Old system, new boiler and lots of air!

[Creeky]

Hi all,
i have a query about a central heating setup at work:
we have a boiler supplying 10 double radiators and a large water heater. Recently the boiler was replaced for a Worcester Bosch condensing floor stander. Since then we have been having a lot of problems with excessive air in the system, to a point where the air blocks flow and shuts down the boiler.
The system was put in a good few years ago, the old boiler was a conventional floor standing unit (with no problems with air.
I have drained the system several times yesterday to try and clean up as there seems to be a lot of rust in the system. All radiators now work but we still have excessive air. I have now added restorer.
i am unsure the setup is correct as I read some where that condensing boilers are fussy about pump location (but I can't remember where). Or is it the rust (ferric oxide) giving of the gas?
the system is sealed, there is a condensing boiler on The floor, a meter up on the flow is the pump. same level on the return is a magnaclean, then the expansion vessel. The pipe work then rises for another 2 meters before running round the walls for 10 meters. It the tees off with two zone valves, one for CH and one for the water heater. The radiators are 5 metres away in another room.
I have never had a sealed CH system, are the notorious for troublesome bleeding?

Sorry for the long post, I can't post photos.
thanks in advance.

 

[Howsie]

Welcome.

Get the plumber back that fitted the boiler. Could be a number of things that are causing this.

 

[AWheating]

sound like the system should have been powerflushed and there may not have been enough inhibitor addded? and its still corroding, hard to say, there maybe system issues and a aav by the pump may be required? but i agree get the installer back.

 

[WHPES]

Probably due to new arrangement on existing system. Old system was probably gravity HW. I'm assuming the system was powerflushed before the new boiler was added. If not, it should have been. Easiest fix is probably conversion to a sealed system. Not normally a problem unless your radiator valves are worn out.

 

[Creeky]

Hi all,
Thanks for your reply, The plumber is on his way back in, There was no power flush when the boiler was installed. and as far as I know, No inhibiter added. Also the system is sealed with Two AAV's fitted at high level, But these are not closing off properly. At the moment to get the system to run we have kept these open which means they are continuly spitting out water and air. I have also noticed the pressure rises to 2.5 bar even though we have not added more water to account for the air loss.

Over the weekend I have drained and flushed the system myself several times. The amount of rusty water was unbelievable. I have now added a restorer to the sytem to try and clean up.
Do you think that the rust is causing excessive air?

Thanks for your help.

 

[Howsie]

Sounds like a mess. Where did you find a plumber that didn't flush and didn't add inhibitor? The wild west?

 

[Creeky]

Sounds like it. Thanks for your help.

 

[Howsie]

Where are you based? Perhaps someone on here could give you a second opinion.

 

[Creeky]

Luton. Bedfordshire.

 

[Creeky]

Hi All,
We have had a second plumber come out yesterday afternoon, He thinks the air is a by product of draining/refilling, and it is just a case of bleeding the air out of the system. I left him to it last night, as he spent a good few hours bleeding the system until the early evening.
He did agree that the system should have been power flushed, but said that now there will be no need as I have drained and flushed through several times and the magna clean will catch the rest, does this sound right?
I will check it out when I go in this morning and hopefully its OK.

 

[Howsie]

Yep. Make sure you add inhibitor.

 

[WHPES]

If it still doesn't fix it, you need to make it into a sealed system.

 

[lame plumber]

If it still doesn't fix it, you need to make it into a sealed system.

op mentioned it was sealed in first post and talks about pressure in others, so one can assume it is sealed already, really needs a clean, inhibitor and time to settle first before investigating further

 

[Creeky]

Hello All,
i managed to have a good look at this at the weekend and managed to find the fault.
The hot water side of the circuit is used as a parts washer with a couple of tanks that the boiler is used to heat up. Also on these tanks are some process valves to close the circuit when temp is correct. These are powered by compressed air.
Now you where I am headed.
One of the valves had a leaky seal that meant compressed air was leaking past it and entering into the return of the heating circuit.

Problem is now fixed. Thanks a lot for you help though. These forums are a god send.

 

[gassafe]

Hello All,
i managed to have a good look at this at the weekend and managed to find the fault.
The hot water side of the circuit is used as a parts washer with a couple of tanks that the boiler is used to heat up. Also on these tanks are some process valves to close the circuit when temp is correct. These are powered by compressed air.
Now you where I am headed.
One of the valves had a leaky seal that meant compressed air was leaking past it and entering into the return of the heating circuit.

Problem is now fixed. Thanks a lot for you help though. These forums are a god send.

Can some one explain that to me? I have never seen a motor valve on a heating circuit powered by compressed air!!!

 

[Creeky]

Hello Gassafe.
My apologies, I should have elaborated on the first post, the system is at work in a factory and the 'Water Heating' side is used to heat up two tanks for a production line. The flow to these tanks are controlled by a process valve, similar to zone controls except they are operated by compressed air which close when up to temp.