Unblocking / Flushing Microbore Central Heating System

[cheungy]

Hi all, having to post for advice having tried all i have found on the internet. Background to problem is as follows. The radiators that i have upstairs do not all heat up properly, there is a total of 4 rads, 1 heats up as normal, 1 is probably about 75%, 1 is luke warm and the last 1 is stone cold. Downstairs works absolutely fine and is on 15mm pipework, don't think that this should make a difference!

I have searched all over about balancing, bleeding etc and have tried all the suggestions that i have found. The TRV's all seem to be working ok as i have taken them off to check that the pins are not sticking. Although i was advised that i should change these but have not done this yet! Is it worth it?

All of this has lead me to belive that there is a some blockages in the system. Does anyone have any easy way to unblock this?

It maybe worth noting that i had a new combi boiler fitted last Aug 09, but it seemed ok at the time! Could they have fitted the pipework in the wrong way?

Thanks in advance

 

[JohnD]

tell us what happened when you balanced them, and if the cold ones heat up when you turn off the hot ones.

Who fitted the new boiler, and how did they clean the system?

 

[cheungy]

To be honest no much really happened when i tried the balancing. Tried all sorts of combinations from closing all apart from one and then introducing another. Have spent countless hours over the last few weeks trying this to no avail.

It was a local plumber that i know well that fitted the boiler. He had put some chemical cleaner into the old header tank a week before fitting to clean it. I been trying to get him back out to look at it but just so busy at the moment!

I forgot to say earlier that there is also valves on both pipes linking the heating between upstairs and downstairs. Have played around with this but they don't seem to make any difference. Also the lockshields on the two that are halfworking are nice and hot but not the rad. The TRV's on this are luke warm.

 

[JohnD]

tell us what happened when you balanced them, and if the cold ones heat up when you turn off the hot ones.

 

[ianfoskett]

if your radiators worked before he replaced boiler then there must be a blockage. did you say that its all 15mm pipes.

 

[cheungy]

tell us what happened when you balanced them, and if the cold ones heat up when you turn off the hot ones.

Sorry!

No they stayed the same as before and only got luke warm

 

[cheungy]

if your radiators worked before he replaced boiler then there must be a blockage. did you say that its all 15mm pipes.

15mm downstairs and 8mm microbore upstairs

 

[JohnD]

are they the same temperature all over?

is it a sealed system or does it have a feed and expansion tank in the loft?

can you find a by-pass?

you did turn off all the hot radiators, including the downstairs ones?

 

[cheungy]

are they the same temperature all over?

is it a sealed system or does it have a feed and expansion tank in the loft?

can you find a by-pass?

yea they the same temp all over.

No tank in loft since the new boiler.

Sorry i'm not sure what the by-pass is! Any idea where i could find this?

yep turned all off including downstairs.

 

[ianfoskett]

if you have microbore upstairs [small pipes] and 15mm downstairs, if not balanced properly the water will take the route of least resistance.
you should have a 10 degree drop from flow to return on the radiators with the 15mm pipes, which is only a very slight opening of the lockshield valve. the microbore valves can be opened fully as they each run on there own pipe. [from the main 22mm flow and return manifold].
the 10 degree drop across the rads all depends on the flow and return temp from boiler.

 

[cheungy]

if you have microbore upstairs [small pipes] and 15mm downstairs, if not balanced properly the water will take the route of least resistance.
you should have a 10 degree drop from flow to return on the radiators with the 15mm pipes, which is only a very slight opening of the lockshield valve. the microbore valves can be opened fully as they each run on there own pipe. [from the main 22mm flow and return manifold].

I'll try opening the valves fully upstairs tomorrow and see what happens. The rads downstairs only have one valve with two pipes going into to it (not sure what these are called). Will this make a difference?

 

[ianfoskett]

the rad with two pipes going into, if im right in thinking have only a white + and - knob on them, and if im not mistaken are microbore as well.
which would lead me to suspect that your problem is sludge related. if you were venting the radiators alot then thats a big sign that you have a build up of sludge. go and get fernox sludge remover or similar good brand name the stronger the better. you can buy them know that inject to your radiators. very easy to do just turn off both sides of the radiator undo the bleed nipple and take out, with a towel as a little water will come out. inject in fernox or similar sludge remover, replace bleed nipple, open valves and leave in for a couple of weeks. but make sure you you drain and refill system. [put fernox in a working radiator].

 

[Agile]

if you have microbore upstairs [small pipes] and 15mm downstairs, if not balanced properly the water will take the route of least resistance.
you should have a 10 degree drop from flow to return on the radiators with the 15mm pipes, which is only a very slight opening of the lockshield valve. the microbore valves can be opened fully as they each run on there own pipe. [from the main 22mm flow and return manifold].

Are you quite sure that this is correct or do you want to edit it?

 

[KingofPowerflushing]

Hello there. A fine series of questions you have asked there. Firstly, please let me tell you that I am biased when it comes to powerflushing and how it shouldbe done properly.

I own a busy heating and plumbing business that specialises in powerflushing. Over 500 done. Right now we;re VERY busy, but I need to unwind after battling snow on the way home and, like I said, you have a fine set of questions.

Downstairs works absolutely fine and is on 15mm pipework, don't think that this should make a difference!

Yes it DOEs make a difference. 8mm can be a bugger to flush if it's not done correctly. Glad to hear that you ahve 15mm d/stairs though - it should be realtively straightforward to sort out.

I have searched all over about balancing, bleeding etc and have tried all the suggestions that i have found. The TRV's all seem to be working ok as i have taken them off to check that the pins are not sticking. Although i was advised that i should change these but have not done this yet! Is it worth it?

No. Not yet.

there is no 'easy ' way' to unblock it.

It maybe worth noting that i had a new combi boiler fitted last Aug 09, but it seemed ok at the time! Could they have fitted the pipework in the wrong way?

If the installer did not powerflush it (which is NOT 'required' by all boiler manufacturers) then the BS for cleaning a system needs two flushes though with chemicals in the system for a time beforehand. However, in my experience, even that does not get rid of larger particles of rust than are not lifted up by the natural gravity exit of water from the system.

forgot to say earlier that there is also valves on both pipes linking the heating between upstairs and downstairs. Have played around with this but they don't seem to make any difference. Also the lockshields on the two that are halfworking are nice and hot but not the rad. The TRV's on this are luke warm.

No idea what you mean by valves on both pipes linking u/stairs and d/stairs. Got any pics you can post?

The two that are half working have the valves on the wrong way around. If the TRV;s are older one-way types that may make a difference to flow. If not, then there is staill a blockage in the pipework somewhere. FYI - it does not take amuch flow of hotwater through a copper pipe to get it and the valve it is attached to hot.

Point of order - to get a condensing boiler up to full speed you will probably need to increase the difference between flow and return quite a bit.

The rads downstairs only have one valve with two pipes going into to it (not sure what these are called). Will this make a difference?

They are double entry valves. Notoriously hard to powerflush well, although I have never seen any on 15mm pipework. Again, got any pics? I'd love to see them.

IMPORTANT

Be very, very, careful about putting in a sludge remove if you have microbore pipework. I have seen it do a lot a damage and sludge up pipes that were not previously blocked. Seriously. Be aware of the risks.

Well, that;s my two-penneth for what it's worth.

If you have any particular questions for your system do feel free to cal me on 07971-270064 or 01225-869036 (office). I'm in Wiltshire too.

Regards

Ian Pritchard

www.********.co.uk


P.S. the free advice bit applies to this post.

 

[ianfoskett]

yes you should have about a 20 degree drop on condensing boilers, but if you haven't put in larger rads you might not get enough heat out to heat the room.