Calorifier 240v switch

clyst

clyst

Well-Known Member
Joined
18 Aug 2002
Messages
3,233
Visit site
Hi all

Having replaced the isolating switch between the shore supply RCD and the calorifier some 6months ago due to the original getting a tad hot and smelling of hot plastic I notice that the new switch now getting a tad hot .

I took the advice of the chap in the electrical shop of the required rating of the switch . Its just a bog standard sort of 13amp plug looking socket but has a little red light and is wired direct .

Question ....... Could the problem be that the calorifier temp be set a bit too high ? What is the ideal temp setting ? Or could it be that I require a higher amp switch . Cant remember what rating to current one is . What rating should it be ? ....... Guess that depends on the heater

Cheers
 
clyst said:
Hi all

Having replaced the isolating switch between the shore supply RCD and the calorifier some 6months ago due to the original getting a tad hot and smelling of hot plastic I notice that the new switch now getting a tad hot .

I took the advice of the chap in the electrical shop of the required rating of the switch . Its just a bog standard sort of 13amp plug looking socket but has a little red light and is wired direct .

Question ....... Could the problem be that the calorifier temp be set a bit too high ? What is the ideal temp setting ? Or could it be that I require a higher amp switch . Cant remember what rating to current one is . What rating should it be ? ....... Guess that depends on the heater

Cheers
Click to expand...

Ideally, it should be a double pole 20A switch, with or without a neon indicator, though, like the one on my boat, it would be preferable to have the indicator.

Similar to this one http://www.ebay.co.uk/itm/20A-Double-Pole-Neon-White-BS3676-Switch-Plate-Flex-O-L-/350326662478
 
Last edited:
clyst said:
Hi all

Having replaced the isolating switch between the shore supply RCD and the calorifier some 6months ago due to the original getting a tad hot and smelling of hot plastic I notice that the new switch now getting a tad hot .

I took the advice of the chap in the electrical shop of the required rating of the switch . Its just a bog standard sort of 13amp plug looking socket but has a little red light and is wired direct .

Question ....... Could the problem be that the calorifier temp be set a bit too high ? What is the ideal temp setting ? Or could it be that I require a higher amp switch . Cant remember what rating to current one is . What rating should it be ? ....... Guess that depends on the heater

Cheers
Click to expand...


I think you will find that domestic immersion heater switches are normally double pole 20amp switches. Domestic immersion heaters usually being 3 KW


Got one here waiting to be fitted ...
 
Last edited:
clyst said:
Hi all
Question ....... Could the problem be that the calorifier temp be set a bit too high ? What is the ideal temp setting ? Or could it be that I require a higher amp switch . Cant remember what rating to current one is . What rating should it be ? ....... Guess that depends on the heater
Cheers
Click to expand...

It won't be due to you setting the temp. too high. The element will use nn Watts and just runs for longer to heat water to a higher temperature. It won't jump from 2kW to 4kW if you run it twice as long, it will still be 2kW.

You have another problem if the switch is getting warmer the longer you leave it on. i.e. A fault (poor connection, undersize switch or wiring, etc.)

Ideal temp.
I imagine it would be as high as you can manage, but no anywhere close to boiling, IF you have a cold water mixing valve on the tank outlet. I'm guessing that 80C would be OK, perhaps other will think that this is dangerous as valve might fail (though longish pipe runs and lack of a bath make it slightly less risky).

Don't put it to that temp. if the tank outlet just feeds the tank. Perhaps someone can give better advice but 60C might be OK if pipe run allows it to drop to 48C or less at the tap. I'm picking these temps. because 60C will kill most bugs and 48C won't instantly scald.

You are correct in stating that you should check the element Wattage. Ones on small boat tanks might only be 1200W rather than 3000W you might expect.
 
Last edited:
Hot switch

The problem with calorifiers is that they draw a lot of current for comparatively long times until the water heats. 3000w element will draw 12 amps Switch ratings on the other hand tend to be optimistic and probably allow for temp rise. Which may be acceptable.
So if the hot switch concerns you then yes buy a greatly over rated switch . good luck olewill
 
The biggest calorifier element listed by ASAP is 1.5 kW, with various others of 0.5, 1.0, 1.25 kW. The one I have in my boat is only 850 watts. It seems that few calorifiers have elements with the power of domestic ones because the marina supply is often limited to around 10 amps. The switch for mine is a very basic one, not special at all and does not get hot.
 
I must admit it sounds to me like corrosion on the contacts. Is the switch in an are where there is a lot of damp, is it used a lot?

A standard home immersion switch should be more than man enough for the job, getting hot indicates something in the switch is causing a higher than normal resistance which results in heating. The two main causes are loose connections and poor contacts
 
Thanks for all your replies and guidance .

Update !! I have had a look and the switch is a double pole 32amp switch . I have checked all connections and they appear sound .
Btw there area and components are completely dry .

Just inspected the calorifier !
it a common cleghorn type and the heater is..... 15amp 3kw !! Seems a tad big to me . the wiring appears to the the same as you would expect to supply a domestic kettle .

What now chaps ??
 
Last edited:
Given the information you supplied above then everything would seem to be OK. I agree that 3kW is quite large for a boat as the hot water tank is usually quite small.

So I'm going to fall back on my first rule for diagnosing any fault. What has changed?

You said "I notice that the new switch now getting a tad hot" and that points to a faulty switch (even though it seems to adequately specc'd).
 
Make sure the feed wires to the switch, and from the switch to the heater coil are of sufficient cross sectional area (thickness) to cope with the high current for long periods.

It may be that the wires are heating up and passing that heat through to the switch.

Also ensure all the terminals (on any high current joint) are screwed down tight on to the wires.

Have you wired the connections so that the current passes through both poles of the switch? Shouldn't be possible to only connect it through one, but worth checking anyway.

Also have you checked your thermostat is working OK and cutting out at required temp? 15A for any length of time will tend to heat up the supply wiring, so unless you have a very large calorifier it should be heated up and cutting out quite quickly - 10-15 minutes I would have thought.

Best solution is to fit a smaller heating coil. 3kw is too big for a boat application where shore power supply current is often quite limited.
 
You must log in or register to reply here.

Share this page

Top