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converting open vented to sealed system

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  • 24-11-2013 2:21am
    #1
    pat35
    Closed Accounts Posts: 63 ✭✭


    Im converting my open vented heating system to a sealed system.Would it be ok to tee off the return heating pipe in the boiler house for the 12 litre expansion vessel.Also after i disconnect the open vent and f and e pipe in the hot press can i put the filling loop in the hot press and if so do i fit it on the feed or return of the copper cylinder.Any thoughts would be appreicated


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    #2
    Dtp1979
    Registered Users Posts: 12,745 ✭✭✭✭Dtp1979


    pat35 wrote: »
    Im converting my open vented heating system to a sealed system.Would it be ok to tee off the return heating pipe in the boiler house for the 12 litre expansion vessel.Also after i disconnect the open vent and f and e pipe in the hot press can i put the filling loop in the hot press and if so do i fit it on the feed or return of the copper cylinder.Any thoughts would be appreicated

    The filling loop can go anywhere on the heating system. Just make sure you use the braided hose type and you disconnect it once the system is full. Also have a pressure gauge at the filler.
    And yes the return pipe on the boiler would be the correct place to put the vessel. Make sure 12 litres is big enough. I'd always oversize mine a bit


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    #3
    Dtp1979
    Registered Users Posts: 12,745 ✭✭✭✭Dtp1979


    And just in case this is not obvious, you cannot seal a system which has a solid fuel boiler attached to it. I'd also pressure test your system first to see if it can hold 1 bar


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    #4
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Size the expansion vessel as Dtp1979 says but at a minimum of 11% of the system water volume. A single 1000 x 500 radiator would be approx 10 litres so you could work from there. Add approx 10% for pipework volume & about 25 litres for boiler volume if it's an oil boiler.

    Generally, I would fit a 12L vessel to 7-8 rad systems, 18L to 10-12 rad systems, 24L to 14-16 rad systems, etc., but it would also depend on rad sizes.

    You could also size by boiler output.

    The following chart could be used as a guide.


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    #5
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    Dtp1979 wrote: »
    And just in case this is not obvious, you cannot seal a system which has a solid fuel boiler attached to it. I'd also pressure test your system first to see if it can hold 1 bar

    Totally agree with a pressure test FIRST as if your system has any weak spots they will leak and this will be under the floor guaranteed. Also your taps may need replacing or re washering. A pressure gauge is not expensive and can be push fit onto a tee off stub of 15mm after an isolating valve or screwed onto a male thread. Well worth the money to save the grief.
    Make sure it is a "dry test" version so you can attach a tyre pump to the valve.


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    #6
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    Thanks.The house is 1975 1300 sq.ft single story,firebird popular boiler running at 90,000 btu.8 double rads,I guess il need a least an 18 litre expansion vessel?,also can i fit a caleffi air vent in both the hot press and the boiler house?


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    #7
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    freddyuk wrote: »
    Totally agree with a pressure test FIRST as if your system has any weak spots they will leak and this will be under the floor guaranteed. Also your taps may need replacing or re washering. A pressure gauge is not expensive and can be push fit onto a tee off stub of 15mm after an isolating valve or screwed onto a male thread. Well worth the money to save the grief.
    Make sure it is a "dry test" version so you can attach a tyre pump to the valve.
    Why would i need to change taps?


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    #8
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    Because taps are sealed by washers in older houses and a bit more pressure in the system will allow water to leak by the seals. You may be lucky but just so you know. If you have recessed shower shower valves etc. these can start to weep and you will not know until the water comes through somewhere many weeks later.
    I am not sure why you want to pressurise the system? What advantage are you looking for?
    You seem to be pressurisng the indirect heating circuit? But if you connect the DHW to pressure you need a pressurised cylinder? Are you changing the boiler and cylinder?


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    #9
    Dtp1979
    Registered Users Posts: 12,745 ✭✭✭✭Dtp1979


    freddyuk wrote: »
    Because taps are sealed by washers in older houses and a bit more pressure in the system will allow water to leak by the seals. You may be lucky but just so you know. If you have recessed shower shower valves etc. these can start to weep and you will not know until the water comes through somewhere many weeks later.
    I am not sure why you want to pressurise the system? What advantage are you looking for?
    You seem to be pressurisng the indirect heating circuit? But if you connect the DHW to pressure you need a pressurised cylinder? Are you changing the boiler and cylinder?

    I'd say he's just sealing the heating. Or at least that's the impression I got


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    #10
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    He's pressurising the heating not the dhw. It won't make any difference to the dhw supply to the taps.


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    #11
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    So what is the advantage??


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    #12
    K.Flyer
    Registered Users Posts: 8,565 ✭✭✭K.Flyer


    freddyuk wrote: »
    So what is the advantage??

    To sealing the C.H. System?

    He may have circulation or pitching issues or both and needs to seal the system to resolve it.


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    #13
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Also pressure equals force & higher heat. Better heat throughout the system. I would always go pressurised when I don't need vented.


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    #14
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,233 Mod ✭✭✭✭Wearb


    shane0007 wrote: »
    Also pressure equals force & higher heat. Better heat throughout the system. I would always go pressurised when I don't need vented.

    I don't understand that Shane. I can see in industrial situations that the extra pressure would allow temperatures of over 100C without boiling, I don't see the pressure benifit in domestic systems.

    I will understand if this is too complicated to discuss here. It may be like trying to explain how to fly a plane in a few sentences.

    Please follow site and charter rules. "Resistance is futile"



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    #15
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    Yes it just the heating circuit i want change from open vented to sealed.The reason i want to change it is the radiators are always getting air locked.There is no sludge in the system.I believe it a poorly designed heating system and im thinking by sealing the system it might fix it


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    #16
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    Well I guess that answers my question. It is an attempt to patch up a problem but is likely to lead to further problems.
    Quite how a system in this scenario will work better or more efficiently I am yet to find out.
    My best advice it to find the problem and fix it not increase the pressure to try and force air out of the system. I do not understand how it can work better at higher pressure.
    I have a vented system that works very well and uses the same boiler. I also have single storey so my guess is the piping goes up to the attic and drops down to rooms thus it need air vents in critical areas to avoid airlocks. I would get all the air out of the system (and pressure test it) then see if it performs. I would fit AAV's above any drops that are off long runs in the attic.
    If you do not have drops from the attic you may need to check the piping for possible issues.
    So tell us where the pipes run?


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    #17
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Wearb wrote: »
    I don't understand that Shane. I can see in industrial situations that the extra pressure would allow temperatures of over 100C without boiling, I don't see the pressure benifit in domestic systems.

    I will understand if this is too complicated to discuss here. It may be like trying to explain how to fly a plane in a few sentences.

    Look up "The Pressure Law" along with "Boyle's Law" along with "Charles Law".
    Each is related but the pressure law is what we deal with on an everyday basis.


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    #18
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    All the pipes are underground.The feed and expansion pipe and open vent go to the hot press.one connected to the flow pipe to cylinder ,the other to the return of the cylinder.there is no air vents in the heating system anywhere


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    #19
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    freddyuk wrote: »
    Well I guess that answers my question. It is an attempt to patch up a problem but is likely to lead to further problems.
    Quite how a system in this scenario will work better or more efficiently I am yet to find out.
    My best advice it to find the problem and fix it not increase the pressure to try and force air out of the system. I do not understand how it can work better at higher pressure.
    I have a vented system that works very well and uses the same boiler. I also have single storey so my guess is the piping goes up to the attic and drops down to rooms thus it need air vents in critical areas to avoid airlocks. I would get all the air out of the system (and pressure test it) then see if it performs. I would fit AAV's above any drops that are off long runs in the attic.
    If you do not have drops from the attic you may need to check the piping for possible issues.
    So tell us where the pipes run?
    Sealing a system that was previously pitching or similar is not patching. It is resolving as the pump location in relation to the feed & osvp is crucial in a vented system. The neutral point is a factor also. In sealed, these are taken out of the equation & the neutral point is exactly half round the system.


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    #20
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    I did change the pump from the return to the flow awhile back and it did improve the system but not fully


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    #21
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    .


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    #22
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    pat35 wrote: »
    I dont follow,where would there be a non return valve

    Sorry I posted that but thought I replying to a different thread. Since deleted the post.


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    #23
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    Grand thanks,Im following that thread too to see if i can learn something


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    #24
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    So when you changed the pump where are the feed and expansion pipes in relation to the pump? Have you got photos?
    By all means take the professional option and pressurise the system but if joints start to leak you are just potentially causing more issues.Leaks under the floor can be difficult to resolve. If we can understand the layout you may be able to make a cheap change and solve the problem.
    If you have air entering the system it may be from a weak point thus pressurising will certainly find the leak. If it is pitching then this should be obvious but this has not been mentioned. The symptoms are simply air in the rads. Are the rads old? Maybe the bleed valves are leaking air.Maybe the valves are old and leaking. I think there are some things need checking before major re plumbing.
    Your property is the same age as mine so let's hope it was not the same plumber that installed the system as mine was a complete joke with a cracked pipe embedded in the screed which leaked for many years until I discovered it after buying the property. Get a pressure test and then go from there is still my (cheap) advice.


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    #25
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    A weak system is a weak system whether it be pressurised or vented. If vented, a weak system will still show it's weary head eventually, but it will do more damage as it can be leaking for years unnoticed as it is discreetly topped up from the f & e tank. Weak systems don't get stronger with time, they tend to get weaker.
    At least if pressurised, if it leaks, the pressure drops & highlights the issue immediately.
    I would pressurise the system to at least 2 bar if not higher with air.
    I would also test pressurised with water but heated as an air test can pass but can fail when filled & heated, due to expansion of the pipework/joints.


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    #26
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    The rads are old ,both feed and return are on the right hand side of rad,one on top and one on the bottom of the rad.Its hard to get the rads fully hot


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    #27
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    shane0007 wrote: »
    A weak system is a weak system whether it be pressurised or vented. If vented, a weak system will still show it's weary head eventually, but it will do more damage as it can be leaking for years unnoticed as it is discreetly topped up from the f & e tank. Weak systems don't get stronger with time, they tend to get weaker.
    At least if pressurised, if it leaks, the pressure drops & highlights the issue immediately.
    I would pressurise the system to at least 2 bar if not higher with air.
    I would also test pressurised with water but heated as an air test can pass but can fail when filled & heated, due to expansion of the pipework/joints.

    Well that should have been your first post in my view. (like mine!)
    Secondly you advocate setting up a pressurised system and then dealing with the leaks which may be inaccessible thus doing plenty of damage and causing the heating to be off for some time in Winter. The pipes are under the floor and possibly behind walls.
    Better to do a simple cheap pressure test first. Then if it does not leak fit a pressurised system if you must (or do a hot test) which if it then leaks because of a slight opening of joints is likely to be very minor and will register. Of course you will not know where the leak is so no real advantage.
    If you pressure test now and find the rads are leaky you can fix the problem for tuppence save all the grief. It would be the sensible first option for a lay person.


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    #28
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    pat35 wrote: »
    The rads are old ,both feed and return are on the right hand side of rad,one on top and one on the bottom of the rad.Its hard to get the rads fully hot

    Ahhh.... The plot thickens.....

    If it the radiator type I'm thinking of, then I'm afraid you have one of the worst designed heating systems that was ever invented.
    I'll see if I can dig up a picture of the valve.

    Are you in D15?


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    #29
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    freddyuk wrote: »
    Well that should have been your first post in my view. (like mine!)
    Secondly you advocate setting up a pressurised system and then dealing with the leaks which may be inaccessible thus doing plenty of damage and causing the heating to be off for some time in Winter. The pipes are under the floor and possibly behind walls.
    Better to do a simple cheap pressure test first. Then if it does not leak fit a pressurised system if you must (or do a hot test) which if it then leaks because of a slight opening of joints is likely to be very minor and will register. Of course you will not know where the leak is so no real advantage.
    If you pressure test now and find the rads are leaky you can fix the problem for tuppence save all the grief. It would be the sensible first option for a lay person.
    Don't understand any of that.
    A "lay person" should not be doing any of this. A professional person on site would know what to look for, know how to,assess the suitability of the system & advice the customer of all the pros && cons of each choice. Then the homeowner can make an informed decision.
    How do you know the vented system is not leaking already going unnoticed. Most are already!
    This is a public forum where people come here to seek advice from professionals in order to assist them with that informed decision.
    The professional is not standing in front of that system, but advising from afar. I would have thought a wee bit of common sense would prevail.


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    #30
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    pat35 wrote: »
    The rads are old ,both feed and return are on the right hand side of rad,one on top and one on the bottom of the rad.Its hard to get the rads fully hot

    Is this what you have?


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    #31
    pat35
    Closed Accounts Posts: 63 ✭✭pat35


    shane0007 wrote: »
    Is this what you have?
    Yes,picture A,Im in limerick,


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