Warm downstairs cold upstairs, anyone any ideas?

[Nixster]

Hi I am a newby to the site so please bear with me. I have a 20 year old Stelrad gas system with 13 radiators. It has worked beautifully until recently when it decided to heat some rads and not others and no hot water. Here is a list of what has already been done within the last month

Powerflush
New grundfos pump (there is a myson aerjec) on the system if that helps.
Thermostatic valves to all rads
New ball valve to header tank
New automatic bleed valves to two downpipes in loft which feed kitchen and downstairs loo.

We now have hot water but we also have

Hot water coming out of the vent into the header tank, not boiling or steaming just warm so assume normal?
The upstairs rads need constant bleeding, you can hear them emptying as soon as the boiler comes on, even for hot water only. Does this mean that the boiler needs bleeding or is that a silly question?
When the rads are bled it is not just air in the rad it seems to bleed the whole house!! It seems that there is more air coming out than would occupy the radiator and it comes out at great speed!

I have turned all the rads off and then opened them one by one and can get heat to each one in turn.
I have turned the pump down from III to I, having looked at a forum suggestion.

I really do not know what else to do, does anyone have any ideas? In woman speak please!!!!!

I really cant afford a new boiler.

 

[75pete]

The water coming out in the vent is "over pumping" this will lead to air getting into the system thus in the rads.
Start be ensuring all your rad valves, inlet and outlet are full open.
If necessary top up the small tank with inhibiter and re-bleed the system.
bleed the whole house? Why do you say that?
Check for water leaks at all new parts fitted, could be sucking in air.
There is just a chance that the trv are shutting and the room stat [ if you have one ] are at odds. Thus rad trvs close but room stat still calling for heat so boiler still fires and system over pumps.

 

[Nixster]

Thanks, all rads are fully open, we were advised (unofficially) to extend the vent pipe below the water line in the tank so that it cannot suck air and this has made no difference. We added inhibitor yesterday. We did have a leak in a downstairs rad after the power flush but this was sorted out about 10 days ago.
I was told that the boiler stat wasnt working properly but was still safe. I think I had over turned it in desperation! I turned it back and the boiler is now clicking on and off. There is a thermostat on the hot water cylinder (based downstairs) which I turned right up in an attempt to get the hottest water but I remember this never seemed to make any difference to the hot water even when it was working properly. With the amount of air I have to bleed I cant believe I wouldnt have noticed a leak, and surely wouldnt it still leak when the system was switched off. Once bled the rads remain full of water whilst the system is off, it is only when on that the upstairs drains out somewhere.

There is a room stat located in the sitting room if that helps at all.

 

[Nixster]

When I said 'bleed the whole house' it seems like there is more air than just in that rad, I can hear a lot of gurgling in the pipes and each rad takes at least 2 mins to bleed as the water comes rushing back in.

 

[Nixster]

/another thing! I dont understand why the rads empty when the system comes on at 4.30am from cold for hot water only. I bleed them every night befor going to bed after the heating has switched off. It is programmed for 1 hour hot water at 4am and then the central heating after that. The rads are empty by the time the heating comes on!!

 

[bengasman]

don't keep bleeding the system, solve the problem
10 t0 1 that the system is sludged up

 

[Nixster]

I dont call £1700 peanuts and I didnt think Plumbob were monkeys..........

 

[Nixster]

Not sure how it can still be sludged up when it has been powerflushed?
If I knew how to solve the problem I wouldnt be asking for help would I? What do you suggest?

 

[Razor900]

Sounds like the airjec is blocked or the new pumps upside down

 

[Nixster]

Thanks for that, the pump arrow on the casing is pointing upwards and towards the honeywell control valves. Is there any way of checking the airjec without removing it?

 

[bengasman]

quite easy for an open vent system to be flushed and still contain sludge in vital areas.

lots of people out there portraying to be experts but effectively only know half of what it takes.

extending the vent pipe into the tank is a complete botch job.

one of the standard things i do with odd cases is testing if the flow actually goes where it is supposed to go by closing all rads and cylinder feed, and check if he feed and return get hot when you turn it on.

with open vent also important to check that pump is in right direction and right position in relation to the f&e.

then check if all rads work one by one.

check if heating and hot water work completely independently.

having said all that, i must admit i have always found open vent systems outdated and bothersome and problem prone.

why not convert to sealed? much better principle.

one thing is for sure, properly powerflushed or not, it does not take a lot of time for your system to corrode again the way it is going.

 

[Nixster]

Thanks for your advice, I realise the vent extension is a botch but we had run out of ideas. Just checked pump and arrow appears to be pointing toward the control valves. I will try the flow test tomorrow. I can get the rads to work one by one (mentioned at the beginning). I am almost certain that the hot water and heating work independently but again I will check. If all that fails and you recommend converting to sealed, do you mean that I need a new boiler?

 

[bengasman]

no new boiler.
exit tank, cap off, install expansion vessel and safety valve plus filling loop and pressure gauge. job done
this is provided your boiler is approved for it, don't know a lot that aren't
still need to get rid of basic problem, get strongest magnet you can find and trace all copper with it, as soon as magnet clicks, you found at least one deposit.
which reminds me, what chemical did they use for the powerflush? it should be something that desolves calcium as well as loosens up rust; fx2 easily the best.

 

[gash2024]

just out of interest is it possible to wire the pump the wrong way round?
Just an idea .
Something else, just as a check can you make sure the stop cocks either side of the pump are fully open as we had a pump replaced once and one stop cock was'nt open fully so it wasnt able to push out the air.
All things you could try

 

[Nixster]

Just read the last two posts this morning, thank you, will check the pump again, and try the magnet although part of the house is concrete floor and part demi cellar so may not get to all of it, eg through walls etc but worth a go. Certainly a closed system sounds ideal especially if I can use the existing boiler as long as I can find the problem, which leads me onto this mornings update............

I bled the system last night - same old, same old, and left everything off till I got up. First put on the hot water for about 15mins. Boiler thermostat working set to 4 not 6. 2 bedroom rads upstairs gurgled and emptied. Noticed that overflow had dripped water and melted the frost outside. There are 4 rads upstairs, 2 bedroom, 1 bathroom and 1 landing. Bedroom ones are at opposite ends of the house. Both bedroom ones had emptied. Bathroom and landing were still acceptably full. I turned the hot water off and bled the rads upstairs. - rad in bedroom, above boiler traditionally known for being the hottest one in the house bled air and rad was quite warm. Rad on landing was warm at the top. Bathroom was no change. Bedroom on opposite side of house bled and water was cold. So I suppose we have another avenue to explore? ie the warm water in the radiator having only had the water on? I feel sick!