hot water for central heating not circulating

[ChrisR]

...

 

[puntaprimapete]

Sorry if I haven't been clear. I have not replaced all the rads and pipework. I had 3 big old rads with microbore pipes downstairs. I replaced these only and changed the pipework to 15mm. The rest of the house was updated about 4 years ago I'm guessing because that is the age of the boiler.
As for not answering direct questions I have done my best but I am no expert. I called the engineer out because I have breakdown cover but boiler only. He said there is nothing wrong with the pump or the boiler and that there was a blockage in the system (not his problem).
I rigged up a hose and disconnected the 22mm return pipe where it joined to the new 15mm pipes and also at the boiler and then flushed it through. I did blow through a fair amount of black sludge and flakes but encountered no restriction to the flow. I then did the same to the flow pipe but in the opposite direction.
I have called a local company that does power flushing and was told it would cost £200. I don't want to spend this if it's not neccesary.
Yesterday I did improve the circulation by releasing some air but today it seems that all the rads although getting something are barely luke warm.
I am mystified as to where the hot water is going as the boiler keeeps firing up.
The boiler is a Baxi 105 HE I don't know what a gas council number is.

 

[Softus]

My advice to you is to draw out (for yourself) the route of the distribution pipes and the connection points that you've used, and identify which sections you've flushed out and which you haven't.

Don't forget that, in a two pipe system, water can circulate through the radiators and thereby bypass a section of blocked pipe.

So, if you're aiming to flush out the distribution pipework, then close all of the radiator valves.

However, if the upstairs and downstairs circuits are piped in parallel, which isn't universal but is very common, then you won't be able to isolate one particular circuit without lifting some flooring.

Regarding the boiler firing up, how long does it run for before shutting down? If it's a short duration then it's possible that the heated water is circulating through a deliberate bypass (which might even be an automatic one) and not heating the radiators.

Do you have an airing cupboard and a digital camera?

 

[puntaprimapete]

Thanks Softus. When I did the flushing I did have all the valves closed.
I do have a digital camera but no airing cupboard. What did you have in mind?
By the way some possibly inportant info I haven't given yet is that if I now shut off all the upstairs rads I can get most of the downstairs rads quite hot but still struggling with the furthest ones. and the same visa versa.
Cheers Pete

 

[puntaprimapete]

There is no bypass valve on my system automatic or otherwise.
The boiler fires up for about a minute each time and all the teperature lights come on so it is getting hot.

 

[Bamber gaspipe]

Thanks Softus. When I did the flushing I did have all the valves closed.
I do have a digital camera but no airing cupboard. What did you have in mind?
By the way some possibly inportant info I haven't given yet is that if I now shut off all the upstairs rads I can get most of the downstairs rads quite hot but still struggling with the furthest ones. and the same visa versa.
Cheers Pete

Bit late in the day to pop in that little beauty. May be a simple case of balancing your rads mate. Can take a considerable amount of time especially with a small boiler struggling to feed rads on a long run.
How many rads & what`s the Kilowatt rating of your boiler, how big is your house, how far away is the furthest radiator?

 

[puntaprimapete]

I have 13 rads the furthest one is about 15 metres away the boiler output is 31k. It is a 4 bed 3 reception 2 bathroom house over 3 floors.
Hope this helps
Cheers
Pete

 

[Softus]

Thanks Softus. When I did the flushing I did have all the valves closed.

OK. But since you have three floors, you might have three circuits, so please note my comment about that.

I do have a digital camera but no airing cupboard. What did you have in mind?

I was going to suggest a picture of the pipework in the airing cupboard, but just remembered that you have a closed system, so please forget that.

By the way some possibly inportant info I haven't given yet is that if I now shut off all the upstairs rads I can get most of the downstairs rads quite hot but still struggling with the furthest ones. and the same visa versa.

Is there any other important information that you're saving up?

Meanwhile, I don't know if anyone answered this question of yours from earlier:

Can the power of a pump fade as it gets older or is it simply a case of working or not working.

They can, and do, suffer from wear, and become less effective. Corrosion products accelerate the rate of wear.

I agree with Bamber's earlier statement of belief that it's the pump.

 

[puntaprimapete]

Thanks softus. There is only one rad on the top floor ( attic Bedroom) and this has been run off the 15mm pipework in one of the 2nd floor bedrooms so I don't think it condtitutes a third system.
Is there any way I can test the pump efficiancy?

 

[Bamber gaspipe]

Thanks softus. There is only one rad on the top floor ( attic Bedroom) and this has been run off the 15mm pipework in one of the 2nd floor bedrooms so I don't think it condtitutes a third system.
Is there any way I can test the pump efficiancy?

Fit a new one & see if it improves, for the size of your house I can`t see you being unable to afford it. Tightwad. Would you like me to come and fit one and see if it works, they are only about 50 quid.

Pity the poor plumber coming to fit this at your house with you armed with this info, he won`t have a leg to stand on will he?

 

[puntaprimapete]

Thanks Bamber. I know it's a big house but we are in Hartlepool where you can buy a house for what most people spend on thier cars. I'd love you to come and fit a new pump but aren't you in the states?

 

[ChrisNason]

This has all the symptons I had. The generally slow loss of radiators until I forced heat in to them one by one. The next morning I had nothing.

Mine was blocked pipes and the plumber cut out a section of the return where a few bends met the T from the Hot Water Cylinder and the T of the Bypass.

Now toasty warm and incredible quick heat up.

See the pictures here...
//www.diynot.com/forums/viewtopic.php?t=126303

 

[puntaprimapete]

Thanks Chris. How did your plumber locate where the bad pipe was?

 

[puntaprimapete]

Do you all wear flat caps up there & stink of soot

Not Me I'm a londoner married to a northern lass

 

[puntaprimapete]

I have the engineer coming out again Tuesday. I'll try to persuade him to try a new pump. If he won't I'll buy one myself and give it a try,
Thanks for the advise I'll let you know how it goes.
Pete