I have tried everything to fix my Central Heating

[t_smithy]

Hi I hope someone can offer some advice to help me out with this problem. This is a DIY problem. I recently moved into a house 70's build.

I have an open vented central heating system.
Boiler: Worcester 9/14CBi
Controller: Potterton EP 2000
Pump: Grundfos 15/50
Valve: 3 way mid position ( HoneyWell V4073A1039)

The issue I have is that the downstairs radiators never get very hot. Only luke warm at best. Therefore the CH thermostat never cuts out the CH as the temp downstairs never gets above 15 degrees.

So I though it must be a balancing issue. If I turn the radiators off upstairs then the ones downstairs get nice and hot. So I balanced the system. I Started from upstairs and restricted the LSV's on all radiators. The downstairs radiators got a tiny bit hotter but not much. I spent many hours messing around with the balancing with no results.

So I though it must be sludge in the system. So I took off the downstairs radiators and flushed then out with a hose outside, there was a lot of sludge that came out. No change.
So i though it must be a pump issue. So I replaced the pump. No change.
So i thought it must be a 3 way Valve issue. So I drained down the system and replaced the valve. No change.
So i then added a cleaning chemical to the system for a week. Making sure I ran it through each radiator individually. No change.

When refilling the system I went through all the usual processes e.g. bleeding radiators, bleeding pump etc.

I then decided to attach a hose to the furthest radiator from the boiler downstairs and reverse flush the system using the mains pressure until the water came up into the F&E tank. After doing so I then drained the system, the water was pretty clean no sludge. No change.

So now I am stuck as where to go. Not sure I should waste my money on a power flush?
I just cant understand how the system can be so inefficient.

Any ideas.

Thanks

Tom

 

[Gray0689]

Do you always put heating and hot water on together

 

[Gray0689]

How many rads you got

 

[t_smithy]

I have 8 rads. 4 upstairs and 4 down.

Yes the HW and CH are always on together. I checked the mid position valve to make sure that when the HW has reached the correct temp the termostat changes the valve to the CH postition.

 

[Marc.White]

Ok so the radiators downstairs work fine when the upstairs are turned off?
If so then it sound like there is a restriction to either the flow or reurn to the downstairs rads. It might pay to check the pipework and make sure it is correctly sized and routed, also is there any valves in the pipework that may be restricting the flow. Check there pins on the trv's they are renowned for stick in the off position or nearly off which would restrict the flow. Check the pipe work by following the flow from the boiler to the rads and back again. Have they ever worked?

 

[fuzzy]

try heating on only

must be a flow fault in circulation pipework, can u see all the pipework?

 

[t_smithy]

I was thinking the same thing about the flow restriction. The boiler seems to be cutting in and out alot more than I would expect. But when heating the HW the boiler stay lit up for longer.

I am unable to see the pipework, as it runs under the floorboards or under concrete.

The system is quite old and the controller only allows the CH to be on if the HW is on also.
I have adjusted the TRV's previously to fully open to test each individual radiator one at a time. Each radiator gets very hot when all other rads are closed. So the TRV valves seem fine.

 

[t_smithy]

Oh forgot to say the system has been like this since I moved in. So I guess it has been like this for a while.

 

[street elbow]

Smithy

I know you have tried everything, but here is another thing or two.

some questions first,

A, Has the system been fitted with a bypass, that is a pipe with a gate valve, between the flow and return which will be after the pump but before the 3port valve .

B, is there a gate valve on the return pipe from the cylinder.

if there is turn them both off counting the number of turns.

Turn off all up stairs radiators,

turn off all downstairs rads execpt one.

turn on the heating the radiator should get hot,

when the first D/stairs rad is hot turn on the next rad and turn off the first,

when this one gets hot go on to the 3rd turning off the 2nd rad and so on
till all the D/stairs rads have been hot. But allow each rad to run for a good
5 mins before going on to the next one.

This should drive any air in the pipework into the rads

now turn on all downstairs rads, they should all get hot,

now all down stairs are working turn on all upstairs rads, but check D/s are still working after each U/s one is turned on.

Now turn on gate valve on hot water return pipe but only 1/2 way

are all the rads still hot?

now open gate valve on bypass pipe but only 1/4 open.

are all the rads still hot?

both gate valves should be less turns open than they were before.

some minor ballanceing may be required.

check for air in all rads and any other bleed points.

You should now be warm as toast🙂

I think you will find that the bypass and or the hot water cylinder were taking all the water from the pump, as the pump will take the water round the easiest path
and the downstairs rads are the most difficult.


Try the above and let us know how you get on

David

 

[Gray0689]

Smithy

I know you have tried everything, but here is another thing or two.

some questions first,

A, Has the system been fitted with a bypass, that is a pipe with a gate valve, between the flow and return which will be after the pump but before the 3port valve .

B, is there a gate valve on the return pipe from the cylinder.

if there is turn them both off counting the number of turns.

Turn off all up stairs radiators,

turn off all downstairs rads execpt one.

turn on the heating the radiator should get hot,

when the first D/stairs rad is hot turn on the next rad and turn off the first,

when this one gets hot go on to the 3rd turning off the 2nd rad and so on
till all the D/stairs rads have been hot. But allow each rad to run for a good
5 mins before going on to the next one.

This should drive any air in the pipework into the rads

now turn on all downstairs rads, they should all get hot,

now all down stairs are working turn on all upstairs rads, but check D/s are still working after each U/s one is turned on.

Now turn on gate valve on hot water return pipe but only 1/2 way

are all the rads still hot?

now open gate valve on bypass pipe but only 1/4 open.

are all the rads still hot?

both gate valves should be less turns open than they were before.

some minor ballanceing may be required.

check for air in all rads and any other bleed points.

You should now be warm as toast🙂

I think you will find that the bypass and or the hot water cylinder were taking all the water from the pump, as the pump will take the water round the easiest path
and the downstairs rads are the most difficult.


Try the above and let us know how you get on

David

Good advice I would think the coil is probably starving the rads if there a gate valve on coil throttle it down

 

[PLUMB-KING]

Your d/s rads could be drop fed from up stairs,can you see which way the flow leaves the boiler? IE: can you see it split to go up,to feed u/s rads & drop down to floor,to feed down d/s rads at the actual boiler?

Also you said the house is 70s build,you may have a one pipe system.?

Is the pump on the flow or return?

IMO a heating system works better with the pump on the return,not the flow.

 

[Gray0689]

Your d/s rads could be drop fed from up stairs,can you see which way the flow leaves the boiler? IE: can you see it split to go up,to feed u/s rads & drop down to floor,to feed down d/s rads at the actual boiler?

Also you said the house is 70s build,you may have a one pipe system.?

Is the pump on the flow or return?

IMO a heating system works better with the pump on the return,not the flow.

On a sealed system pump should be on flow and expansion on return

 

[PLUMB-KING]

On a sealed system pump should be on flow and expansion on return

You talking gas or oil fired boiler? I am an oil fired fitter never fitted gas.

I have worked with many plumbers over the years I have never been told this before? I was always told to fit pump on return,sealed system & open vented system.

 

[Gray0689]

You talking gas or oil fired boiler? I am an oil fired fitter never fitted gas.

I have worked with many plumbers over the years I have never been told this before? I was always told to fit pump on return,sealed system & open vented system.

I'm gassafe but mainly oil
The expansion should be on the cooler side ie return

 

[Dannypipe]

Agree expansion vessel should be on return, but I think we're discussing an open vented system here....can't remember the original post now!! Whoops.

 

[Spike295]

I have come across this problem in the past, it was on a combi system, 8 rads, 4 up & four down. Upstairs rads were cooking but could not get any warmth in the downstairs rads, even with all the upstairs rads closed, i checked all the trv's & tried a chemical for a couple of weeks but did not get anything moving. After getting under the downstairs floor & crawling around on my hands & knees i could feel warmth in the flow pipe till it got to a tee & no warmth past it, i drained the system, cut the tee out & it was blocked solid with muck, i re-piped as far as i could using hep20 & hey presto, problem solved. I would think your system is probably blocked the same somewhere on the ground floor, most probably on the flow pipe, possibly return but i would be more inclined to say the flow, between from where it drops from upstairs to the first tee on the lower circuit, this would explain the reason all rads are cold instead of just 1 or 2.

 

[t_smithy]

Hey thanks for everyones help so far.
David here is the answer to your questions;


A, Has the system been fitted with a bypass, that is a pipe with a gate valve, between the flow and return which will be after the pump but before the 3port valve .

As far as I am aware there is no bypass. I can see a gate valve after the pump and before the 3 way valve. But I think this is just used to isolate the pump. Please see attatched picture for the layout of the pipe work.

B, is there a gate valve on the return pipe from the cylinder

There is no gate valve on the return from the cylinder.

 

[t_smithy]

I have checked and the d/s rads are drop fed from up stairs, When the flow leaves the boiler it goes straight upstairs. The pump is on the flow.
I then followed the flow after the pump under the floor boards. It splits and one route goes to the rads upstairs and the other drops downstairs.

 

[t_smithy]

Also this is definitely a feed and return system rather than a single pipe loop.

 

[Toddyplumb]

That pump looks like its on spped 2 , try 3. Did u fit a new 15/50 or a 15/60

 

[t_smithy]

Yeah I have tried speed 3 but there is no improvement, just more noise.
I replaced the pump with a 15/50

 

[Toddyplumb]

Any pump over at the header when its on ?

 

[t_smithy]

No there is no overflow into the header tank when the pump is on.

 

[Toddyplumb]

It does sound like a partial restriction on the downstairs then
Just as a note to anyone looking at the photo , its not good to take a 15mm pipe straight into a cylinder coil on a reducer . You can get a section of air trapped along the top of the coil

 

[t_smithy]

I can follow the pipe work downstairs to the gound floor, and the flow pipe is hot all the way down. But after that it seems to be under the concrete so cant follow it any longer.
I did use a chemical to clean out the system for a week, but it was only a brand from foucs DIY (Kilrock central heating Cleanser k-03) Maybe I should try something much stronger, maybe Fernox F3?

 

[Toddyplumb]

Maybe try a Sentinal X400 use it with the upstairs rads isolated . Failing that a power flush, worst case is there is something wrong under that concrete. Its always difficult without being there. Is there no one local who can give it a look to make sure you havnt missed something ?

Or Fernox

 

[street elbow]

Smithy,

as you do not have the gate valves I asked about,

I would surgest that you follow the sequence I put in my earlier post.
but make sure that only the heating is on and not the hot water.

After reading your post again, you say that the D/S rads do get hot with the U/S switched off. This does make me think you have got an air lock in the pipe work.

I would run each D/S rad for at least an hour and also put the pump on to speed three (ignor the noise) after you have run each D/S rad put the 3port valve into the mid position to allow any air to get to the bleed valve and bleed it off.

The way the system has been plumbed in your airing cupboard does not allow any air in the heating to escape to a bleed valve with out the hot water being on. which is not helping your situation.

David


Hopefully this will move the air lock to a bleed valve somewhere on the system

 

[street elbow]

Smithy,

just thought, make sure the pump is off when you open the bleed screw in the airing cupboard.

David

 

[t_smithy]

Smithy,

just thought, make sure the pump is off when you open the bleed screw in the airing cupboard.

David

Thanks David,

I will try what you have suggested.
Is it true if you bleed the pump when it is running, it can it draw air into the system?

 

[Toddyplumb]

Yes it can

 

[Blackcatgas]

What size is the pipework? does it go from 22mm under the floor into 15mm wher you cant see it, ie have you got 15mm pipe trying to run 8 rads, if you turn off alll the upstairs rads do the downstairs rads get hot?.

 

[t_smithy]

What size is the pipework? does it go from 22mm under the floor into 15mm wher you cant see it, ie have you got 15mm pipe trying to run 8 rads, if you turn off alll the upstairs rads do the downstairs rads get hot?.

the pipe work is 22mm until it branches of to a rad. so the flow pipe from the mid position valve all the way downstairs is 22mm. when i turn off upstairs rads the down stairs do get hot.

 

[t_smithy]

It does sound like a partial restriction on the downstairs then
Just as a note to anyone looking at the photo , its not good to take a 15mm pipe straight into a cylinder coil on a reducer . You can get a section of air trapped along the top of the coil

Hi Toddyplumb, you mentioned its not good to take a 15mm pipe straight into a cylinder coil on a reducer because you get air trapped along the top of the coil. I did wonder why the water tank was so noisey, you can hear it bubbling and gurgling when heating the HW. Is there any way to get rid of the air trapped at the top of the coil?

 

[PLUMB-KING]

Hi Toddyplumb, you mentioned its not good to take a 15mm pipe straight into a cylinder coil on a reducer because you get air trapped along the top of the coil. I did wonder why the water tank was so noisey, you can hear it bubbling and gurgling when heating the HW. Is there any way to get rid of the air trapped at the top of the coil?

The best way for the flow to be piped to the cylinder coil is to take the pipe up above the tapping then drop down into it then a auto vent/or manual fitted at the upright of the feed.This is how old gravity hot water system were piped & worked well.

As for your d/s rads being drop fed as I thought in my last post,the u/s rads are getting priority heat,you need to balance the heat.IMO open all flow valves to u/s rads,& have all the return valves on u/s rads to just a crack ( hardly open but enough for the water to return ) this will slow down the heat returning to the boiler at a much slower rate,letting the heat flow on to other rads, IE d/s rads,make sure all d/s rad valves are fully open flow & return. Let this run for a good 30mins to an hour,then vent/bleed the system,always turn the pump off when venting/bleeding the system. Being you have a drop fed system IMO I would of fitted a 15/60 not a 15/50.

Small pic of the way I have been taught to pipe cylinder primaries.

 

[Toddyplumb]

The bubbling ang gurgling may not be air , are you sure that motorised valve is shutting off the HW when at temp ?
However to remove air from your coil top you would have to split the joint. It should run into the cylinder in at least 22mm to keep air entrained , on gravities we sometimes fitted a 28mm T at the connection to the cylinder flow to make sure coill was fully vented, ohh the good old days

 

[t_smithy]

The valve is definately shutting off the HW. I took the case off the valve and watched it move to the CH only position once the HW thermostat had reached the right temp.

At some point I will look to improve the water tank plumbing and add an auto vent fitted at the upright of the feed.

When I purchased a new pump I was unsure if I should purchase a 15/60. I think once I have run through the process of trying to get all the air out of the system, if there is no improvement I may well go a buy an 15/60.