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expansion

Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions.Temperature is a monotonic function of the average molecular kinetic energy of a substance. When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves. Substances which contract with increasing temperature are unusual, and only occur within limited temperature ranges (see examples below). The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of linear thermal expansion and generally varies with temperature. As energy in particles increases, they start moving faster and faster weakening the intermolecular forces between them, therefore expanding the substance.

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  1. J

    Pressure problems

    Hi, wondering if anyone has had this issue before; i have just just put an external expansion vessel onto a main combi 30he as the old one had perished. However after about a day the pressure is dissing again above three bar. The filling loop is not passing. My only other thought is there is...
  2. I

    Qualified G3 Plumber to Replace/Repair Expansion vessel ,Harrow area

    Hi Am looking to service or change expansion vessel as it is full of water. Connected next to Pressurized water tank. Live in the Harrow area Can you PM or reply if you are interested in the Job and if can provide estimate with parts and labour or Labour only ... Cheers Indi
  3. bright spark

    Sizing expansion vessels

    Lads which calculation do you use to size expansion vessels on jobs. I have to confess if I'm in a hurry I'll go with 1 litre vessel per kw of boiler. It's just that I go to so may domestic system boilers where only it's internal vessel is installed, at correct air pressure but there's a wide...
  4. C

    Can I use a standard/'heat only' boiler instead of a system boiler?

    Hi - my first post here, so apologies if I'm breaking any protocols! :-) I am fitting an entire new system, 5 beds, 3 floors, 2 bathrooms. It will be an unvented indirect cylinder/tank, a boiler and a potable water expansion vessel. The boiler in such a setup would normally be a system...
  5. R

    DHW cylinders - internal versus external expansion pressure vessel

    Anyone got any views on whether a DHW cylinder having an internal expansion 'bubble' e.g. TribuneXe is better or worse than having a cylinder with an external expansion tank e.g RM Prestel. It strikes me that if there is air in the new water entering the cylinder, it will rise up to the...
  6. woodsy

    Popped new expansion vessel

    Went to a job yesterday on a Biasi with a leak which turned out to be the expansion vessel. Ordered a new one, fitted it and started to fill and the new one popped too which freaked me out. Prv appears to be lifting which was my first thought but just wondering if anyone has had this before and...
  7. R

    Falling pressure on boiler

    Hi, I'm looking for some advice please My worcester boiler (greenstar 24i junior) was constantly losing pressure, dropping down to zero now and again. I called a local engineer who quoted £190+vat to supply/fit a new expansion vessel and pressure relief valve. The engineer who came to do...
  8. C

    What boiler is this?

    Does anyone know the manufacturer and model of this boiler.
  9. K

    Unvented hot water system noise when hot water demand is made

    Hi all, Ready for War and Peace ? Hope you are all sitting comfortably, so let me begin...p.s. I am not a plumber, I work in IT so sorry if incorrect or wrong terms used ! We have a unvented hot water system, installed in Jan 2014. FlowMaster cylinder; Zilmet 11H HY-PRO (18ltr / 3bar...
  10. S

    Sealed System Pressure Issues

    Hello all, Thank you for taking the time to read my post. Background: Micron Glow worm 40FF boiler. Modern 4 bed, 2 floor house, 11 radiators. Leaking pressure relief valve, failed expansion tank behind boiler. Work undertaken so far: I have fitted a new expansion tank, specified by online...
  11. F

    Open vented system,advised to cap off expansion pipe??

    Hi, im a GSR engineer but not from a plumbing background. I have a customer with an open vented system that is having to bleed radiators downstairs and upstairs every few weeks. I asked a plumber about this and he said it was either 1. A leak allowing air into system 2. The expansion pipe rises...
  12. ShaunCorbs

    s plan

    any one see anything wrong with this eg t rule etc sealed system as normally any suggestions welcome and thnx again
  13. W

    H/w expansion vessel

    I need advice but I'm not a plumber, I'm a joiner.We have a house in Portugal and last year had c/h installedwith new 200litre h/w cylinder. The h/w system is non vented and the cylinder is also heated by a solar panel. A month ago the 7 bar pressure relief valve started to leak when the guage...
  14. J

    F and e tank question

    Just wondered if anyone has worked on a back boiler and the f&e tank has backed up from the feed and not from faulty ball valve or filling up from expansion pipe ?..
  15. N

    system design and air problem

    Hi, I seem to be getting a lot of air in the system if I take the pump off its bare minimum setting, just left of the venting setting. I have a open vented S-plan, originally a british gas installation, fitted to a bungalow. The pump and valves are in the airing cupboard together with the...
  16. M

    Legionella risk of expansion pipe to water tank

    Hi, been asked to do a job which seems a little strange. Large office building in London, expansion pipe to roof mounted cold water taken has broken off leaving a hole in the tank, this was noticed when the annual legionella risk carried was out and they have said that the hole needs to be...
  17. A

    Combi Boiler Expansion Vessel Replacement Needed (Halifax area)

    Hi, I am new to the forum and I am hoping members can help. The internal expansion vessel has gone on the combi, I need a 12L external vessel fitting. Job should be simple boiler is located in garage with very easy access and plenty of locations to fix the new expansion vessel. Located in...
  18. B

    Mini Expansion Vessel

    First post since intro! Worcester 28cdi in property when we bought. Worcester engineer when servicing says should have a mini expansion vessel in cold supply because a water meter is fitted. Boiler has worked with very few problems over the years so why is mini expansion vessel needed now...
  19. C

    IDEAL ICOS HE24 - losing pressure after heating is turned off

    Hello, I am new to the forum so hello to you all and here's hoping someone can help pin point what our issue is? I have some knowledge of our system from researching the internet. We have a three storey house. On the first floor is an Ideal Icos HE24 boiler. On the third floor is a Megaflow...
  20. cr0ft

    Expansion Vessels

    Quick one folks. I have a spare potable water expansion vessel kicking around our unit. Rather than skip it, I was wondering if I can use it for a sealed CH circuit? I know you can't do it the other way round but my understanding is potable water expansion vessels are built to a better...
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