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Myson Heat Loss Program



 
 
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  #1  
Old February 16th 06, 10:11 AM posted to uk.d-i-y
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Default Myson Heat Loss Program

Hi,

Does anyone have a copy of the Myson program? Can't find it anywhere on
t'internet.

Reason I need is that I have had a ch guy round and I think he's
oversizing everything to avoid comeback. For example about 10,000 BTU
for a 4mx2mx2.7m bedroom (2 external walls) Also suggested a 37.9kW
boiler for a 3 bed end terrace house (100 yr old). The reasoning is
that the boiler (not a combi) would not need to work as hard etc. I
understand that oversizing condensing boilers is not as much as an
issue as they are modulated but surely this is enough to heat the
neighbours house too.

I thought I'd try calculating some rooms last night. Found the formula,
and have taken into account wall sizes, windows, doors, U-values,
ventilation rate etc but it all seems on the low side the bedroom was
coming out at about 1.4Kw. As an experiment I put a 2kw electric heater
in there for 30 mins and it just managed to heat the room up.

Also labour for all fitting is 800 - resited and new boiler,
converting to a sealed S-Plan and 7 rads (one resited). Does this sound
reasonable?


Cheers!

Ads
  #2  
Old February 16th 06, 10:33 AM posted to uk.d-i-y
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Default Myson Heat Loss Program

On 16 Feb 2006 02:11:21 -0800, "Lunny" wrote:

Hi,

Does anyone have a copy of the Myson program? Can't find it anywhere on
t'internet.

Reason I need is that I have had a ch guy round and I think he's
oversizing everything to avoid comeback. For example about 10,000 BTU
for a 4mx2mx2.7m bedroom (2 external walls) Also suggested a 37.9kW
boiler for a 3 bed end terrace house (100 yr old). The reasoning is
that the boiler (not a combi) would not need to work as hard etc. I
understand that oversizing condensing boilers is not as much as an
issue as they are modulated but surely this is enough to heat the
neighbours house too.


If he's working in BTUs then he should be shown the door anyway.

If he's mixing BTU and kW units then the above should apply together
with a steel capped boot.

If you would like the Myson program, send me an email.

I would be surprised if 38kW were needed for this application. I
might believe 25.



I thought I'd try calculating some rooms last night. Found the formula,
and have taken into account wall sizes, windows, doors, U-values,
ventilation rate etc but it all seems on the low side the bedroom was
coming out at about 1.4Kw. As an experiment I put a 2kw electric heater
in there for 30 mins and it just managed to heat the room up.

Also labour for all fitting is 800 - resited and new boiler,
converting to a sealed S-Plan and 7 rads (one resited). Does this sound
reasonable?


Cheers!


--

..andy

  #3  
Old February 16th 06, 10:52 AM posted to uk.d-i-y
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Default Myson Heat Loss Program

Supposing that the BTU calc for the rads comes to about 50,000
(calculated at -3 degrees outside and with an extra 20% to be on the
safe side) and domestic HW is required, would the boiler below be a
good choice?


http://www.worcesterbosch.co.uk/inde...&con_id=125930

88,000 BTU max output, fully modulating etc, etc...

Cheers,
Matt

  #4  
Old February 16th 06, 11:29 AM posted to uk.d-i-y
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Default Myson Heat Loss Program

Andy Hall wrote:

I would be surprised if 38kW were needed for this application. I
might believe 25.


It does sound excessive... worst case I could calculate for my place was
about 8kW and that included the 2nd floor as well (although compared to
the rest of the house that is well insulated).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
  #5  
Old February 16th 06, 11:42 AM posted to uk.d-i-y
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Default Myson Heat Loss Program

Lunny wrote:
Supposing that the BTU calc for the rads comes to about 50,000
(calculated at -3 degrees outside and with an extra 20% to be on the
safe side) and domestic HW is required, would the boiler below be a
good choice?


http://www.worcesterbosch.co.uk/inde...&con_id=125930

88,000 BTU max output, fully modulating etc, etc...

Cheers,
Matt


Sizing boilers and radiators on heat loss is not always such a good idea.

The peak output determines how FAST the place will heat up..

Then, providing you have proper thermostats, the heat loss will only
determine the duty cycle of the boiler.

And provided that you have a bit of hysteresis on the stats, that will
prevent short cycling.

So efficiency of heating is not really a function of the boiler or
radiator SIZE.

They just need to be big enough to heat the place up quickly enough.

If you are at home all day in the winter..you may run the heating more,
and need less peak output..OTOH if you leave the house empty in the day,
you should go for a bit more radiator size and a bit more of a boiler.

By the sound of it, something around 25KW for the boiler, and about 4KW
in the larger rooms and less in the smaller sounds fairly sound.

Pay more attention to thermostats and controls than to rad and boiler
sizing.

I think that if I were to do a rad installation again, I'd go for an
electrical stat in every room, with a motorized valve for every room,
and connect the switches all in series to control the boiler - no master
stat.. :-)


  #6  
Old February 16th 06, 12:06 PM posted to uk.d-i-y
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Default Myson Heat Loss Program

In an earlier contribution to this discussion,
The Natural Philosopher wrote:


I think that if I were to do a rad installation again, I'd go for an
electrical stat in every room, with a motorized valve for every room,
and connect the switches all in series to control the boiler - no
master stat.. :-)


I presume you mean *parallel*? If wired in series, the boiler will only fire
when *all* rooms are cooling for heat simultaneously. Saves on gas, I
suppose. g
--
Cheers,
Roger
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Reply address IS valid, but is disposable in the event of excessive
spam.


  #7  
Old February 16th 06, 12:08 PM posted to uk.d-i-y
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Default Myson Heat Loss Program

In an earlier contribution to this discussion,
Lunny wrote:


I thought I'd try calculating some rooms last night. Found the
formula, and have taken into account wall sizes, windows, doors,
U-values, ventilation rate etc but it all seems on the low side the
bedroom was coming out at about 1.4Kw. As an experiment I put a 2kw
electric heater in there for 30 mins and it just managed to heat the
room up.

Did you take air changes into account? That can account for a substantial
extra heating requirement.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but is disposable in the event of excessive
spam.


  #8  
Old February 16th 06, 01:27 PM posted to uk.d-i-y
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Default Myson Heat Loss Program

Yes. Sorry, this is what I meant by ventilation rate.

I'm getting the impression that I don't really need a boiler as big as
the ch installer suggested....

I'll see what the Myson calc says.

Cheers.

  #9  
Old February 16th 06, 01:30 PM posted to uk.d-i-y
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Default Myson Heat Loss Program

Andy,

Have PM'ed you with my email address. Let me know if you don't get it.

Cheers,
Matt

  #10  
Old February 16th 06, 03:59 PM posted to uk.d-i-y
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Default Myson Heat Loss Program

On Thu, 16 Feb 2006 11:29:11 +0000, John Rumm
wrote:

Andy Hall wrote:

I would be surprised if 38kW were needed for this application. I
might believe 25.


It does sound excessive... worst case I could calculate for my place was
about 8kW and that included the 2nd floor as well (although compared to
the rest of the house that is well insulated).



Sure, but here we are talking about three external walls that are
probably just double brick. That makes a huge difference.


--

..andy

 




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