Can a CH pump wear out?

[Softus]

Blimey what a mess.

At this point I would drain down again and carefully disconnect the primary connections at the cylinder. If any part of the pipework appears to be blocked then take the opportunity to replace it (using 22mm, not 15mm). There a good chance that you'll find debris at one (or both) coil connection(s), which would also need clearing.

If you gently pour water in the upper coil connection (using, for example, a few inches of hosepipe and a funnel), then you should see water come out of the lower coil connection. If it doesn't, then start to think seriously about replacing the cylinder.

 

[ChrisR]

RIght - so we're here?

In which case, note the new green area, and that it doesn't stop the system filling, through the cylinder.

That sort of blockage can be very hard, and isn't touched by draining and refilling

 

[DIYedboy]

ChrisR, I can't see your pic? cos I'm at work n the security filters them out. I can say that the heating now works fine (there's only 5 rads but the areas within them that aren't sludged up get hot). So, Chris n Softus, is it pumping over because the cylinder return is in 15mm? in which case it must have been doing it since 1970, or is it pumping over because there is a bit of a blockage around the feed/cylinder area?

 

[DIYedboy]

just checked diag. if you change rad flow n return for 15mm you have it Chris

 

[Softus]

At this point I would drain down again and carefully disconnect the primary connections at the cylinder. If any part of the pipework appears to be blocked then take the opportunity to replace it (using 22mm, not 15mm). There a good chance that you'll find debris at one (or both) coil connection(s), which would also need clearing.

is it pumping over because there is a bit of a blockage around the feed/cylinder area?

Eh?

is it pumping over because the cylinder return is in 15mm? in which case it must have been doing it since 1970

What?!

 

[GPlumb]

What do you use to draw those pics ChrisR?

 

[DIYedboy]

Softus, you have advised me what to do (super-smashing I'll give that a bash soon). BUT I am asking whether the 15mm return is a fundamental design flaw which would result in pumping over

 

[jackthom]

RIght - so we're here?

In which case, note the new green area, and that it doesn't stop the system filling, through the cylinder.

That sort of blockage can be very hard, and isn't touched by draining and refilling

It looks to me like the maximum head between flow and return to the radiators before pumping over occurs will be half a metre (or so), i.e. equal to the height of the overflow above the water in the F/E tank.

Shouldn't both the cold feed and overflow be on the same side of the pump (ideally the low pressure side)?

 

[Softus]

Shouldn't both the cold feed and overflow be on the same side of the pump (ideally the low pressure side)?

Too right it should, but this is a litany of how to do everything wrong, including fault-finding, so it would be a shame to spoil it.

 

[ChrisR]

This is getting better
Victor Meldrew would have had a good phrase for it!

It needs a lot of changing.

These Pics are done very simply in MS Paint,
I store them as "untitled.gif" if I don't want to keep them, as in this case.
I've downloaded the Image-Shack toolbar.
Then I just click Upload, can easily find the file, whatever I've called it , with "My recent documents".
Image-shack then provides a link which I CTRL-C and CTRL-V, then click the Img button.

It's about 12 clicks.

You can upload them to the DIYnot network but it takes longer.

 

[DIYedboy]

Now who's not answering questions Softus? .......Great pic Chris n accurate too. Had a look at the cylinder, don't fancy tackling that, looks original, iron reducer, loads of scale around joints n rust (I'm scared!).

Is there any chance I can lower the FE tank to the same height as the cold storage tank then raise the loop of the expansion pipe and that will stop the pumping over?

 

[sambotc]

15mm retun has been put in to reduce circulation around the coil to stop it stealing the flow off the radiator circuit i reckon. A gate valve would do the same thing but with a little more control. Dont think it is the cause of the problem though. the cf&vent are more of an issue but the system would probably work if it was clean and free from any obstructions.

What speed is the pump on? (have asked a few times) should be on 1 i reckon.

Raising the vent would be a short term fix for a long term problem (if it worked) and i can't see what odd's lowering the tank would do unless you had no room to raise the vent pipe. You want a min of 1000mm from highest point on system to water level in f&e.

 

[Softus]

Now who's not answering questions Softus?

I don't know, but let's not forget that my own heating system works, and so do the three others that I fixed today, so you're not well placed to be making smart ars*d comments.

Is there any chance I can lower the FE tank to the same height as the cold storage tank then raise the loop of the expansion pipe and that will stop the pumping over?

There are lots of ways of stopping the pumping over, but there's only one way of dealing with the cause of it.

 

[DIYedboy]

Pump pumps over even on 1 (currently I put it on 3 to push the X400 around)

The bend at top of FE tank touches the apex of the roof, n tank currently is 6 inches below that bend.

FE tank is about 6 feet above top of HW cylinder (bet Softus couldn't have done that drawing Chris)

 

[DIYedboy]

You'll never know how happy the news that your heating system works well makes me Softus, but that don't help me uncle or make the nightmare of trying to fix his system with the minimum of effort any easier does it.