Radiator sizing

[Chalked]

Hi all
doing a complete refurb in an 8 bed house at the moment. The job has been specified and drawn up by a consultant.
ive checked today the outputs for a couple of rooms and don't get anywhere near his outputs!
example. Master bedroom 6.5 m x 5m. 2.6m high. Window (1.2x3.5m) 2 outside walls, heated above and below. New quality double glazing and the outside walls are 300cavity, with 100mm of exterior insulation. It's been done to 2010 building regs. It's a gas boiler system with weather comp.
between a mears calculator, and a couple of apps (Mr combi & btu calculator) I get between 2050w-2450w. The consultant has 1250w!
Can anyone get near that with other calculations?
dont really want to question the consultant, without getting facts right.

Cheers guys

 

[SimonG]

I was closer to 2500w. Looks like he's dropped a gonad.

 

[kris]

Ive always used mr combi heatloss apps like yourself ,,, i trust it and have never had a problem. just remember that the mr combi app also has sections about the 2010 regs as far as the house insulation and build is ,, they mustve updated it because it didnt use to till recently,,,

 

[plumben]

I got 2075watts with Mr Combi but that's only with 300mm cavities not including the additional 100mm exterior insulation

and doing it on Mr Combi to 2010 regs I get 1944 watts

 

[rpm]

Send him an email advising that he puts new batteries in his calculator ! lol

 

[kris]

When sizing rads i always use the app but realise theres huge differences between different apps so what i do is simply use my judgement and take into account if the customer likes or dislikes heat , i never go below the lowest reading or above the highest but simply choose a middle ground , or if its in a bedroom and the customer hates warm bedroom which many do then i use the lower result, but the mr combi is my most used , i have another one simply called radiator calculator,,

 

[plumben]

When sizing rads i always use the app but realise theres huge differences between different apps so what i do is simply use my judgement and take into account if the customer likes or dislikes heat , i never go below the lowest reading or above the highest but simply choose a middle ground , or if its in a bedroom and the customer hates warm bedroom which many do then i use the lower result, but the mr combi is my most used , i have another one simply called radiator calculator,,

I only use the Mr Combi app and usually go for a rad of the closest output and size that will fit in the gap, although most people round my way either just stick that same size rad in that was there before or just complexly guess at the size

 

[townfanjon]

I know we all use apps these days, but on rad sizing I tend to do it the long way round as we were taught in plumbing school . When I have done calcs against mears / app's they all tend to be oversized

 

[oz-plumber]

dont really want to question the consultant, without getting facts right.

Cheers guys

Why not?

Voice your concerns and ask him to re-check his calculations.
Just because he is a Consultant doesn't make him correct.

At the end of the day, the customer will be calling and blaming you for the inefficient heating if it doesn't work.
And you will probably have to rectify the problem at your expense.

 

[Ray Stafford]

You can word it in a neutral way, which reduces the risk of being seen as critical or creating controversy:

"Dear Mr Consultant,

I have undertaken some ancillary calculations in relation to the project at 123 Four Street, and I am struggling to reconcile anomalous heat loss outcomes for Bedroom 1.

I was wondering if you would mind sharing your calculations for that room with me so that I can isolate any potential error in my figures.

Best regards

Mr Hard Working Plumber"

 

[Riley]

You can word it in a neutral way, which reduces the risk of being seen as critical or creating controversy:

"Dear Mr Consultant,

I have undertaken some ancillary calculations in relation to the project at 123 Four Street, and I am struggling to reconcile anomalous heat loss outcomes for Bedroom 1.

I was wondering if you would mind sharing your calculations for that room with me so that I can isolate any potential error in my figures.

Best regards

Mr Hard Working Plumber"

So eloquent ray

 

[oz-plumber]

You can word it in a neutral way, which reduces the risk of being seen as critical or creating controversy:

"Dear Mr Consultant,

I have undertaken some ancillary calculations in relation to the project at 123 Four Street, and I am struggling to reconcile anomalous heat loss outcomes for Bedroom 1.

I was wondering if you would mind sharing your calculations for that room with me so that I can isolate any potential error in my figures.

Best regards

Mr Hard Working Plumber"

Is that how you do it?

I could never manage to be that eloquently condescending.

My general way is that thing go from mediocre to woeful.

Hello...

I think you may have stuffed the heatload calcs for bedroom x.

Why do you think that?

Gut feeling!!

Who are you?

The contactor.

Do I know you?

Hope not!

Can you email me the heatloads so that when things hit the fan at the end of the job, I can forward the email onto the builder and the client and then let them figure out who to sue for the heating system that doesn't perform.

Really?

Yeah... I text you my email ...cheers