On 22 Sep 2004 05:08:11 -0700, (Alan
Campbell) wrote:


Yes I do.

Basically, they back off the power as flow restriction increases, so
for example, if you have TRVs, the pump doesn't run its nuts off and
become noisy. It has a peak pressure point at just below 0.5 m^3/hr.
Above this it has a typical head/flow curve. Below it the power is
reduced as restriction increases.

I found that mine therefore runs a lot quieter than erstwhile models.

There are a few other features such as a deblocking function.

http://www.grundfos-www.com/alpha/frames_html.htm

Nice product and well worth having.


Would it work as well on a microbore system ?

My installation consists of 22mm (may be 28) pipe which does a circuit
under the 1st floor. From this, each rad has a tee down to microbore
(probably 10mm). Only a short distance for the upstairs rads and down
behind the plasterboard walls for the downstairs rads.

I guess there is more resistance in this setup than an 'ordinary'
setup.

Alan

Generally the pressure drop across a microbore system is a bit more
than on 15mm systems but not hugely so if the system was designed
properly.

Tube resistance is higher, but as long as the flow carrying capacity
was taken into account, it should be OK. You can do a sanity check
on this if you go to the Copper Development Association website.
There is a downloadable paper on pipe sizing for domestic systems.
If you know the lengths of pipes reasonably you can calculate the
maximum flow rate and heat transfer possible. The basis is no more
than 1.5m/sec to avoid noise from the pipework. Since flow rate and
heat transfer are linearly related you can determine the heat transfer
allowable.

Rule of thumb, this equates to about 1500W over typical house
distances of a few metres for 8mm and 2500W for 10mm.

You can then check your radiators. Measure them and look at the
number of panels and fins. Then look at a/the manufacturer's web site
at the datasheet and you can get the nominal power output. If you
have a conventional non condensing boiler, multiply the radiator
manufacturer number by 0.9 to get the true output. You only need to
do this for the largest radiators.

As long as you are reasonably close to being within the limits, then
all should be well.

Some installers through laziness or incompetence or just hoping, may
have overloaded the pipes. This may not be a problem. All that
will happen is that you may hear noise from that part of the system or
the radiator runs below capacity.

I have an 8mm system, and when it had an Alpha pump on it, it worked
well. Some of the radiators were 20% over the nominal limit for the
pipework. I should add that the reason for moving it was because I
now have a boiler with integrated pump and that is controlled linearly
by the boiler controller according to heat load, so nothing upon which
the Alpha could improve.
The Alpha is still doing good service in a separate circuit for my
workshop






..andy

To email, substitute .nospam with .gl