Sealed heating system - draining for pipe alterations

[Tony Brooks]

17 minutes ago, Neil Smith said:

You can buy a pipe freeze kit from tool station, screw fix etc and not loose any water and minimal mess.

Neil

Except that such boat systems should contain at least 20% antifreeze and may well contain 30% or more. I very much doubt such freezing kits would get the part cold enough to freeze the liquid solid. You would probably get ice crystals suspended in liquid that is like a Slush Puppy so there is a good chance of draining the system via a failed ice plug and that will likely be at a location where it causes maximum damage and disruption.

[Poppin]

As a short term measure... what if I just depressurised the system, disconnected the pipe and quickly put some stop ends and socket plugs on? Should loose minimal water and would be able to move the radiator. Then when I re pressurise from the domestic water pump it would replace the lost water, which as I say should be minimal if it's just glugging out. Also trapped air shouldn't be a problem with the auto bleed valves?

 

I can then drain and refill the system properly towards the end of summer when I have more time!

Edited July 14, 2018 by Poppin

[Tony Brooks]

7 minutes ago, Poppin said:

As a short term measure... what if I just depressurised the system, disconnected the pipe and quickly put some stop ends and socket plugs on? Should loose minimal water and would be able to move the radiator. Then when I return pressurise from the domestic water pump it would replace the lost water, which as I say should be minimal if it's just glugging out. Also trapped air shouldn't be a problem with the auto bleed valves?

 

I can then drain and refill the system properly towards the end of summer when I have more time!

That should work and as its a sealed system you may find very little liquid glugs out. Especially if you have a helper to block one side with a thumb or something while you cap the other. Be aware that I have had a case of a Webasto corroding away more than one heat exchanger (the one in the Webasto) and the antifreeze is also a corrosion inhibitor so its vital to keep the antifreeze content of the heating system within limits AND within age. Its the corrosion inhibitors that get "used up", not the antifreeze part.

[Poppin]

12 minutes ago, Tony Brooks said:

That should work and as its a sealed system you may find very little liquid glugs out. Especially if you have a helper to block one side with a thumb or something while you cap the other. Be aware that I have had a case of a Webasto corroding away more than one heat exchanger (the one in the Webasto) and the antifreeze is also a corrosion inhibitor so its vital to keep the antifreeze content of the heating system within limits AND within age. Its the corrosion inhibitors that get "used up", not the antifreeze part.

Good to know. The instructions you posted seem to suggest for a pressurised system, to fill up the radiators themselves as much as possible with the antifreeze water mixture. I suppose with a flexible  funnel or something. Then pressurising with domestic pump tops it up. I guess all trapped air escapes during first fire up via the via the bleed valves. 

 

 

[Tony Brooks]

48 minutes ago, Poppin said:

Good to know. The instructions you posted seem to suggest for a pressurised system, to fill up the radiators themselves as much as possible with the antifreeze water mixture. I suppose with a flexible  funnel or something. Then pressurising with domestic pump tops it up. I guess all trapped air escapes during first fire up via the via the bleed valves. 

 

 

That is what the instructions say but as it involves take the large bleed plugs (not the bleed screws) I think its asking for leaks and mess, especially as it is likely to be a two yearly job for ordinary antifreeze. This is why I suggested that with the system drained down you fit a "stand pipe" to a low part of the system in an unobtrusive position and where a bit of spilled antifreeze will do no harm. That way you can fill the "stand pipe", bleeding the radiators in the normal way, cap the standpipe and pressurise the system.

 

I very much doubt any air trapped in a radiator will escape via that automatic bleed valve. In fact I suspect it might be on the engine calorifier circuit but as I can't see the whole pipework I can't be sure. I suspect you just have to hope the Webasto circulating pump manages to send any residual air into the radiators so you can then bleed them and re-pressurise later.

[Poppin]

On 13/07/2018 at 07:51, Tony Brooks said:

 

 

The biggest problem will be refilling but if can fit a vertical pipe into the lowest point of the system to well above the radiator tops you can probably put a larger funnel on the end and do the initial filing with antifreeze mixture into that, bleeding the radiators and any other high points in the pipe work as you go (two person job). Once you are sure the system is full and bled cap the vertical pipe and connect the filling loop if it is not already connected to the domestic water system.  Carefully open the filling valves and pressurise the system to one bar (15 psi).

 

 

 

 

 

Tony, quick question! Having to deal with this has made me a lot more confident now. I've done my job but I've decided to go ahead and drain the system anyway and fit a proper drain cock and vertical filling pipe. I have no idea how old the fluid is so i want to avoid corrosion!

 

Regarding the vertical pipe, would it not make sense to put an auto bleed valve on the end instead of a cap? It would be the highest point in the system and there isn't one currently (exiting one, you are quite right, is on the engine coolant circuit). 

 

You mentioned bleeding the radiators as I refill (2 person job). How would this work? Have them all open until they start to leak from the top? Would like to do this without another person if possible.

[WotEver]

51 minutes ago, Poppin said:

You mentioned bleeding the radiators as I refill (2 person job). How would this work?

I don’t believe that @Tony Brooks meant “as you refill” to be a concurrent operation. More that you fill it as far as you can, bleed a rad, refill, bleed the next rad, refill etc...  

[Tony Brooks]

1 hour ago, WotEver said:

I don’t believe that @Tony Brooks meant “as you refill” to be a concurrent operation. More that you fill it as far as you can, bleed a rad, refill, bleed the next rad, refill etc...  

Absolutely. Once filling via the suggested stand pipe seems done the radiators and possibly other parts of the pipework will still have air in them so each radiator needs bleeding. just like at home. One at a time, however filling just one radiator will drain the standpipe and then some so you need two people. One to keep the stand pipe full and one to do the bleeding.

 

Although the standpipe might collect air as it needs to be fitted into  a low part of the system air is more likely to collect in high parts like the radiators. I see no advantage of an automatic bleed valve there - its just one more potential leak.

 

If you Poppin could source a largish header tank at reasonable cost and fit that on the end of the stand pipe with an isolation valve to be closed when the system is full and bled teh extra volume might make bleeding not too boring for just one person.soerone