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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. M

    Unvented cylinder problems - over pressure or faulty expansion tank?

    Hi, New to this forum and also complete novice who knows pretty much nothing about plumbing. However I have done quite some google searching trying to find some answers. I live in a 1st floor flat which uses an electric duel element direct unvented water heater cylinder (150 litres). Recently I...
    • MrJack2021
    • Thread
    • america cylinder expansion faulty pressure problems tank unvented unvented cylinder usa
    • Replies: 5
    • Forum: USA
  2. D

    Leaky Gledhill expansion relief valve

    Hi I have a leaky Gledhill expansion relief valve block a little like this one with the same spec 3bar on the black input and 4.5 bar on the red expansion relief value. It protects a 250L Gledhill unvented tank. All the input pipes have isolation valves so pretty easy to exchange components...
    • diy_massacre
    • Thread
    • america expansion gledhill leaky relief usa valve
    • Replies: 2
    • Forum: USA
  3. S

    Hi all our boiler has just had a new expansion vessel fitted but pressure is still going to 2.9 bars when using central heating . Is this normal? Than

    Hi All our boiler has just had a new expansion vessel fitted bit the pressure is still rising to 2.9 bars . Is this normal ? Many thanks
    • Sangita
    • Thread
    • boiler central central heating system expansion expansion vessel fitted going normal pressure still using vessel
    • Replies: 5
    • Forum: Central Heating Forum
  4. C

    What expansion vessel should i order for Boiler

    Hi, Currently have a Potterton Promax Combi 28 HE A boiler and looking to replace expansion vessel due to issues with it. Looking to make sure i get the right part for it Found this part online but it says it will Fit a Promax Combi 28 HE Plus A,Is the HE plus A and my boiler HE A the same...
  5. M

    System boiler kw sizing and expansion vessel

    Hi, After a bit of a saga with my plumber, I need to chose boiler size as soon as possible, the plumber is not going to do any heat loss calculations or do anything to work out accurately so I am on my own. Appreciate this is not what should be doing but after some level of finger in the air...
  6. J

    Expansion like vessel

    Currently installing air to water and underfloor.theres this expansion like vessel with two 3/4 iron male threads on top and bottom of it with no bladder on between.its goes before the primary flow hits the cylinder and underfloor manifold.anyone know of its function??we don't do alot of air to...
  7. D

    Unvented system and expansion tank pressurisation

    I've recently had a prv changed by a British Gas engineer under the homecare contract that I've taken out. The valve had failed and water was pouring out from the overflow pipe. The valve was replaced without too much issue. However, the red expansion tank above the boiler was NOT re-pressurised...
    • depr11259
    • Thread
    • america expansion system tank unvented usa
    • Replies: 14
    • Forum: USA
  8. I

    Over-pressure on CH, but expansion tanks fine and related to unvented tank

    Not looking to fix this myself but could do with some insight as to what’s wrong…due to sell the house on a few weeks and not comfortable doing that without this being fixed. CH pressure getting up to 4-5 bar and pressure relaxing through the 3 bar pressure relief valve. Connected to unvented...
  9. J

    Hot water expansion

    Hi Just wondering in a vented hot water cylinder,when hot Does the water expand back up the cold feed into tank or via the vent pipe
    • Johnyc86
    • Thread
    • america expansion hot hot water usa water
    • Replies: 4
    • Forum: USA
  10. C

    Dripping Expansion Tank - Please confirm diagnosis!

    Hi, I've got an oil fired Central Heating system and the overflow pipe drips intermittently. There's a blue expansion chamber just above the overflow that sounds 'full' (compared to the red one that sounds empty. In other systems I've had, when this blue expansion tank was full of water, it...
    • CutAndPaste
    • Thread
    • america confirm dripping expansion please tank usa
    • Replies: 1
    • Forum: USA
  11. M

    Expansion position heat only boiler

    I know when installing an expansion vessel it must be connected to the system without any isolation valves. How is best to pipe in to the system so it can't be isolated. In the diagram below a potential way I was going to pipe in to a heat only boiler. It could be isolated by isolating the...
    • Matt0029
    • Thread
    • america boiler expansion heat heat only position usa
    • Replies: 39
    • Forum: USA
  12. M

    Expansion vessel pre charge

    I have a 35litre central heating expansion vessel that has come with a pre charge of 1.5 bar. Does this sound a little heigh? As the pressure in the system will have to rise above 1.5bar for it or absorb any expansion? Thanks
    • Matt0029
    • Thread
    • america charge expansion expansion vessel usa vessel
    • Replies: 44
    • Forum: USA
  13. H

    Tankless Water heater: Expansion tank burst

    Hi. It's cold as heck in Austin. Temps dropped to single digits last night in Austin. Last night loss power @ 2AM. This morning around 11:30am, heard a loud explosion coming from outside area where the tankless water heater system is installed. Noticed that the expansion tank exploded. You can...
    • hughten
    • Thread
    • america burst expansion heater tank tankless usa water water heater
    • Replies: 1
    • Forum: USA
  14. R

    Promax Combi HE Plus recharge expansion valve

    Hi all, a little advice and validation of current advice (from dad). So boiler has been loosing pressure with an error code of E119. The pressure drops over a day or two and I top it up to around 1.5 by means of loop. This temporarily allows the boiler to fire up and do its thing. I can't carry...
    • RussMB
    • Thread
    • america combi expansion plus promax usa valve
    • Replies: 11
    • Forum: USA
  15. E

    How to recharge an expansion vessel?

    Hi, When my boiler (regular vented I believe) is on there's a constant trickle of water flowing out a pipe to outside (coming off the red vessel in the image below). It's happened in the past and IIRC the expansion vessel needs recharging. I'm pretty sure it's the case again as when I take the...
  16. K

    Intermittent Overflow of Feed and Expansion Tank

    Hello my parents have a house with an open vented system. It has an oil boiler feeding 4 circuits of radiators and also an indirect hot water cylinder. It also has a solid fuel fireplace back boiler (with 4 pipes) to it. The fire can heat both the radiator and the hot water. The fire is never...
    • Kenspark
    • Thread
    • america expansion intermittent overflow tank usa
    • Replies: 8
    • Forum: USA
  17. S

    Correct Expansion Vessel Pressure

    Evening all, So I've been losing pressure from my boiler on a daily basis and having to top it up. The pressure gauge is up at around 3.5 bar when the boiler is on so I assumed the expansion vessel has either failed or is low on pressure. I had a look on both the Cimms website (the EV is a Cimm...
  18. M

    Expansion position on zoned heating

    Just wondering if anyone had any thoughts/ objections to position of expansion vessel. 3 zones on heating upstairs, downstairs and UFH. All zone valves on flow, pump on flow, loss header as well. Expansion vessel it situated on the return from the upstairs zone. I suppose it can’t be cut off by...
    • MethodPH
    • Thread
    • america central heating system expansion forum heating plumbing position usa zone zoned
    • Replies: 3
    • Forum: Plumbing Zone
  19. danieljamesphoto

    Changing kitchen taps with an expansion vessel

    Hi, i'm a complete newcomer to plumbing so be gentle, basically i'd like to change the kitchen taps (just a simple monobloc mixer tap) and have looked on YouTube and think I have everything ready. I've had a look at the system and it seems to be setup to include an expansion vessel (image...
    • danieljamesphoto
    • Thread
    • america changing expansion expansion vessel kitchen taps usa vessel
    • Replies: 1
    • Forum: USA
  20. P

    Combi KW Rating (High or low?) - Fit De-aerator and Extra Expansion Vessel?

    Hi All, I am looking to replace an Ideal Classic FF350 in a 4 bed detached house, 1 main bathroom with a bath and electric shower, also en-suite with a thermostatic shower that is currently pumped (knackered) from a DHW cylinder (essex flange weeping). F&E and CWS tanks in the loft, gravity fed...
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