Hi all,
This boiler choice FAQ is nearly twice the size of the original and has incorporated a number but not all of suggestions.
Phil - you may certainly add this to the main FAQ site. However there are still some hopefully small edits needed.
Anyone know where the simplified boiler sizing estimator from the SAP of the building regs can be found?
Either of these what you're looking for?
Great stuff: thanks for your work on this Ed.
There are a few rough edges and typos which I'm assuming you'll fix, but here are a few more substantial points I hope you'll consider.
"2. Help! Help! The boiler has died! What Next? ... The fear of having a cold house in winter can push some people to make unwise or hasty decisions"
Even if the boiler hasn't died .... I had an email discussion with a client along these lines:
Where you say: "If you have a stored HW system you can turn the electric immersion heater on (if the original installer added one!)" maybe add: "or even install one to get hot water immediately (especially if you would be keeping the stored HW system even if you were replacing the boiler)."
"3. Why can?t I have ?old faithful? back again? ... [Footnote: There is an exemption procedure but unless you have a back-boiler in a terraced house or flat you can forget it.]."
This reads (to me) that you have to have a back boiler (in either a house or a flat) to get an exemption. How about rewording as: "There is an exemption procedure but unless you are in a flat or have a back-boiler in a terraced house you can forget it.]."
"6 Conservatory type extensions also must be an independent heating zone." Where did you get this from? I haven't scoured the ADs but I don't recall it.
The next point is a bit OT to the FAQ. "For non-combi boiler systems where there is stored HW you also will need: 1. Independent time control for the heating of HW. 2. Temperature control of the HW (usually done by a cylinder thermostat)."
I phoned Gledhill today but forgot to ask about this. I've just done a job at a flat with a Boilermate installed in it, and that has no time control on the DHW. I'm not sure it even has a temp control. I wonder what the position is there?
Nice work Ed.
A few odd bits that jumped out:
"As a rough rule of thumb using 2005 figures I estimate any repair of less than £100 is worth doing. For a boiler less than 20 years old you may want to allow a bit more on a sliding scale so that with a younger boiler you are prepared to much more for its repair"
Seems like you need a "spend" toward the end of that.
"The condensate is slightly acidic same as fruit juice it might just rot a metal pipe given time but not overnight."
Needs a comma or perhaps a "the" in there.
"This is not a disadvantage nearly always there is more wall space than floor space."
"since nearly always"?
Very end of section 5 you have a embedded tag after the end paragrapoh tag - that upsets the formatting (causing the end of the sentance to be chopped) when the font sizes are increased in Mozilla.
On the flue location bit toward the end of chapter 8, might it be worth including the building regs minimum distance (600mm?) from a boundary as well as your recommendation for 2.5m as a distance that ought to completely avoid the issue?
"The third group obvious have relatively little influence"
"obviously"?
Glossary:
"A feature where the boiler can alters it power output usually to suit conditions."
"alter"?
"The cloud of steam (actually a mist of tiny water droplets) often seen coming out of a condensing boiler flue in cold damp weather. "
"cold dry weather" would cause a more noticable effect would it not?
"or electromagnetically bewitching the input mains water (efficacy uncertain)." LOL - I like that turn of phrase!
That'll do nicely.
I didn't want to encourage peoples hopes too much here. It may well be possible to add one, but there may be no electrical supply. Also it may not be possible to get the blanking plug out with out destroying the cylinder.
About 12 month ago this happen to a customer, I was able to replace the failed immersion and check the gas fire over and so buy a few days time for the replacement.
No really, AIUI, if you look at the procedure more or less you need a back-boiler AND a flat or terraced house. A back-boiler in a semi won't cut it. A flat might do it if the drain is difficult but it probably won't be.
Isn't it about the fact that conservatories are not meant to be year round habitable spaces. It's something I picked up. It's certainly best practice even if not mandatory. Since there is some uncertainty I'll just drop it out.
Does the CH come form the boiler or form the store? I'll, just change it to a HW cylinder (for which the comment is certainly true).
Part of my motivation for the work was that I'd be able to use it for 'work'. At the back of my mind this FAQ was written with a view to trying to persuade, perhaps an older customer, that is very happy with the existing setup why a lot of things have to be changed.
Ta!
All the above accepted with thanks.
I check on the ODPM site they are saying 2.5m either as the rules or as a proposed amendment, I was unable to work out which. The 600mm would be from the installation manual and typically would be repeat the contents of BS 5440. I.e 600mm to face a wall or fence and
1200mm to another terminal.In practice I take into account all sort of factors like: How they get on with the current neighbours. Which boiler might be fitted and what bits are available. Does the neighbour have a pluming flue already fitted.
In dry weather which in winter is usually cold weather the plume dissipates but in damp still conditions (Foggy weather) it lingers. However the two effects might well work against each other so I'll just say "cold weather".
As Terry Pratchett says: "Writing is as much fun as anyone can have by themselves." My favourite bit is the "Hades Utopia 80 CF" anyone in the game will picture exactly the model of boiler I mean.
Unfortunately it still seems to me to be broken. If a mid-floor flat is specified then there should be no heatloss factor for the roof, but the results show a non-zero figure for "ROOF heat loss". If one changes the type of roof (e.g. thickness of insulation) then this factor (and consequently the reported boiler size required) changes.
My spreadsheet is at http://82.24.138.95/~john/boiler_sizing.xls (or http://82.24.138.95/~john/boiler_sizing.sxc if you have OpenOffice)
I suppose it would have the Part P-p-p-police down on us like a ton of bricks to even think of plugging it into a 13A socket, pro tem.... ?
True, but that may happen with replacing an existing immersion heater too. And in these circumstances at least it doesn't leave the customer without HW which they had before :-)
The point I was trying to make was that getting a new boiler is a pretty significant expenditure, and an opportunity to change other aspects of the ch + dwh system to better suit the users (e.g. conventional ->
combi or combi -> mains pressure stored hw), so one oughtn't rush into it just because it's cold outside (or even inside!). Spending even a few £100 on electric heating for a few weeks may pay off if one then ends up with the right system.
My C&G 6084 tutor pointed out that in some flats there's just nowhere to site a condi where the flue isn't too close to the boundary. Also I'm not sure I've even seen a bb in a flat, but I suppose there must be some.
Or how about putting in what you've just said? It's useful info.
Well as I said it's OT to the FAQ - I should prolly have put my comment in a separate post really. It's just that what you said reminded me of this question that had occured to me when I'd seen the Boilermate installation. The CH comes off the thermal store so I guess there's an argument that the store becomes part of the boiler system (like the thermal store inside a storage combi) but I'd like to see what Gledhill say about it. They're supposed to be sending me a manual for it so I'll wait to see what that says. As regards the FAQ however I think this sort of arrangement is so unusual it doesn't qualify for the 'F' part :-)
I can see myself pointing folks in that direction too!
Never thought of doing that mate!
Quite, this is more or less what the FAQ says. In my experience may people don't even know they have an immersion until you point it out.
According to the ODPM the angle of the flue should be taken into account. So if the flue's straight out through the wall even if it's close to the boundary there shouldn't be a problem.
Round here there is an estate of 1950s partly ex council housing where BBUs were installed about 25 years. These are low rise blocks of flats.
Seems to be broken on your spreadsheet too. (OO version).
Ok, let me know when you have finished your updates. I think you said you are working in Word doc, in which case it's best if you give me your doc file to put into FAQ css style.
Phil The uk.d-i-y FAQ is at
I've spotted a few more typos. which I'm fixing now. The main text was written using open office (an Office clone). But it was always saved/opened in HTML. The link fixing was done in Mozilla's composer.
What you see is what I have.
Too true: came across a brand spanking new upmarket flat with an Ideal I-whateveritscalled boiler+unvented cyl and the immersion was switched on full time, presumably because it was on an unlabelled neon switch next to the FCU which it seemed obvious to switch on.
True, but to put a condensing flue through the wall of the kitchen of a flat which is next door to - and about 1m away from the window of - the lounge of the flat next door then that's quite likely to wind up the nieigbours. I think that's what our tutor was getting at.
How do you mean?
Not in respect of the roof of the flat - if you don't put a 1 in any of the roof options boxes then the 'roof heat loss' figure (cell B18) is 0.
I _think_ I've got the calculations right, but if you can show me that I've got them wrong somewhere I'll be very happy and keen to fix it.
Unlike the folks at idhe.org.uk who simply ignored my email in which I pointed out the error I think I found on theirs.
Perhaps it is just rather confusing then; a case of the user interface rather than the calculation itself. A note that putting 0 in the roof section is an option rather than "Put '1' in one of these boxes"
Perhaps as the the roof calc is conditional on B9 being 1, a note to the effect that "Nr. of external walls,roof,floor" can be modified from the default. I realise a roof and a ceiling are not the same thing but these things do confuse, even if the roof is not imediately below my flat I still have a roof over my head.(Is there always a floor value for a flat or does floor in this case mean ground floor?) Also I need to set the window factor to 0.35 rather than 1 to make window area represent my window area, And External walls 1.5 allowing for the stairwell in common parts. Water heating default is 2000kW, not 2kW?
Depending on how I interpret the required input my results vary from
4.6kW to over 7kW. [No matter in my case, as that's less than the lowest modulated output of my combi.]
It was never meant to be particularly user-friendly, just something I knocked up for myself to do the calcs to my own satisfaction. I thought I'd better put in some explanatory notes if I was going to put it up for others to use, but thanks anyway on how I could explain it better. However it does really presuppose an understanding of the method, which I think is described on one of the sites I mentioned in my post in reply to Ed's about the boiler FAQ.
Ground floor: this is a simplified calculation which ignores heat losses through party walls etc assuming that adjacent buildings will be equal temperature. I was skeptical at first about many of the simplifying assumptions but it seems that whoever devised this method have checked it out reasonably well and made sure that the simplifications involve small enough errors that the overall results are still valid.
I'm not clear what you mean about the window factor - the value for a flat is 0.25, which is what you should set.
I'd treat the stairwell as external unless it's well heated.
The point about this method is it is simplified so don't try and fine-tune it for your particular place: if you want a more accurate calculation you can do a full heat-loss calc for each room as per the Myson or Barlo calculators (I also have a spreadsheet I use to do this but I wouldn't dream of exposing it to public scrutiny!)
Oops, yes.
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