Planning to replace my old combi with a new boiler.
I plan to use a Vaillant Ecomax 635e system boiler hooked up to a
250litre unvented cylinder.
Im thinking about using a weather compensator:

http://tinyurl.com/qre3a

Anybody got one?
Any opinions on how good/bad/indifferent this boiler is?

--
Mark Roberts

On Wed, 1 Mar 2006 21:19:18 +0000, mark
wrote:

Planning to replace my old combi with a new boiler.
I plan to use a Vaillant Ecomax 635e system boiler hooked up to a
250litre unvented cylinder.
Im thinking about using a weather compensator:

http://tinyurl.com/qre3a

Anybody got one?
Any opinions on how good/bad/indifferent this boiler is?


I can't comment on that boiler specifically, but I do have one (MAN
Micromat) with a weather compensator based on the same principle of
monitoring the outside temperature and adjusting the boiler output to
match.

It works very well in terms of maintaining the set temperatures in the
house without needing to cycle the boiler on and off.
For example, I noticed this afternoon that there was a drop in
temperature of about 2 degrees over quite a short time. The boiler
had been poodling along at about 5kW output across the middle of the
day, but began increasing output as it became colder.

The room thermostat is also "analogue" in behaviour in that it will
indicate temperature changes to the boiler, again modulating it rather
than cycling it. This results in very constant temperatures -
typically under half a degree of variation. I notice from the
brochure that the Vaillant one has this feature as well. Again I'd
say worthwhile.

I also have the same thing for the hot water cylinder - i.e. an
analogue sensor rather than strap on thermostat. This fits into a
pocket in the cylinder. With this, the boiler switches to hot water
mode when the temperature is 5 degrees below the set point
(adjustable) and then modulates down at the end of the burn to avoid
overshoot and higher temperature than the set point. This is nice,
but I think not as important as the other two.


One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


--

..andy

In message , Andy Hall
writes

One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.
--
Mark Roberts

In message , mark
writes
In message , Andy Hall
writes

One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.



OK so no opinions on the boiler then

More food for thought.
rcm say that the cylinder will reheat in 28 minutes given 21kw of input.
My calculations indicate I need about 14kw, sedbuk site says 22kw (!!!)
I plan to have a y plan type diverter and I'd put up with the odd
occasion that I'd need the cylinder re heated from scratch for 28
minutes.

Does this mean I could go for a smaller boiler?
I could use a 622e as this pumps out 22.4 kw or is this too small a
margin?


--
Mark Roberts

On Fri, 3 Mar 2006 21:38:13 +0000, mark
wrote:

In message , mark
writes
In message , Andy Hall
writes

One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.



OK so no opinions on the boiler then

More food for thought.
rcm say that the cylinder will reheat in 28 minutes given 21kw of input.
My calculations indicate I need about 14kw, sedbuk site says 22kw (!!!)

How did you do the sums for the heating? Did you take into account
air changes?

If you mean that SEDBUK says 22kW for a house of a given type, that's
pretty meaningless. It's about as useful as the leaflets in B&Q
which tell you to measure the room, add a fiddle factor and multiply
by aunty's telephone number.

There are a number of web sites around that purport to do the sums -
these seem highly variable.

The only two methods I would trust are

- Radiator manufacturer calculator programs (e.g. Myson, Barlo - I
have the Myson one if you want it) but check the U values they use
with those in the Building Regulations Approved Documents and other
sources.

- Calculator or spreadsheey and do the sums by hand.



I plan to have a y plan type diverter and I'd put up with the odd
occasion that I'd need the cylinder re heated from scratch for 28
minutes.


28 mins reheat is not super-fast and you could get better than that if
you wanted it.

Remember that if the boiler is reheating the cylinder then the house
will begin to cool - more rapidly if not well insulated. If you have
any rooms where there is a particularly large heat loss because of
exterior walls and large window areas then you will notice more
quickly.





Does this mean I could go for a smaller boiler?
I could use a 622e as this pumps out 22.4 kw or is this too small a
margin?

It doesn't matter for the cylinder. It would be OK for the house if
it really is 14kW.

Both boilers will modulate, although curiously, the 635E goes from
10.5 to 35kW, whereas the 622E is from 13.4 to 22.4kW at 80/60
operation.





--

..andy

"Andy Hall" wrote in message
...
On Fri, 3 Mar 2006 21:38:13 +0000, mark
wrote:

In message , mark
writes
In message , Andy Hall
writes

One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.



OK so no opinions on the boiler then

More food for thought.
rcm say that the cylinder will reheat in 28 minutes given 21kw of input.
My calculations indicate I need about 14kw, sedbuk site says 22kw (!!!)

How did you do the sums for the heating? Did you take into account
air changes?

If you mean that SEDBUK says 22kW for a house of a given type, that's
pretty meaningless. It's about as useful as the leaflets in B&Q
which tell you to measure the room, add a fiddle factor and multiply
by aunty's telephone number.

There are a number of web sites around that purport to do the sums -
these seem highly variable.

The only two methods I would trust are

- Radiator manufacturer calculator programs (e.g. Myson, Barlo - I
have the Myson one if you want it) but check the U values they use
with those in the Building Regulations Approved Documents and other
sources.

- Calculator or spreadsheey and do the sums by hand.



I plan to have a y plan type diverter and I'd put up with the odd
occasion that I'd need the cylinder re heated from scratch for 28
minutes.


28 mins reheat is not super-fast and you could get better than that if
you wanted it.

Remember that if the boiler is reheating the cylinder then the house
will begin to cool - more rapidly if not well insulated. If you have
any rooms where there is a particularly large heat loss because of
exterior walls and large window areas then you will notice more
quickly.





Does this mean I could go for a smaller boiler?
I could use a 622e as this pumps out 22.4 kw or is this too small a
margin?

It doesn't matter for the cylinder. It would be OK for the house if
it really is 14kW.

Both boilers will modulate, although curiously, the 635E goes from
10.5 to 35kW, whereas the 622E is from 13.4 to 22.4kW at 80/60
operation.

The Glow Worm HXi 30 (Made by Valliant) goes from ~5kW to 30kW. Mate this
to a heat bank and Voila!!! Mate it to an integrated heat bank and have the
CH off the store in two zones (a flow and return on the store for each zone)
and an optimised stat/programmer on each zone and you will not be
disappointed. May as well do it properly.

In message , Andy Hall
writes
If you mean that SEDBUK says 22kW for a house of a given type, that's
pretty meaningless. It's about as useful as the leaflets in B&Q
which tell you to measure the room, add a fiddle factor and multiply
by aunty's telephone number.

I did wonder..........

There are a number of web sites around that purport to do the sums -
these seem highly variable.

The only two methods I would trust are

- Radiator manufacturer calculator programs (e.g. Myson, Barlo - I
have the Myson one if you want it) but check the U values they use
with those in the Building Regulations Approved Documents and other
sources.

I think I do have one of these somewhere; pretty tedious as I recall.
Perhaps I will impose on you if I can't find my copy ?

- Calculator or spreadsheey and do the sums by hand.
I could do them as well
Again it gets pretty tedious



I plan to have a y plan type diverter and I'd put up with the odd
occasion that I'd need the cylinder re heated from scratch for 28
minutes.


28 mins reheat is not super-fast and you could get better than that if
you wanted it.

Hmmm.I shall look into that...

Remember that if the boiler is reheating the cylinder then the house
will begin to cool - more rapidly if not well insulated. If you have
any rooms where there is a particularly large heat loss because of
exterior walls and large window areas then you will notice more
quickly.





Does this mean I could go for a smaller boiler?
I could use a 622e as this pumps out 22.4 kw or is this too small a
margin?

It doesn't matter for the cylinder. It would be OK for the house if
it really is 14kW.

Both boilers will modulate, although curiously, the 635E goes from
10.5 to 35kW, whereas the 622E is from 13.4 to 22.4kW at 80/60
operation.


More sums then
--
Mark Roberts

Andy Hall wrote:
On Fri, 3 Mar 2006 21:38:13 +0000, mark
wrote:

In message , mark
writes
In message , Andy Hall
writes
One comment that I would make is that if you are going to go for a
large cylinder and 35kW boiler, do make sure that the cylinder is a
fast recovery type - not just a part L1 model. Otherwise you will
find that during HW recovery, the boiler may well modulate down to
half to 2/3 output if the heat isn't transferred fast enough. Most of
the major manufacturers have these - e.g. Albion cylinders. etc.


RMC Ultrasteel; I believe they are fast recovery.


OK so no opinions on the boiler then

More food for thought.
rcm say that the cylinder will reheat in 28 minutes given 21kw of input.
My calculations indicate I need about 14kw, sedbuk site says 22kw (!!!)

How did you do the sums for the heating? Did you take into account
air changes?

If you mean that SEDBUK says 22kW for a house of a given type, that's
pretty meaningless. It's about as useful as the leaflets in B&Q
which tell you to measure the room, add a fiddle factor and multiply
by aunty's telephone number.

There are a number of web sites around that purport to do the sums -
these seem highly variable.

The only two methods I would trust are

- Radiator manufacturer calculator programs (e.g. Myson, Barlo - I
have the Myson one if you want it) but check the U values they use
with those in the Building Regulations Approved Documents and other
sources.

Andy, any chance you could send me the Myson one? My e-mail address is
real.

Cheers,
Richard

"mark" wrote in message
...

Planning to replace my old combi with a new boiler.
I plan to use a Vaillant Ecomax 635e system boiler hooked up to a 250litre
unvented cylinder.

Avoid an unvenetd cylinder.
http://www.waterheaterblast.com

You also need an annual service for an unvented cylinder and that
cost...just to store a cylinder of hot water. Fit a heat bank. Same price
but better all around...and safer. Do a google on this groups and
"Pandora".

The boiler is good. Try the Glow Worm condensing range. Vaillants inside
(same company) but cheaper....and very quiet.
http://www.uselessenergy.org.uk/boilers_prices.asp

Im thinking about using a weather compensator:

http://tinyurl.com/qre3a

Anybody got one?
Any opinions on how good/bad/indifferent this boiler is?

The weather compensator is worth it. Also zone off the CH upstairs and have
a stat/clock on downstairs and upstairs. That will save a hell of a lot of
gas not heating parts of the house unnecessarily.