No hot water after radiator change

[mcprinter]

Replaced an upstairs radiator yesterday.
Partially drained the system, modified the pipework, refilled and check for leaks. All good.

Run the HW 30 mins in the morning and again in evening.
Noticed not much HW yesterday evening and none this morning.

Conventional boiler (old Ideal Elan) with HW Tank in the loft
ST699 timer. Boiler springs to life if I override HW
Wiser controlling CH only. All working.
V4073A 3 port - changed the motor in 2007 due to no CH (My first post on here!)
There is very little resistance on the lever. Should there be?

I can't think how changing a radiator would have caused this. Maybe just coincidence?
Quite a lot of gunge in the F&E tank. I did clean out before refilling.
Pump a bit noisy after refill but has settled down again.

 

[cross thread]

Air Vent points on flow connection to cylinder been checked?

 

[mcprinter]

Air Vent points on flow connection to cylinder been checked?

Thanks
Not familiar with that
Where would that be and what am I checking for?

 

[DetlefSchmitz]

At the top of the hot pipe from boiler where it enters the cylinder (coil).

 

[mcprinter]

Found the vent I think.

My Cylinder is a Fortic with built in cold tank.
I can feel hot water going into the cylinder from the feed.
The return is cold.
The cylinder is cold to the touch. Not as cold as the top with cold water feed but not warm.
Have been running the HW for about 30 Mins. Water from taps still not warm.

 

[Johntheo5]

Conventional boiler (old Ideal Elan) with HW Tank in the loft
ST699 timer. Boiler springs to life if I override HW
Wiser controlling CH only. All working.
V4073A 3 port - changed the motor in 2007 due to no CH (My first post on here!)
There is very little resistance on the lever. Should there be?

If HW only selected I think there should be resistance on the lever as the valve is completely unpowered and should should he hard over via spring pressure with the HW only (B) port open.
There should be power directly from the HW ON contacts to the cylinder stat, if the stat is not satisfied the contacts close and provide 230V to the boiler, once the stat is satisfied the contacts open and shut down the boiler.
How did you override the the HW to start the boiler??
If both HW&CH are selected ON and the cylinder stat and the Roomstat are calling for heat then the valve should move to midposition so cylinder should also heat up. The return from the cylinder coil shold be fairly hot and quite hot when cylinder is getting up to temperature, it certainly shouldn't be "stone" cold

 

[mcprinter]

If HW only selected I think there should be resistance on the lever as the valve is completely unpowered and should should he hard over via spring pressure with the HW only (B) port open.
There should be power directly from the HW ON contacts to the cylinder stat, if the stat is not satisfied the contacts close and provide 230V to the boiler, once the stat is satisfied the contacts open and shut down the boiler.
How did you override the the HW to start the boiler??
If both HW&CH are selected ON and the cylinder stat and the Roomstat are calling for heat then the valve should move to midposition so cylinder should also heat up. The return from the cylinder coil shold be fairly hot and quite hot when cylinder is getting up to temperature, it certainly shouldn't be "stone" cold

By override HW I mean, I push a button on my programmer to switch on HW outside of programmed time.

Just to be clear, the flow from the HW tap is fine. It is just not warm.

I am guessing an air lock in the HW coil???

 

[Madrab]

You have an airlock in the primary pipework through the coil on the return to main system. You will have drained it down below that section of system pipework and when filling it back up it has become airlocked.

Have you removed the red cap off of the AAV, is it loose? if that hasn't shifted it then try cracking the nut loose (not off) the return pipe on the cylinder and tap the pipe away from the connection and see if that releases it. Have a container/towel under it.

 

[mcprinter]

You have an airlock in the primary pipework through the coil on the return to main system. You will have drained it down below that section of system pipework and when filling it back up it has become airlocked.

Have you removed the red cap off of the AAV, is it loose? if that hasn't shifted it then try cracking the nut loose (not off) the return pipe on the cylinder and tap the pipe away from the connection and see if that releases it. Have a container/towel under it.

Thanks Rob,

I have heard of AAV but never had to touch one.
Do I need to remove the red cap? What am I looking for?

Was having a bit of a search for coil air locks and the suggestions are never to undo the connection to the cylinder and find a compression joint elsewhere on the return pipe instead.
I have followed the return pipe through the ceiling and no compression joints that I can see !!

I do have have a magnaclean on the boiler return.
Anything I can do there? Boiler is upstairs if that makes any difference.

Would another drain and fill help?
I opened the drain valve downstairs but only opened the upstairs rad bleed valves to change an upstairs rad.

 

[Johntheo5]

There will be a compression joint nut where that hot top pipe joins the cylinder coil, slacken that back ~ a 1/4 turn or so and pull back on the pipe to break the joint, you should get air then water released there, then retighten, (HW forced on while doing so), maybe repeat on bottom coil outlet if the return doesn't get hot.

 

[mcprinter]

There will be a compression joint nut where that hot top pipe joins the cylinder coil, slacken that back ~ a 1/4 turn or so and pull back on the pipe to break the joint, you should get air then water released there, then retighten, (HW forced on while doing so), maybe repeat on bottom coil outlet if the return doesn't get hot.

I understand the suggestion but I am a bit nervous of doing that having seen on a plumbing forum it is best avoided.
Don't really want a loft full of water on a Sunday evening

There is an immersion in the cylinder so could use that temporarily for our hot water.

 

[DetlefSchmitz]

My system never refills itself automatically, so I connect the cold mains water to the cock at the bottom of the boiler and back fill it. Doesn't involve disconnecting anything, just running round opening air vents, until the header tank overflows (through the appropriate overflow pipe).

 

[mcprinter]

Had a read up about AAVs
The cap was loose and judging by the residue has vented before.

 

[Madrab]

The AAV is the pic you posted - Cyl Vent - the red cap is the bit on top, if that isn't loose it cant release any air it captures. Just needs to be checked that it's loose. They also have a tendency to get blocked or stuck and don't vent properly or at all.

Crack the pipe @ the cylinder for sure ... why were the suggestions saying not to crack that one? The trick is not to take it right off, just enough to tap it free and get the primary to vent. Invariably that's where the air locks the flow through the coil

 

[mcprinter]

The AAV is the pic you posted - Cyl Vent - the red cap is the bit on top, if that isn't loose it cant release any air it captures. Just needs to be checked that it's loose. They also have a tendency to get blocked or stuck and don't vent properly or at all.

Crack the pipe @ the cylinder for sure ... why were the suggestions saying not to crack that one? The trick is not to take it right off, just enough to tap it free and get the primary to vent. Invariably that's where the air locks the flow through the coil

Cheers Rob
Yes. Have the AAV sussed now. Have never had a problem before so not really come across them.
If working properly (and open) should it have prevented this airlock?

I think they were suggesting that the tank connection could be disturbed.
Had a good look and I think if I make sure only the pipe joint moves should be OK. Will give it a try.
Appreciate the advice

Edit....
HW on or off when venting?