Radiators and BTU Requirements

[Caroline6192]

Hello

I'm looking at calculating the BTU requirements for several rooms for our central heating system installation.

I have done several online calculators and the requirement for one of our rooms seems to range from 5000 up to 8000 depending on the calculator.

Is there anything that I should be taking into account?

I am guessing that as the property is not insulated then this would require a higher BTU than one that is for instance?

Thanks in advance

 

[oldbuffer]

1. The online calculators are pretty variable. To do the job properly requires a great deal of measurement, and knowledge of the heat loss through the different materials and constructions making up the room. The calculators make various assumptions about these factors, and different assumptions give you different results.
2. Your assumption is correct. No insulation means the room will lose heat faster than an insulated one, so a more powerful one is needed to make up for the increased heat loss.
3. Things to take into account:
3a. Walls, ceilings, floors, windows, doors. Then for each
3b. What is on the other side.
3c. How much heat per square metre it loses for each degree (Kelvin) of temperature difference between inside and outside. This is the "U" value of the material.
3d. How many air changes per hour does the room need.
3e. A variety of adjustment factors, including +10% to allow for warming up from cold, a factor to correct the result if the difference between the mean temperature of the water going into and leaving the radiator and the required temperature of the room is not 50 degrees, a few other factors which can generally be ignored, and for practical purposes a contingency percentage uplift to allow for abnormally cold weather (10 to 20%).

 

[oldbutnotdead]

You've obvously discovered that there are loads of calculators. Look for one that ask questions relevant to your setup - ideally that would stretch to floor type and insulation, wall type and insulation, ceiling insulation, square metreage of window and external doors, latitude (its grim up North, outside tends to be a bit cooler that Daan Sarf so more energy will be required to keep inside comfortable). The better ones will go for specifics allowing you to detail, for instance, wall 1 (outside solid) Window x sq m glazing type (single, double, triple, trickle vent, K glass) Wall 2 (internal half brick) wall 3 (party ull brick plus insulation) wall 4 (internal half brick). The more variables you can put in the more accurate the answers will be.

If you're handy with spreadsheets you can probably create your own calculator- the U values for pretty much everything are available online

 

[durhamplumber]

Hello

I'm looking at calculating the BTU requirements for several rooms for our central heating system installation.

I have done several online calculators and the requirement for one of our rooms seems to range from 5000 up to 8000 depending on the calculator.

Is there anything that I should be taking into account?

I am guessing that as the property is not insulated then this would require a higher BTU than one that is for instance?

Thanks in advance

It is really not that big a deal ..Calculate a few and take the average..Not going to be far out...Some will start going on about oversized boilers,what is best temp gradient across flow and return...Delta T....On and on...Then the thermostat position..Differential...Slope.....blah blah...You are warming your rooms not launching a rocket into geo stationary orbit.

 

[Caroline6192]

Thank you.

I'm currently trying to work out how you can lose over 1000 BTU require.

We were originally told that this room (dining room) needed at BTU requirement of 6352. The radiator that was originally planned and agreed has a BTU rating of 8495 but the radiator that has been installed is only 5771.

When we brought this up with the engineer in charge of the project, firstly he said that a few hundred is neither here nor there. Then one of his colleagues commented that it was less than required though so he went and did another quick calculation and suddenly is saying that we only require about 5000 BTU.

I'm not really sure how you can suddenly lose that much need??

The room in question is a dining room. I don't have exact measurements but have calculated from the drawing and a quick tape measure and they are pretty similar (I've got a laser measure coming tomorrow so I can get accurate figures).

It is basically square, approx. 3.5m wide and 3.9m long (to the chimney breast). Ceiling height is 2.4m
There are two external walls, an open fire place (condemned chimney) on one and a window (approx, 1.4m2, uPVC double glazed but leaks/drafty) on the other. I have assumed these are brick cavity based on their style and measurements and as far as we are aware they are uninsulated.
The two internal walls each have doors on, one to the kitchen (and a very short distance to the back door) and one door which leads to the bottom of the stairs and front door area and also a door to the under stairs cupboard. I believe these may be brick (based on seeing bricks in the understairs cupboard) but not 100% sure and what else may be with them.
I know the floors are concrete as that was done about 15 years ago.
I haven't got a clue about the ceilings other than they appear to be plastered and painted and have quite a lot of cracks in.
The room above is a heated bedroom (although that one too is one of the radiators that has been downgraded but still technically meets the original specs.)
The whole house is fairly exposed (we're a farm house).

I've found that the radiator manufacturer has two different calculators, a basic one and a more advanced one so I'm going to do both. The basic one has given me a BTU of 6689.

I'm getting to the point of telling them to come back and rip the system out.

 

[durhamplumber]

I'm currently trying to work out how you can lose over 1000 BTU require.

About 300 watts...neither here nor there really.

 

[durhamplumber]

When we brought this up with the engineer in charge of the project, firstly he said that a few hundred is neither here nor there.

Correct

 

[durhamplumber]

Thank you.

I'm currently trying to work out how you can lose over 1000 BTU require.

We were originally told that this room (dining room) needed at BTU requirement of 6352. The radiator that was originally planned and agreed has a BTU rating of 8495 but the radiator that has been installed is only 5771.

When we brought this up with the engineer in charge of the project, firstly he said that a few hundred is neither here nor there. Then one of his colleagues commented that it was less than required though so he went and did another quick calculation and suddenly is saying that we only require about 5000 BTU.

I'm not really sure how you can suddenly lose that much need??

The room in question is a dining room. I don't have exact measurements but have calculated from the drawing and a quick tape measure and they are pretty similar (I've got a laser measure coming tomorrow so I can get accurate figures).

It is basically square, approx. 3.5m wide and 3.9m long (to the chimney breast). Ceiling height is 2.4m
There are two external walls, an open fire place (condemned chimney) on one and a window (approx, 1.4m2, uPVC double glazed but leaks/drafty) on the other. I have assumed these are brick cavity based on their style and measurements and as far as we are aware they are uninsulated.
The two internal walls each have doors on, one to the kitchen (and a very short distance to the back door) and one door which leads to the bottom of the stairs and front door area and also a door to the under stairs cupboard. I believe these may be brick (based on seeing bricks in the understairs cupboard) but not 100% sure and what else may be with them.
I know the floors are concrete as that was done about 15 years ago.
I haven't got a clue about the ceilings other than they appear to be plastered and painted and have quite a lot of cracks in.
The room above is a heated bedroom (although that one too is one of the radiators that has been downgraded but still technically meets the original specs.)
The whole house is fairly exposed (we're a farm house).

I've found that the radiator manufacturer has two different calculators, a basic one and a more advanced one so I'm going to do both. The basic one has given me a BTU of 6689.

I'm getting to the point of telling them to come back and rip the system out.

What exactly is your problem? And how will ripping out your system over max,,,a few kilowatts help?

 

[Caroline6192]

What exactly is your problem? And how will ripping out your system over max,,,a few kilowatts help?

The problem is that it is not what we agreed to in the original plans. The engineer has changed the plan without any discussion or agreement. As a friend of mine said, would you be happy to buy a car, discuss and agree that you are getting model X and the specs in front of you are the specs for the highest spec vehicle but what arrives is the basic version of model X?

Whilst 300 or so may not be much but how does the requirements suddenly drop about a 1000 BTU once he's been called out on the radiator size?

We are currently running the system with all the radiators on 6 (max) as that is what this engineer has told us to do and the dining room is still cold in comparison to the other rooms. If it is like this in summer then I dread to think what it will be like in the depths of winter.

 

[durhamplumber]

The problem is that it is not what we agreed to in the original plans. The engineer has changed the plan without any discussion or agreement. As a friend of mine said, would you be happy to buy a car, discuss and agree that you are getting model X and the specs in front of you are the specs for the highest spec vehicle but what arrives is the basic version of model X?

Whilst 300 or so may not be much but how does the requirements suddenly drop about a 1000 BTU once he's been called out on the radiator size?

We are currently running the system with all the radiators on 6 (max) as that is what this engineer has told us to do and the dining room is still cold in comparison to the other rooms. If it is like this in summer then I dread to think what it will be like in the depths of winter.

Car arrives with 1550cc engine instead of 1600cc...Take it back.if that bothered...simple...Rip CH out.not simple

 

[oldbutnotdead]

Unless you've gone for super-duper rads there's no real cost difference, it is very likely that he's gone to his wholesaler & they're out of stock of the rad specced, what he's probably come back with is the nearest in output that'll fit in the required location (height & width being the usual determinants).

Have you actually used a thermometer in the rooms (you maybe getting some confirmation bias if it 'feels' cold).

With modern boilers and TRVs, sizing isn't as critical as it used to be but i've always gone a bit big rather than a bit small.

 

[Caroline6192]

Car arrives with 1550cc engine instead of 1600cc...Take It back.if that bothered...simple...Rip CH out.not simple

It's a bit more than just 50cc though. It's almost every radiator in the house that isn't what was agreed. We have had to fight for everything that we have asked for and been met with a degree of hostility for even asking e.g. moving a radiator from one wall to another and a larger oil tank, let alone when we said we would prefer an external boiler - there isn't a suitable location inside, and don't get me started on when he wanted to put one of the pipes outside, it was only the contractor who stepped in and said he wasn't planning on doing that. Even asking a simple question such as why one radiator doesn't have a TRV on it gets met with disdain and treated like an idiot. He's had to be remind on frequent occasions by not just us but his colleagues that we have input into the system and must be kept in the loop because we are contributing financially to the scheme (he's used to dealing with projects where only his boss is paying for it and as such has final say on everything).

I know it's not that simple, I'm just getting to the end of my tether with it (and this engineer in particular, I've already had to put a complaint in regarding his attitude towards me - he had me in tears the other week).

This has been an ongoing problem for at least 2 years and if it had been dealt with then it would have been a simple fix (we were happy without central heating and this all started with dampness in the walls of two rooms and should have been a simple fix of a couple of vents but it's ended up with chimney fires, carbon monoxide alarms/scares and the chimney being condemned as the vent is in the wrong place and yes this engineer was involved in that work too and was awkward to get it done in the first place) So you can probably appreciate why I'm now fed up of it all.

 

[Caroline6192]

Unless you've gone for super-duper rads there's no real cost difference, it is very likely that he's gone to his wholesaler & they're out of stock of the rad specced, what he's probably come back with is the nearest in output that'll fit in the required location (height & width being the usual determinants).

Have you actually used a thermometer in the rooms (you maybe getting some confirmation bias if it 'feels' cold).

With modern boilers and TRVs, sizing isn't as critical as it used to be but I've always gone a bit big rather than a bit small.

I wish it was that simple unfortunately. This engineer hasn't been involved with sourcing any of the radiators etc, he designed and has been overseeing the project. Once the plan was drawn up it was sent out to tender and a contractor won the bid. That's one of the reasons I knew that it was changed after the meeting and before tender (which this engineer has since confirmed much to the surprise of everyone involved) as I have seen the contractor's plan.

I'm in the process of getting some monitors sorted (two kids, three baby monitors with temperature sensors haha) but it was because some rooms felt colder that we looked to see what settings they were on (6 max) and just happened to notice that some of the radiators were a different type (P+ rather than K2) that we then checked all of them and found that several were smaller too, up to 300mm in some cases. I have wandered around with the thermostat (its a wireless mobile one) and two of the rooms are running about 1 degree cooler at least than one of the rooms where the correct radiator is.

I'm thinking about taking measurements in the rooms even when the heating isn't on so we get an idea of which rooms are naturally cooler and as such would require more heating (and just from knowledge, it's mainly those with these smaller radiators which is just typical)

We're of the same opinion, we'd rather go a bit bigger than required than a bit smaller. We know our house is poorly insulated, has two open chimneys and very drafty so lose heat like nothing on earth so considered that we would probably require slightly more because of this.

 

[Caroline6192]

About 300 watts...neither here nor there really.

And besides, it's nearer 600 rather than 300 difference, which is about 10% less

 

[oldbutnotdead]

This sounds like a large project and there are some oddities. Financial contribution? Tender for a domestic heating system?
Is this engineer paid/employed by you- if he is then why haven't you sacked him?