Little Clanger

That's encouraging, John, thanks. Presumably that's with a monobloc ASHP Again, thanks. Great forum

Again, thanks. I can see your point, although I assumed electric radiators in a bathroom wouldn't be safe. Also, I'm reluctant to remove the wet system because eventually I'd like to have an ASHP. Much as I enjoy amateur plumbing and wiring, I assume installing an ASHP would be a step too far, so I'd need to take up a government grant, and I was told that to qualify you have to have no other source of heating (although I couldn't find this condition in the government blurb). I'd miss the woodburner as it gives us some independence from power cuts. So really I'm in a holding situation until I take the plunge. Anyway, thanks again for your help and advice. John

In practice, Nick, the TS isn't really working. Nearly all our heat needs are met with the Everhot and the woodburner, so heating up 250l of water overnight isn't such a good idea, after all. Especially as it loses temperature quite quickly once the CH is running and boosting with the upper immersion heater gives a slow response. When it comes down to it, we seem to just need about an hour in the evenings for the bathroom radiator (600x600 Type 22), and about a couple of hours in the mornings, during off-peak times. As a result I'm leaning towards your idea of an in-line boiler - much simpler and more flexible, and from my calculations, actually a bit cheaper than heating the TS. I've seen on the UFH section that people use WIllis heaters as a heat source. Do you think that would work as an in-line heater in my vented system with such low demands? Or do they require a larger volume of water, e.g., a small cylinder? PS. The noisy return seems to have sorted itself. Possibly trapped air that finally cleared. Silent running now willis.pdf

Thanks for all your help, John. The Stanley had a huge boiler, so that could explain the difference. A higher vent would be difficult, but not impossible, so I'll give it a try. Thanks again John

In that photo, the flow is from right to left, so hits the 22mm vent first (although of course the pump is on the return, so drawing through the flow rather than pumping). I gleaned the power data from the labels on the pump. Not directly comparable as the Trident is derived from 220v, the Grundfos 240v. The Trident draws more current (0.25 amps compared with 0.17), which at 240v gives 60W compared with 40.

Should have been more specific. The old Grundfos is a UPS 15-50. The Trident is a WRS 25/60-130, listed as a replacement for the 15-50.

OK, John, so the height from the pump to the water level on the F&E tank is 3.7m. By 'the pump head', I assume you mean the suction pressure of the pump. The blurb for the pump (a Trident) only says that the maximum head is 6m (presumably maximum pressure when pumping on the flow). The pump is set on the lowest speed, 1, although actual rpm aren't given, and I've a feeling it runs a bit faster than the old Grundfos. It uses a bit more power. With the glass of water test, the level stayed the same, but when the pump first started up - before I'd got the glass under the vent - water was pumped out of the vent a couple of times. Previously, we had a big Stanley solid fuel range, burning wood. Thanks John

Brilliant idea, thanks. Presumably a falling level in the glass means it's drawing air in? I did try stuffing a cork in the vent - temporarily - but that made no difference. Do I even need a vent now I don't have a boiler? Presumably any expansion in volume as the water heats up would be accommodated by the F&E pipe, since even if a thermostat goes, they have a safety cut-out?

Well I did the swap on Friday and bizarrely the noise has lessened a bit. Can't understand why. Almost tolerable now, but still not right. Considering moving the pump to the flow, although the only long enough straight run of pipe for it is just above the outlet on the cylinder, where vibration-proofing support will be tricky.

Thanks, Nick, will swap and see.

...... although I still don't understand how restriction on the F&E pipe would cause the noise. It's not as if there is a continual flow once the system has filled, is it?

Pretty sure it's right way round (arrow is on other side of body). F&E tank is on left of picture. And I checked it's fully open. But as you said it offers more resistance than a gate valve, so could have been a mistake to fit it. I'll change it for a gate valve and see if that sorts things out.

Both the 15mm F&E pipe and the 22mm vent pipe are teed into the 22mm flow on the first floor. They have been like this for the last 40-odd years without the noise. The only difference is that where the 15mm pipe exits the tank, there used to be a gate valve. This had seized solid and so I decided to replace it while the system was drained down, and did so with a stopcock that I already had of the type in the photo. I assumed that any expansion in volume as the water heated up would be accommodated by the vent pipe since it teed off the same flow pipe. Since the noise has only occurred after making this change, I now suspect my assumption was wrong, but can't see how that would cause the noise. But then I'm not a plumber! I suppose I could swap the stopcock for a gate valve and see if that makes any difference, but I would like to know how. Again, thanks, Nick

For now, emphasis is on sorting out the noisy return!

OK, Nick, thanks for your input. We have a small, rural cottage with pretty good insulation and, being a retired joiner, have pretty efficient doors and windows. And we are used to low temperatures. Even when we had the Stanley range, we only ever turned on the upstairs radiators on the coldest of winter days, so the demands on the CH is extremely low. We have an Everhot in the kitchen and there is an open staircase from the kitchen to the first floor. It's quite surprising how much it helps the general temps. So a far from standard situation. I'll see how we get on this winter, as you suggested, and review things in the Spring. Thanks again for your input

Thank you both. I did consider an online boiler, but the thermal store gives us some of our heating on the overnight Economy 7 rate. An air source heat pump would be ideal (although our neighbours are worried about the noise), but I was just attempting a shoestring system that used up bits and pieces that I already had hanging around. In In fact I remember that I've got some Taco air separators in my shed. Perhaps one of those would help. Thanks again

PS. We have a woodburner that provides most of our space heating (the heat seems to spread through our little house surprisingly well). The radiators are for top-up/background

Thanks, Nick. That looks like a good idea. Is DIY installation allowed?

The weird thing is that each time the pump starts up, it's really quiet, only getting noisy after it's been running for a while. Does that suggest that when it shuts down, the system purges itself of air, but then slowly draws air in when it's running?

Thanks for your reply. The stove has gone, so the whole system is electric now, with the only heat source being the immersion heaters in the thermal store. The water from the thermal store isn't very hot - about 60 degrees

Thanks for your reply. I am assuming there is air somewhere. I've bled the radiators and the pump a number of times. One radiator is always open, the others have TRVs I've just bled the pump again and was surprised that when I took the vent plug out (with the pump turned off!), water gushed out under pressure. I know that's not surprising, but I'm pretty sure that when I bled the old Grundfoss, water didn't gush out.

Recently, I've had to change our heating system. Previously, we had an indirect hot water cylinder, on the ground floor, near the Stanley solid fuel range that heated the water in the cylinder. I've installed a new Economy 7 hot water cylinder upstairs for the DHW, and replaced the old, downstairs one with a 250l Economy 7 cylinder, to act as a thermal store. for the central heating circuit. As far as possible, I've left the existing pipework in place. This included the pump on the return, as fitted by the plumber about 40 years ago (he said something about putting it on the return to avoid 'over topping', which I assumed meant the risk of pumping the flow up into the F&E tank in the loft, via the swan neck expansion pipe). It all seems to work OK with the exception of noise building up on the return. When the pump first turns on, its so quiet that I have to check it's running. After about 15 minutes, the return pipe near the pump starts to get noisy, sounding like - not surprisingly - gushing water. After a while the noise gets annoyingly loud. I didn't experience this with the previous set up. I've attached a video to give some idea. So basically, all that is different with the new system is that now the water in the radiator circuit is being drawn from the thermal store, rather than from the Stanley - cylinder coil circuit. And that I've replaced the ancient Grundfoss pump with a new Trident one (I tried changing the pump back again, but it made no difference). I had a mad theory that drawing the water form the thermal store is too demanding, and that the system is actually drawing air in from the F&E swan neck, as that is easier. Once I shake off this fluey cold, I'll get up in the loft and check. But in the meantime, has anybody any idea what is happening? Incidentally, if my mad theory is true, can I extend the swan neck down below the water level of the the F&E tank, with a non-return valve? Thanks noisy return.mp4

I've been searching, unsuccessfully, for a timed switch that would change from one circuit to another. I have two immersion heaters in a thermal store, fed by a single 2.5mm cable. I only want to power one immersion at a time - the lower one overnight and the upper one at specific times during the day. Something like a timed version of one of those bath/basin selector switches. I've drawn a blank. Can anybody help? Thanks PS An ordinary Economy 7 timer wouldn't work because the 'boost' function isn't automatic

Thank you both for your replies, which will feed into my decision-making. My apologies for a delayed response - been a bit busy

I've just installed a new 160 litre vented Economy 7 hot water cylinder (twin immersions) for our domestic hot water. My plan has been to run it with the immersion thermostats as maximum (650 to 700) to store as much overnight energy as possible, and to avoid any Legionella risk. I assume this would mean that the temperature at the top of the tank could be up to 850 or more. Since we don't have mixer taps in the kitchen or bathroom, I would be concerned about scalding risk when the grandchildren are visiting. As a result, I have bought a thermostatic mixing valve to mount on the hot water outlet of the cylinder to deliver all our hot water at a safe temperature. It would be easiest to connect the cold inlet of the valve to the supply from the loft tank, although mains would be possible. Am I making the whole system too complicated? Would it be preferable to simply set my immersion heater thermostats lower?