Grundfos Alhpa & Potterton Suprima 'bug'?
 

I installed an Alpha during the summer and, now the CH is on, I've
noticed that whenever the Suprima re-fires after the boiler stat has
shut it down, then the Alpha speeds up before gradually settling down
again. This means that, contrary to the way it's supposed to work, the
noise through our TRV's is quite loud, and all the more noticeable
because it comes & goes each time the boiler cycles. The Alpha is set
at the lowest point on its variable scale.
I *think* that what's happening is that the Suprima is momentarily
disconnecting the pump as the boiler fires? If this is true, then the
pump is acting correctly.
Is this (disconnection of the pump) a known *bug* with the Suprima?
Thanks
Rory

In an earlier contribution to this discussion,
Rory wrote:

I installed an Alpha during the summer and, now the CH is on, I've
noticed that whenever the Suprima re-fires after the boiler stat has
shut it down, then the Alpha speeds up before gradually settling down
again. This means that, contrary to the way it's supposed to work,
the noise through our TRV's is quite loud, and all the more noticeable
because it comes & goes each time the boiler cycles. The Alpha is set
at the lowest point on its variable scale.
I *think* that what's happening is that the Suprima is momentarily
disconnecting the pump as the boiler fires? If this is true, then the
pump is acting correctly.
Is this (disconnection of the pump) a known *bug* with the Suprima?
Thanks
Rory

I would hazard a guess that the boiler is controlling the pump, and that it
has a pump over-run stat to stop the boiler from overheating.

If this is the case, the pump will run when either or both of two conditions
are satisfied: a) the boiler is receiving an "I want heat" demand from the
CH and/or HW system, b) the boiler outlet temperature is above the over-run
stat setting.

So you get the following scenario: The boiler is firing and the pump is
running. The room (or cylinder) stat (but *not* the boiler stat) opens. The
boiler and pump stop. The residual heat in the metal parts of the boiler's
heat exhanger continues to heat the water to the point where the over-run
stat switches on (maybe several seconds after the boiler has stopped
firing). The pump starts up again in order to carry the residual heat away
from the boiler.

If this is what you're experiencing, it's quite normal.
--
Cheers,
Set Square
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In message , Set Square
writes
In an earlier contribution to this discussion,
Rory wrote:

I installed an Alpha during the summer and, now the CH is on, I've
noticed that whenever the Suprima re-fires after the boiler stat has
shut it down, then the Alpha speeds up before gradually settling down
again. This means that, contrary to the way it's supposed to work,
the noise through our TRV's is quite loud, and all the more noticeable
because it comes & goes each time the boiler cycles. The Alpha is set
at the lowest point on its variable scale.
I *think* that what's happening is that the Suprima is momentarily
disconnecting the pump as the boiler fires? If this is true, then the
pump is acting correctly.
Is this (disconnection of the pump) a known *bug* with the Suprima?
Thanks
Rory

I would hazard a guess that the boiler is controlling the pump, and that it
has a pump over-run stat to stop the boiler from overheating.

Well not a stat, it's software controlled and pump overrun in a Suprima
is 20 minutes

As I explained when he posted this question the first time, the pump is
pulsed at the beginning of a heating cycle

The information contained in this post
may not be published in, or used by
http://www.diyprojects.info

--
geoff

raden wrote:


Well not a stat, it's software controlled and pump overrun in a Suprima
is 20 minutes

Sorry about the double post - I've just started using Thunderbird and
thought I'd deleted this message.
I've followed on to the earlier post, but one additional point is that
my (4yr old) Suprima overrun is only 2 mins (I've timed it a few times).

"Rory" wrote in message
...
raden wrote:


Well not a stat, it's software controlled and pump overrun in a Suprima
is 20 minutes

Sorry about the double post - I've just started using Thunderbird and
thought I'd deleted this message.
I've followed on to the earlier post, but one additional point is that
my (4yr old) Suprima overrun is only 2 mins (I've timed it a few times).

Maxie always does things x 10.

In message , Rory
writes
raden wrote:

Well not a stat, it's software controlled and pump overrun in a
Suprima is 20 minutes

Sorry about the double post - I've just started using Thunderbird and
thought I'd deleted this message.
I've followed on to the earlier post, but one additional point is that
my (4yr old) Suprima overrun is only 2 mins (I've timed it a few times).

Strange, this can only be a software timing thing and if everything else
is working, I don't see how something like that can happen

--
geoff

In message , IMM writes

"Rory" wrote in message
...
raden wrote:


Well not a stat, it's software controlled and pump overrun in a Suprima
is 20 minutes

Sorry about the double post - I've just started using Thunderbird and
thought I'd deleted this message.
I've followed on to the earlier post, but one additional point is that
my (4yr old) Suprima overrun is only 2 mins (I've timed it a few times).

Maxie always does things x 10.

It's normally what I have to count up to when reading your posts ..

--
geoff