Here are further comments.
I am assuming that your vent loop is after the heat exchanger
in my views it is where it should be, it prevent drainage of the heat exchanger
therefore scaling of the tube with consequent loss of thermal conductivity, it prevent more water
draining into the water
lock, disadvantage is a higher water temperature.
A common problem with the above configuration is that sometime there is no physical room to install the vent loop hose out of the heat exchanger and back into the mixer, normally a very tight rubber elbow
does the connection, which need to be removed. I use automotive heater hoses, you can find them with all sort of suitable bends.
The way to overcome this is to manufacture a flanged spacer out of steel
pipe, thick and seamless the better. In your case you could angle the flange in such way that the mixer looks toward the water lock. I would not go more than 7 degrees. This will reduce the bend in your hose. Vetus recommend a maximum radius of 4 D for its hose and a minimum of 30 cm or 12 inches between mixer and water lock and in some countries also sell suitable hoses. If short (60mm) I do not think the flange requires insulation
. If insulation
is required make sure it is of the correct heat rating and fireproof. I dislike fiberglass
because it as a tendency to fall apart and find its way into the motor
, it is all depending how good is your motor
air intake filtration. I still use good old asbestos with SS gauze wrapping to keep heat inside the exhaust
In my view the water lock should be installed fore and aft for best performance as heel and roll can be detrimental to its working. Vetus manufacture one with a rotating inlet.
To totally prevent water ingress into the wet exhaust
a ball valve can be installed after the gooseneck into the discharge line. I use a fiberglass
reinforced one which are normally tested at 70 degree C without any problem but I have a sailing boat.
The last test is to run everything and stop and measure the amount of water inside the water lock just to check that the right size as been installed.
Vetus couplings can be pretty rough and hard to seal, filing the lip smooth and using some neutral cure silicone and double clamps can overcome the problem.