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Calorifier insulation


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My calorifier is in the engine bay and I’m considering how to add additional lagging. I’ve seen posts about adding jackets and wrapping in celotex sheets but was also considering creating some sort of cylindrical frame and using expanding insulation foam and wrapping the cylinder in aluminium foil. The foil would not only reflect back the heat but also enable me to get the foam off the cylinder if it all goes horribly wrong 😛
any ideas on which gives the best insulation per inch of thickness as space is at a premium. 

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My calorifer is on the semi-trad swim.  Despite being well insulated I liberally applied expanding foam, especially between the calorifer and the hull side.  Easy to trim off excess after.

 

Made a very noticeable difference to temperature in the morning after cruising the day before.  Well worth doing for a few quid.

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There is a trade off when insulating something round, like a cauliflower. As the insulation thickness goes up, so does the external surface area, which increases convection heat losses from the surface. If the insulation contacts the hull, particularly below the water line, then the losses increase considerably through conduction to the cold water. There is going to be a sweet spot of insulation thickness, though what it is is difficult to say, without some complicated sums and perhaps some experimentation. It isn't as simple as more thickness = better. On the first calorifier on my boat I added a domestic glass fibre cylinder blanket to the foam insulation it came with. Can't say if it made any noticeable difference and when the cauliflower was replaced I didn't bother and just went with the supplied foam coating.

Jen

Edited by Jen-in-Wellies
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51 minutes ago, Machpoint005 said:

The OP doesn't say whether there is a stopcock on the hot water inlet to the caulifower. If there isn't, the engine heats the cauliflower when it's running, then the cauliflower keeps the engine warm when it is switched off.

Point taken but that is by no means certain. careful pipe runs can prevent it as can a flap valve in the upper calorifier coil pipe/hose.

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15 minutes ago, Machpoint005 said:

Fairy Nuff, but I can tell the difference next morning when I forget to close the valve.

So fit a flap type NRV and you won't forget to close the valve - just get it the right way round or else no hot water.

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4 hours ago, Machpoint005 said:

The OP doesn't say whether there is a stopcock on the hot water inlet to the caulifower. If there isn't, the engine heats the cauliflower when it's running, then the cauliflower keeps the engine warm when it is switched off. 

 

 

This is usually a problem on boats with horizontal calorifier mounted on the floor, I.e. lower than the engine. I’ve also had it with a vertical calorifier mounted close to the engine.  Fixed with a flap valve.

 My current boat with horizontal calorifier on the swim is fine, as it is higher relative to the engine.

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This is great stuff all - thanks. Sorry for a late response - a common boating problem (or joy😊) - lack of signal. 
I’ve routed the pipes to the engine that seem to prevent siphoning and I’ve also got a manual valve to shut it off if need be. While I want to maintain heat over night my main concern is freezing in the winter. We live aboard part time normally 3 days most weeks so my main concern is to minimise the risk of damage between visits and not have to drain down the system every time I think there is going to be a cold spell.

obviously if the forecast is sub zero for weeks I might have to drain down but want to avoid this as much as possible. 
The bubble wrap and foam idea sounds interesting. As space is at a premium have you any idea how efficient this is compared with just foam for say a 2” covering. I think maybe a final wrap of foil backed matting might also be on the cards. 

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1 hour ago, Strettonman said:

 We live aboard part time normally 3 days most weeks so my main concern is to minimise the risk of damage between visits and not have to drain down the system every time I think there is going to be a cold spell.

 

The most important things to do is for short term is to shut off the stopcock from the water tank and to open all the taps and leave them open.

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19 hours ago, Tony Brooks said:

So fit a flap type NRV and you won't forget to close the valve - just get it the right way round or else no hot water.

 

I don't forget. Once was enough.

 

19 hours ago, dor said:

This is usually a problem on boats with horizontal calorifier mounted on the floor, I.e. lower than the engine. I’ve also had it with a vertical calorifier mounted close to the engine.  Fixed with a flap valve.

 My current boat with horizontal calorifier on the swim is fine, as it is higher relative to the engine.

 

Hmm - vertical cauliflower, in my case.

2 hours ago, Strettonman said:

obviously if the forecast is sub zero for weeks I might have to drain down but want to avoid this as much as possible. 

 

If it isn't the forecast, you will be all right. It is very unusual for the temperature inside the boat to drop below 0° for long enough to freeze a tank. Just do as Dor suggests: shut off the main stopcock and leave all the taps open (then switch off the water pump). 

Edited by Machpoint005
typo
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  • 2 weeks later...

Not sure anyone is really interested but here is my attempt so far. I lined the foam covered calorifier with tin foil and then built up 2 sections of slight loose bubble wrap and injected fire retardant foam to create about a 1” layer. Once (sort of) set I put on 3 sections of very loose bubble wrap to create a second layer another couple of inches thick. I’d ordered 1m wide bubble wrap but it was out of stock so they gave me several 30cm wide rolls. This was actually better for getting the foam in. 
the only problem is it is taking days for the foam to set as the air can’t get to it. 
next step will be cover it with foil backed laminate underlay and then sort the plumbing end and lag the inlet and outlet pipes. 
I’ll certainly be shutting off and opening taps as a matter of routine over the winter and may even do a partial drain down if i need to leave it when it is really cold. 

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