Calorifier Questions

[Dibble]

Forgive my ignorance here guys, here goes. I have a 58' narrowboat and I'm looking to replace my calorifier from a 50l to 75l. Other than increased capacity, are there any other benefits like economy etc? Is an expansion tank essential, and do I get a single coil or twin coil? There's four radiators on the boat if that means anything 🤔

[MtB]

9 minutes ago, Dibble said:

Other than increased capacity, are there any other benefits like economy etc?

 

Nope!

 

A drawback though is with more hot water available to use, you'll probably find you need to fill the cold water tank more often. 

 

And yes an expansion vessel is essential for long life of the calorifier. and get the same number of coils as your current calorifier, whatever that is.

 

 

[Tony Brooks]

7 minutes ago, Dibble said:

Forgive my ignorance here guys, here goes. I have a 58' narrowboat and I'm looking to replace my calorifier from a 50l to 75l. Other than increased capacity, are there any other benefits like economy etc? Is an expansion tank essential, and do I get a single coil or twin coil? There's four radiators on the boat if that means anything 🤔

 

What engine?

 

If your engine is water cooled then probably a twin coil calorifier, one for the engine and the other for the hearing to heat the water. Not if by a slim chance it is direct raw water cooled.

 

you don't have to have an expansion vessel and so rely upon the PRV to limit the pressure in the system, but doing that is likely to eventually split the calorifier, so yes, you do need an expansion vessel. That keeps things simple, but it is possible to plumb the boat, so the accumulator also acts as an expansion vessel, but in view of your question I would not advise this.

 

 

[cuthound]

8 minutes ago, Dibble said:

Forgive my ignorance here guys, here goes. I have a 58' narrowboat and I'm looking to replace my calorifier from a 50l to 75l. Other than increased capacity, are there any other benefits like economy etc? Is an expansion tank essential, and do I get a single coil or twin coil? There's four radiators on the boat if that means anything 🤔

 

The only benefit is more hot water.

 

single or twin coil depends on weather you just want to heat it with a single source (engine , backboiler or Webasto or similar) or two sources (engine and Webasto for example).

 

If you want the calorifier to have a long life then an expansion vessel is a must, as it prevents the flexing of the calorifier as the pressure in it varies, limited only by the PRV.

 

Another useful thing to have is a thermostatic mixer valve, set to a usable temperature. This effectively increases the amount of hot water available, by delivering it to the taps and shower at the temperature needed, rather than then having to mix it with cold water to reduce the temperature.

[Tracy D'arth]

An expansion tank is essential if you have a non return valve in the cold feed to the calorifier and you don't have an accumulator on the cold supply. It will save the strain on the calorifier when it warms up which is often why they fail.

You need twin coils if you heat from more than one source, ie. engine and  stove.

No real economy other than you can store more hot water.

[Dibble]

Thanks for the advice all, 👍

[ditchcrawler]

Waiting for all the posts that say "I have had a boat for 30 years and never had an expansion vessel its what the PRV is for".

[GUMPY]

4 hours ago, ditchcrawler said:

Waiting for all the posts that say "I have had a boat for 30 years and never had an expansion vessel its what the PRV is for".

If you don't have an NRV then the accumulator acts as an expansion vessel 🤔

[MtB]

7 hours ago, ditchcrawler said:

Waiting for all the posts that say "I have had a boat for 30 years and never had an expansion vessel its what the PRV is for".

 

My hypothesis is that a calorifier is typically good for perhaps, 10,000 pressure cycles from pump cut-in pressure to pump cut-out pressure. By having an expansion vessel, the calorifier is exposed to one cycle every perhaps ten or fifteen seconds while without one, the pump cycles on and off maybe once a second. So one might expect a calorifier with a vessel to last ten or fifteen times as long as one without, before metal fatigue gets it and causes it to split. 

 

Metal fatigue became famous as the cause of the airborne disintegrations of the De Havilland Comet back in the 1950s.

 

https://www.planeandpilotmag.com/article/why-did-the-de-havilland-comet-keep-crashing/

 

 

[blackrose]

The phenomenon is the same but if your calorifier splits the effects are unlikely to be quite as catastrophic. 

 

I wonder if they could have kept the square windows in the Comet if they'd fitted an expansion vessel?

[robtheplod]

18 hours ago, ditchcrawler said:

Waiting for all the posts that say "I have had a boat for 30 years and never had an expansion vessel its what the PRV is for".

thats me, although only 4 years!

[Jen-in-Wellies]

Just now, robtheplod said:

thats me, although only 4 years!

That's about when my first calorifier failed. No expansion vessel.

10 hours ago, blackrose said:

The phenomenon is the same but if your calorifier splits the effects are unlikely to be quite as catastrophic. 

 

I wonder if they could have kept the square windows in the Comet if they'd fitted an expansion vessel?

At cruising altitude, modern airliners are kept at a pressure of 80% of sea level to reduce the difference to the outside and the cyclical stresses on the cabin. It's equivalent to being at around 2,000m altitude on a mountain. Most people sitting down will notice no ill effects, but they would if they were working out on an exercise bike. It's why your ears pop on the climb up and descent to the airport at each end.

The square windows would have been fine if they'd either hedge hopped, or had the passengers and crew on oxygen masks above 10,000'.

[robtheplod]

1 hour ago, Jen-in-Wellies said:

That's about when my first calorifier failed. No expansion vessel.

 

looks like i have something else to add to the list....

[Tony Brooks]

19 minutes ago, robtheplod said:

looks like i have something else to add to the list....

 

Before doing that, trace the pipework to see if you have an accumulator. If you do, then see if there is a non-return valve in the cold feed into the calorifier. If there is not one, then the accumulator will also be acting as an expansion vessel.

 

Mine was like that for the 20 years we owned it, and no split calorifier.

[Slim]

12 minutes ago, Tony Brooks said:

 

Before doing that, trace the pipework to see if you have an accumulator. If you do, then see if there is a non-return valve in the cold feed into the calorifier. If there is not one, then the accumulator will also be acting as an expansion vessel.

 

Mine was like that for the 20 years we owned it, and no split calorifier.

Mine was 28 years. Mind you I suspect that the difference in quality between a 28 year old calorifer and a modern one is significant. ‼️

[Tony Brooks]

Just now, Slim said:

Mine was 28 years. Mind you I suspect that the difference in quality between a 28 year old calorifer and a modern one is significant. ‼️

 

Is that with a NRV and no expansion vessel, or without a NRV using the accumulator as an expansion vessel? Just for clarity for others.

[MtB]

A further 'gotcha' is there might be no external visual evidence of the existence of a NRV. They are sometimes built into the cold water inlet connection on the calorifier itself. 

 

So inspecting the installation and not seeing one does not mean there isn't one. To find out for sure, read your calorifier manual.

 

 

[ditchcrawler]

14 hours ago, MtB said:

 

My hypothesis is that a calorifier is typically good for perhaps, 10,000 pressure cycles from pump cut-in pressure to pump cut-out pressure. By having an expansion vessel, the calorifier is exposed to one cycle every perhaps ten or fifteen seconds while without one, the pump cycles on and off maybe once a second. So one might expect a calorifier with a vessel to last ten or fifteen times as long as one without, before metal fatigue gets it and causes it to split. 

 

Metal fatigue became famous as the cause of the airborne disintegrations of the De Havilland Comet back in the 1950s.

 

https://www.planeandpilotmag.com/article/why-did-the-de-havilland-comet-keep-crashing/

 

 

But what you quote is the expansion between pump off and pump on, it takes no account of the water heating and expanding above pump cut off until relief valve lifting which is what the expansion vessel takes up.

[Slim]

7 hours ago, Tony Brooks said:

 

Is that with a NRV and no expansion vessel, or without a NRV using the accumulator as an expansion vessel? Just for clarity for others.

No NRV, no expansion vessel, using the 5 ? litre accumulator for expansion. 

[Tony Brooks]

That is OK then.