Pumping over - Configuration ?

[yoda]

I've started a new thread for this - my previous thread dealt with a blocked 15mm feed to a rad. In sorting that problem, a new one has appeared.

Vented system
GlowWorm Ultimate 120FF
New pump just over a month ago
Motorised diverter valves checked (one valve was stuck and has now been released, both powerheads work OK)
System flushed through with Furnox Heavy Duty Restorer (to be drained tomorrow and refilled)

After draining the system, clearing a blocked rad pipe and refilling, I now have very reduced flow to all radiators. Some get lukewarm and some are stone cold. Also, air is getting into the system and the rads are needing to be bled / vented very often.

The Feed and Expansion tank in the loft is steaming and the vent pipe is pumping over like a good 'un. The top of the vent pipe is about 18" above the top of the expansion tank. Sometimes the F&E tank is half full, sometimes it is almost overflowing..

Being a layman (but learning rapidly !), I'd just like to double check something. The 15mm cold feed pipe exits the base of the F&E tank, runs across the loft, takes a 90 degree turn downwards and reappears in our airing cupboard. Here it 'T's into a 28mm pipe which exits the immersion heater about half way up. The 28mm pipe goes back to the pump / boiler which are in a boiler room connected to the back of the house.

After reading many threads on diynot, am I correct in my thinking that the pumping over is probably associated with a blocked cold feed and the likely place for this to occur is at the T piece where the 15mm feed meets the 28mm main pipe ?

Many thanks for your advice and patience...

 

[fitz1]

feed cant be blocked because u keep filling rads.try turning ur pump down to number 1. also feed and expansion should be within 150mm of each other.

 

[Soggy_weetabix]

as i posted before, ds40.

You need your system properly cleansed.

It appears you have some serious sludge problems.

David

 

[yoda]

feed cant be blocked because u keep filling rads.try turning ur pump down to number 1. also feed and expansion should be within 150mm of each other.

Feed is fine - checked that first. Water pumps over on lowest pump setting. Water even pumps over when the pump is off and the system is filling !!

F & E pipes are less than 150mm apart and about 10 ft below F&E tank.

as i posted before, ds40.

You need your system properly cleansed.

It appears you have some serious sludge problems.

David

I think you are correct, a sludge build up does tick all the boxes. I have already dumped a litre of sludge remover into the system - this has probably disappeared down the drain after pumping over, though. And I'm not sure I want to loop the F & E pipes together..Worried about the consequences...

Also, how would a de-sludger do its job if there is very little flow around the system ??

I have tried flushing the system with mains water (rads turned off) from the pump connections.

During flushing with mains water in either direction, I only get a trickle from the opposite side of the pump with occasional brown, sludgy pockets.. HW diverter off. CH diverter on..

If I flush in the normal pumped direction, the F & E tank fills.

If I pump backwards, the system pressurises and when I take the hose from the tap, I get about 6.5 litres of water coming straight back out...The pipework should take a lot more than that.

Any ideas on tracking down a blockage ? Am I correct in thinking that I can use the 6.5 litre value to determine how far up the return pipe (22mm) the block is ??

Current status - 3 upstairs rads lukewarm, nothing downstairs at all...

Mrs is convinced problem started when she turned on a rarely used (and now very cold) upstairs rad...

Thanks for any more pointers...

 

[meldrew's_mate]

Can't work out what you mean clearly from your descriptions, but if the cold feed pipe (now clear) and the (usually 22mm) vent pipes are less than 6" apart there is very little chance of pumping over.....

So.....

1. Are the cold feed and vent connected to the same piece of 28mm pipe, and does this pipe go straight to the suction side of the pump?

2. By pumping over, do you mean water is issuing from the vent pipe into the header tank, to be fed back into the system via the cold feed. This is not the same as overflowing.

3. The DS40 chemical will cause much gassing, so the venting may not be relevant.

4. You seem to be fairly competant, have you considered hiring a powerflushing machine to clear out the copious quantities of crud in your system?

5. If the system pressurises when you mains flush "backwards" have you looked for a non-return pipe in the primaries? 28mm or 1" pipework is very common in gravity circuits, some of which incorporated non-rtn valves when semi-pumping became popular, yours may have developed from one of these.

 

[yoda]

Can't work out what you mean clearly from your descriptions, but if the cold feed pipe (now clear) and the (usually 22mm) vent pipes are less than 6" apart there is very little chance of pumping over.....

Apologies for the lack of clarity..

Both cold feed and vent tube are 15mm pipework.

The system pumps over - water is issuing from the vent tube. Hot when the boiler is on and I have also seen this occurring when I was filling the F & E tank after the system had been drained. The F & E tank fills and water escapes down the overflow pipe.

1. Are the cold feed and vent connected to the same piece of 28mm pipe, and does this pipe go straight to the suction side of the pump?

I'm at work now and can't honestly remember.. Both pipes drop down from the loft and 'T' into 22mm pipework in a first floor airing cupboard behind the immersion heater. I'll check the configuration tonight..

2. By pumping over, do you mean water is issuing from the vent pipe into the header tank, to be fed back into the system via the cold feed. This is not the same as overflowing.

Yes, pumping over - except the cold feed cannot replace the water at the same rate as the vent delivers it, the F & E tank fills and water runs out of the overflow pipe...

3. The DS40 chemical will cause much gassing, so the venting may not be relevant.

OK, but the pumping over occurred prior to any de-sludger being introduced to the system. Because the water cannot get back into the system as fast as it is being pumped over, the rads start to empty and fill with air..

4. You seem to be fairly competant, have you considered hiring a powerflushing machine to clear out the copious quantities of crud in your system?

If I can't clear any gunge with chemicals, I might have a crack this weekend. Any pitfalls to be wary of ?? I should point out I am not a plumber - have steered well clear of anything to do with water until a couple of weeks back !! I'm learning fast though..

5. If the system pressurises when you mains flush "backwards" have you looked for a non-return pipe in the primaries? 28mm or 1" pipework is very common in gravity circuits, some of which incorporated non-rtn valves when semi-pumping became popular, yours may have developed from one of these.

The 'primaries'...these being the 28mm pipes that run either side of the pump ? One of these goes to to the boiler, another exits the boiler and looks like it feeds the HW loop with a 28mm pipe. There is a 28mm/22m 'T' piece which spurs off this and feeds the CH loop. The suction side of the pump is 28mm for about 3 feet before it reduces to 22mm, then 'T'ees to the CH & HW returns. Motorised diverter valves live here (both work fine)...

There doesn't appear to be any valves in the larger diameter pipework that I can see..Do you mean something like this ?

There are a couple of these on both the feed and the return side in the 22mm pipework within 6 feet of the boiler where additional pipes spur off to a lower CH circuit - I think these are add-ons to the original system. The valves are at the very lowest part of entire CH circuit..

Thanks again for your advice. It is very much appreciated

 

[yoda]

OK, just checked the pipe runs.

The HW pipes travel from the ground floor boiler via a 2 port diverter valve to a first floor airing cupboard, through the cylinder and then return to the boiler room.

The cold feed pipe from the F&E tank tees into the lower 22mm which exits the HW cylinder. The vent pipe tees into the upper 22mm pipe entering the cylinder.

I thought the vent and feed needed to be teed into the same 22mm pipe ? Is this a fundamental error in system configuration which might explain constant pumping over and the associated poor flow around the CH system ??

Note that the system has been installed for some time (probably >10 years) and has worked fine in the past.

Any suggestions or comments much appreciated...

 

[yoda]

Update - found a couple of fairly major problems...

The downstairs loop had two monumental blockages of rust and crud about 12 feet apart. One needed a section of pipe to be cut out, the other was dealt with by a mains flush. There were creaking pipes and screeching TRVs during the flush, a couple of loud thuds and bingo, a rush of cruddy water and rust from the outlet.

I know which rad is the culprit for the rust and will replace it ASAP...

We now have scorching rads downstairs but very little upstairs. Still, thats way better than we've had for the last 2 weeks...

I'm just hoping the rust has not found its way into the upstairs loop. That would be a major PITA...

 

[yoda]

After repeated mains flushing and removal of a couple of completely blocked pipes, we have heating and hot water. I think most of the crud has been removed but plan to remove rads one by one and give them a proper flush in the garden over the next week or so. Fitted a strainer just behind the pump to catch any flakes which may be remaining.

I've been having a think and, after reading many posts here, I am not convinced that we inherited an entirely correctly laid out system when we bought the house 2 years ago.

For starters, the 2 port diverter valves for HW & CH sit on the return side of both circuits, just before the pump. Also, the vent and cold feed spur into the HW pipework at the HW cylinder (and not into the same pipe).

I have quickly sketched a schematic of the current system layout. Can anyone verify whether it is laid out correctly.

Is it worth investing in a three port motorised diverter and fit it at the 'X' point on the drawing - where the boiler out tees off to HW & CH - and then lose the 2 port valves ?

Many thanks for any opinions

 

[croydoncorgi]

From the schematic, the pump's upside down! If the flow went the other direction, more of the system might work better.
BUT it's still far from right because the vent (15mm is too small) and cold feed are a long way from the pump (it appears). They BOTH should be close to the suction side of the pump and (as stated) close together so that it won't pump-over.
If the layout is a dog's breakfast, the TRVs may be on the wrong end of the rads too (if they're non-reversible).

You have to ask yourself the question: 'Where did all this crud come from?' Even if the system had no inhibitor, it sounds like it's been running with aeration problems for a long time (which creates the crud).

 

[yoda]

From the schematic, the pump's upside down! If the flow went the other direction, more of the system might work better.
BUT it's still far from right because the vent (15mm is too small) and cold feed are a long way from the pump (it appears). They BOTH should be close to the suction side of the pump and (as stated) close together so that it won't pump-over.
If the layout is a dog's breakfast, the TRVs may be on the wrong end of the rads too (if they're non-reversible).

You have to ask yourself the question: 'Where did all this crud come from?' Even if the system had no inhibitor, it sounds like it's been running with aeration problems for a long time (which creates the crud).

Thanks for the reply..

I've been getting my head around the configuration of the system and I'm glad you agree the pump appears reversed..

We've been in the house for a couple of years and judging by the corrosion on the end of the vent pipe and the build up of sludge in the bottom of the F & E tank, it looks like the system has been wrong for a number of years. We had assumed the system was correctly configured...but then assumption being the mother of all cock-ups etc...

The crud and sludge has probably formed because of constant pumping over, F&E tank filling and water running off down the overflow pipe. Inhibited water is then replaced with fresh water and the solution is diluted..Over time, all inhibitor is gone, corrosion builds up inside rads which is made worse by lots of air in the system and it all gets progressively worse and worse...

The boiler is a GlowWorm Ultimate 120FF. The manual shows a sensor (water pressure ??) on the inlet side. This is correct with the direction of the pumped flow at present. I do not want to just simply change the direction of flow if I am then bypassing or undermining this sensor.

It may be that a new boiler (with backwards inlet / outlet) was fitted a few years back and rather than re-route the boiler inlet and outlet pipework, the installers simply reversed the pump. As for the incorrectly located vent and feed pipes, maybe the previous system was sealed, they changed it to vented and were just too lazy to run the pipework the additional distance from 1st floor airing cupboard to downstairs boiler room...

So, am I correct in thinking the solutions (as well as checking position of TRVs) are as follows:

1) Swap boiler inlet and outlet pipes, reverse pump and extend feed and vent pipes into boiler room on suction side of pump, or

2) Lose both diverter valves, install a three way diverter valve at Point X, keep pump in current direction and move vent and feed pipes as above.

Apologies for lengthy post

 

[jobloggs]

I think your solution (1) would be OK except for one thing. If you change the flow direction round your system (and check out/reposition your TRV's) then you have the flow going into the bottom of your indirect coil in the HW cylinder. This would need to be swopped.

If you go for (2) you would be better moving the pump to the flow side of the boiler before X. Why not reuse the 2 port valves on the branches of the Tee at X??

In either case you need the feed & vent pipes close together on the "sucking" side of the pump. Reading other posts I think you can use a single feed and vent pipe as long as it is 22mm. Experts can confirm.

 

[yoda]

I think your solution (1) would be OK except for one thing. If you change the flow direction round your system (and check out/reposition your TRV's) then you have the flow going into the bottom of your indirect coil in the HW cylinder. This would need to be swopped.

If you go for (2) you would be better moving the pump to the flow side of the boiler before X. Why not reuse the 2 port valves on the branches of the Tee at X??

In either case you need the feed & vent pipes close together on the "sucking" side of the pump. Reading other posts I think you can use a single feed and vent pipe as long as it is 22mm. Experts can confirm.

Some top advice there, joebloggs Why didn't I think about re-using the 2 port valves

The schematic shows the HW flow going into the upper part of the cylinder - I haven't verified this conclusively (requires lifting floorboards). It may be that if the installers did just swap the pump direction, then maybe the HW cylinder pipework is OK for option 1).

Certainly wasn't aware that a single, combined 22mm vent & feed was a possibility . Looks like some more research is in order...

Cheers !

 

[jobloggs]

You can verify what direction of flow there is now through your indirect coil.

Run a bath then grab a hold of the top and bottom pipes going into the side of your HW cylinder to the coil. The top should be noticeably hotter than the bottom one.

Then have a bath with a glass of wine and ponder the wonders of modern plumbing.

(the bath is optional)