Rad sizing

[chris watkins]

New EU regulations come into force next year re sizing. They take into account the behaviour of inhabitants and calorie burn.

The assessment involves a questionnaire that is mandatory and must record certain information in relation to all occupants, such as: how much time they spend watching TV, and use of the remote; how many times a-week they have sex; how much time they spend arguing; whether the kids are HDD, etc.

Apparently, research shows that randy parents with six rowdy kids who fight over the remote require 50% less heat input per square metre than a couple who live the quiet life.

Assessors will need to register, and be able to show that they have level one C&G 6372 in counselling, and Relate 217 in mediation skills.

The Government are calling it the: 'Small Clean & Green Radiator Assessor's Program', or SCRAP for short.


Watch this space for more details.

Absolute brilliant Peter. Well Done

 

[chris watkins]

Can I sign up be a SCRAP assessor, pleaseeeee.

 

[wheeto]

how does a bigger rad allow for lower running temps????

You set the boiler 'stat lower to account for the fact that a larger emitter will require a lower temperature to put the same amount of energy into the room.

Obviously this assumes that all the emitters are oversized.

 

[fuzzy]

You set the boiler 'stat lower to account for the fact that a larger emitter will require a lower temperature to put the same amount of energy into the room.

Obviously this assumes that all the emitters are oversized.

not oversized but sized correctly for the correct running temps.

rad schedules allow for correct running temps so no need to oversize anything

 

[mfgs]

It would take me 2 days on my own, 2 1/2 if i paced myself but i don't price things on a day rate:smile:

A week should do it easily. Just think ahead of what you are doing and it all falls into place.

2 days is seriously impressive. I would love to see it done, I have never known or worked with anyone that could do that amount of work in that time. Personally I would be thinking about 5-7 days to do it.

 

[mutley racers]

5-7 days and at £200 a day is not a lot of money for a whole install though i think

 

[chris watkins]

It would take me 2 days on my own, 2 1/2 if i paced myself but i don't price things on a day rate:smile:

A week should do it easily. Just think ahead of what you are doing and it all falls into place.

Its amazing how quick you can be now, using the plastic piping systems isn't it Tamz !! are you still working em 27.5 hour days ??

 

[tamz]

2 days is seriously impressive. I would love to see it done, I have never known or worked with anyone that could do that amount of work in that time. Personally I would be thinking about 5-7 days to do it.

It is even harder doing 1 a day (2 men) for years on end with a clerk of works going over them with a fine tooth comb (because he hates subbies) picking you up for a dirty handprint on the wall because he can find nothing else to complain about.
You get used to it and the money is ok :lol:
The body is too old for doing it every day now. It is a young mans game but there are lots of good guys out there doing just that every day.

 

[tamz]

Its amazing how quick you can be now, using the plastic piping systems isn't it Tamz !! are you still working em 27.5 hour days ??

I don't use shyte Chris. Strictly copper.

At one time i was doing tenement flats, 6 rads and a combi and was back in the house for 2 every day..........loadsamoney :lol:

 

[mutley racers]

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

 

[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.

 

[mutley racers]

a nice watch i hope!! It is hard when your day rate is usually 200. But then i don't want to over price and especially under price. Quoting is just as difficult as plumbing. never an easy job!!!

 

[tamz]

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

55 in 4 weeks.
Speed comes the more you do and i must have done around 5000. Also if you know how houses are built that saves you lots of wasted time and todays power tools (i wish i had half the gear i have now 30 years ago) speed things up too.

BG would take around £9k+ depending on what mood they are in.

 

[tamz]

Quoting is just as difficult as plumbing. never an easy job!!!

Aint that the truth!

Sekonda do some nice watches :smile:

 

[fuzzy]

i dont think its wise to get too hung up on speed. some newbies think the faster you are the better you are and aim to compete

 

[mutley racers]

9k. as long as i come in cheaper than that i should be laughing. i have done around 4 whole new installs!!! geesh, 5000 i can only hope i get to that many!!! I better start delivering those leaflets!! It will take me half a day to insulate all the pipes let alone wire the system too.

Am not about speed, as long as its nice and neat and i am happy with what I have done I will be chuffed and be able to sleep well that night.

I have been checking out prices on websites down this way and to convert from an open vented to a combi is 3k. that is expensive. That's including all the scrap. so around £3200

 

[mutley racers]

being a plumber I was half expecting a Rolex!!!!!

 

[tamz]

As Fuzzy said don't worry too much about being fast. Better to do it right first time.
Speed comes when you don't need to think about what you are doing because you thought about it half an hour before while you were doing something else.

You can but a fake rolex for a tenner and wear it to your work. Makes them think what you are getting for their money :lol:

 

[kay-jay]

rad schedules allow for correct running temps so no need to oversize anything

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.
Sent from my GT-I9100 using Tapatalk 2

 

[AWheating]

i find the city plumbing web site rad calculator very good if your after a quick rad cal. Long hand is better but takes time which unless you need to provide heat loss cals to a builder/specifier then a computer/web based calulator is good enough for most small domestic jobs.

 

[chris watkins]

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.
Sent from my GT-I9100 using Tapatalk 2

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.

 

[fuzzy]

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.
Sent from my GT-I9100 using Tapatalk 2

no, nothing should be oversized, it should just be sized correctly

rad schedules consider lower running temps so you just size the rad and pick one from the schedule that has the required output, therefore correct size

 

[MickBrown]

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.

 

[chris watkins]

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.

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.
You are right to say that people make adjustments but not all the time, TRV's & stat are there to make automatic adjustments (along with a number of other controls) to the water flow through rads or to switch the boiler on or off.
The main thing that changes is the outside air temperature we cant stop this, we have to work on something when we are designing (normally -3deg C down here), boilers, controls & shorty pumps are all designed to take account of this & keep the boilers in condensing mode for as long as possible.
What is absolutely certain is engineers should not be guessing at rad or boiler sizes.

 

[petercj]

Obviously anyone fitting a boiler / radiators within a commercial contract will be well advised to follow the accepted scales re sizing.

However, my boiler is well undersize by such ratings, being only 18.5 kw running 13 radiators (one being a double) and a HW cylinder, and it rarely gets maxed out - about twice in the last 5 years, which was slight rad-lag when heating the system from cold.

Having kept a watchful eye on the condensing aspect, it seems pretty limited, bearing in mind that the boiler is mainly topping up, rather than heating the system from cold, which is when the condensing side of things really comes into its own. But then with an ambient room temperature of 20c, which rises on the return as the boiler ramps up, the 20 degree differential required for condensing mode is short lived.

Although my hot-water is off between 10am and 5pm, the temperature prior to the boiler kicking in at 5 is usually 30c, so even more of a sprint for the boiler to catch the condensing sweet spot.

What I have found to make a hell of a difference for lowering the gas bill is the use of a wireless room stat, which has meant that the boiler is off much longer than previously. 'Off' being the most economical mode of all. Wireless room stats may be more troublesome, but I reckon they are worth the extra hassle. Mine paid for itself in the first cold month of winter.

It seems to me that Valliant have created a high performance heat exchanger by employing the small bore pipe they use in the eco max pro, but unfortunately it is very vulnerable to restriction should any kind of debris enter the system.

I'm not aware of the formula they've applied when creating the sizing scales, but I suspect there is quite a discrepancy between theory and practice.