Pump Hum and poor Power Flush

[ChrisNason]

Earlier in the year I posted the end of a seven year saga to improve the heat in a vertical radiator. It turned out that it had been installed upside down with the diverter sitting in the top rail rather than the bottom beside the input flow. Once turned over it was lovely and warm.

But a couple of weeks later I got a noticeable hum on the pump. So I installed a new UPS2 and got back to an acceptable noise. In hindsight I probably should have flushed the radiator out. Maybe the lack of flow to the top stopped inhibitor getting at all the internals and now I'm suffering the consequences.

At the end of November the noise increased. Turning the speed up to 3 increased the noise but running at speed 1 caused the boiler to 'Kettle'. So I bit the bullet and paid for a Power Flush.

About 2 hours after the plumber left the boiler noise was worse than it's ever been. So I called out Vaillant. They turned up the next day but pronounced the boiler perfect but diagnosed a lack of flow. The first picture below is the state of my new pump. The plumber had connected his kit to the flow and return of the DHW and left the pump in place. His company is not responding to my emails.

So the system is back with the old pump and I thought running acceptably. But Christmas Eve the pump noise returned with a vengeance. I've now set the pump back to speed 1 and reduced the Bypass Valve pressure. The boiler is noise free and running better than ever. The whole system performs its functions well with all radiators coping with the cold and the DHW recovering within 40 minutes. It's just this 'hum' all the time.

The hum is there on DHW, Heating or both. Curiously the noise reduces when both valves close and the flow is just through the bypass. Also I've tried all radiators in turn and the bathroom by itself also reduces the noise. It's the first on the circuit. But the DHW is shorter still and on brand new pipes (only the DHW coil is original).

The second picture is the contents from the pump (with cotton bud for sizing)

. Anybody recognise the origin?

 

[ironsidebod]

That's magnetite e.g your system is full of hardened crap. The poor flow is caused by this stuff. If you paid for a power flush you were robbed, those sorts of bits would come out even with the worst use of a power flush machine.

Are you sure he didn't just dump some chemical in and then empty and refill?

 

[Phill Peck]

That's magnetite e.g your system is full of hardened crap. The poor flow is caused by this stuff. If you paid for a power flush you were robbed, those sorts of bits would come out even with the worst use of a power flush machine.

Are you sure he didn't just dump some chemical in and then empty and refill?

By the sounds of things this pump was left in place.
Once jammed in the impeller those bits won’t cone out with a powerflush.

Can’t understand why you’d powerflush with that pump in place though.

After the powerflush did he not test the system?

I’ve done powerflushes before where the system works fine with the powerflusher on but not well with existing pump.

You’d expect him to have noticed and checked this.

 

[Terry lambert]

As said should always bypass or take out a pump when flushing

 

[ChrisNason]

The shape of the bits is difficult to understand. If you look at the pump picture at about 2 O'clock you can see the bits have a rounded profile. The shape is quite small and no relation to 22mm pipes. Have they come out of the boiler? Plus they are magnetic and crumble if you really compress them.

 

[Phill Peck]

The shape of the bits is difficult to understand. If you look at the pump picture at about 2 O'clock you can see the bits have a rounded profile. The shape is quite small and no relation to 22mm pipes. Have they come out of the boiler? Plus they are magnetic and crumble if you really compress them.

Inside the heat exchanger

They were probably released during the powerflush

 

[ChrisNason]

So perhaps the Power Flush did do some good?

 

[mcmoby69]

So perhaps the Power Flush did do some good?

Yep, it shifted **** from a to b.

 

[ChrisNason]

So, getting back to the hum. What causes it? The system is clear of air and the boiler is firing properly without any 'kettle' noises. All the radiators get warm together so are well balanced. The two radiators in the lounge and dining room are at the end of their runs and fully open on their lockshields. The Lounge is the last radiator on the front of house pipe runs and the dining room is the last radiator on the back of the house runs. All other radiators are close to 1.5 turns open on the lockshields.

Also, this noises reduces when both the DHW and Heating valves close. The flow is then just going through the ABV and boiler so I assume at maximum resistance.

In my head if blockage was the cause of the hum I would expect it to get worse when both valves close?

 

[ChrisNason]

Answered my own question (Photo below)

The older pump I fitted back is now also showing debris. So now back with the new (and cleaned) UPS2 and mostly silent. It's on speed 1 constant with plenty of air bubbles working their way through. But the boiler has a bit of a whine I've not heard before. I'm reluctant to change the speed with my previous problems.

So more debris is coming out of the boiler and I'm not sure what to do. The flow side goes up and across to meet the Vent then the Supply (from the loft tank) then down to the pump (pumping down to the Honeywell Valves). On the return side is a Fernox TF1 which had very little debris in it. Just a little powder on the first notch of the magnet.

 

[ChrisNason]

Pump today seems very quiet but I must be due more debris working through. As I've had a poor power flush perhaps I should do my own next time. The one I had at the end of November was clearly connected to the wrong place and I saw no evidence of magnets in the unit. Just a big pump and a container of water with valves on.

Can you hire a machine with magnets to trap the debris once it's out?

 

[Phill Peck]

Magnets are not needed.

 

[cross thread]

when we power flush a system we have a twin in line magna clean to collect magnetic debris on the feed to/from the powerflush machine

 

[Terry lambert]

Magnets speed up the process for the person power flushing but they are not a requirement, also good for showing the client what you have removed

 

[ChrisNason]

So, if you can do it without magnets, how do you catch those bits coming out the boiler. I'm assuming the best place to connect is the pump valves and what I don't want is to push stuff into the other side of the boiler.

Also, I've found a piece of pipe beyond the CH Valve that a magnet can stick to. It seems to last until the first divide (bathroom T) so I would want to cut this bit out. Is it good practice to push a small brush into the remaining pipe or would this cause larger lumps to get into the boiler?