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bridgesjon

heating hot water

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hi. I am looking to fit a instantaneous water heater on my narrowboat. I have a calorifier which is heated currently by a back boiler and my engine, so I often have like warm or hot water. so can i fit my water heater on my hot water circuit coming from the calorifier so that it has less  (or no) work to do, or must I fit it in the cold circuit? any help appreciated! jon

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I believe standard practice is to have 2 heating circuits in the calorifier.  The lower one is connected to the engine cooling system, providing a large volume of hot water but taking a long time to heat up the whole tank, while the upper one can be powered by a water heater, heating up a smaller volume of water more quickly, or to the back boiler.  How many heating coil connections do you have?

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2 minutes ago, Murflynn said:

I believe standard practice is to have 2 heating circuits in the calorifier.  The lower one is connected to the engine cooling system, providing a large volume of hot water but taking a long time to heat up the whole tank, while the upper one can be powered by a water heater, heating up a smaller volume of water more quickly, or to the back boiler.  How many heating coil connections do you have?

Not the sort of heater the OP talks about.

 

10 minutes ago, bridgesjon said:

hi. I am looking to fit a instantaneous water heater on my narrowboat. I have a calorifier which is heated currently by a back boiler and my engine, so I often have like warm or hot water. so can i fit my water heater on my hot water circuit coming from the calorifier so that it has less  (or no) work to do, or must I fit it in the cold circuit? any help appreciated! jon

 

It is potentially dangerous to feed an instantaneous gas water heater with water from a calorifier.  It would be easy to get water at 100C and stem coming from the taps/shower. This would probably fur up the heater's hate exchanger.

 

We usually recommend a two way valve so you either feed water from the calorifier to the taps or water from the heater that is fed by cold water.

 

 

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my calorifier has a blender valve fitted, so the water feeding the gas heater should be no more hotter than the hot water currently coming from my taps. if the water is already hot, then the heater would not come on, and if it was only like warm  the heater would have less work to do, and therefore use less gas?

 

29 minutes ago, bizzard said:

Why would you need to heat water that's already hot. :unsure:

often my water is only partially heated, but it is warner that the water from the cold water tank

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7 minutes ago, bridgesjon said:

 if it was only like warm  the heater would have less work to do, and therefore use less gas?

Instantaneous water heaters don't work like that.  Its either on or off, so if you feed it warm water, the hot water coming out will be too hot.

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1 hour ago, bizzard said:

Why would you need to heat water that's already hot. :unsure:

You don't, the op wants to heat water that is cooler than hot.

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7 minutes ago, Chewbacka said:

You don't, the op wants to heat water that is cooler than hot.

Geez, isn’t this all getting a bit over-complicated?  If OP has an instantaneous water heater then feed it with cold and hot comes out. If he wants the calorifier water hotter then run the engine for a bit longer (or add some cladding). 

 

Or am I missing something?

 

 

Edited by WotEver
I don’t know what a water Hester is...
  • Greenie 1

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2 hours ago, Tony Brooks said:

Not the sort of heater the OP talks about.

 

yeah - didn't read it thoroughly. sorry  ......   :blush:

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Just now, Murflynn said:

yeah - didn't read it thoroughly. sorry  ......   :blush:

We all do it, I do it more each year that passes!

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31 minutes ago, WotEver said:

Geez, isn’t this all getting a bit over-complicated?  If OP has an instantaneous water heater then feed it with cold and hot comes out. If he wants the calorifier water hotter then run the engine for a bit longer (or add some cladding). 

 

Or am I missing something?

 

 

Don't all these heaters 'heat the water by X degrees', rather than 'heat the water to X degrees ?

 

So if the heater is capable of increasing the temperature by (say) 60 degrees 'above ambient', then if cold water (15*) is put thru the heater it will come out at 75*.

 

If hot / warm water from the cauliflower  (at 30*) goes into the heater, it will come out at 90*

 

If the cauliflower water happens to be still at 40*, then the heater will be outputting 'boiling water'

 

Sounds (potentially) dangerous.

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It's also worth noting that if you have the calorifier and a gas heater plumbed in without a changeover valve you get extra cold water mixed with your warm calorifier water through the unlit gas heater.  You will end up with tepid at best.

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The OP hasn'tmentioned gas. All the instant water heaters on the screwfix site are electric AND some of them have built in thermostats.

 

Of course he will need a reasonably powerful inverter. It seems like a lot of trouble to me.

Edited by Cheshire cat

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2 minutes ago, Cheshire cat said:

The OP hasn'tmentioned gas.

Very true - just goes to show what assumptions can do.

 

Surely no normal boat owner would go for electric water heating unless they were on 'mains'. 

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50 minutes ago, Cheshire cat said:

Of course he will need a reasonably powerful inverter.

 

Understatement of the decade! 

 

Any 240Vac instantaneous heater delivering more than a feeble trickle will be 10kW or more.  How to beat your batteries to death in one easy lesson...

 

 

 

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I suppose it depends on what the OP means by instantaneous. I typed instaneous water heater into the screwfix search facility and it came up with several in the 2Kw - 3Kw range. The water may be hot and instantaneously drawn from a resevoir but granted the heating of it will not be. 

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Would it be simpler to put a "Tee"joint in the cold feed after the pump and pipe it to the water heater.?

With a tap and swivel spout on the water heater.

Edited by Mad Harold

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15 hours ago, Alan de Enfield said:

Very true - just goes to show what assumptions can do.

 

Surely no normal boat owner would go for electric water heating unless they were on 'mains'. 

And even then many shoreline installations wouldn't cope. Some are as low as 5A.

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Not sure if this is of any interest. On my boat I only had a single coil calorifier with nothing else. That means long periods of engine running in the marina. I had an old 3 gallon tank with a 240v immersion. I put aT in the cold water feed. I used a second pressure relief valve and T into the original outgoing pressure relief pipe. I bought a simple 2 input 1 output change over valve on eBay so it either takes water from the engine tank or my mini immersion tank. When I apply power to the immersion tank it energises the valve and changes it over. The immersion is only 1Kw ( less than 5 amps on 240v )  but heats enough for a nice shower in about 20 minutes.

 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F122778968124

Edited by Bobbybass

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