T
tamz
5-7 days and at £200 a day is not a lot of money for a whole install though i think
You should try to forget the £200 a day rubbish. Just price it accordingly. If you are fast you win a watch.
Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
5-7 days and at £200 a day is not a lot of money for a whole install though i think
he he am glad to hear you use copper. Well i think i am going to go in between what my old boss says and what you guys say and go for 2 weeks at £300 a day. it is london after all.
i take my hat off to you tamz. i don't know how old you are but i am young and i could never imagine doing it that fast. i would like to though, and still charge the 3k.
I wonder what BG would charge for a whole house install
Quoting is just as difficult as plumbing. never an easy job!!!
rad schedules allow for correct running temps so no need to oversize anything
Sorry if it seem that I keep nit picking but there really does appear to be a lack of understanding on this condensing melarky I no it is very new & all that ha ha (what is it about 15 years old technology) The dew point is normally taken as 53deg C below this the water vapour in the flue gases can condent's back into a liquid & realising it energy the cooler the returning water back to the boiler the more effective this process is & the more of the trapped energy is released up to an extra 13% if the returning water is more than 53 then this 13% extra heat is lossed out the flue. So systems should be designed, including sizing rads & boilers, to maintain a return water temp of less than 53. If you have to heat an indirect HW cylinder then it is recommended that you design the system to work at 70 F & 50 R because you need a +65deg C F to heat the domestics but with a combi or with U/F system the F&R temps can be much lower to maintain the boiler in condensing mode for as long as possible. So, please no more of this oversizing boiler or rads.I was taught to oversize on a combi and rads swap if the original boiler was not condensing. Because to set up the new boiler correctly and to maximize condensing capability the return temperature must be as you quite rightly say 55 degrees (dew point) this means that same size rads won't be jumping hot like with the previous boiler so to get the same btu output (not surface temperature) from the new rads the replacements
Must be oversized.
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I was taught to oversize on a combi and rads swap if the original boiler was not condensing. Because to set up the new boiler correctly and to maximize condensing capability the return temperature must be as you quite rightly say 55 degrees (dew point) this means that same size rads won't be jumping hot like with the previous boiler so to get the same btu output (not surface temperature) from the new rads the replacements
Must be oversized.
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Not so Mick, heat or better to think in terms of energy used to heat the room up & then maintain it at the required temp is the same whether you are running the boiler at the traditional 82 Flow or at much lower temps. Its the rate at which the heat is exchanged between the boiler into the heating water then to the Rad & then into the air in the room, that is important.Not being a boiler engineer I do not fully understand everything discussed. However even if all the rads and the boiler are sized correctly the customer will turn off rads and also turn down thermostatic valves so less heat will be used. So I would assume that the return temperature will be higher and thus all the calculations would not mean a lot.
Well Peter where do you want me to start? As heating engineers whether domestic or commercial & I really do not see any difference between the two, (I have done both) they require exactly the same levels of knowledge, understanding & professionalism.
Systems in the past have being sized correctly to match the heat losses & then at least 10% has been added to allow a capacity to heat the rooms up from cold, known as intermittent heating (& not to hold a steady stat). Not having the benefit of the details of your house & system it is difficult to comment but I bet you leave your heating on longer than most when it gets cold & that's not a bad thing but you should know the why's.
Re the condensing please have a look at my earlier post, it is not the differential that is important but the returning water temp back to the boiler. (less than 53deg C)
I agree with you about the modern controls but it is not just the wireless stats you can get the same results if you exchanged your old mechanical / electrical room stat for an electronic one & they only cost a couple of £ more than the normal Honeywell ones.
All the manufactures use the same types of heat exchangers with small waterways (I would not install one without protecting it with a filter on the return before it) they are all trying to come up with boilers which will adjust there heat outputs automatically right the way down as low as possible to match the required heat output with the demand thus maintaining a cool return water temp & a boiler that is up to 13% more efficient that exactly the same one that not condensing. 13% saving!!!! in any other industry if I could offer that, people would be biting my arm off.
Hi Pete
I am not going to tell you it is too small, its of an output that suits you & as most people know the harder a boiler works the more efficient it is likely to be (you told me "about twice in the last 5 years, which was slight rad-lag when heating the system from cold". If I sold a customer a system then they might well come back & say that I had miss sold it, if it didn't heat the house in the winter. Thats not to say it should be oversized either but because I have done the calc's I can show what is happening or not.
The Valliant MI's do state 20deg C temp diff as an indication of the flow rate through the boiler to carry the heat away, it has nothing to do with the boiler being in or out of condensing mode, this is basic science not rocket, please have a look on google.
I understand what you are saying about the wireless stat & if you are using it like that & it is working for you, great, but most people would not be so diligent in moving it around & this is not how it is designed to be used. The TRV's on each of the rads control the individual room temperatures by adjusting the amount of water going to each one, with the exception of one rad (normally the hall) which does not have one fitted but this is where the room stat is installed, so long as this rad is correctly sized it should give a fair representation of the rest of the dwelling & shuts the heating off or on giving overall control along with the programer. So you can see that if the room stat is in the same room as a TRV they could well be competing with each other.
So all in all right choice of boiler when you know the theory.
Simple is most certainly the best, that's for sure, have you met the wife !!!Not that I go that far - lol - but the ten pounds I spent on a door closer, plus the wireless stat, was definitely money well spent. Seems strange to think that something so simple can make such a difference.
People get hung up about doing a few calculations that take a few minutes a room and give you an accurate, approved and logical reasoning for sizing the radiators, something that will make you look much more professional, experienced and can provide you with something to fall back on if you need it.
Radiators in 90% of UK households are well oversized, partly because of this ft2x5 business thats been going on for years, and partly because houses were not insulated like they are today.
I newish house can have a 450x400 single panel in a single room, something that you'd find in most people airing cupboards but works just fine.
Come on lads, we have got to earn the 'engineer' in heating engineer some how, other wise the term 'pipe monkey' becomes a little more accurate!
P.S no offence intended to anyone 🙂
No offence taken, and as a professional plumber and heating engineer I will continue to use the method that is proven and works for myself. 🙂
and you could cut the crap 🙂
Reply to the thread, titled "Rad sizing" which is posted in UK Plumbers Forums on Plumbers Forums.
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