Installing an immersion heater

[Jennifer McM]

Our boat for some reason doesn't have an immersion heater fitted. We initially thought the calorifier didn't have a place to install one, but thanks to Mrsmelly for the suggestion, we dismantled the back of the boat to take another look.  At the top of the upright tank/calorifier, there looks to be a 'disc/bung' where an immersion heater would fit. 

 

Water is normally heated by the engine or by the Mikuni diesel central heating boiler.

 

We're thinking of buying either a 1Kw or 2Kw immersion heater from Midland Chandlers, but which one?

 

OH is thinking of installing the immersion element in the calorifier, then getting an electrician to wire it in. 

 

Are there any tips or warnings we should know about? Thank you muchly  

[philjw]

Make sure that you cannot inadvertantly power the immersion from the inverter, even if the shore supply drops out.

You will need to check the length of the element which your tank can take but this should not be an issue with a vertical tank.

Loosen the blanking boss with the tank full - there should be no need to drain yours anyway. Sometimes it helps to tighten slightly before undoing the boss.

[Jennifer McM]

1 minute ago, philjw said:

Make sure that you cannot inadvertantly power the immersion from the inverter, even if the shore supply drops out.

You will need to check the length of the element which your tank can take but this should not be an issue with a vertical tank.

Loosen the blanking boss with the tank full - there should be no need to drain yours anyway. Sometimes it helps to tighten slightly before undoing the boss.

Brilliant Phil, exactly the info we need  thanks

[dmr]

They come in different lengths. A short one will make a smaller amount of hot water but do it more quickly, so the choice depends upon you boating lifestyle.

Likewise for power, if you are always on a good hookup to shore the bigger one might be better unless you want to have a lot of other big stuff running at the same time, If you hope to run off  a smallish generator then the lower power would be better.

 

,,,,,,,,,,,,,,,,,Dave

[Jennifer McM]

? Thanks Dave  

[Boater Sam]

Buy a good inconel sheathed one not a cheap copper one as you may well fill up with slightly aggressive water at some places  and cheapies corrode away. 1kW is an advantage if the shore supply is limited to 5 or 6 Amps as some are. But of course takes twice as long to heat up compared with 2kW

2kW would need at least 10 Amps if you are to avoid tripping on switch on.

You will lose a small amount of water when you remove the 2 1/4" brass plug, an old towel should cope, but do remember to switch the pump off and open the hot taps first!

[bizzard]

The standard screw thread size of the element is 2.1/4'' BSP,  but there is a chance that your calorifier has a smaller diameter one of which I can't remember the size. 2'' maybe. Once the blanking plug is removed the inside diameter of the threaded bush can be measured either with a ruler or ideally with the internal prongs of a calliper vernier. If standard the internal diameter will be a touch over 2.1/4''.

Edited February 22, 2019 by bizzard

[bizzard]

If the smaller non standard size one, the seating part of the threaded bush will be tapered to correspond with the tapered seat of the element and sealed with an ''0'' ring instead of a gasket.

[Jennifer McM]

6 minutes ago, Boater Sam said:

Buy a good inconel sheathed one not a cheap copper one as you may well fill up with slightly aggressive water at some places  and cheapies corrode away. 1kW is an advantage if the shore supply is limited to 5 or 6 Amps as some are. But of course takes twice as long to heat up compared with 2kW

2kW would need at least 10 Amps if you are to avoid tripping on switch on.

You will lose a small amount of water when you remove the 2 1/4" brass plug, an old towel should cope, but do remember to switch the pump off and open the hot taps first!

Just googled 'inconel sheathed' - that's a very good point. The 1kW would suffice for the two us! Turning off the water pump and opening hot taps, I would never have thought of that.

 

Thank you  

6 minutes ago, bizzard said:

The standard screw thread size of the element is 2.1/4'' BSP,  but there is a chance that your calorifier has a smaller diameter one of which I can't remember the size. 2'' maybe. Once the blanking plug is removed the inside diameter of the threaded bush can be measured either with a ruler or ideally with the internal prongs of a calliper vernier. If standard the internal diameter will be a touch over 2.1/2''.

Thanks for the tips Bizzard - perfect  

2 minutes ago, bizzard said:

If the smaller non standard size one, the seating part of the threaded bush will be tapered to correspond with the tapered seat of the element and sealed with an ''0'' ring instead of a gasket.

That's a bit gobbledegook to me, but OH is nodding your advice is clear  Thank you

[bizzard]

7 minutes ago, Jennifer McM said:

Just googled 'inconel sheathed' - that's a very good point. The 1kW would suffice for the two us! Turning off the water pump and opening hot taps, I would never have thought of that.

 

Thank you  

Thanks for the tips Bizzard - perfect  

Yes I'd go for the 1kw one too.  2KW might be a problem with the marina's electrics especially if you have other high powered appliances running at the same time. A 2kw element obviousely uses the same power as an 2kw electric kettle or a 2 bar electric fire not to mention micro waves and washing machines ect.

Edited February 22, 2019 by bizzard

[Onewheeler]

You may find (almost certainly will) that the blanking plug is scaled in and an utter bastard to remove. A blowlamp helps.

[WotEver]

14 minutes ago, Onewheeler said:

You may find (almost certainly will) that the blanking plug is scaled in and an utter bastard to remove. A blowlamp helps.

And Screwfix sell the big spanner thingy...

https://www.screwfix.com/p/box-immersion-spanner/29549

 

or...

https://www.screwfix.com/p/plumbing-tools-by-rothenberger-cranked-immersion-spanner-122mm/20266

[Jennifer McM]

19 minutes ago, Onewheeler said:

You may find (almost certainly will) that the blanking plug is scaled in and an utter bastard to remove. A blowlamp helps.

Thanks for the heads up  Think a blowlamp is out of the question though as the tank is moulded in polystyrene, it doesn't have loose jacket.

5 minutes ago, WotEver said:

And Screwfix sell the big spanner thingy...

https://www.screwfix.com/p/box-immersion-spanner/29549

 

or...

https://www.screwfix.com/p/plumbing-tools-by-rothenberger-cranked-immersion-spanner-122mm/20266

That's kind of you to search, the top one looks the right one. Cheers  

[frahkn]

Just now, Jennifer McM said:

Thanks for the heads up  Think a blowlamp is out of the question though as the tank is moulded in polystyrene, it doesn't have loose jacket.

 

For practical reasons you may have to cut back the insulation around the plug. It can be replaced later using a can of spray foam.

[WotEver]

3 minutes ago, Jennifer McM said:

the top one looks the right one. Cheers  

You can get improved leverage with the bottom one but you might not have the access it requires. 

[Sea Dog]

And in case you're still in two minds Jennifer, we have a 1kW immersion and it copes perfectly well in our ubiquitous narrowboat Surecal tank (55 litres is it?).The practicality of being able to use it on almost any shore supply far outweighs the unnecessary higher performance of the 2kW version imho. 

[Flyboy]

If my memory serves me correct you should use a marine grade immersion heater that has a secondary overheat thermostat. This prevents the normal thermostat tripping if you run the engine at the same time. A domestic immersion heater would not be suitable if you use the engine to heat the calorifier as well.

[Jennifer McM]

29 minutes ago, Sea Dog said:

And in case you're still in two minds Jennifer, we have a 1kW immersion and it copes perfectly well in our ubiquitous narrowboat Surecal tank (55 litres is it?).The practicality of being able to use it on almost any shore supply far outweighs the unnecessary higher performance of the 2kW version imho. 

That's good info, thank you! The 1kW is on the shopping list now  Don't know how big the tank is, it's now encased again in cupboards. But I found a picture from a log book at the time the boat was being fitted out.

 

 

 

15 minutes ago, Flyboy said:

If my memory serves me correct you should use a marine grade immersion heater that has a secondary overheat thermostat. This prevents the normal thermostat tripping if you run the engine at the same time. A domestic immersion heater would not be suitable if you use the engine to heat the calorifier as well.

I wondered about that  , guess we'll be safe if we get the heater from Midland Chandlers?

[mrsmelly]

6 hours ago, Jennifer McM said:

Our boat for some reason doesn't have an immersion heater fitted. We initially thought the calorifier didn't have a place to install one, but thanks to Mrsmelly for the suggestion, we dismantled the back of the boat to take another look.  At the top of the upright tank/calorifier, there looks to be a 'disc/bung' where an immersion heater would fit. 

 

Water is normally heated by the engine or by the Mikuni diesel central heating boiler.

 

We're thinking of buying either a 1Kw or 2Kw immersion heater from Midland Chandlers, but which one?

 

OH is thinking of installing the immersion element in the calorifier, then getting an electrician to wire it in. 

 

Are there any tips or warnings we should know about? Thank you muchly  

Pleased you found it. Its weird how many people put these cauliflowers in without the heating element fitted. If done from new it takes less than five minutes and costs 35 quid ish and basic to wire in. By far the most convenient and cheapest method for constant enough hot water. Be careful to not overtighten the heating element when you fit it.

[Onewheeler]

As an alternative you might like to consider an external immersion heater, which connects between the cold feed and top outlet of your calorifier (as close to the tank as possible), fitted with a 1 kW or whatever element. Google "Willis heater" (pronounced Will-iss). It would save having to extract the blanking plug.

 

Martin/

[ditchcrawler]

5 hours ago, WotEver said:

And Screwfix sell the big spanner thingy...

https://www.screwfix.com/p/box-immersion-spanner/29549

 

or...

https://www.screwfix.com/p/plumbing-tools-by-rothenberger-cranked-immersion-spanner-122mm/20266

I dont think that will fit the bung

[jonathanA]

Possibly not but it will fit the immersion 

[Dr Bob]

We've got a 1KW one. Plenty of hot water for two. The advantage of the smaller power is that you can leave it on when running other high power items i.e. hair driers, oil filled rads, etc. If you had a 2 KW one then you'd be ok in our marina but the minute the other load goes on then the shore power would trip. 

[blackrose]

10 hours ago, Jennifer McM said:

Thanks for the heads up  Think a blowlamp is out of the question though as the tank is moulded in polystyrene, it doesn't have loose jacket.

 

Polyurethane

[Boater Sam]

The plug will have a hex head around 40mm, use a wrench on it, whack it if its tight.  Loosen it with the cylinder full and warm if you can.

Marine use element will have 2 stats inside, one for setting the temperature other as a safety overheat. Comes with a new gasket, grease it and the threads before fitting. You should get away without the big spanner if you have a chain or strap wrench for your oil filter? It only needs to be tight enough not to leak. I have done them with a bit of rope and a screwdriver twisted in it when stuck.

That cylinder will take a 27" element.

Buy a metre of heat resistant immersion heater cable as well and wire it into the element before you fit it, much better than trying to do it in the cupboard!

Edited February 23, 2019 by Boater Sam
added more