Little Clanger

OK, so as a temporary measure, I've decommissioned the TS and installed a Willis heater. Actually works really well for our limited needs and very simple - both pump and heater are controlled by the same time and thermostat switch. Reflecting on the relative failure of the TS, I realised that a lot of heat was being 'lost' by convection (and possibly expansion), with the TS on the ground floor and the 6.5 metre run of uninsulated flow and return pipework on the first floor. As HeatGeek point out, this heat isn't lost to the house as it is within the thermal envelope, but it still meant that it was a loss of stored heat energy. In the mornings, the one open radiator was hot even though it is on the ground floor, and the pipework was hot all day. Possibly explains why the thermometers on the TS and the flow pipe rarely showed more that 60 degrees, even with the overnight thermostat at 75. Now I'm wondering if I could have retained more heat in the TS if I had tried to break the convection by sweeping the flow pipe from the top of the TS downwards before looping back up to the existing pipework, but not sure if this would work.

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!