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A Range Powermax cylinder might make a good heat exchanger, like a domestic water cylinder with 8 or 10 fire tubes up the middle. Not the later Potterton Powermax, those are different. Lots of them are being ripped out. It's not copper, but some harder alloy, a bronze maybe. Try a few...

I'd suggest; wire it generally as Fig 5.3 (Connection with two 2-port valves) in the VR65 installation instructions, with two exceptions. The 2 cylinder thermostats are wired just to a 2-port zone valve, adjacent to each cylinder. On a hot water demand, the thermostat contacts close, the...

You don't say!

I thought their main function was to maintain a minimum flow rate through the boiler. A by-pass may be useful on a system with TRVs fitted on most radiators, but the Building Regs (ISTR) require them to be ABVs, rather than fixed by-pass valves.

Double the flow at the same head on the pump curve, i.e., in theory. The actual flow, for any one pipework system, is the point of intersection of the pump curve and the system curve, so in reality you get neither the same head nor the same flow.

You don't seem to show where the upstairs and downstairs split. The flow and headlosses through the boiler would be calculated on the total flow rate. I won't be calculating this, so don't wait for my answer.

A 0-10V signal from a controller to a VR34 (if they still offer those) in the boiler, as for Opentherm boilers. It doesn't work with any other Ebus control devices, so the controller needs to do everything else. Only way I know.

Plastic pipe is permeable to oxygen, oxygen is absorbed from the atmosphere by the water in the system and then corrodes the radiators. Plastic pipe used in central heating systems must have a barrier layer that prevents the passage of oxygen. barrier tube isn't needed for H&C water supply...

Possibly poor mains flow rate, which may be why the property was plumbed with a supply from a loft tank. Get hold of a data logger and record the water pressures. It goes down during peak demand. If supplied from one service pipe, riser & meter, the pressure may drop to virtually nothing in...

3+ years old, but I fee compelled to note the the advice above is on the website of a company that sells heat banks/thermal stores.

That port shows the pressure downstream of the PRV which will/should be about 3 bar, or 2.8 bar with your meter. It would only fall below 2.8 bar with a draw-off if excessive restrictions in the pipes prevented enough water passing to maintain 2.8 bar (what you're checking for), or if the...

You could get oxygen generated by electrolysis if the fill water is acidic, and the steel and copper act as a galvanic corrosion cell. That's usually as a result of active flux residues and not flushing after installing. The hydrogen air locks the radiators or escapes from the vents. Do you...

Your '22mm pipe' is pre-1970 imperial 3/4" pipe. Go to a plumbers' merchants, buy an adaptor, compression or solder. Or call a plumber.

Pressure reducing valve set at 2.8 bar. Mains/street pressure is 5 bar, say. Turn on kitchen tap, pressure would typically fall to say 1.8 bar, except PRv opens up to keep the downstream pressure at 2.8 bar. Do you have a Megaflo?

The pump sizing is a separate issue which weather compensation isn't intended to deal with. Installing a constant-flow primary circuit with variable flow secondary circuits will raise the temperature of the return and reduce the boiler efficiency for most of the heating season and is probably...

A different approach here. What you seem to have is a thermostat controlled ON/OFF system which runs at a pre-set flow temperature, say 70 degC (I'm assuming a lot, you'll have to confirm this). The TRVs control the room temperatures, throttle the flow (as they should), boiler fault code...

Agreed; not a very effective gimmick either.

Or assuming that there must be a boiler in the circuit that needs flushing. There would almost certainly be a heat exchanger of some sort, a boiler being one sort. Flushing usually does work and is often the only practical means of removing solid particles or contaminants from pipework...

Simon, you really should resist the urge to use the eye-rolling emoticon thing when you're trying to put people down; it comes across as very childish. Maybe you could even try to resist the urge to put down people you know nothing about, even though you may find it gratifying that you have...

Quite; but, unlike gas installation work, there are no legal restriction on who can do power flushing, or a lot of other tasks related to heating. So why are such non-gas discussions in the Combustion Chamber? Questions are asked on this forum and answers are posted. Sometimes you learn...