Blocked distributor pipe?

[mgf102a]

I've moved into a house with a floor standing Glowworm hideaway 100b, approximately 20 yr old. The system is (was) a slighly unorthodox s-plan, with the pump on the return and the heating valve on the flow and hw valve on the return. It's an open vented system, with the feed and vent coming from the vicinity of an old back boiler that's now been removed. There's also a 3bar PRV on the boiler top tapping, which I've never seen unseated. Here's a picture of the installation.

http://s192.photobucket.com/albums/z313/mgf102/?action=view&current=100_1055.jpg

The problem is that the pump is making a lot of noise and the boiler's kettling. I changed the pump to the flow side (top front boiler tapping), and reconnected an old feed and vent to the boiler, and now it's started pumping over on all but the lowest pump setting, and everything takes ages to warm up. Apart from the fact it's still kettling like mad!
Here's a picture of the changed installation, pump's just off picture on the left side.

http://s192.photobucket.com/albums/z313/mgf102/?action=view&current=100_1060.jpg

If I drain off some water before the boiler, on the return, everything gets nice and hot very quickly, leading me to think that the restriction might be in the boiler itself. The only thing I can think of is the distribution tube, but the dammn things rusted in tight.

Am i on the right lines? Any idea how to get it out?

 

[EliteHeat]

What about moving the pump to a conventional position in relation to the cold feed and open vent?

 

[gas4you]

You could now be making the pump suck in air, your pipe work may not be designed for the pump in the flow.

 

[Garfeild]

on these old style systems,the pump should be pumping into the boiler,now youve upset it..return it to how it was,you possibly neeed a flush.

 

[namsag]

If you want to get that fitting out it is going to be drain down get a lot of heat onto the casting round about it, a big pair of tight fitting stillsons onto it and jump on them to shock it free.. Just remember after removing and cleaning it . When refitting that the groves must line up with the marks on the casting .

 

[mgf102a]

Thanks for the replies.

I can't think how you'd design the pipework to work with the pump only on the return, please could you tell me how it might be different? The water's still flowing in the same direction. The boiler manual definitely shows the pump sucking water from the top tapping.

I tried flushing it with DS40 already, just a 24hr boiler circuit de-crud, but it didn't seem to fix it.

I've got to drain down to swap the pump back, so I'll try and get the distribution pipe out as you say. If that doesn't look blocked, I'll swap the pump back and get some earplugs!.

 

[mgf102a]

Regarding EliteHeat's reply, I can't get to the feed and vent as it's either somewhere in the floor or buried behind the new fireplace that's replaced the old back boiler.

This is a concern for me as the feed and vent are at the opposite side of the house to the main boiler. i thought they should be as close as possible to the boiler, so i connected up the old feed and vent near the boiler that had been cut off (see pictures). With the pump still on the return, it started pumping over. i guess this is why someone replaced the vent with the PRV. That's when I decided to put the pump on the flow pipe, which stopped it pumping over at the main boiler vent, but it then started pumping over at the back boiler vent.

 

[Softus]

I can't think how you'd design the pipework to work with the pump only on the return, please could you tell me how it might be different? The water's still flowing in the same direction.

It's down to relative pressure. Generally (but not exclusively), the pressure in the circuit is at its highest at the pump outlet, and lowest at the pump inlet.

The cold feed and open vent have to match the position of the pump in order to discourage pumping over. If you move the pump without changing the pipework, then you can encourage, or even directly cause, pumping over.

When you had the pump off, did you inspect it and check for damage? Is it possible that the noise is just a faulty pump? It would certainly explain the kettling.

 

[mgf102a]

I must confess, i didn't check the pump. I'm not sure how. It's a Grundfos UPS 15-50. Is it just a matter of removing the four allen key bolts and having a look round? or just firing it up when it's dry, and checking for noise?

 

[Softus]

If draining down is no effort then you could remove the pump entirely and check its flow rate using a pipe stuck into a bucket.

If draining down is difficult, then summer is an excellent time to modify the system to make it easier, e.g. add a full bore lever valve somewhere handy.

 

[Bambergaspipe]

"Softus"]

Generally (but not exclusively), the pressure in the circuit is at its highest at the pump outlet, and lowest at the pump inlet.

Would that be because Generally the water going into the pump is gravity fed & the water coming out is speeded up by the pump

The cold feed and open vent have to match the position of the pump in order to discourage pumping over.

Can you explain how this set up could be achieved in an open vented system? Please include distances from cold feeds to pumps etc.

If you move the pump without changing the pipework, then you can encourage, or even directly cause, pumping over.

Generally there is only one place the pump must be situated on an open vented system to maximise the systems efficiency, maybe it would be quicker if you could explain this to him & also the theory of Negative & Positive pressure & the effect this has on this type of system.

I await with baited breath.

 

[Softus]

I await with baited breath.

Please bait your breath to your heart's content. As before, I shall leave the OP to your unassailable quality of help and support.

Bye y'all.

 

[Bambergaspipe]

I await with baited breath.

Please bait your breath to your heart's content. As before, I shall leave the OP to your unassailable quality of help and support.

Bye y'all.

Which usually means that Softus is once again out of his league & will leave it to the proper Heating Engineers.

 

[corgiman]

distinct lack of quality to your jibs of late bamber

are u feeling ok?