Hi all

Thanks to all respondents to original thread.
Have shifted emphasis here so new thread in order.

My concern is pump over!
As roughly outlined in my previous thread, the solenoid valve for heating is
half way between ground and first floor, with upstairs feed to all rads in
15mm pipe from this point.
The feed to the cylinder and vent is 22mm with the solenoid close to the
cylinder on the first floor.
On advice from previous thread, I tried to "force" flow to 2 upstairs rads
by turning all downstairs rads off (this is a likely scenario if all trvs
close doownstairs).
I didn't get as far as checking these 2 rads because water started to pump
over into the header tank immediately, even with the upstairs bathroom rad
fully open (both lockshield and control valves).

My dilemma is that it appears pump over is inevitable with this piping.
With downstairs rads off, the pump runs and is faced with 2 routes, either
22mm up passed cylinder and over to header tank, or 15mm with fittings and
rad valve resistance.
Surely, as installed, this arrangement will always pump over rather than
feeding the upstairs rads?

I have two theories:

1. The systems were never designed to have trvs, therefore some down stairs
flow would always avoid the pump over.
2. There is a problem with the heating solenoid valve (although it seems to
work OK) and it is presenting some restriction. So add the further
restriction of only 15mm pipe available and pump over occurs.


Anyone shed any further light on this please?


TIA

Phil

Anyone shed any further light on this please?

Yes, switch to sealed pressurised operation, if your boiler allows it. Much
quicker and simpler than diagnosing a pump over problem.

Christian.

In article ,
TheScullster wrote:
My dilemma is that it appears pump over is inevitable with this piping.
With downstairs rads off, the pump runs and is faced with 2 routes,
either 22mm up passed cylinder and over to header tank, or 15mm with
fittings and rad valve resistance. Surely, as installed, this
arrangement will always pump over rather than feeding the upstairs rads?

Is it possible to extend the expansion pipe so it goes higher? Possible to
site the entire header tank higher in the roof void?

--
*Procrastinate now

Dave Plowman London SW
To e-mail, change noise into sound.

TheScullster wrote:

My dilemma is that it appears pump over is inevitable with this piping.
With downstairs rads off, the pump runs and is faced with 2 routes, either
22mm up passed cylinder and over to header tank, or 15mm with fittings and
rad valve resistance.
Surely, as installed, this arrangement will always pump over rather than
feeding the upstairs rads?

What speed was the pump running at?

What is the height difference between the rads and the apex of the vent
pipe? That (converted into an equivilent pressure) will tell you the
maximum flow resistance that can be accomodated in the upstairs rads
without pumping over.

Are you sure you don't have a restriction or blockage of some sort in
the upstairs rad loop?

I have two theories:

1. The systems were never designed to have trvs, therefore some down stairs
flow would always avoid the pump over.

Do you have a bypass radiator or a bypass valve?

If it is all TRVs and there is no bypass, then there is always the
possibility of pump over unless you also include a flow switch as an
interlock.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"John Rumm" wrote:


What speed was the pump running at?

Meant to include that - it's at speed 2 of 3.


What is the height difference between the rads and the apex of the vent
pipe? That (converted into an equivilent pressure) will tell you the
maximum flow resistance that can be accomodated in the upstairs rads
without pumping over.

Approx 3.5m above top of rads (not towel rail)


Are you sure you don't have a restriction or blockage of some sort in the
upstairs rad loop?

Only the pipe size of 15mm mains rather than 22mm I think. Original
radiators heat up in just-about-acceptable time.



Do you have a bypass radiator or a bypass valve?

As stated, the bathroom rad valves were both fully open on the first floor.


Thanks for the help John

Phil

TheScullster wrote:

Approx 3.5m above top of rads (not towel rail)

So that is about 1/3rd of a bar then...

Are you sure you don't have a restriction or blockage of some sort in the
upstairs rad loop?


Only the pipe size of 15mm mains rather than 22mm I think. Original
radiators heat up in just-about-acceptable time.

What happens if you close off the downstairs rads and set the pump to
speed 1? Do the upstairs rads heat then or do you still get pump over?

It seems that with the downstairs rads closed, and a differential
pressure such as you have, you ought to be able to get decent
circulation through the upstairs rads. If even in that circumstance you
don't get decent flow through them that suggests some form of blockage
to me, rather than just a flow restriction.

Do you have a bypass radiator or a bypass valve?


As stated, the bathroom rad valves were both fully open on the first floor.

I was asking for a different reason ;-) More a case of without a bypass
of some form and TRVs everywhere there would come a point (when the
house is up to temperature) that the only place the pump can send water
is up the vent!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

I was asking for a different reason ;-) More a case of without a bypass
of some form and TRVs everywhere there would come a point (when the
house is up to temperature) that the only place the pump can send water
is up the vent!

Yes, Grundfos Alpha and sealed circuit. You know it makes sense.

Christian.

"John Rumm" wrote:

So that is about 1/3rd of a bar then...

Yes


What happens if you close off the downstairs rads and set the pump to
speed 1? Do the upstairs rads heat then or do you still get pump over?

Didn't try that. What would this show if it worked? The system is pretty
slow to heat up as is without lowering the pump speed.
I will try this tonight and report back.


It seems that with the downstairs rads closed, and a differential pressure
such as you have, you ought to be able to get decent circulation through
the upstairs rads. If even in that circumstance you don't get decent flow
through them that suggests some form of blockage to me, rather than just a
flow restriction.

Still not clear why the water would want to take the tortuous route through
15mm pipe/rads rather than the clear 22mm route via the vent pipe.

The heating solenoid valve did start making noises some time ago and has
since gone quiet.
But as this controls water flow to both upstairs and downstairs I'm not
clear on whether this is likely to be the cause.
Could this be causing a partial restriction which, when added to the 15mm
pipe reduction, might cause the pump over?


Do you have a bypass radiator or a bypass valve?

Other than the bathroom, there is also a rad piped direct to the flow and
return of the boiler before either solenoid valve.
Opening this last night did not stop the pump over but may have reduced it.
valves were both fully open on the first floor.



I was asking for a different reason ;-) More a case of without a bypass of
some form and TRVs everywhere there would come a point (when the house is
up to temperature) that the only place the pump can send water is up the
vent!

Do you not think that the bathroom rad should perform this function?

Thanks again for your time with this


Phil

In article ,
TheScullster wrote:
Didn't try that. What would this show if it worked? The system is
pretty slow to heat up as is without lowering the pump speed.

The pump speed makes little difference to this. All it needs to do is to
provide sufficient flow to get the correct temperature differential
between flow and return. Speeding up the flow beyond this only results in
more noise.

--
*Upon the advice of my attorney, my shirt bears no message at this time

Dave Plowman London SW
To e-mail, change noise into sound.

TheScullster wrote:

So that is about 1/3rd of a bar then...


Yes

Ought to be plenty... (the vented system I used to have ran fine on 2m
of head)

What happens if you close off the downstairs rads and set the pump to
speed 1? Do the upstairs rads heat then or do you still get pump over?


Didn't try that. What would this show if it worked? The system is pretty

It would show that the upstairs rad loop is not blocked. If however it
still failed to heat (or did so very slowly, or still pumped over) then
that would suggest something wrong in that pipe loop.

Still not clear why the water would want to take the tortuous route through
15mm pipe/rads rather than the clear 22mm route via the vent pipe.

Because the 22mm path requires 1/3rd of a bar more pressure to get water
to pump over. Even if the flow rate is not as fast through the smaller
pipe, the pressure required to achieve *some* flow through it ought to
be a good deal less.

The heating solenoid valve did start making noises some time ago and has
since gone quiet.
But as this controls water flow to both upstairs and downstairs I'm not
clear on whether this is likely to be the cause.
Could this be causing a partial restriction which, when added to the 15mm
pipe reduction, might cause the pump over?

Perhaps... Is the valve one that can be operated manually (perhaps by
removing the solenoid)? If so does it move freely?

I was asking for a different reason ;-) More a case of without a bypass of
some form and TRVs everywhere there would come a point (when the house is
up to temperature) that the only place the pump can send water is up the
vent!


Do you not think that the bathroom rad should perform this function?

Yes it should, sorry I must have missed this detail before. A rad can be
used as a bypass (should have lockshield valves at *both* ends in which
case).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"TheScullster" wrote in message
...
Hi all

Thanks to all respondents to original thread.
Have shifted emphasis here so new thread in order.

My concern is pump over!

You can't get pump over in my system.
The vent and filler pipe are combined.
It takes a little longer to fill but thats about the only problem.

You can't get pump over in my system.
The vent and filler pipe are combined.
It takes a little longer to fill but thats about the only problem.

The main issue with combined feed/expansion is that it requires the same
safety features in the boiler as sealed pressurised operation.

Personally, if the boiler did have the safety features, then I'd go sealed
instead of combined gravity feed, as the benefits are great.

Christian.

In an earlier contribution to this discussion,
TheScullster wrote:

Hi all

Thanks to all respondents to original thread.
Have shifted emphasis here so new thread in order.

My concern is pump over!
As roughly outlined in my previous thread, the solenoid valve for
heating is half way between ground and first floor, with upstairs
feed to all rads in 15mm pipe from this point.
The feed to the cylinder and vent is 22mm with the solenoid close to
the cylinder on the first floor.
On advice from previous thread, I tried to "force" flow to 2 upstairs
rads by turning all downstairs rads off (this is a likely scenario if
all trvs close doownstairs).
I didn't get as far as checking these 2 rads because water started to
pump over into the header tank immediately, even with the upstairs
bathroom rad fully open (both lockshield and control valves).

My dilemma is that it appears pump over is inevitable with this
piping. With downstairs rads off, the pump runs and is faced with 2
routes, either 22mm up passed cylinder and over to header tank, or
15mm with fittings and rad valve resistance.
Surely, as installed, this arrangement will always pump over rather
than feeding the upstairs rads?

I have two theories:

1. The systems were never designed to have trvs, therefore some down
stairs flow would always avoid the pump over.
2. There is a problem with the heating solenoid valve (although it
seems to work OK) and it is presenting some restriction. So add the
further restriction of only 15mm pipe available and pump over occurs.


Anyone shed any further light on this please?


TIA

Phil

In order to get pump-over, you need a difference in dynamic pressure between
the vent pipe and fill pipe. This can happen if they are connected on
opposite sides of the pump, or even on the same side - but at two distant
points on a pipe carrying a lot of flow. If at all possible, they should
both be connected on the suction side of the pump, and not more than 100mm
apart. Mine actually have a *single* 22mm connection into the flow pipe -
which then splits into a 22mm vent pipe and 15mm fill pipe.

Have a close look at how your pipes are connected, and see whether you can
move one of them to prevent this problem. Take care to ensure that both
pipes have a clear path to the boiler which cannot be interrupted by closing
any motorised (or solenoid) valves.
--
Cheers,
Set Square
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