Yep, that’s correct. The company ASAP that does sell the Hotpot Calorifier (made in Italy BTW) does come with the wrong installation instructions.

Not sure if the language barrier is the problem or perhaps is just a silly mistake. I know for personal experience that ASAP is a great company to deal with and if you are in the market for a Calorifier I strongly recommend them.

Let’s have a look at the instruction provided with the calorifier..

There are actually two mistakes in this picture:

  1. ┬áThe last sentence state that “An expansion bottle (tank) should be fitted on the hot supply between the thermostatic mixer and the first take off”. Now it is true that you need to have an expansion tank, but the location chosen in the picture is wrong. By putting the expansion tank there, you will lose quite a bit of water waiting for the hot water to turn up as the expansion tank has got about 8 litre (depending on the size of your calorifier) of cold water in it that doesn’t get warmed up. The reason why they tell you to put it there is because of the second mistake..
  2. In the picture where the cold inlet is it says “Cold feed with built in non-return valve (NRV), that’s also wrong. There is no NRV there, or at least it was not in mine, and the problem with that, is that your hot water will find its way into your cold water tap when the heater is on. If an NRV was there, then yes the expansion tank could go where they have it pictured, but you would still lose large quantities of water every time you have a shower, in particularly if you also have a special shower head (low water consumption). Wasting water like that, on a boat or in an RV is not an ideal solution..

The other problem is that these calorifiers do come with a relief valve made by Caleffi (311) factory set at 4 Bar. Once you have the expansion tank mounted on the hot water feed, that doesn’t leave much room to play for water pressure between the pump, the expansion tank and the relief valve..

So if you use one of these system and you have hot water coming out of the cold tap, you already know that even your Hotpot did not came with the NRV installed. And in all honesty, that’s not a bad thing, because it allows you to mount the expansion tank in the correct location that should always be between the NRV and the calorifier, so not to waste any water..

The picture below does show you the correct location of both the Accumulator and/or the expansion tanks..