Jump to content

Sealed heating system - draining for pipe alterations


Featured Posts

It seems that we have a sealed / pressurised heating system on our new boat. A webasto heats 5 radiators and the domestic water. The engine also heats the water, and it seems also the radiators via a separate circulation pump if activated. 

 

I am finding it very hard to get my head around the mess of pipes, pressure gauges and capped ends. There seems to be a callorifier, red expansion tank, and another white accumulator / expansion tank. 

 

It all works right now, but I need to move the first radiator back a couple of feet to expand the bedroom. Luckily, this can be done without too much alteration to the pipes as they seem to branch off separately to feed this one before heading on to the other rads. All I need to do is shorten the two pipes in the photo and move the radiator back.

 

The problem is the pressurised system. At first I thought I could simply act fast and cap the ends after removing the pipe for shortening. Now I'm told I should really drain the whole system, but it's really not obvious how to go about this without a clear drainage valve. Also once drained I'm not sure how to refill a sealed system, somone told me I'll need mains pressure? 

 

It really would be much simpler If i didn't have to drain the system for this. I realise it will need to happen at some point eventually for servicing, but I have so many other things to do aboard right now. Could I perhaps use molegrips on the surrounding pipes while I cap them off properly? Any advice at all is really appreciated! 

 

 

IMG_20180712_140446276.jpg

IMG_20180712_140505442.jpg

IMG_20180712_182657423.jpg

Link to comment
Share on other sites

Well, I guess you could hire a pipe freezer kit (and use mole grips to slightly distort the pipe after the plug to stop it moving) but that’s a load of hassle. Far better I’d have thought to draw out your installation to understand what everything does and then drain down from the lowest point. You could take the opportunity to fit a drain cock if there isn’t already one there. 

Link to comment
Share on other sites

Cor, you lot got better photos than I did. My reply by PM:-

 

The instructions for fitting a sealed system are at the end of this document https://www.butlertechnik.com/downloads/4110310A_Thermotop_C_E_Install.pdf

 

basically think domestic combi boiler as far as the wet side of things are concerned except the expansion vessel is usually inside the domestic boiler case while yours is somewhere else. Probably very close to the pressure gauges.

 

First you need to de-pressurise the system but as the liquid inside is at whatever pressure one of the gauges shows it could be messy unless the installer has fitted a drain point. If its a good installation you may find a drain to one side of the engine bay poking through the bulkhead. Otherwise choose a point where    antifreeze mixture spraying everywhere will do least harm (preferable as low as possible in the system to facilitate future draining), drill the pipe so you can direct the mixture flow into a bowl and when de-pressurised I expect with plastic pipe you would be able to quickly cut the pipe and fit a T with a drain cock on it.  If you can find a suitable drain cap then use that.

 

Once its de-pressurised you can either drain it or work fast with the full system but I would drain it and then do the work.

 

Once the system is pressurised check the air pressure in the expansion vessel. Those introductions say it should be at 3 bar (45psi).

 

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).

 

A tip. If you are connecting plastic pipe to a normal compression fitting it is VITAL that you use METAL pipe inserts. The plastic ones soften and allow the pipe and insert to collapse under the olive.

 

 

 

Link to comment
Share on other sites

1 hour ago, Tony Brooks said:

A tip. If you are connecting plastic pipe to a normal compression fitting it is VITAL that you use METAL pipe inserts. The plastic ones soften and allow the pipe and insert to collapse under the olive.

 

Interesting that you mention that. I've used plastic inserts in compression fittings for years without issue. Recently however, Toolstation were selling inserts that were a bit loose in the pipe. Foolishly I went ahead and used them to elbow chrome tails from a wall for a towel rail and cost myself two days' labour fixing the problem. 

I'm not aware of many manufacturers that make metal inserts; possibly only Hep²O. 

Link to comment
Share on other sites

I bought my metal inserts from a proper plumbers supply company, possibly Plumb Centre but I had to ask for them. They were not on show. In my case the problems came trying to connect a metal full bore ball valve to 15mm plastic. After my experience with plastic on the boat's gas boiler I would never use plastic on a solid fuel stove, I think that if it ran away you could easily end up with leaks all over the place, grip rings or not.

Link to comment
Share on other sites

 

At first I thought i had found the drainage hose which leads from the pipework to one side of the engine bay! But alas, you'll see from the second picture that inside the cabin it isn't actually connected to anything! There is what looks like a brass nossel at the lowest point of the system inside the cabin, you'll see that in these pictures. This is close to an underfloor Sump pump tray which I wonder if was on purpose, engine bay seems to make.moe sense for draining. If that brass nossel is indeed for draining, I could connect it to the engine bay outlet by hose, but the hose itself would raise a couple of inches in the process. Curiously, the pressure gauge seems to read 0. There is also what looks like a brass copper pipe with a kind of end cap higher up, filling point? Or perhaps it's the top of this white tank with a black cap that unscrews?

 

I would very much like to pay someone to come and teach me how this works, and perhaps service/ drain the system. Anyone reccomend in the Bath area? 

IMG_20180713_120431343.jpg

IMG_20180713_120730593.jpg

IMG_20180713_120806731.jpg

IMG_20180713_121046466.jpg

IMG_20180713_122346723.jpg

IMG_20180713_122355520.jpg

IMG_20180713_122512105.jpg

Link to comment
Share on other sites

FWIW and only from what I can see.

 

This looks like  jumble of domestic water and central heating systems to me.

 

The vertical pipe with the pressure gauge on is, I think, the central heating. The brass thing on top with a red knob is a pressure relief valve just in case the system boils and the expansion vessel can't cope.  From that we can conclude the red "tank" is the expansion vessel for the central heating while the larger white one is an accumulator or probably more likely an expansion vessel for the domestic water system.

 

The braided silver hose connected to just below the pressure gauge is the filling loop so if you turned on the white plastic service valve think I saw on one photo and the service valve connected to the valve with the black wing knob on it and then, with the domestic water pump turned on very carefully "cracked the black knob valve open a touch you should find the central heating system pressurises. At 1 bar (15psit) close the valve and close the service valves. That is the  central heating system pressurised.

 

Inspect the "bottom" of the red vessel. Hopefully you will see  car type valve cap there. This is where you check and if necessary replenish the air pressure with NO PRESSURE IN THE CENTRAL HEATING SYSTEM. Webasto say 3 bar (45psi).

 

The brass pot like thing on a short length of copper pipe that is connected to the white plastic pipe looks like an automatic bleed valve to me (others will confirm or deny). Without tracing the pipes I do not know what system its on. I suspect the domestic water but it may be the  engine calorifier circuit or even for the central heating.

 

To my eye the oblong box like metal thing on the floor looks a bit odd. I f it has four pipes on it I think it may be a heat exchanger to allow the engine to pass heat to the central heating system when under way. To be sure the pipes would need tracing and the calorifier heating coil(s) connections identifying. It looks as if this may be a single coil calorifier and if so the heat exchanger (if that is what it is) might be pacing heat to the central heating system to heat the calorifier. On the other had the engine may heat the calorifier directly and the heat exchanger passes heat from the central heating to the engine calorifier circuit.

 

The black cylinder that is in front of the red expansion vessel looks like a circulating pump to me that may or may not be related to that heat exchanger operation. The blue box like thing below the white vessel I have no idea about. Possibly an electric flow control valve or some  form of thermostat. Hopefully others will recognise it. I fear there may be 240V AC involved din the operation of at least some of this and if so and if it is a single coil calorifier then I suspect a lot of simplification could be done by getting a twin coil calorifier and doing away with the heat exchanger, pump and blue thing.

 

Not sure about the calorifier because I think I can see three potential coil pipes but a twin coil one needs four.

 

Hope this helps.

 

 

 

 

Link to comment
Share on other sites

31 minutes ago, Chewbacka said:

You can probably depressurise the system by making sure the valves either end of the filling loop are close, then disconnect one end of the flexible, hold the end over a bucket and slowly open the valve.  I can’t see a non return valve.

Very good idea.

Link to comment
Share on other sites

1 hour ago, Tony Brooks said:

FWIW and only from what I can see.

 

This looks like  jumble of domestic water and central heating systems to me.

 

The vertical pipe with the pressure gauge on is, I think, the central heating. The brass thing on top with a red knob is a pressure relief valve just in case the system boils and the expansion vessel can't cope.  From that we can conclude the red "tank" is the expansion vessel for the central heating while the larger white one is an accumulator or probably more likely an expansion vessel for the domestic water system.

 

The braided silver hose connected to just below the pressure gauge is the filling loop so if you turned on the white plastic service valve think I saw on one photo and the service valve connected to the valve with the black wing knob on it and then, with the domestic water pump turned on very carefully "cracked the black knob valve open a touch you should find the central heating system pressurises. At 1 bar (15psit) close the valve and close the service valves. That is the  central heating system pressurised.

 

Inspect the "bottom" of the red vessel. Hopefully you will see  car type valve cap there. This is where you check and if necessary replenish the air pressure with NO PRESSURE IN THE CENTRAL HEATING SYSTEM. Webasto say 3 bar (45psi).

 

The brass pot like thing on a short length of copper pipe that is connected to the white plastic pipe looks like an automatic bleed valve to me (others will confirm or deny). Without tracing the pipes I do not know what system its on. I suspect the domestic water but it may be the  engine calorifier circuit or even for the central heating.

 

To my eye the oblong box like metal thing on the floor looks a bit odd. I f it has four pipes on it I think it may be a heat exchanger to allow the engine to pass heat to the central heating system when under way. To be sure the pipes would need tracing and the calorifier heating coil(s) connections identifying. It looks as if this may be a single coil calorifier and if so the heat exchanger (if that is what it is) might be pacing heat to the central heating system to heat the calorifier. On the other had the engine may heat the calorifier directly and the heat exchanger passes heat from the central heating to the engine calorifier circuit.

 

The black cylinder that is in front of the red expansion vessel looks like a circulating pump to me that may or may not be related to that heat exchanger operation. The blue box like thing below the white vessel I have no idea about. Possibly an electric flow control valve or some  form of thermostat. Hopefully others will recognise it. I fear there may be 240V AC involved din the operation of at least some of this and if so and if it is a single coil calorifier then I suspect a lot of simplification could be done by getting a twin coil calorifier and doing away with the heat exchanger, pump and blue thing.

 

Not sure about the calorifier because I think I can see three potential coil pipes but a twin coil one needs four.

 

Hope this helps.

 

 

 

 

 

Thanks Tony,

 

I think this is a two coil calorifier because there are two outlets for the webasto and two others for the engine. I'll try and take a photo to show this. There are also another two outlets (bottom and top) to feed domestic taps.

 

You are correct, the metal box is a heat exchanger, and the black pump is a circulation pump. If the engine is running and the pump activated, it looks like it draws the water from the webasto pipes through the heat exchanger and then pumps through the rads to provide heat when underway. The heat exchanger seems to be heated via the engine coolant at the same time as the domestic water, as the coolant passes through the exchanger on the way back to the engine. The heat exchanger is effectively a part of the return circuit. 

 

Do i understand your message correctly? Because I think you are saying that I can re-pressurise or refill the system via the domestic water pump by opening the two, currently closed, valves that lead from the red tank to the domestic water? This pipe also seems to lead to the white accumulator.

 

Am i correct in thinking that cold water is drawn into the calorifier at the bottom and leaves at the top? There must be two separate compartments inside it, otherwise newly added cold water would bring down the storred hot water temp. 

 

I suppose the black circulation pump could be used to drain the heating pipes completly if I just depressurised first and then unscrewed the outlet currently leading to the heat exchanger and connected to that disused outlet pipe leading to the engine bay. Those hose would reach so perhaps this was originally setup. 

 

I really want to do this myself, and whilst it's becoming clearer I am still leaning towards finding someone to explain this in person!

15314943866081636500486.jpg

15314945074571910763218.jpg

Edited by Poppin
Link to comment
Share on other sites

You said “Am i correct in thinking that cold water is drawn into the calorifier at the bottom and leaves at the top? There must be two separate compartments inside it, otherwise newly added cold water would bring down the storred hot water temp. “. 

 

The answer is ‘yes the water enters at the bottom and leaves at the top’ but it is a single cylinder, the hot water being less dense floats on top of the cold water and does not mix. There is some heat conduction from the hot layer into the cold but it takes a while.  On my tank if we go to bed with it full of hot water we can both have a shower in the morning without reheating.  As an aside, a vertical calorifier is better as the layer between hot and cold with a half full of hot water tank is much smaller than with a horizontal tank.  That said most have a horizontal tank as it more efficiently fits in the boat.

Link to comment
Share on other sites

29 minutes ago, Boater Sam said:

A heating "pump" is a misnomer, they are circulators, will not positively displace water. The pressure gauge should show some pressure, maybe a half to one bar, even when cold.

Not if sufficient water has been lost from the system it wont.

 

Link to comment
Share on other sites

1 hour ago, Poppin said:

Thanks Tony,

 

I think this is a two coil calorifier because there are two outlets for the webasto and two others for the engine. I'll try and take a photo to show this. There are also another two outlets (bottom and top) to feed domestic taps.

 

You are correct, the metal box is a heat exchanger, and the black pump is a circulation pump. If the engine is running and the pump activated, it looks like it draws the water from the webasto pipes through the heat exchanger and then pumps through the rads to provide heat when underway. The heat exchanger seems to be heated via the engine coolant at the same time as the domestic water, as the coolant passes through the exchanger on the way back to the engine. The heat exchanger is effectively a part of the return circuit. 

 

Do i understand your message correctly? Because I think you are saying that I can re-pressurise or refill the system via the domestic water pump by opening the two, currently closed, valves that lead from the red tank to the domestic water? This pipe also seems to lead to the white accumulator.

 

Am i correct in thinking that cold water is drawn into the calorifier at the bottom and leaves at the top? There must be two separate compartments inside it, otherwise newly added cold water would bring down the storred hot water temp. 

 

I suppose the black circulation pump could be used to drain the heating pipes completly if I just depressurised first and then unscrewed the outlet currently leading to the heat exchanger and connected to that disused outlet pipe leading to the engine bay. Those hose would reach so perhaps this was originally setup. 

 

I really want to do this myself, and whilst it's becoming clearer I am still leaning towards finding someone to explain this in person!

 

 

1. Heat exchanger - much as I expected.

 

2. As far as I can see the silver braided hose is the filling loop so, yes you can pressurise the central heating from the domestic water system. The white "tank" is part fo the domestic water system so running the filling loop from a T in its base is acceptable.

 

3. No really. Cold water is forced into the lowest connection on the calorifier when a hot tap is opened so pressure drops. Water stratifies in the calorifier and house domestic direct and indirect cylinders. Hot at the top and cold below so basically apart from a small degree of convection the hot and cold water do not mix.

 

4. As the system is presently apparently de-pressurise you will not get   anything spraying out of any joint in the central heating system but it might "glug out". I would look for a low central heating pipe in a situation where a the liquid will not cause too much mess and drain from there. Then fit a proper drain point and hose tail.  As someone said the "pump" is a centrifugal circulator and its fairly high up. It will stop pumping when the level drops to its impeller. That will leave all the liquid below it in the system.

 

 

 

1 hour ago, Poppin said:

By the way, I have just noted that the pressure gauge rests at 0 unless the heating is actually on, then it begins to climb. 

That's the water in the system expanding - apart from it being de-pressurised all seems normal. Webasto say pressurise the water-antifreeze mixture to one bar.

Edited by Tony Brooks
Link to comment
Share on other sites

46 minutes ago, Tony Brooks said:

1. Heat exchanger - much as I expected.

 

2. As far as I can see the silver braided hose is the filling loop so, yes you can pressurise the central heating from the domestic water system. The white "tank" is part fo the domestic water system so running the filling loop from a T in its base is acceptable.

 

3. No really. Cold water is forced into the lowest connection on the calorifier when a hot tap is opened so pressure drops. Water stratifies in the calorifier and house domestic direct and indirect cylinders. Hot at the top and cold below so basically apart from a small degree of convection the hot and cold water do not mix.

 

4. As the system is presently apparently de-pressurise you will not get   anything spraying out of any joint in the central heating system but it might "glug out". I would look for a low central heating pipe in a situation where a the liquid will not cause too much mess and drain from there. Then fit a proper drain point and hose tail.  As someone said the "pump" is a centrifugal circulator and its fairly high up. It will stop pumping when the level drops to its impeller. That will leave all the liquid below it in the system.

 

 

 

That's the water in the system expanding - apart from it being de-pressurised all seems normal. Webasto say pressurise the water-antifreeze mixture to one bar.

Ok so just so I'm clear, when I'm pressurising the system I'm just adding more water to it from the domestic water pump? And I want it up to one bar when cold. Presumably this also means diluting the antifreeze currently in the system?

 

If I understand correctly I can do this pressurising by opening the Phillips screwdriver type isolation valves around the black valve, and then slightly opening the black lever valve until sufficient pressure is reached? 

Link to comment
Share on other sites

33 minutes ago, Poppin said:

Ok so just so I'm clear, when I'm pressurising the system I'm just adding more water to it from the domestic water pump? And I want it up to one bar when cold. Presumably this also means diluting the antifreeze currently in the system?

 

If I understand correctly I can do this pressurising by opening the Phillips screwdriver type isolation valves around the black valve, and then slightly opening the black lever valve until sufficient pressure is reached? 

 

The Webasto instructions I sent you tells you to fill the systems with the antifreeze mixture via the radiator bleed plugs. I think they usually recommend 25% to 30% but check that. So if you are draining the system refill with that mixture plus a small amount more if it makes you happy, put all the plugs and back in up and then pressurise. I doubt more than a pint of water will go in so nothing to worry about dilution.

 

Yes the pressuring procedure is as you state as long as there is no service valve on the other end of the braided pipe.

 

The reason I suggested that once drained down you fitted an upright "filling pipe" to a low point that you can fit a funnel to and blank off/isolate was to avoid the taking the radiator plugs out. You could then just fill via the funnel and bleed as you might at home.

 

The service valve by the black "butterfly" knob valve uses a conventional flat bladed screwdriver.

Link to comment
Share on other sites

26 minutes ago, Tony Brooks said:
 

The Webasto instructions I sent you tells you to fill the systems with the antifreeze mixture via the radiator bleed plugs. I think they usually recommend 25% to 30% but check that. So if you are draining the system refill with that mixture plus a small amount more if it makes you happy, put all the plugs and back in up and then pressurise. I doubt more than a pint of water will go in so nothing to worry about dilution.

 

Yes the pressuring procedure is as you state as long as there is no service valve on the other end of the braided pipe.

 

The reason I suggested that once drained down you fitted an upright "filling pipe" to a low point that you can fit a funnel to and blank off/isolate was to avoid the taking the radiator plugs out. You could then just fill via the funnel and bleed as you might at home.

 

The service valve by the black "butterfly" knob valve uses a conventional flat bladed screwdriver.

Thanks so much Tony, super knowledgable as always! By the way, just to see what would happen, I tried to pressurise a bit just now. I turned the black lever and it did indeed start to climb. However after it reaches about 0.5 bar it stops and goes no further. I also expected the domestic water pump to kick in when pressurising, but I heard nothing, does that mean all the water is pushed in via the accumulator? I thought the domestic pump should kick in, especially since it does so when it fills the calorifier as hot water is used, and this is basically the same pipe.

Link to comment
Share on other sites

Pumps have a cut-in and a cut out pressure.  Mine cuts-in a bit below 0.5bar and cuts off at about 2 bar.  If you want to up the pressure when filling, turn on a sink cold tap to drop the pressure and get the pump to turn on.  I can’t see a non return valve on you filling loop, so be careful because if the pressure in your heating system is higher than your cold drinking water when you open the filling valve coolant will flow from the boiler system into the drinking water.

Link to comment
Share on other sites

1 hour ago, Chewbacka said:

Pumps have a cut-in and a cut out pressure.  Mine cuts-in a bit below 0.5bar and cuts off at about 2 bar.  If you want to up the pressure when filling, turn on a sink cold tap to drop the pressure and get the pump to turn on.  I can’t see a non return valve on you filling loop, so be careful because if the pressure in your heating system is higher than your cold drinking water when you open the filling valve coolant will flow from the boiler system into the drinking water.

Can confirm there is not a non-return valve in the filling loop, which seems remarkable. Basically I have two service isolation valves either side of the black lever valve. Presumably I could easily put a non-return valve in here, even without draining the system (by closing both isolation valves, disconnecting the flexipipe and screwing one in?)

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.