Heating

[Bob692]

We have just bought our second hand nb and everything seems fine. We are a bit confused about the radiator heating. The setup seems standard. 2coil calorifier ( engine and webasto). Both webasto and engine produce lashings of hot water but only the webasto heats the radiators. Should the engine heat the radiators by convection from the calorifier as there is no separate circulation pump or do we need to operate the webasto and use its pump and rely on it throttling back when the engine is running. I have checked there seem to no valves shut etc. Thanks from a newbie!

[IanM]

On ours certainly only the Webasto heats the radiators. 

[Mike on the Wey]

Your setup is typical. Some engine/calorifier circuits also heat a bathroom towel rail, but if linked to the full heating circuit there is a risk of over-cooling the engine.

[robtheplod]

15 minutes ago, IanM said:

On ours certainly only the Webasto heats the radiators. 

same here..... would be great to have the option for winter cruising though!

[Boater Sam]

Quite normal that the diesel heater only will heat the radiators. As has been said there is a very small risk of overcooling the engine if it feeds the radiators as well. There is also the difficulty of keeping the water in the radiators separate from the engine water and coping with the expansion and header tank differences.

The way to do it if you want to is to put a plate heat exchanger  in the engine circuit at the calorifier coil return position and feed the output of it into the radiator circuit with a small circulation pump with a switch and a gate valve to shut it off when not required in summer.

Needs careful design and a bit of thought as to where and how to tap it into the radiator circuit so that it does not interfere with the diesel heater circuit. May need a gate valve in that circuit as well but care must be exercised not to close it off when the heater is on.

[cuthound]

4 hours ago, Bob692 said:

We have just bought our second hand nb and everything seems fine. We are a bit confused about the radiator heating. The setup seems standard. 2coil calorifier ( engine and webasto). Both webasto and engine produce lashings of hot water but only the webasto heats the radiators. Should the engine heat the radiators by convection from the calorifier as there is no separate circulation pump or do we need to operate the webasto and use its pump and rely on it throttling back when the engine is running. I have checked there seem to no valves shut etc. Thanks from a newbie!

 

Only the Webasto will heat up radiators, unless you have a second circulating pump in the heating circuit (the first is built into the Webasto) and a PHE (plate heat exchanger) between the engine cooling and Webasto heating circuits.

 

My boat has the second circulating pump fitted but not the PHE. This allows the calorifier to be used as a crude heat exchanger, but the radiators only get warm, not hot when the second circulating pump is operated with the engine running.

[Bob692]

Many thanks for your answers, I now understand.