Webasto header tank height

[TandC]

I'm juggling the options on my Webasto install.   Specifically, the location of the header tank.  

 

The Webasto unit will be in the engine compartment - as is the calorifier, which is the first heat demand, then through the bulkhead and onto the radiator ring. 

 

How much height difference is required for the header over the rest of the system (boiler, calorifier, rads, pipework)?  

 

If it is just "higher than" - then I would hope that I can keep it all in the engine compartment - achieving a bit of height difference while also still being able to fill/top it up. 

 

But if it needs a significant height difference, then i would have to take the header into the main cabin - into what will be the bathroom - and locate it on the rear bulkhead wall and run the pipes down and back out into the engine bay.   this is a faff as it takes up wall space in the bathroom and will require boxing into a cupboard etc, and means more pipe holes in the steel bulkhead. 

 

in time honoured fashion, a splendid options diagram included below:

 

Any thoughts?  

 

Option 1:

 

 

 

 

 

Option 2: 

 

 

 

 

 

 

Edited July 31, 2023 by TandC

[Tonka]

Are you putting the calorifier and the rads on the same circuit ? When you say engine compartment are we saying under floor in a cruiser stern

[Tracy D'arth]

Higher than the highest point on the system is fine.  Take one pipe only from the bottom of the tank onto the circuit at the high point, no over the top pipe required. It will vent and allow for expansion. Volume needs to be 5% of the total water volume or more.

[David Mack]

13 minutes ago, Tracy D'arth said:

Take one pipe only from the bottom of the tank onto the circuit at the high point, no over the top pipe required.

That pipe should also rise continuously from the high point or the radiator/calorifier circuit to the header tank. Not so easy if the high point is a radiator at the front of the cabin.

[TandC]

18 minutes ago, Tonka said:

Are you putting the calorifier and the rads on the same circuit ? When you say engine compartment are we saying under floor in a cruiser stern

Yes - cruiser stern 10ft wide.  The webasto will be on the right side just above the uxter plate, and the calorifier will be sat on the baseplate up against the bulkhead, to the right of engine.    22mm pipes to 15mm feeds to first the calorifier then on to a ring of 1 towel rail then 4 radiators in "there-and-back" single line going along the right side across the bow back down the left side.

 

 

This is the installation diagram from Webasto - describing this two-pipe/bypass valve arrangement with the header tanks as "the most efficient non-pressurised system"

 

I haven't really got my head into thinking much further at this stage - I was just trying to work out the issue of the header tank location first before I go try and plan some more. 

 

No doubt I shall be back for more shortly....

 

 

 

The pipe work is going to require to come from Webasto horizontal at the height of the Uxter plate through the bulkhead, and then drop down to within the boxing just above floor level - so two right angles effectively - before running off and then back in 22mm.  There will then be 15mm tee feeds to calorifier, towel rail, then the sequence of 4 rads. 

 

 

 

 

 

 

 

And looking like this ish

 

 

 

 

 

[matty40s]

The bypass valve/ tap does indeed give you the best system, and makes it far easier to bleed all the air as well.

This system used an existing loop from an old Alde boiler and we just inserted the 22mm from the Webasto to the first and last radiators. So long as the bottom of the tank is above every other bit of the system, the engine bay install will be OK.

[Tracy D'arth]

40 minutes ago, matty40s said:

The bypass valve/ tap does indeed give you the best system, and makes it far easier to bleed all the air as well.

This system used an existing loop from an old Alde boiler and we just inserted the 22mm from the Webasto to the first and last radiators. So long as the bottom of the tank is above every other bit of the system, the engine bay install will be OK.

How does the bypass valve, which needs to be open when the system is working, aid bleeding air?

[Chris G]

12 minutes ago, Tracy D'arth said:

How does the bypass valve, which needs to be open when the system is working, aid bleeding air?

With the bypass valve closed, all the return flow has to go through the header tank easily releasing any air.  It's not often you don't know all the answers 🙂!

[David Mack]

5 hours ago, TandC said:

Yes - cruiser stern 10ft wide.  The webasto will be on the right side just above the uxter plate, and the calorifier will be sat on the baseplate up against the bulkhead, to the right of engine.    22mm pipes to 15mm feeds to first the calorifier then on to a ring of 1 towel rail then 4 radiators in "there-and-back" single line going along the right side across the bow back down the left side.

 

 

This is the installation diagram from Webasto - describing this two-pipe/bypass valve arrangement with the header tanks as "the most efficient non-pressurised system"

 

I haven't really got my head into thinking much further at this stage - I was just trying to work out the issue of the header tank location first before I go try and plan some more. 

 

No doubt I shall be back for more shortly....

 

 

 

The pipe work is going to require to come from Webasto horizontal at the height of the Uxter plate through the bulkhead, and then drop down to within the boxing just above floor level - so two right angles effectively - before running off and then back in 22mm.  There will then be 15mm tee feeds to calorifier, towel rail, then the sequence of 4 rads. 

 

 

 

 

 

 

 

And looking like this ish

 

 

 

 

 

You'd probably get better circulation with the port and starboard side radiators on separate loops. Just tee off the port side loop within the engine room and run the transverse pipes on the engine side of the rear bulkhead. Less pipework overall and less resistance to the pumped flow.

[Tracy D'arth]

1 hour ago, Chris G said:

With the bypass valve closed, all the return flow has to go through the header tank easily releasing any air.  It's not often you don't know all the answers 🙂!

I don't see what difference 2 connections to the same pipe 6" apart make when one would do. And the valve is totally unnecessary. Forcing the circulation into a partially filled tank and out again will simply cause turbulence and possibly air entrainment into the water.

I reckon its bunkum.

[Chris G]

7 minutes ago, Tracy D'arth said:

I don't see what difference 2 connections to the same pipe 6" apart make when one would do. And the valve is totally unnecessary. Forcing the circulation into a partially filled tank and out again will simply cause turbulence and possibly air entrainment into the water.

I reckon its bunkum.

Perhaps RTFM.🙂

[TandC]

Good stuff.

 

 

On splitting into two separate loops - one serving the two rads on the port, one serving the three on the starboard...  I've had conflicting advice, with some saying it'd be more efficient run as I propose - one continuous loop.    It is easier to not have to take a second loop across from the starboard to the port side for various reasons of other electrics etc in the way.   So unless there is a really glaring reason, i think i will stick to the single loop.   It's marginal whether there is any more pipe involved and the boat is only 45ft long anyway. 

 

On the bypass valve - the Webasto manual and the folk at ButletTecknic recommend the two pipes/bypass valve to do what ChrisG says - micro air bubbles better expunged apparently.  

 

Well it's all a while off yet but the thinking bit is the bit that takes the longest...

 

[matty40s]

Single loop is more efficient, header tank works as described by ChrisG.

[Floaty Me Boaty]

Quick Question when refilling.

I am in the process of replacing two of the Rads and installing a towel rail.

When i refill, is it best to dose the system with an inhibitor, or do i have to use a special solution suited for a Webasto?

Thanks in advance.

[blackrose]

I just use a 30% solution of antifreeze. 50% may be too strong for some reason which I can't remember. The antifreeze has corrosion inhibitors which last anywhere from 2 to 5 years (standard blue or red longlife) essential in central heating systems to stop your rads corroding from the inside, but instead of draining down the system and refilling every few years you can drain some out and add a small amount of Morris Ankorsol to the bucket before refilling. I think the dose is about 3% of the entire systems volume so you need to do a rough calculation or write down how much fluid you originally put in.

Edited August 5, 2023 by blackrose

[Floaty Me Boaty]

22 hours ago, blackrose said:

I just use a 30% solution of antifreeze. 50% may be too strong for some reason which I can't remember. The antifreeze has corrosion inhibitors which last anywhere from 2 to 5 years (standard blue or red longlife) essential in central heating systems to stop your rads corroding from the inside, but instead of draining down the system and refilling every few years you can drain some out and add a small amount of Morris Ankorsol to the bucket before refilling.

Just normal Car Antifreeze would be OK then?

I will more than likely drain her down completely as i did have a small leak, so will make good all joints. 

Once it is renewed, i will know its history, if that makes sense.

Edited August 6, 2023 by Floaty Me Boaty

[blackrose]

23 minutes ago, Floaty Me Boaty said:

Just normal Car Antifreeze would be OK then?

 

Yes. But if it's ready mixed it will probably be 50% and I was advised on here that C/H systems preferred 30% antifreeze solution.

Edited August 5, 2023 by blackrose

[Tony Brooks]

2 hours ago, blackrose said:

just use a 30% solution of antifreeze. 50% may be too strong for some reason which I can't remember.

 

It is to do with the specific heat capacity of antifreeze, which is lower than that of water. The higher the antifreeze concentration, the less heat the liquid can carry to the radiators. Note; Heat and temperature are two different things, that many seem to think are the same.

[ditchcrawler]

Blue sky and the remains of the sun here at the moment 

[Tracy D'arth]

On 31/07/2023 at 21:38, TandC said:

Good stuff.

 

 

On splitting into two separate loops - one serving the two rads on the port, one serving the three on the starboard...  I've had conflicting advice, with some saying it'd be more efficient run as I propose - one continuous loop.    It is easier to not have to take a second loop across from the starboard to the port side for various reasons of other electrics etc in the way.   So unless there is a really glaring reason, i think i will stick to the single loop.   It's marginal whether there is any more pipe involved and the boat is only 45ft long anyway. 

 

On the bypass valve - the Webasto manual and the folk at ButletTecknic recommend the two pipes/bypass valve to do what ChrisG says - micro air bubbles better expunged apparently.  

 

Well it's all a while off yet but the thinking bit is the bit that takes the longest...

 

They are obviously not plumbers or heating engineers!

[cuthound]

I filled both the engine and the Webasto central heating of my boat with Ford Premium 10 year antifreeze at a 50/50% mix.

 

The radiators refused to get hot unless I heated the radiators with a paint gun first. They then worked normally until the heating went off and they cooled down when I had to repeat the process. 

 

I drained the antifreeze and diluted it to a 25% mix and all worked normally, so too strong a mix causes heating issues.