Search the forum,

Central Heating Flow pipes burning hot - Return Pipes cold

Post new thread

Discuss Central Heating Flow pipes burning hot - Return Pipes cold in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Status
Not open for further replies.
J

Jodi Thomson

Hello Folks.

Looking for some extra advice regarding our new CH System. We recently replaced our Old Electric System with a Worcester Greenstar Camray Condensing External Boiler (Oil) which has been connected to a new Megaflow Systemfit within the house. We had some problems after installation which we posted on this site, and a very helpful guy gave us the no. for a Aberdeen based plumber. We did contact him, but he never got back to us, so finally got hold of another one, who has spent the last 2 days checking over every part of our system: -

All Megaflo System working as required (plenty of hot water) including motorised valves, pump, pressure vessel etc (and plenty of hot water).
All pipework in correct places (double checked this by swapping pipes just in case)
Whole System was Power Flushed this morning for 5 Hours.

Problems still arising: -

No return flow on rads. Flow pipe coming in so boiling hot, no circulation.

Have tried heating rads one by one. This works and all rads get roasting, but turn on more and the heat dissappers, return pipes still cold. Have tried balancing to no avail. The plumber has said there must be a blockage somewhere in the pipework, but where, we have no idea. We had tried power flushing but it has not shifted the blockage. Is there anything else we can try, as we really don't want to have to go change all the pipework. Is there a different stronger chemical we can try? Any ideas would be helpful and much appreciated.
 
Did he use FX2 ? and you could go round each rad hitting it with a rubber mallet on the return pipe work. Not too hard obviously. If the plumber only did a coursery power flush he would not have done one rad at a time but left the system open and the blocked rad would be bypassed as it is just clogged with magnatite.
 
hiya

I was the plumbers apprentice today. We did use FX2 and we did each rad seperate at first whilst hitting them with a mallet, then did them all together for one final blast, it didn't shift the blockage at all. Whilst flushing each rad we listened for flow in the rads, and each rad seemed to be getting. Turn it to CH mode and the return pipe gets boiling hot to touch, boiler runs for 2.37 mins and cuts off, and return pipe flow dosn't seem to go anywhere. The plumber doing the works now, was not who installed it. The installed has done a runner and we can't get hold of him to rectify the fault, so were having to pay out even more money to get the original fault sorted. Our new plumber has said to leave the CH on full blast for the whole weekend, and he'll pop in past again Mon am to see if theres any change. This system was fitted in March and has never worked, but it wasn't such a problem in the summer months, now it 0 deg c here in the northof scotland and were freezing! thank god we have a gas fire or we'd really be us the creek without a paddle!!!!
 
You could try changing the lockshields on each of the rads. These are normally on the return pipe work. Or if you feel the flow pipe work and it is not heating the rad then it might be the wheel head (or TRV) is blocked.
 
There should be no mystery about whether there's a blockage or not if you have a power flush. When you switch to drain, you see how freely the water flows. If the water flows with the power flush, it will flow with the system's pump, unless the pump is blocked. Have you stripped the pump to make sure the impeller is clear?

Can't you call out the installer under guarantee?

Is it a very old system? Has the performance been gradually reducing? Did the flow suddenly stop? You are looking for something very simple. I'm tempted to think you have not told us the whole story. All you've got to do is work out what should be connected to what and then connect it. I sense some trial and error in your methods. Why the trial and error?
 
Bloomin eck !!! Still no joy . At least the new guy is calling back Monday. Agree with the Gas Engineer that if its a blockage it will be evident right away .
But you say that each rad heats up if on individually .
 
It cannot possibly be a blockage if the rads will all work individually. Start with closing the bypass completely. If you had posted the other day i may have been able to help as i was up in Buckie at the new Tesco shop. Unfortunately Buckie is a 4hr drive from me £300 traveling time.

This will not be hard to solve for anyone who knows their stuff.
That is the hard part though. Getting the right guy.
 
hi toddy plumb - yeah me again!! Yeah when we had the power flush on the pressure on the megaflo was 1.5 bar, but when reversed to the return it stayed at 0 bar. If each rad is switched on by its self it heats - roasting, but the return pipe on the rad is still cold. The plumber we have in at the moment has all the correct certs for this system, and hes scratching his head now. Its all just seems weird. Hes saying that there defo a blockage somewhere as when you ask for CH the boiler kicks in for 2.37 minutes, shuts off and then the flow pipe at the megaflo for the CH gets boiling hot (you can't touch it), goes through the motorised valve, (which is hot) carries on into the return pipe and then it goes cold just below the bypass valve (this has been checked and is ok). He tried cutting a part of the pipework out where it went cold this afternoon, but it was all clear, so had to fix it back up again. He has also spoken to megaflo and worcester and they have said circulation rather than an equipment problem. Hes wanting to replace all the pipework for the Central Heating, but we just replaced all the rad piping 6 weeks or so, i don't want to be doing this all over again. I am sure it must be something really silly, but no-one can pin point anything. My thoughts were a stronger solution to breakdown and rubbish in the system, that we could run for a fews day and try draining. Its really beginning to get my goat now, and of course the guys that installed it are now where to be found - Typical.
 
I assume this is a two pipe system? If the pump is ok and you really want to check if there is a blockage, disconnect the boiler flow and return and fix a hose to each to drain. Remove the nearest rad to the pump. close one valve on all other rads. Seal the DHW circuit. Seal the feed and vent pipes and pump from the rad flow and return separately and see what comes out the other end.

I still think you have not told us the whole story...
 
Hi Gas Engineer: - Whole Story so far: - Replaced an Old Electric Churchilll System with Worcester External Conensing Boiler & Megaflo System Fit. Megaflo is about 12Metres away from Boiler. Got a qualified plumber to fit. He removed old system and replaced with new, connecting to old pipework and rads. Old system worked perfect but the churchill boiler cost a fortune to run, and was noisy. They did not flush the system when new boiler went in. Qualified Electrician connecting electrics. Switched on - Circ Problem happened straight away. This was fitted in March 2010. He returned shook his head and said he'd be back, never heard from him since, and ca't contact him. He has had no money for labour, and i bought all the equipment. Another plumber in, tested all rad, work on there own, replaced grundfos pump, checked over boiler etc, all the usual stuff, balanced rads, replaced all copper pipework to rad with 22mm plastic - still nothing. New plumber in - Checked over everything with a fine toothcomb including connections of pipwork under floor - all ok. Spoke to Worcester and Megaflo - they said circ prob. Replaced Pressure Vessel (just in case) powerflushed each indiv rad, still nothing. Its a bamboozling one! I am brain fried with this one.
 
More of the story was posted a few weeks ago , they have had new pump . As I said last time and as Tamz has just said it should not be that hard to solve , you just need the right guy and a bit of logical thinking . When he cut the pipe did he blank one side off and then the other ?
THe bisection method works for this ( any mathematicians will know this one )
 
Last edited:
No he just cut the pipe about 1/4 metres worth off and looked through it and stuck something in it - nothing there. He did mention that in his usual practise that the grundfos pump should be as close to the boiler as possible, and with ours being the megaflo sysem fit its on the megaflo which is 12 metres away from the condensing boiler. Worcester say this is not the problem, what do you think? Should we disconnect the pump and motorised valves and put them beside the boiler under the floor. If so, we bought a system fit one for nothing.
 
Cutting a section out and looking through it will do nothing and only prove that the piece of pipe in your hand is clear !!
I dont think moving the pump will do anything !
You must be pulling your hair out !
 
I think we will try flushing again, as per the gas engineers reply, by removing a rad and doing it that way. We hire the machine ourselves from HSS so we have it until Monday. We will try this ourselves on Sunday as were working tomorrow and see how we get on.

Its really beginning to irrate me now, as its getting really col up here now. At least we have plenty Hot Water from the Megaflo though - it could be worse.

I will keep yous posted on how we get on on Sunday. Thanks again for your great and helful advise, it really is very much appreciated.
 
Powerflushed or not it worked before so there is no reason why it would not work now especially as it has been repiped.
Have they checked the pump valves are fully open?
Unfortunately it can sometimes be quite hard to diagnose something where you can't actually see/feel what is happening.
Here is an easy way to check if the problem lies with the megaflow set up or the system.
Get a couple of bits of speedfit and join directly to the flow and return from the boiler to the rad circuit and put the pump onto the bit speedfit. This will cut out anything to do with the cylinder and can be done quickly. If it works then the problem is with the way the megaflow has been connected or set up.
12m away from the boiler for the pump is not a problem even for a 15-50. What size pump was on the electric system and what size house is it?

Btw fyi. Having the certs doesn't mean you actually know what you are doing, just that you know the regs. Nowadays they seem to get given for good attendance as nobody fails anything anymore. Personally i don't see the problem in telling someone they are useless at the job if they are :eek:

I had to water the last bit down there as Redsaw or Puddle would have been on my case :D
 
I will get my partner to try this with the speedfit fittings on Sunday, and test it. The pumps we had on the oldshurchill system which did the CH & DHW (a huge kettle) were grundfos 15/50 x 2, with a major brass fitting inbetween them. We now have a Grundfos 15/60 (only 1) which came fitted on the megaflo, and have replaced it already to rule it out. Our house is 4 bedroom - 1 bathroom - 2 shower en-suite. Our KW for the rads was under 18,000, and our boiler is a worcester 18/25. I am loosing trust in plumbers in general within NE Scotland, i think we must get all the ones that fried braincells at school!! Its not easy getting a great competent plumber without them costing an arm and a leg.
 
Jodi Thomson said:
I am loosing trust in plumbers in general within NE Scotland, i think we must get all the ones that fried braincells at school!! Its not easy getting a great competent plumber without them costing an arm and a leg.
Click to expand...

You'll be near Peterheed then :D. Been there a few times.

I know loads of guys, me included who do work up that way but the money has to be good to consider it.
Usually you get what you pay for and if they pay the premium then i do it. I've got my eye on a quality zimmer and it aint cheap:D
 
Aboot 20 mins from Peterheed - nnae too far. I always like to use self employed guys with smaller companies rather than the larger companies we have in this general direction. Were self employed ourselves , so like to use the local boys, keeping the work going in the area, doing our bit for the community and all that!! If the options i've been given from yous tonight don't work, then i may just purchase that zimmer for you. White gold? !! He He
 
Jodi Thomson said:
The pumps we had on the oldshurchill system which did the CH & DHW (a huge kettle) were grundfos 15/50 x 2, with a major brass fitting inbetween them. We now have a Grundfos 15/60 (only 1) which came fitted on the megaflo, and have replaced it already to rule it out.
Click to expand...

You may just need a bigger or additional pump fitted if your house is well spread out
 
Can we fit an additional pump - another 15/60, as we have a spare handy. Our plumber said we could not fit another one on the system beside the original one as they would not pump in sequence or something along that line, is this incorrect?

We have a normal sized bungalow - livingroom at front with large rad, diningroom/kitchen backing onto livingroom, rads here are back to back, and the bedrooms come of the side of these. House length must be around 24 metres, and two rads upstairs (one is a towel rad and works as a bypass as no TRV fitted)
 
24m long house is quite a spread for a 15-60. It can be worked out to see what pump head is needed.
If you have another pump use it as big pumps cost big bucks.
You can put another pump on without causing any problems. Just wire it through the heating motorised valve so it only comes on with the heating. Stick it on the main run return.
 
Toddyplumb said:
... As I said last time and as Tamz has just said it should not be that hard to solve , you just need ... a bit of logical thinking ...
Click to expand...
Toddyplumb is right on all counts and you have it within you to think it through. I suspect you're in headless chicken mode and you need to get out of it. Sit down and think logically and make a plan. Draw the circuit and plan to pump-test each bit. I'm serious here. You have to ask the obvious questions and the answer will be staring you in the face. It's true though - if you want to hide something, put it in plain view. Humans have a habit of ignoring the obvious...

After all, you are only trying to find a blockage. And actually, it would be possible to use lengths of plastic barrier pipe running around the house to bypass different sections. This could be a useful fault-finding tool and a temporary solution while the offending pipe is replaced.

Look at my previous post about removing a rad and disconnecting the boiler. Draw out the circuit. Plan which pipe runs to test and where to block the other pipe runs to achieve that eg by closing valves or using push-fit stop-ends etc (Use SpeedFit pushfits; they demount cleanly). Plumb the power flush into a rad tail (one pipe only - the return to the powerflush need not be used - use it to pump only and not collect return water).

Keep a record of each section that appears ok. That also has a value for obvious reasons.

Ureka moment!* a guess?? when a new boiler isfitted there are often plastic bungs in the flow and return. I wonder if they were removed. One may have gone down the pipework too. It's very unlikely but not to be discounted.

Don't move the pump for the time being. I could go into positive and negative heads but you only get that problem when the water is flowing... Eeek!
 
Jodi Thomson said:
Hi Gas Engineer: - Whole Story so far: ...They did not flush the system when new boiler went in. ... Switched on - Circ Problem happened straight away.
Click to expand...
At least you haven't paid the chap.

Another plumber in ... balanced rads
Click to expand...
How was he able to do this if the return is cold?

You say that, if one rad is turned on at a time, it heats up OK but the return pipe is still cold. Have you checked that the lockshield valves are not closed?

You say that all 22mm cooper pipe has been replaced with plastic and the problem is still there. This would suggest that the problem is elsewhere.

If you disconnect both ends of the plastic pipe where it joins the rest of the system, close down all rad valves, connect a hose to one end of the plastic pipe and send some water down the hose, you will be able to check if the plastic pipe is clear. If it is, you will know the blockage is not in the plastic pipe and must be in the rest of the system, i.e before or after the plastic pipe.
 
Are the rads on drops from the loft or are they under the floor? And just wondering if the rads have been bled? Stupid questions but these things are over looked.
 
Have you got the flow and return the wrong way round on the boiler? just a thought
Also negative and positive pressures do not apply to a sealed system!
 
Generally in Scotland the houses all have solumns so most likely all under the floor.
 
You would need a strong back and some big rawlbolts to get a camray on a wall.
F&R is irrelevant.
 
tamz said:
The space under a suspended wooden floor.
A cellar is just a cellar but it is like a cellar for midgets :D
Click to expand...
Did a google for "solumn" and it asked if I meant "solemn"; so I said no. I then had to trawl though many search results where the word was a mis-spelling of "solemn"! But I eventually found a relevant one; the specification for a building in the Shetlands!
 
Well now you know;)
It probably is a Scottish word as everyone up here knows what it means. For those who don't,

Solumn: The space under a suspended wooden floor (crawlspace).
 
this is an interesting thread I suspect it is something really simple that has been over looked ,if they are getting hot water that proves the pump and boiler are working correctly, I would cut the flow in the middle and run a length of hep to the return , if it gets hot you know the problems on the return pipe, i did have a similar problem before years ago where all the rads had been replaced but for the life of me I could not get the rads permanently hot, I must have spent over a week back and fourth with the boiler manufacturers coming out every few days also, they had recommended putting an extra pump on blah blah blah ,All this turned out to be rubbish as the boiler was wired incorrectly internally ,
 
New posts
Status
Not open for further replies.

Reply to Central Heating Flow pipes burning hot - Return Pipes cold in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Similar plumbing topics

L
My son has an Apprentice interview- please help.
My son has an apprenticeship interview for to become a plumber and heating engineer. The have said there will be a multiple choice exam for this for suitability. The thing is my son panics during tests/exams. Is there any book I can buy him to practice the multiple choice test for the exam? What...
Replies
3
Views
405
Chuck
C
johndave
Outdoor stopcock doesn't fully close
Hi all I'm hoping someone can shine a light on this for me Since our stop tap on the pavement has now been filled with sand for whatever reason, we are relying on our property fitted stopcock (this is outside on our garage wall) Unfortunately turning this to the closed position only reduces...
Replies
3
Views
240
exedon2
exedon2
C
How to identify dripping tap.
Our kitchen mixer tap has started dripping. Like so much of the plumbing in our almost new build bungalow, it is lacking! The plumber didn't install any isolating cocks in the H&C feed to the tap so how can I identify which of the valves is passing? Shut the whole H&C water system down?
Replies
12
Views
318
Timmy D
T
P
Repeated Airlock in Bathroom
Hi, Can anyone advise as to why the cold water to my bathroom keeps airlocking? This originally happened about 12 months ago and has happened 3-4 times since. It’s an upstairs bathroom, fed from a tank in the attic. The tank is about 8 Meters away and feeds a bath, sink and toilet. The tank...
Replies
9
Views
316
Chuck
C
F
Mystery Mira Elite QT Leak
Hi All I have a leak coming from within my Mira Elite QT shower. It seems to be flowing from behind the switching Control. Any ideas what could be causing this leak. Already Changed the Pump Elbow as one of the clips had popped which was causing a second small leak, Any idea? Is it time to buy...
Replies
0
Views
229
Firefox
F
Creating content since 2001. Untold Media.

Newest Plumbing Threads

Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock