Cool October nights have highlighted another fault with our Olympic
Thorn boiler/Grundfos pump system... When "hot water only" is selected
on the boiler, the upstairs rads get hot (and the bathroom rad is
scalding! -- furthest from the pump?), while the downstairs rads stay
cold. When "hot water plus central heating" is selected, the upstairs
rads remain hot, while the downstairs rads cool off when the thermostat
temperature setting is reached.

The pump is a Grundfos 15-60. I'd like to be able to check for a
sticking impeller before I have to call out the plumber again to look
at this relatively young pump (installed a couple of years back). Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation? It
doesn't move yet, and I'm afraid to shift it in case it's an adjustment
screw of some sort.

Also, is there a built-in non-return valve? Perhaps in the box on the
side of the pump? If that has failed, can it be replaced separately or
is it a whole new pump?

On Oct 5, 6:06 pm, wrote:
When "hot water only" is selected
on the boiler, the upstairs rads get hot (and the bathroom rad is
scalding! -- furthest from the pump?), while the downstairs rads stay
cold.

Probably an installation defect . You should have two separate return
pipes from upstairs, one for the upstairs heating the other for the
return from the hot water cylinder. The upstairs heating return joins
with the downstairs heating return before joining the HW cylinder
return. Joining the two returns upstairs & having one retrun pipe will
allow a flow path through the heating when the HW only is selected.
Sketch out a schematic and you'll see what I mean. The water can flow
backwards through the upstairs HTG return, along upstairs HTG flow,
along downstairs HTG flow, up downstairs HTG return and back to the
boiler (or something like that).

The bathroom rad is commonly connected to the circuit heating the HW
cylinder, so you can dry towels when the heating isn't required

Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation?

Yes. A little water spills. You should undo it to vent air after
installation.

Also, is there a built-in non-return valve?

No. If you want a NRV you buy one.

Perhaps in the box on the side of the pump?

Electric conections are in there.

wrote in message
ps.com...


The pump is a Grundfos 15-60. I'd like to be able to check for a
sticking impeller before I have to call out the plumber again to look
at this relatively young pump (installed a couple of years back). Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation? It
doesn't move yet, and I'm afraid to shift it in case it's an adjustment
screw of some sort.

Yes that is what it is for, you will probably get a dribble of water out so
stand by with the Bounty. The shaft of the impeller has a slot to rotate it
manually if it has stuck.

In an earlier contribution to this discussion,
wrote:

Cool October nights have highlighted another fault with our Olympic
Thorn boiler/Grundfos pump system... When "hot water only" is selected
on the boiler, the upstairs rads get hot (and the bathroom rad is
scalding! -- furthest from the pump?), while the downstairs rads stay
cold. When "hot water plus central heating" is selected, the upstairs
rads remain hot, while the downstairs rads cool off when the
thermostat temperature setting is reached.

The pump is a Grundfos 15-60. I'd like to be able to check for a
sticking impeller before I have to call out the plumber again to look
at this relatively young pump (installed a couple of years back). Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation? It
doesn't move yet, and I'm afraid to shift it in case it's an
adjustment screw of some sort.

Also, is there a built-in non-return valve? Perhaps in the box on the
side of the pump? If that has failed, can it be replaced separately
or is it a whole new pump?

I don't understand why you think that this indicates a problem with the
pump. You say that when HW+CH is selected, the downstairs rads cool off when
the stat setting is reached. As long as they get hot initially, and only
cool off when the stat switches, this is exactly what is supposed to happen.

Your problem surely is that the upstairs rads get hot when they shouldn't -
and you need to find out why that is - but it's unlikely to be anything to
do with the pump. Do you have any motorised valves in the system? If so, how
many, where are they, and what type (2 or 3 port)? If there are no motorised
valves, it is probably a gravity (convection) HW system with the pump only
being used for the CH. If this is the case, it sounds like you're getting
gravity circulation through the upstairs rads whenever the boiler is
running - even when there's no CH demand.

But tell us a bit more about the layout of your system - and the components
used - and we will be better able to advise.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Thank you for all your replies. I will be posting a proper reply
shortly. Have been trying to sort things out.
Cheers!

Roger Mills wrote:
In an earlier contribution to this discussion,
wrote:

Cool October nights have highlighted another fault with our Olympic
Thorn boiler/Grundfos pump system... When "hot water only" is selected
on the boiler, the upstairs rads get hot (and the bathroom rad is
scalding! -- furthest from the pump?), while the downstairs rads stay
cold. When "hot water plus central heating" is selected, the upstairs
rads remain hot, while the downstairs rads cool off when the
thermostat temperature setting is reached.

The pump is a Grundfos 15-60. I'd like to be able to check for a
sticking impeller before I have to call out the plumber again to look
at this relatively young pump (installed a couple of years back). Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation? It
doesn't move yet, and I'm afraid to shift it in case it's an
adjustment screw of some sort.

Also, is there a built-in non-return valve? Perhaps in the box on the
side of the pump? If that has failed, can it be replaced separately
or is it a whole new pump?

I don't understand why you think that this indicates a problem with the
pump. You say that when HW+CH is selected, the downstairs rads cool off when
the stat setting is reached. As long as they get hot initially, and only
cool off when the stat switches, this is exactly what is supposed to happen.

Your problem surely is that the upstairs rads get hot when they shouldn't -
and you need to find out why that is - but it's unlikely to be anything to
do with the pump. Do you have any motorised valves in the system? If so, how
many, where are they, and what type (2 or 3 port)? If there are no motorised
valves, it is probably a gravity (convection) HW system with the pump only
being used for the CH. If this is the case, it sounds like you're getting
gravity circulation through the upstairs rads whenever the boiler is
running - even when there's no CH demand.

But tell us a bit more about the layout of your system - and the components
used - and we will be better able to advise.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Thank you all again for your replies...
Nothing at all may be wrong with the pump. It works, both for HW and
CH. The perplexing thing has been that with only HW selected on the
boiler, the upstairs rads were heating up. Heating up water in the
summer meant that all the rooms upstairs were baking! If CH is used,
and it shuts down at the appropriate temperature on the lounge
thermostat, the upstairs rads remain on, and REMAIN hot -- they don't
cool down until the CH is completely shut down.

I have been investigating the setup out in the garage where the pump is
located and have discovered what I have now confirmed to be a
non-return valve, in the run of pipe that runs parallel to the pump and
it's inlet and outlet pipes. Further advice now suggests that the
fault lies with the non-return valve, which I will attempt to replace
myself in the near future, rather than pay a plumber £100 to replace a
£3 valve.

Thanks again for your tips and advice!
Regards,
dennmac


wrote:
Thank you for all your replies. I will be posting a proper reply
shortly. Have been trying to sort things out.
Cheers!

Roger Mills wrote:
In an earlier contribution to this discussion,
wrote:

Cool October nights have highlighted another fault with our Olympic
Thorn boiler/Grundfos pump system... When "hot water only" is selected
on the boiler, the upstairs rads get hot (and the bathroom rad is
scalding! -- furthest from the pump?), while the downstairs rads stay
cold. When "hot water plus central heating" is selected, the upstairs
rads remain hot, while the downstairs rads cool off when the
thermostat temperature setting is reached.

The pump is a Grundfos 15-60. I'd like to be able to check for a
sticking impeller before I have to call out the plumber again to look
at this relatively young pump (installed a couple of years back). Can
anyone confirm for me that the large brass screw head in the centre of
the pump can be undone, in order to check for impeller rotation? It
doesn't move yet, and I'm afraid to shift it in case it's an
adjustment screw of some sort.

Also, is there a built-in non-return valve? Perhaps in the box on the
side of the pump? If that has failed, can it be replaced separately
or is it a whole new pump?

I don't understand why you think that this indicates a problem with the
pump. You say that when HW+CH is selected, the downstairs rads cool off when
the stat setting is reached. As long as they get hot initially, and only
cool off when the stat switches, this is exactly what is supposed to happen.

Your problem surely is that the upstairs rads get hot when they shouldn't -
and you need to find out why that is - but it's unlikely to be anything to
do with the pump. Do you have any motorised valves in the system? If so, how
many, where are they, and what type (2 or 3 port)? If there are no motorised
valves, it is probably a gravity (convection) HW system with the pump only
being used for the CH. If this is the case, it sounds like you're getting
gravity circulation through the upstairs rads whenever the boiler is
running - even when there's no CH demand.

But tell us a bit more about the layout of your system - and the components
used - and we will be better able to advise.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!