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heat only

In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define heat are stated in the next section of this article.
Like thermodynamic work, heat transfer is a process involving more than one system, not a property of any one system. In thermodynamics, energy transferred as heat contributes to change in the system's cardinal energy variable of state, for example its internal energy, or for example its enthalpy. This is to be distinguished from the ordinary language conception of heat as a property of an isolated system.
The quantity of energy transferred as heat in a process is the amount of transferred energy excluding any thermodynamic work that was done and any energy contained in matter transferred. For the precise definition of heat, it is necessary that it occur by a path that does not include transfer of matter.Though not immediately by the definition, but in special kinds of process, quantity of energy transferred as heat can be measured by its effect on the states of interacting bodies. For example, respectively in special circumstances, heat transfer can be measured by the amount of ice melted, or by change in temperature of a body in the surroundings of the system. Such methods are called calorimetry.
The conventional symbol used to represent the amount of heat transferred in a thermodynamic process is Q. As an amount of energy (being transferred), the SI unit of heat is the joule (J).

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  1. tom_plumb

    Vaillant Heat Only Boiler - Water Flow Problem?

    I have a Vaillant EcoTEC Plus 415 Heat Only Open Vent Boiler throwing up a F.22 fault code as soon as it ignites and then goes idle. It then sits with pump running and an S.98 status until the boiler is switched off and reset. F.22 = Too little water in the appliance, water pressure sensor...
  2. hammers4spanner

    Heat only boiler sizing

    Current in situ is an Ideal classic. Need something sized near as possible to this model due to space.
  3. king of pipes

    Gloworm flexion 18 kw rear flue heat only

    Morning guys any ideas the best way to go vertical on this boiler if possible , the builder couldnt have made it more awkward i would rather not remove the boiler from the wall we have all been there and old boiler dont like being moved cheers kop
  4. L

    What to install, heat only...

    Boys and girls, I have a boiler to install next week, it will be a heat only, customer doesn't want a Vaillant (all I fit typically) as their neighbour had one and got charged for a call out which wasn't repaired under warranty for reasons unknown, but that leaves me out of my comfort zone...
  5. king of pipes

    Ideal icos heat only 24he power fault

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  6. Scott_D

    Heat only with no pump over run?

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  7. I

    Ideal Logic+ 18kw heat only boiler - advice please

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  8. Hobo128

    Worcester 30 ri heat only boiler problems

    I put this boiler in a few month back and have started to get a problem with it. Every now and then it wont fire up and thr blue light starts to flash, the manual says its fast flash. Not been back to check yet but can anyone tell me some possible causes. Its a fairly new boiler so im looking at...
  9. Scott_D

    Heat only size

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  10. G

    heat only boiler

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  11. Robert Tyrrell

    Another BAXI heat only problem?

    I fitted a BAXI heat only boiler a few weeks back and it's been working fine, I think, up until last night when they switched the heating on. They have had the heating on before now btw. Now it appears to work only when the heating and hot water are on together, and then only for a while. as it...
  12. Robert Tyrrell

    BAXI heat only flue question

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  13. Robert Tyrrell

    Baxi Heat Only wiring - another dilema :(

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  14. Jock Spanners

    Potterton Gold heat only electric boiler

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  15. GQuigley67

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  16. Robert Tyrrell

    Baxi heat only problem

    Just installed a BAXI Heat only 19KW in a garage as a replace,meant for an old BAXI Solo 2. Everything went fine up until this afternoon when I tried to fire it. It fired for a while and the flow got hot but then it shut down and the sweep button started flashing about once every four seconds...
  17. F

    Floor standing, heat only, natural gas boilers????

    Evening all Hope everyone is well & have plenty of work. Been really busy myself for as long as I can remember although I'm not complaining lol Need everyone's thoughts on a floor standing heat only please Been to a WB Greenstar 30 CDI regular today & it's f*&ked to be kind lol Custard not...
  18. clarky101

    What's a good Heat Only boiler?

    Got a customer who's lost confidence in there Potterton Suprima & was wondering what's a good Heat Only replacement. Fitted a fair few Logic plus combi's but don't know how the heat only stands up. Viessmann is another but not keen on Worcesters, never dealt with Valiant, so what do your guys think?
  19. A

    Which heat only boiler..?

    First off I am a Gas Safe Engineer, I've just never got round to PM my details sorry. Parents need a new boiler fitted as their potterton netaheat is beyond economic repair. We generally just fit glowworms at work, which are fine and is what I will go with unless someone can suggest something...
  20. KingDoey

    Vaillant Heat Only losing pressure

    Gentlemen good afternoon Bit of an awkward one. Last year my nan had a new boiler fitted and system converted to sealed. Now for the last few months my grandad has had to top boiler up on a daily basis. His local plumber is a bit of a cowboy and is trying to charge them a lot of money to...
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