Calorifier connections

[Plevier]

I found yesterday that my calorifier connections are reversed, i.e. the hot flow from the engine goes to the lower connection not the upper as recommended by Cleghorn Waring.
To change them over I would have to extend or replace one pipe.
Is there any point? It seems to work OK as it is (installed on behalf of M Jeanneau.)

 

[superheat6k]

The reason for downward flow is that the engine water will tend to sink naturally as it cools, whilst heating the colder domestic water I.e. thermosyphon. However, if it works as installed then I would leave sleeping dogs to lie.

 

[David2452]

Normally fitted that way as it is better at bleeding any air from the system, but..... if it ain't broke, don't fix it.

 

[Plevier]

Normally fitted that way as it is better at bleeding any air from the system, but..... if it ain't broke, don't fix it.

Interesting point. I noticed it because I changed the coolant yesterday. I blew through the calorifier pipes - which have a dip in them - to empty it. On refilling and running the engine it doesn't seem to be bleeding itself as I expected, the flow pipe warmed very slowly and the return stayed nearly cold. Looks as tho I'll have to bleed it anyway.

 

[PCUK]

Fitted either way depending on point of view, neither is incorrect.

 

[vyv_cox]

In a system heated by indirect cooling, i.e. driven by the engine's circulating pump, it may be slightly less efficient if connected the 'wrong' way around but probably of no consequence. In a raw water cooled system with a small inline electric pump there can be difficulties in establishing flow. The convective flow of the coil can be nearly as much as the relatively low flow of the pump, in which case they balance each other out.

 

[Plevier]

In a system heated by indirect cooling, i.e. driven by the engine's circulating pump, it may be slightly less efficient if connected the 'wrong' way around but probably of no consequence.

This is a Volvo MD2020. I thought the pump would whoosh enough water round to flush out any trapped air but it seems not. There is quite a big dip in the pipes between engine and cal, maybe that's it.
Allied to my overheating problem last weekend I can't help wondering if the pump is OK but other than seals - which are OK - what can go wrong with an iron centrifugal pump esp at only 450h total time?
BTW Vyv, I don't think my overheating was a gasket problem as you postulated, I've run for several hours at lower revs since the incident with nothing coming out of the overflow. I suppose conceivably the gasket might only leak at high power but my car experience is that once a leak starts it happens all the time.

 

[vyv_cox]

I had doubts as I wrote it but it seemed to fit the symptoms. My experience with old cars has been that when a head gasket goes it almost always shows up first as the heater failing to work due to 'gas lock'. Presumably a calorifier would suffer in the same way, which IIRC was not the case for you.

 

[markdj]

I had doubts as I wrote it but it seemed to fit the symptoms. My experience with old cars has been that when a head gasket goes it almost always shows up first as the heater failing to work due to 'gas lock'. Presumably a calorifier would suffer in the same way, which IIRC was not the case for you.

Do you know the size of the fittings required for connection to the engine? Is it 3/8 or 1/2 bsp?

Thanks

 

[vyv_cox]

Do you know the size of the fittings required for connection to the engine? Is it 3/8 or 1/2 bsp?

Thanks

I understand that the correct thread is 3/8 PT, which is a metric thread form in Imperial sizes. It seems it is possible to re-cut the thread to 3/8 NPT but there is a risk of reducing the thread thickness excessively. I have been searching my parts list for their numbers but cannot find them, sorry.