What's this mystery gate valve?

[Mike4]

And since then, no vibration. The return pipe to the boiler is significantly cooler that the out pipe, which is what you'd expect if it's delivering all its lovely heat to the radiators. We'll have to see how it affects the boiler's firing cycle in the morning, or I might have to speed up the pump again - but so far so good.

Ahem, not necessarily. Think what the Δt would be if the flow was really low....

[bungeejumper]

And since then, no vibration. [b]The return pipe to the boiler is significantly cooler that the out pipe, which is what you'd expect if it's delivering all its lovely heat to the radiators.

Ahem, not necessarily. Think what the Δt would be if the flow was really low....

LOL, I didn't go that far with the slower pump speed. Just so that there was a very perceptible difference between the pipes - one was too hot to want to touch it for more than ten seconds or so, while the other would have been bearable for maybe a minute. But thanks for the caution anyway.

This morning the vibration is nearly gone, but not quite. I've checked the motorised valve, and it's moving correctly between W, MP and H, and reverting to hot water when the power is off, so that all looks okay. The pump is self-bleeding, but maybe I'll do another round of the radiator bleed valves, and also check that the TRVs aren't setting up any vibrations.

WRT Stewamax's reservations about using an automatic valve with a self-adjusting pump, maybe I should say that the Alpha 2 has four fixed speed settings as well as three self-adjusting positions? So the option is always there to do things the old-fashioned way. From here, it looks like I'm back to experimentation. But getting there. Thanks again!

BJ

[Mike4]

And since then, no vibration. [b]The return pipe to the boiler is significantly cooler that the out pipe, which is what you'd expect if it's delivering all its lovely heat to the radiators.

Ahem, not necessarily. Think what the Δt would be if the flow was really low....

LOL, I didn't go that far with the slower pump speed. Just so that there was a very perceptible difference between the pipes - one was too hot to want to touch it for more than ten seconds or so, while the other would have been bearable for maybe a minute. But thanks for the caution anyway.

It used to be generally considered the pump speed should be adjusted until the difference in temperature between flow and return pipes settles at 11c. In practice the ΔT will be all over the place depending on the conditions at the time, but having a value in mind to aim for is always helpful. (On modern steamers, this changes to 20c in order to raise the chances of a bit of condensing happening.)

And tangentially, the human hand makes a great thermometer. If you can bear to hang onto a pipe for several seconds but have to let go, you can be reasonably sure the temp is about 60 degrees C, give or take a degree or two.

This morning the vibration is nearly gone, but not quite. I've checked the motorised valve, and it's moving correctly between W, MP and H, and reverting to hot water when the power is off, so that all looks okay. The pump is self-bleeding, but maybe I'll do another round of the radiator bleed valves, and also check that the TRVs aren't setting up any vibrations.

The cause of vibrations as you describe is generally near impossible to trace in my experience. All you can do is adjust stuff until it goes away (hopefully). Is this a new phenomenon or has it always done it? (Translation: I've no idea.)

WRT Stewamax's reservations about using an automatic valve with a self-adjusting pump, maybe I should say that the Alpha 2 has four fixed speed settings as well as three self-adjusting positions? So the option is always there to do things the old-fashioned way. From here, it looks like I'm back to experimentation. But getting there. Thanks again!

Yer welcome. I know little to nothing about these over-complicated pumps, I need to do some reading up but my attention is currently being absorbed by the need to fix a leaking "Hi-VEE" warm air system water-to-air heat exchanger installed in 1968 and just started leaking. Their regular plumber's proposed solution is 'rip it all out and fit radiators', for an 83 year old lady with a heart condition living alone. Jeez!

But getting back on topic, given your comments about your system design, i.e. not all rads have TRVs and your have a three port valve (which is never closed whatever state it is in), that bypass valve could prolly be fully closed.

[88V8]

I put that down entirely to the water treatment. Well worth looking after your heating system properly, it takes very little effort, but pays back in spades over the years.

Yes, water treatment I think is crucial. And because it costs, there might be that temptation for installers to skimp or even omit, heaven forefend.
I would say that radiator bleeding is a good measure of system health. If you ever need to bleed any of the rads, there's something wrong. Air getting in or inadequate treatment.

As to vibration, the boiler fan if any... but the actual wet side, vibration as distinct from hums and bloops & swooshes, I think it has to be the pipes, but what causes the pipes to vibrate, ahh, well, hmmm.

V8

[bungeejumper]

Late update: Thanks Mike, I think I might have finally cracked it.

This morning the vibration is nearly gone, but not quite. I've checked the motorised valve, and it's moving correctly between W, MP and H, and reverting to hot water when the power is off, so that all looks okay. The pump is self-bleeding, but maybe I'll do another round of the radiator bleed valves, and also check that the TRVs aren't setting up any vibrations.

The cause of vibrations as you describe is generally near impossible to trace in my experience. All you can do is adjust stuff until it goes away (hopefully). Is this a new phenomenon or has it always done it? (Translation: I've no idea.)

Well, the process of adjusting stuff took me further and further away from the suspected scene of the crime. Pump OK, motorised valve OK, all rads bled, so what was left? Yes, check the TRVs and lockshields even on the rads that aren't in use. So I eventually ventured into the haunted west wing, where the heat is off and only the spiders normally go - and there it was, on the first rad out from the boiler, a sticky TRV that wasn't quite shutting. That bogger has been rattling the pipes for bloody months!

I'm feeling rather stupid, since you ask. I'll make a point of replacing the valve when I do my scheduled drain down in a couple of months. And will also check the pump impeller and a few other bits for crud while I'm at it, and will replace a lockshield valve on the landing that's been weeping a bit but doesn't respond to a spanner on the gland nut. These things are sent to try us.

BTW, I also closed the mystery gate valve on the bypass, or 90% anyway, and absolutely nothing bad happened. No explosions, no flooding, no shipwrecks and nobody drownded - in fact nothing to laugh at at all. (Stanley Holloway.) Suddenly, life is quieter. Thanks again!

BJ