The heating system installed on the boat by the boatbuilder is a webasto termotop diesel powered boiler providing the both the heating and hot water. Inside we have 4 standard radiators, these are installed in the galley, saloon, dinette and bedroom, and a towel radiator in the bathroom.
We had not tested the heating prior to purchasing and I guess a “survey” does not do this either. I am assuming this because we had issues pretty much from day one.
The boiler was noisy and the radiators in the dinette and bedroom (these are the ones furthest away from the boiler) did not get hot – warm sometimes but not hot.
Because of the noise the boiler was making I assumed this was at least part of the issue. I set about removing this from the boat, clamping the flow and return pipe to conserve the fluid (which to be far looked pretty awful brown in colour, but I could smell it was antifreeze). I removed the boiler and took it to an authorised webasto dealer (Kings Lock) and they dismantled the boiler. They initially said that someone had tampered with it at some point and it had not been reassembled correctly, they they went on to say the burner tube ws pretty knackered and the fan was making the noise I had heard. They did offer to replace these parts but the cost was so much I decided to get a replacement unit, £600 paid and a few days later a replacement arrived.
I installed this replacement and immediatley I could tell it sounded better but unfortunaley it did not fix the two radiators that were not heating correctly. I started doing some research on what the problem may be but didnt find much that helped me.
I then started to think about flushing the system through, as stated above the fluid was pretty brown and the header tank pretty stained.
I worked thoguh the plumbing and decided I would attached a hose from the mains tap at one point, and a hose to a large container for the flushed water to go into. Once all connected I turned on the water from the hosr (I had installed a local tap) I could see water starting to come through the outlet host, it was awful, there was so much sediment collected I donlt think the inhibitor had been working fro some time.
I kept this going for a while and kept closing all but one of the radiators, I could hear the water going through the “bad” radiatiors so I was hopeful that this may clear the problem. Once the water was running clear I remived the hose and retuned the plumbing to how it was. I topped up the header tank and started the boiler. This had been the issue, all the radiators got very hot. The last step was to drain the system down and refill withe an antifreeze mix, I decided on a 50/50 mix. I premixed the solution and refilled the system. Its been working great ever since.