipework between the engine and the calorifier that is the likely cause of the trouble....... but check the engine coolant level in the heat exchanger or header tank as appropriate ( I don't believe you have told us what engine you have) as that could be the underlying cause if ( very) low.
 
When this happened to me, I found sludge blocking the HW coil inside the calorifier. I was able to blow it out without too much difficulty.

Curious as to where it had come from, I discovered a serious problem in the engine manifold. The internal pipes of the heat exchanger were disintegrating. Obviously that was bad news for the engine cooling system generally (even though the engine wasn't overheating at this stage, but raw water was mixing into the engine coolant). In practice it was easy enough to flush the debris out of the cylinder block passageways. The bad news was a new manifold needed - £450, ouch.
 
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AndrewB said:
When this happened to me, I found sludge blocking the coil inside the calorifier. I was able to blow it out without too much difficulty.

Curious as to where it had come from, I discovered a serious problem in the engine manifold. The internal pipes of the heat exchanger were disintegrating. Obviously that was bad news for the engine cooling system generally (even though the engine wasn't overheating at this stage, but raw water was mixing into the engine coolant). In practice it was easy enough to flush the debris out of the cylinder block passageways. The bad news was a new manifold needed - £450, ouch.
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Might that have been because the concentration/effectiveness of antifreeze in the coolant system had not been maintained properly, perhaps by a previous owner?

Or was there an underlying technical issue?

Richard
 
RichardS said:
Might that have been because the concentration/effectiveness of antifreeze in the coolant system had not been maintained properly, perhaps by a previous owner? Or was there an underlying technical issue?
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No technical issue. It was a 25 year old engine in a boat that I had just bought - these problems happen. Quite probably the previous owner was aware that the calorifier wasn't working but didn't disclose and the surveyor didn't pick it up.

The boat had always been kept in warm countries so antifreeze might have been neglected - good antifreeze does offer protection against rusting.
 
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AndrewB said:
No technical issue. It was a 25 year old engine in a boat that I had just bought - these problems happen. Freezing was not an issue, but good antifreeze does offer some protection against rusting which might well have helped.
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OK thanks. I would say that any commercially available antifreeze offers 100% protection against rusting ... provided the effective concentration is maintained. But that's detail.

Richard
 
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