Where's all that air coming from?

[Blijj]

Good day all. I seem to have more air in my system than I know what to do with. Here it is, as concise as possible:

Original system: Gas boiler on ground floor (two pipes and a mains lead). Hot water cylinder; rads; a-b valve/pump/Honeywell controls on first floor immediately above.

All the following alterations have been carried out by me.

Second stage (ok for years): Boiler removed; rayburn installed. Change to physical layout: boiler was in room directly below cylinder, etc. Rayburn positioned at opposite corner of house via 28mm copper; reducers into original 22mm pipework near cylinder, etc. Pump still pulling from hot side of boiler (rayburn). Old boiler pipes chopped and capped under floor bellow cyl, etc. Heating always set to permanent on therefore wall stat became on/off switch for pump.

Latest version: New pump fitted because of running noise from existing pump via pipes & floorboards. Position of new pump: directly before inlet to rayburn boiler. Old pump left in situ as a standby (rewired directly to a switched spur). Thermal switch fitted to outlet pipe (upper) of rayburn to automatically enable pump when boiler warms up. System drained/filled/additive/bled. Pump running noise throughout the house significantly reduced. Wall stat left full up. Heating left set to always on.

Problem:

Bubbles in pipes at pump switch on. Huge amounts of air remaining (appearing?) in system, mostly at on/off & off/on transitions of hot water switch. Loads of bubbles can be heard in h/w coil when it’s first selected. Bloop bloop bloop throughout the house; rads producing air; pump missing and catching the flow as the air goes round; auto vent by cylinder producing loads of air. Valve operates ok (verified by touching pipes and sound of water flow).

Turning the pump up to mid or max increases production of air (cavitation?) Using both pumps at max in an attempt to purge the system seems to produce more air than system volume! Header tank warm.

Thought 1: Move new pump to outlet of rayburn (hassle).

Thought 2: Reverse pump in situ to draw from rayburn boiler lower port, but this reverses the pressure gradient on the whole system. Will the a-b valve be happy with this?

Any takers? Thanks.

 

[twgas]

Adding the new pump in a new position is probably your problem.
Pump pressure will cause pumping over if the system is not right.

 

[John506]

Do you have one of those Gas Safe thingys that don't seem to matter to some people who carry out a DIY remove a boiler?

Just curious......

 

[bengasman]

I'd say the problem is trying to design/install a heating system without the required knowledge and experience. You can't just change boilers and move pumps and alter pipes and just expect thing to work fine.
On top of that, it appear you have an open vent system which imho is pants anyway.

 

[Blijj]

well guys, thanks for the positive responses. The cause of the problem was that the new situation for the pump had put the breather on tje high pressure side of the pump so I reversed the pump and I now have a system that's quieter than it's ever been in 15 years. Job Done.

 

[bengasman]

...so I reversed the pump and I now have a system that's quieter than it's ever been in 15 years. Job Done.

But now you have another problem. By reversing the flow, your over heat safety could be effectively on the incoming side which means it won't activate until part of the boiler is at about 104C or maybe even higher.
You now have a working time bomb.

 

[Blijj]

As this is a plumbing forum, I didn't bother to complicate the original post with the fact that I had included a 2 hour delay-off timer to the pump so that once it sees the temperature from the initial start up, the pump switching is debounced for 2 hours; long enough for the fire to reduce to a low level before the pump is disabled. Also, as part of the pump reversal excercise, I've added a 40 deg switch on what is now the outlet port, in parallel with the top switch.

 

[Blijj]

Do you have one of those Gas Safe thingys that don't seem to matter to some people who carry out a DIY remove a boiler?

It was an LPG installation that had been "dry" for years.