All pipework replaced - still little to no heating downstairs

[knightime]

Hi,

Yesterday we had all the pipework for our central heating replaced, as we were having an issue with the rads downstairs not working (after a recent rad replacement and power flush).

When the guys left yesterday all the rads were working - we had full heat in all rads - boiling hot! We had the central heating on till around 10.30pm before shutting the system off.

However this morning, when the central came on, only the hallway rad was on, and it was barely hot. The rads for the dining room and the lounge were stone cold.

I dialed back the lockshields for the rads upstairs, as they were left fully on, and am confident they're nicely balanced as there's good heat coming out of them. The flow pipes into the rads upstairs are roasting hot.

The flow to the rad in the hallway is hot, not roasting, but hot. I've checked the pins on the TRVs on the two rads in the other rooms and they're pushing down/popping up ok i.e. not stuck. The lockshields on the rads downstairs are also fully open.

I checked the main flow pipe from the boiler to the heating downstairs - the pipe is boiling hot. But the return is cool to touch - not stone cold but not warm either.

I'm trying to get hold of the plumber but he's not answering, so will try again later.

In the meantime does anyone have any suggestions as to why, with new pipework, and with the rads working fine yesterday, they've suddenly stopped?

Any advice would be greatly appreciated!

 

[Stu Davis]

Sounds like a circulation problem and i would have thought an air lock would be the problem.
I would check the pipework to the boiler and see of the flow is red hot and the return cool, if so definate circulation problem or blockage

 

[knightime]

*UPDATE* The central heating system has now failed - no heat in any if the rads...

 

[Tonycane]

This should make it easy for your next engineer to diagnose. Keep us posted

 

[knightime]

Hopefully Tony, and will definitely keep you posted!

 

[dave1]

I know its been said already but defo get the filter checked, I've normally found however that if that's blocked you get a bit of banging coming from the boiler. Good luck with it

 

[knightime]

Cheers Dave - I'll get the plumber to check the filter too. You know you normally get that central heating 'sound' when it's on (water flowing through pipes sound), well that isn't there anymore - will keep you all posted!

 

[knightime]

*UPDATE*

Ok, so a new plumber came in, replaced the pump and checked the filter on the return valve (which was clear of blockages).

Whilst it initially appeared that the new pump was working (and in fact it is working - it's firing away once it drops temperature, which it wasn't doing before), the rads upstairs and downstairs aren't working as they should be.

Let me clarify - the downstairs rads aren't heating up at all, even though the flow pipe from upstairs to downstairs is scalding hot! Non of the flow pipes to those rads have any heat in them. Upstairs, all the flow pipes to the rads are burning hot. However, whilst the batchroom radiator and the one in our bedroom are 'warmish' (thermostats and lockshields are fully open), the rads in both the boys rooms are cool to the touch i.e. little to no heat at all.

I've told my plumber that I'll be monitoring it over today and tomorrow, but to be honest, that fact that the downstairs rads are stone cold (they've all been bled and are full of water), clearly a new pump has only solved a part of the problem.

Incidentally, I checked the two 22mm copper pipes coming out of the boiler (flow/return) - one of them is scalding, the other is very hot. The return pipe from downstairs back to the boiler is cold.

If anyone has anything they'd like to add to this thread, something I can relay back to the plumber for him to investigate on his next visit, please let me know and I'll pass the message on to him.

Cheers!

 

[jonnyswamp]

Look for a manual bypass valve that maybe fully open
If there is one it should be near boiler/airing cupboard

 

[newcastle phill]

I still think there is a pjping issue. Is it or some parts an old 1 pipe converted into a 2 pipe system or setious air lock. How old is the system. Sorry havent looked through all posts as been busy ?

 

[Subby]

Rads need balancing if return pipe at boiler is very hot and some rads are cool

 

[knightime]

*UPDATE*

The plumber came round today and removed the Spirotrap MB3 that had been fitted to the return pipe as he wanted to elimintae it from the equation. Unfortunately it didn't work. He's ruled out any issues with the boiler and believes that there must be an issue with the pipework that was done.

His reasoning is that both the flow and return pipes connected to the boiler are both scalding hot - in particular the return, which is much hotter than the flow! He thinks there must be a piping 'loop' issue, and the flow is just returning without circulating. The only thing he can't get his head around (and neither can I), is why the central heating worked for one day.

He will be coming back on 8th April to begin pipework connection diagnosis. I'll be taking pictures and assisting him, and will continue to update this post.

Cheers!

 

[knightime]

**UPDATE**

So, 2 months now without central heating...

The plumber is coming around again tomorrow to take a look at the pipework, but I've noticed something weird that I want to know if anyone can help with...

So I took up the floorboards in the bathroom and identified the flow and return pipes the original plumbers cut into. These of course lead from the boiler to service the central heating.

This morning I turned the central heating on and left it to run for an hour. The flow and return pipes that are directly connected to the boiler were both scalding hot. I went upstairs and identified the flow pipe, which was also scalding hot. But the return pipe was cold!!! How is this possible? If, as the plumber suspects, there's some issue with the original pipework and the flow is leading straight back to the boiler via the return and isn't circulating properly, how can the return pipe directly attached to the boiler be hot, but the return pipe upstairs in the bathroom be cold???

When I spoke to him just now he seemed as baffled by this as I was. Can anyone shed any light as to what might be going on? Once again the boiler is a Potterton Main Combi 30 Eco. The plumber asked me to look in the manual for an automatic bypass section but I couldn't see anything in there about that. The boiler isn't making any strange noises when the central heating is on and the pump has already been changed.

Cheers!

 

[Tonycane]

I would be chopping the flow and return and make a loop, add one rad at the end of the loop just to verify circulation. I'm still thinking it's a pipework issue.

 

[knightime]

The plumber believes that the pipe with the green paint is the flow as the other pipe had a Spirotrap on (which he removed last visit).

Both pipes are scalding when the heating is on.

 

[Howsie]

Get someone else in, this long without heating is unacceptable.

 

[knightime]

Here's the main flow an return upstairs in the bathroom.

The lower pipe (furthest away from the sink) is the flow as it gets scalding hot within 3 minutes of the central heating being on. The pipe above it is the return, which remains cold during the test I mentioned in the previous post.

 

[knightime]

I have Howsie - this is the 2nd plumber I'm on!

 

[knightime]

Cheers Tony - i'll pass that on to the plumber tomorrow!

 

[Tonycane]

Can't see the pic, can you get to the pipe work directly above the boiler and show a pic?

 

[knightime]

Hiya Tony - the original plumbers couldn't access the pipework directly above the boiler as the bath is in the way - they had to cut the flow and return which came out from the boiler just in from of the sink, then used push connectors to join them to the new plastic pipework.

 

[newcastle phill]

Well if its a 2 pipe system i fail to see how it can be just returning without providing any heat to rads.
As I asked earlier...Is part an old 1 pipe system.
Sounds like the flow to upstairs is coming back into the flow somewhere else and not the return lol

 

[Tonycane]

I had an install with a similar problem, was 22mm speedfit on the first floor, the first 22mm speedfit tee off the flow blocked. Found the speedfit pipe insert had come loose and completely blocked the flow causing the same issues you have. I cut the flow and return and put a speed fit loop in connected to one rad to prove the boiler was doing good it's job and then passed it back to the installer. Just something to consider.

 

[knightime]

lol - you're probably right with the flow thing Tony! What I can't understand is why it worked for one day (the day the original plumbers left), but why the next day it failed!

I also don't understand how the flow and return pipes that I can see on the boiler are both hot, but in the bathroom only the flow is hot, while the return is cold!!!

It could have been that waaay back it was a 1 pipe system - the plumbers removed a lot of redundant pipework - but the 2 pipes above the boiler have been there since we moved in - 16 years now - so I'm assuming it's a 2 pipe system. All seems very strange to me...:ack2:

 

[knightime]

Thanks again for that Tony - I'll certainly pass on your experience to the plumber before he turns up tomorrow!

 

[Tonycane]

Flow and return being hot is the heat building up in the boiler and creeping up the return abit because it has nowhere to go.