Boiler Flow and Return Pipes

[richardhill84]

I have a Baxi 51/3 RS boiler (standard system with HW Cylinder)
I've been having what appearing to be circulation problem for some time as the rads do not get very hot (and take a long time to warm up) and the HW also takes a dogs age to warm up.
The boiler also kettles (sounds like it's boiling water inside)

On touching the boiler flow and return (22mm pipes) i noticed that the flow is very hot (obviously) but the return is tepid.

Would this suggest a blockage or is a cold/tepid return normal?

 

[corgiman]

check the pump

 

[richardhill84]

check the pump

I've changed it! And it's the right way round.

I used to think it was a circulation problem on the CH side of things but even when i have just the hot water on only, the HW cylinder takes ages to heat back up. The pipe feeding the HW cylinder gets very hot though.
The wife has just had a bath and the hot water has been on for over 2 hours but the tank seem barely tepid.

Does a boiler kettle if the flow rate/circulation is poor?

 

[ChrisR]

Yes it does. Blockage somewhere - pump valves, motorised valves, or just in the pipes - unless it's an air lock. Bled everything?

 

[richardhill84]

Yes it does. Blockage somewhere - pump valves, motorised valves, or just in the pipes - unless it's an air lock. Bled everything?

I've bleed all rads and the pump. Can a bleed anything else?

 

[gas4you]

Vent on h/w flow next to h/w cylinder if you have one

 

[corgiman]

Yes it does. Blockage somewhere - pump valves, motorised valves, or just in the pipes - unless it's an air lock. Bled everything?

I've bleed all rads and the pump. Can a bleed anything else?

make sure you have opened the pump valves

went to three jobs this week where they had not

 

[richardhill84]

Vent on h/w flow next to h/w cylinder if you have one

Don't think i have one.

 

[richardhill84]

Yes it does. Blockage somewhere - pump valves, motorised valves, or just in the pipes - unless it's an air lock. Bled everything?

I've bleed all rads and the pump. Can a bleed anything else?

make sure you have opened the pump valves

went to three jobs this week where they had not

Do you mean the valves that isolate the pump? If so, they are fully open.

 

[corgiman]

are you sure?

if so how are your sure

 

[richardhill84]

are you sure?

if so how are your sure

Well I closed them and them fully opened them.

To cut a long story short, the problem started about a year ago when the downstairs rads stopped working. I though the had pump failed so i replaced it but the problem remained.
On examining the pipe work near the pump and MV, i released that the bypass valve was open. The only way to get the rads to work downstairs was to close this bypass. The downstairs rads have never been right since the initial problem, even with the bypass closed. i.e. If the upstairs rads come on or the HW then downstairs goes cold.

 

[corgiman]

how are you sure they are fully open

pump valves spindles can undo and you think they are open, when they are not

it does happen

 

[richardhill84]

how are you sure they are fully open

pump valves spindles can undo and you think they are open, when they are not

it does happen

Ok... I'll check them again.
Just so i understand your thinking, do you mean the gate values with the red wheel handles?
I have one before the pump and two after (one HW side of the MV and one CH side of the MV)

 

[richardhill84]

Just fully closed the gate value feeding the pump and fully opened it again.
Burnt my p*****g arm in the process

 

[richardhill84]

Just a quick update and hopefully some useful information for others suffering from similar problems.

As i mentioned in the original post, my CH system has been suffering from circulation problems for the last 12 months or so (i.e. Cold rads downstairs that only heat up when the upstairs ones are turned of, HW cylinder very slow to heat up, House generally cold and very slow to warm up etc...) The boiler was also kettling.

I tried all the standard solutions to resolve the probs (Bleeding, Balancing, Taking all rads off banging and flushing, Tried SM4, Fernox Central Heating Restorer, Sentital X400 twice manual flushing the pipework with a hose etc... but all to no avail.)

As you can imagine, by this point i was sick of the problem and thought the only solution was an expensive powerflush. Before I got the specialists in, i thought i'd try (and dare) one last thing... Fernox DS40 !!!

That stuff is amazing. Within an hour or so of filling the system, all rads were red hot, the HW cyclinder heated up very quickly and the boiler stopped kettling. I'm one happy chappy. Just wish i had the bottle to use DS40 before. I read on these forums that its can eat your CH system if your unlucky.

Just need to flush the system, netralise it and add inhibitor at the weekend.

Hope the info helps others with the same prob.