Circulation problem - and my plumber is desperate!

[Gasguru]

Are you saying the flow pipe from the boiler then routes downwards to the boiler floor level and then rises up to the airing cupboard?

Also looking at the image of the boiler the original pipework should have had a seperate feed, a seperate vent and a flow and return pipe to the heat exchanger.

Are some of these pipes now disconnected within the boiler casing? ie just the flow and return are connected. The expansion vessel (when it was connected joins to a 15mm pipe - presumerably the old cold feed). Is one of the pipes shown gas?

 

[paulhodson]

I think the flow from the boiler comes up from the garage through the cloakroom etc, appears at the back right of this cupboard and is met by the combined cold feed and vent coming down from the F&E in the loft. It then goes off left to the pump.

No pipes disconnected as far as I know - and one of these is gas.

He added a cold feed for the temporary change to sealed system - (Speedfit across the ceiling of the garage ) It is connected to the flexible braided pipe you can see via a length of copper pipe.

I just know you will love the plumbing here - the cold feed is the white pipe at the top

and no - I didn't do it myself

 

[Agile]

Remember folks that it worked alright when it was pressurised.

I would say that rules out a major blockage.

That leaves air ingress at the suction side of the pump as the most likely cause of the problem.

Just possibly painting with washing up liquid and water mix will show a pump joint as sucking in. Normally that would have produced a leak when pressurised though. However air has a much lower viscosity than water.

Tony

 

[paulhodson]

Remember folks that it worked alright when it was pressurised.

I would say that rules out a major blockage.

That leaves air ingress at the suction side of the pump as the most likely cause of the problem.

Just possibly painting with washing up liquid and water mix will show a pump joint as sucking in. Normally that would have produced a leak when pressurised though. However air has a much lower viscosity than water.

Tony

Thank you for that Tony - to me the two points of major significance are that it worked for 30 years as it was and it worked when pressurised. Any discussion of the current plumbers obsession with plastic and ideas about different plumbing layouts are really irrelevant.

I have had another guy today (Registered Plumber) looking at it who is equally baffled. (His view mind you is that pressurising the existing boiler would be safe enough).

He has found that the pump is very noisy with air and we cannot seem to get rid of it. He is fitting automatic venting valves to the two air bleeds in the cylinder cupboard - the one from the circs to the cylinder and the one to the right of the pump. (*but see update below)

My view is that you may be right - although the amount of air that seems to get in does seem most peculiar as it did not leak when pressurised.

However, the hot feed does show evidence of magnetism and my feeling is that it may be significantly restricted. This, as I understand it, would also make it even more likely that the pump is dragging in air from somewhere.

I may try and get the hot feed cut to check this - the difficulty is that replacing more than the top foot of it would be very difficult and the magnetism seems to extend down the pipe to the point where this difficulty would occur.

Update:

The automatic vents have made no difference. The pump still sounds as though it is pumping an air water mixture but there is no indication of the fairy liquid test revealing air ingress. There is no logic in the sealing and pressurising transforming it into a working system - but it did. The combined cold feed and vent has had the vent temporarily blocked off so in theory there canbe no air ingress. Unless some obstruction moved and has reblocked the return I can find no answer.

Second engineer has admitted defeat - says last time he failed was 1979!

Next step is to replace a length of the reurh in the downstairs by new pipe This should cut out about 10 meters of old pipe - suppose this might be the blockage.

Frankly there seems no solution - without replumbing entire system - which for some reason I am reluctant to do.

 

[Gasguru]

The cloakroom where the pipes run under the tiles is on the 1st floor level ie garage ceiling level?

 

[paulhodson]

The cloakroom where the pipes run under the tiles is on the 1st floor level ie garage ceiling level?

No - boiler in garage, cloakroom at same level i.e. ground floor. Cylinder cupboard on floor above (2 storey house).

It is a suspended floor - but inadequate room for crawling under. And the pipes from the upstairs are boxed in to form part of the wall adjacent to fitted furniture, worktop etc - would have to uninstall this and destroy boxed in area etc to gain access to both hot feed to and return from upstairs.

 

[Gasguru]

In a previous posting

Are you saying the flow pipe from the boiler then routes downwards to the boiler floor level and then rises up to the airing cupboard?

And your reply was that you though the pipes rise continuously to the airing cupboard.

Now you say the pipes from the boiler di indeed run back down to the garage floor level (ie cloakroom floor level) and then up to the cylinder.

If this is the case then you should have air vents on the flow and return pipes on the vertical upstands from the boiler. Otherwise these sections of pipe and the boiler will contain trapped air and the pump may well be unable to dislodge the air. Form a tee at the top of each initial rise from the boiler followed by a short upstand with a manual air vent.

 

[paulhodson]

In a previous posting

Are you saying the flow pipe from the boiler then routes downwards to the boiler floor level and then rises up to the airing cupboard?

And your reply was that you though the pipes rise continuously to the airing cupboard.

Now you say the pipes from the boiler di indeed run back down to the garage floor level (ie cloakroom floor level) and then up to the cylinder.

If this is the case then you should have air vents on the flow and return pipes on the vertical upstands from the boiler. Otherwise these sections of pipe and the boiler will contain trapped air and the pump may well be unable to dislodge the air. Form a tee at the top of each initial rise from the boiler followed by a short upstand with a manual air vent.

Think we may be at cross purposes! The pipes from the boiler do not run back down to the garage floor level - they start there at the boiler (as per photos on page 4) . They run from there up the garage wall, through into the laundry room, along there at high level boxed in, down to floor level in another boxed section, through from there to the study, continue across the hall, under the cloakroom floor, up through the boxed in area at the left of this photo and into the cylinder cupboard on the first floor.

There is now a newly installed vent in the return pipe at the highest level in the laundry room - but no air comes from it when checked.

Bear in mind it worked for 30 years -so should be OK even if not ideal

 

[Gasguru]

Totally confused now.

If there are any loops ie inverted "U"'s they will need vents and must be vented until water comes out.

Perhaps the system was backfilled off the boiler drain cock.

 

[paulhodson]

Totally confused now.

If there are any loops ie inverted "U"'s they will need vents and must be vented until water comes out.

Perhaps the system was backfilled off the boiler drain cock.

It was certainly backfilled from the mains, either from there or from the new vent in the return pipe in the garage.

 

[Gasguru]

So if you are saying you have unvented high points on the flow/return pipework then this may be the problem. Clearly filling the system from the boiler end via the temporary filling loop setup helped to expell the air in these loops.

Where boilers are connected by flow/return pipework that loops up in this way it is normally only acceptable if the boiler has an additional overheat thermostat. From what I can see the Hideaway does not have an additional overheat thermostat and is also likely to be the reason it was never approved for sealed systems.

 

[paulhodson]

So if you are saying you have unvented high points on the flow/return pipework then this may be the problem. Clearly filling the system from the boiler end via the temporary filling loop setup helped to expell the air in these loops.

Where boilers are connected by flow/return pipework that loops up in this way it is normally only acceptable if the boiler has an additional overheat thermostat. From what I can see the Hideaway does not have an additional overheat thermostat and is also likely to be the reason it was never approved for sealed systems.

No it doesn't have the stat. Not sure about your other point - getting beyond my knowledge (not difficult ) But the two engineers who have been stumped so far have about 80 years experience between them and they can't spot anything.

There is certainly a vent in the cylinder cupboard (now with an automatic vent unit fitted) on the flow just before the pump and as I say the return has a new one at garage roof level - but as it has worked for 30 years - there must be something that has changed - leaks, blockages or something that has causedthe recent problems rather than the original design.

 

[ChrisR]

There is no logic in the sealing and pressurising transforming it into a working system - but it did.

If theory and practice don't agree, you got the wrong theory!

Two of us have suggested why pressurising it might make the difference. Air ingress through micro leaks. Have known a system need pressurising up to 1.4 bar before it stopped sucking air in. Your pump won't pump frothy bubbly stuff, and cavitation is possible too.

Can you get to the pipes on the inlet side of the pump? If so change a few feet, and the pump valve. Unless you fancy going over all the joints with LS-X (Or spray-on car body underseal). Cover the pumpbleed screw too.

If you're worried about blockages in the pipes, go to Wickes and buy their drain clearing springs, 2 sizes both very cheap, about 6 - 8mm diameter. Go in where you can - pump valves, vent pipe, etc, and open somewhere to let the grot flow out.

 

[doitall]

What you are saying is the pipe rise from the boiler, goes through the wall somewhere, then drops back down to the floor, goes under the floor then back up to the cupboard.

And the plumbers realise this or did you keep it a secret.

So in practice the boiler has no open vent, that Sir is Bloody stupid, take it how you like but the boiler is dangerous and should be turned off.

 

[paulhodson]

There is no logic in the sealing and pressurising transforming it into a working system - but it did.

If theory and practice don't agree, you got the wrong theory!

Two of us have suggested why pressurising it might make the difference. Air ingress through micro leaks. Have known a system need pressurising up to 1.4 bar before it stopped sucking air in. Your pump won't pump frothy bubbly stuff, and cavitation is possible too.

Can you get to the pipes on the inlet side of the pump? If so change a few feet, and the pump valve. Unless you fancy going over all the joints with LS-X (Or spray-on car body underseal). Cover the pumpbleed screw too.

If you're worried about blockages in the pipes, go to Wickes and buy their drain clearing springs, 2 sizes both very cheap, about 6 - 8mm diameter. Go in where you can - pump valves, vent pipe, etc, and open somewhere to let the grot flow out.

I may get the guy to try the pressurising again even though the boiler is not strictly suitable. Then run it for a few days to see if continues working well. If so - I will have two choices - a new condensing boiler fitted in a sealed system (£ouch!) or accept the risk of the boiler leaking and perhaps fit an additional pipe stat instead of the overheat stat the boiler should have. Presumably this should, in conjunction with the safety valve on the pressure unit, be relatively OK? The second "Registered Plumber" said he had converted many theoretically unsuitable boilers to sealed system operation without problems (and without an additional stat)

The other advice I would leave to the plumber. Writing to forums is more my skill!