Seized secondary hot water return pump

TheGreenFrog

The pump on my secondary hot water return (picture attached) appears to have seized (it had not been used for a very long time as the attached timer had broken and I have only just replaced that).  I am tempted to try to fix it myself but I am not entirely sure of all the steps.  There are isolators on either side of the pump.  I think that the first step (after isolation, or maybe that is not required) is to unscrew the silver screw on the front of the pump and then use a screwdriver to turn the impeller inside and hope that does the trick.  It seems simple but just want to check that there is nothing too much that can go wrong.  I guess if that trick does not fix the issue pump may need replacement (also seems straightforward if I buy same type but that is for another day!).  

diveunderthebonnet

Yes you can do what you described ,just place a container under the screw hole to catch the small amount of water that will run out plus any that weeps passed the shut off valves ,if it dous not free of then a new one will be required as you say.

nofoollikeold

1. The purpose of the large screw in the centre is to bleed air from the pump,  It can also be used to give the impeller a turn or to see if it is rotating,
2. Provided the pump is is generally good condition, you should not need to isolate the water to it.  Some water will leak out when it is removed, but should be very little and easily caught with an old towel.
3. If you do decide to isolate the water, be aware that the valves each side are likely to be screw down gate valves or 1/4 turn isolation valves.
4. Gate valves often seize up and can be very difficult to turn. If you force them (e.g. large spanner on square spindle) it is possible to shear the spindles, often leaving the valve fully open or fully closed.
5. Quarter turn valves often leak once used.
6. If the pump hums but doesn't turn there is a fair chance the capacitor inside it has failed.  These can be replaced but must only be replaced with the same capacitance value (micro farads) and must be suitable for mains voltages.  An 8 micro farad 400 volt motor capacitor is usually about right.  400V because the 230 mains voltage swings from +330V to -330V 50 times / second, and 230 is a sort of average.  

EssexExile

A clout to the casing with a hammer often frees them up.

ThisIsWeird

Between nflo and EE, you have it covered
Just to reiterate nflo's advice, there's no need to isolate the pump first, and it's initially best not to for the reasons mentioned. 
Power off, towel or shallow tray under pump, undo end screw - it's usually just a few drips. Large flat screwdriver in, and turn the shaft. Any initial stickiness?
Power up with screw still off, and see if it spins. Replace screw.
Is the pump fully 'dead' - no lights, hums or anything? If so, obviously worth checking the supply from the timer before buying a new pump.

diveunderthebonnet

ThisIsWeird said:

Between nflo and EE, you have it covered
Just to reiterate nflo's advice, there's no need to isolate the pump first, and it's initially best not to for the reasons mentioned. 
Power off, towel or shallow tray under pump, undo end screw - it's usually just a few drips. Large flat screwdriver in, and turn the shaft. Any initial stickiness?
Power up with screw still off, and see if it spins. Replace screw.
Is the pump fully 'dead' - no lights, hums or anything? If so, obviously worth checking the supply from the timer before buying a new pump.

I was in our local B & Q the other week and noticed the price of the CH pumps on sale ,really expensive since i last changed one and then it was a Grundfos ,i think they were considered the best .

TheGreenFrog

I finally got around to trying to deal with the pump.  Access does not allow me to look into the pump, so I took a picture (attached).  I managed (I think) to put a screwdriver into the slot inside the pump and I tried to turn it.  Would not budge.  Is next step a new pump?

diveunderthebonnet

I would think so ,can you change it yourself ? a replacement is about £200 ,easy done if you have a small pair of stillsons or a heavy duty waterpump pliers plus a hammer to give the nuts a smart tap to help to loosen them.

FreeBear

diveunderthebonnet said: I would think so ,can you change it yourself ? a replacement is about £200

Where are you buying circulation pumps ???

Can get a basic one for less than £50 on ebay.

OK, Screwfix do a Wilo one for £199.99 - https://www.screwfix.com/p/wilo-4035479-sb30-secondary-circulating-pump-230v/74599

TheGreenFrog

diveunderthebonnet said:

I would think so ,can you change it yourself ? a replacement is about £200 ,easy done if you have a small pair of stillsons or a heavy duty waterpump pliers plus a hammer to give the nuts a smart tap to help to loosen them.

I can probably do myself but may get a plumber to do it if it needs the whole unit replaced.  I am sort of hoping that if I get exactly the same pump (Wilo SB30) I might be able to replace just the head unit:  but I have no idea?

ThisIsWeird

TheGreenFrog said:

I finally got around to trying to deal with the pump.  Access does not allow me to look into the pump, so I took a picture (attached).  I managed (I think) to put a screwdriver into the slot inside the pump and I tried to turn it.  Would not budge.  Is next step a new pump?

Blimey, no movement? Are you sure?
When pumps 'seize', it's usually down to a small buildup of sludge around the shaft where it enters the bearing. It doesn't take much, usually only for the pump to not have been used for a season or more - and for the system water to be slightly dirty...
There's just little else going on - it's commonly a stainless steel motor shaft sitting in a ceramic bearing, lubricated by the system water. Nothing to corrode or mess up.
I find it very surprising that you cannot make the spindle turn. Of course summat else might have gone wrong, but I cannot think what this could be.
So, could you confirm, please - that is a slot visible in there? You do have a screwdriver of a suitable size? Ie, you haven't chosen a big 'un that won't even go through the hole?! Or a titchy one that doesn't grip enough to apply enough torque?
Could you try again, please? With a proper SD. Tobesuretobesure?