Head Melter - Replacement boiler gone horribly wrong

[Sevilo]

Hi - I had a couple of the lads replace an oil fired boiler that was leaking. It was a 4 piper with two pumps on the central heating side for two zones and one pump on the hot water side. The new boiler - Grant 90/120 - has only a a single flow and return tap in. The lads linked all together and off they went. All good until the customer on hot water only on his time clock is getting heat in the radiators as well.
I had a look and realised - obviously - there is heat getting back through the return to the central heating circuit. I installed a non return valve on the return to the boiler so that when hot water alone is called there cant be any back flow to the rads. Then mysteriously I didnt get any heat to the rads. Hot water ok but something weird going on. Blasted for airlocks and no sign. Had to take the valve off again for the weekend. Yes it was on the right way.
Any ideas - customer loosing patience. Was thinking of an anti gravity valve instead........

 

[Best]

If it was working before on old boiler correctly & all pumped circuits, then something wrong with the pipework at boiler.
Check that the tee off for the heating returns is only a single tee off from main pipe.

On another point, although perhaps not an issue here, - make sure the flow for the rads is not rising, as that will mean gravitation will occur & upper rads will heat when boiler on. (motorised valves close when off, a pump stays open, obviously).

 

[Sevilo]

cheers, yes single tee off on return. No zone valves. Boiler is in the garage on the ground floor with rads upstairs, same floor and basement. Nearly feels like the the pumps dont have enough power to open the non return valve but that doesnt seem right. Thanks for the reply.

 

[tamz]

Sounds like it will take you a shift to pipe it right.
Non return valves won't work. Get the pipes altered and do it right.

 

[Best]

Wonder did they fit a bypass & it is linked in wrong to a circuit rather than f & R at boiler?

 

[Mike Jackson]

My money is on hot water return incorrectly piped breaking the three tee rule.

 

[happyflyer]

Hi - I had a couple of the lads replace an oil fired boiler that was leaking. It was a 4 piper with two pumps on the central heating side for two zones and one pump on the hot water side. The new boiler - Grant 90/120 - has only a a single flow and return tap in. The lads linked all together and off they went. All good until the customer on hot water only on his time clock is getting heat in the radiators as well.
I had a look and realised - obviously - there is heat getting back through the return to the central heating circuit. I installed a non return valve on the return to the boiler so that when hot water alone is called there cant be any back flow to the rads. Then mysteriously I didnt get any heat to the rads. Hot water ok but something weird going on. Blasted for airlocks and no sign. Had to take the valve off again for the weekend. Yes it was on the right way.
Any ideas - customer loosing patience. Was thinking of an anti gravity valve instead........

This is always going to be a problem area, you see the old boiler was what we say in the trade a LOW LOSS HEADER, this means that there should be no interference with any of the circuits coming into the boiler, one from the other, if you were to fit zone valves on each of the incoming circuits this may cure it but you need to make sure of the venting of the system is not compromised, you could also fit a low loss header above the boiler and drop the 2 F/Rs into it, the problem is you will need another pump to pump the water from the boiler into the header, perhaps the two lads who fitted should have sourced a boiler with 4 connections, good luck with it

 

[Sevilo]

Thanks everyone. Going to take some thought. Cheers

 

[Bunker]

perhaps the two lads who fitted should have sourced a boiler with 4 connections

One of the reasons I like Firebirds....;-)

 

[mitchellcook]

The veissmans have seperate flow and returns on some models as well.

 

[mitchellcook]

sorry, just realised this is the oil part of the forum, take no notice of me. I'll just walk back to the gas part with my head in shame lol.

 

[SimonG]

One of the reasons I like Firebirds....;-)

I knew somebody had to be fitting them.

 

[SimonG]

Hi - I had a couple of the lads replace an oil fired boiler that was leaking. It was a 4 piper with two pumps on the central heating side for two zones and one pump on the hot water side. The new boiler - Grant 90/120 - has only a a single flow and return tap in. The lads linked all together and off they went. All good until the customer on hot water only on his time clock is getting heat in the radiators as well.
I had a look and realised - obviously - there is heat getting back through the return to the central heating circuit. I installed a non return valve on the return to the boiler so that when hot water alone is called there cant be any back flow to the rads. Then mysteriously I didnt get any heat to the rads. Hot water ok but something weird going on. Blasted for airlocks and no sign. Had to take the valve off again for the weekend. Yes it was on the right way.
Any ideas - customer loosing patience. Was thinking of an anti gravity valve instead........

Next time you'll need a couple of lads that know what they are doing. Forget non return valves and anti gravity valves. Get yourself a couple of 2 ports and re-pipe it how it should have been done the first time round.

I take it the 'lads' and yourself are not oftec?