Work this one out... Coz I can't...

[fubar1000]

Right here we go

A mate has just got a house, free standing heat only boiler in garage, pump in garage & 2x 2 ports in airing cupboard. Boiler very old, but system has had new rads, trv's, 2 ports & pump.

When I first went there I got the boiler running but it was pumping over into the heating header tank in a bad way!.!.!

System power flushed (not as dirty was we expected). After the power flush, the system was working pukka, all rads was getting hot, no pumping over.

I was popping in there every other day & turning the heating on for half a day or so & it was fine.

Yesterday I was there to service the boiler ready for rental Monday.

This is when it get's just wrong.

Service was fine, no pumping over, boiler firing up good.

I was checking the rads but none was hot, pipe work in airing cupboard cold, flow from boiler was cold but return was hot (pump on return). When I looked at the boiler the over heat stat had cut in & the boiler wouldn't go in to full fire.

Pulled over heat stat out, boiler fires up & within 5min it was pumping over (all rads & pipe work in airing cupboard was cold)

I've tried it in heating & hot water but both times it pumps over into the heating header tank.

Phone my mate that done the power flush & he was thinking 2ports, so I stripped them out, both working fine. He also said about turning the pump around which I done, still pumps over.

If I leave the over heat stat in the boiler cuts out before any pipe work in the airing cupboard gets hot. If I remove the over heat stat all pipe work + rads get hot, but it makes so much noise it sounds like it's gonna blow up. Then pumps over.

When the power flush was done we had very very good flow both in forward & reverse.

I just can not understand how it was all working fine for the first couple of days & now 3 days before someone is due to move in it's not.

Now I've turned the pump around it don't pump over via the heating vent pipe but boils up via the cold feed pipe, it starts to boil up before the pipe work in airing cupboard is hot or any rads are hot. But if I leave it running all upstairs rads get RED HOT, but down stairs are cold.

The system has a 15mm by-pass with no valves in the garage, pipe work from boiler to within a foot of the airing cupboard is 28mm, then 22mm in the airing cupboard.

I'm really stuck with this one & need some help please peeps. I've got to be missing something.

Thanks people hope everyone has a smashing Friday....

 

[galaxy_plumbing]

seems like a blockage to me. did you clean f+e tank? pump ok?

 

[dancinplumba]

Pump or blockage somewhere

 

[fubar1000]

Pump works fine was cleaned at time of power flush, aswel as the f&e tank.

I was thinking blockage but then I think power flush & how quick & easy the system drains down/ fills up.

 

[dancinplumba]

Try a new pump

 

[galaxy_plumbing]

can you check pump impeller? as DP suggested, you could try different pump

 

[Reg Man]

System controls configuration? Boiler thermostat? If the pump is on the return pipe, it is likely that the open vent and or cold feed are on the positive side of the pump. Should be Boiler/ flow pipe/ open vent/ cold feed/ pump/ bypass/ zone valves, in that order. Open vent and cold feed within 150mm of each other pump just after, therefore the open vent and cold feed are on the negative side of the pump. Check the boiler thermostat, as it sounds like the overheat keeps tripping.

 

[hammers4spanner]

Airjec?

 

[AlexGas]

Defo sounds like the flow issue... Dislodged debris would explain your situation or an air lock (pipe work layout)?!

 

[Alpha man]

Pump or cold feed issue.

 

[bewsh]

sounds like a blockage. get a magnet and try stick it to the copper pipework - if it sticks, you've got your blockage.

 

[REDSAW]

'h'h section blocked, or weak pump?

 

[stevetheplumber]

logic tells me the boiler stat has gone all works without the overheat so cant be a blockage but then it boils over

 

[fubar1000]

Massive thanks for the replys/help guys.

I'm there today, I'm thinking after it had a power flush it my have dislodge some crap in the pipe work that has now worked it's way around & is making the system play up.

There are a couple of TEE's blanked off in the airing cupboard way a build up can start, so I'm gonna start with cutting them out & renewing some pipe work.

Fingers crossed I can get it sorted.

Thanks peeps

 

[GasmanxxxR1]

Please let us know the outcome, interesting problem

 

[fubar1000]

Yeah will do, gonna renew the overheat stat & cut out the disused TEE's etc etc

 

[ambrosia]

I'm thinking after it had a power flush it my have dislodge some crap in the pipe work that has now worked it's way around & is making the system play up

that would be my guess,
nightmare feel for you

 

[fubar1000]

Well lads it's sorted & I am the happiest man on earth....

I changed the overheat stat, turned the pump around & bingo....

1 very happy plumber....

Thanks people, all your advise really helped....

Now time for a bloody good beer....

 

[galaxy_plumbing]

well done 😉 don get too many beers :d

 

[glenno1]

well done you