Wiring – Hot water twin impeller pump wiring to the boiler

I'm in the UK, we got a new recently due to the rebate recently offered on really old boilers.

If you get a decent boiler it provides savings because it is more efficient. They are called "condensing" combination boilers - the condensing action reclaims lost heat, I think.

We got a Vaillant, who also make the glow-worms. Never heard of Ferroli. And yes we get decent hot water pressure. I would check with a few plumbers/gas engineers, just get a few quotes, and also check the boiler specification for max flow rate.

Couple of tips if you do get a new boiler be sure to specify exactly where the pipes go (if you change location), get one of the remote controls (very handy, and allows you to put boiler in loft), and also specify exactly how you want the magnaclean device fitted (collects sludge from central heating). Ours is unfortunately very prominent - we need to move it.

Also, we went for a really big powerful boiler, so more than enough water but tbh probably a bit too big for our house: bigger may not necessarily always be better.

I'd only get vaillant, glowworm, or worcester-bosch, btw.

If the hot water is hooked up to your faucets, then hot water should eventually come out regardless of the re-circulation stuff. That is, unless the check valve is the wrong way or the pump isn't letting water flow. Then you would just get cold water.

EDIT I see from your comment that the system was previously working and no work has been done. The check valve must be installed in the correct direction. I don't know your entire system, so, it's difficult to know what's wrong. It seems like there would need to be a check valve between the hot and cold line at last faucet in the plumbing run. Then water from the cold side wouldn't be allowed to come out the hot side in case of a restriction in the hot side.

EDIT 2 Thanks for the drawing. I thought you had a recirc pump so that hot water was always instantly available at the outlets. I think the check valve would be better placed on the output of the pump, but I don't think that's why it stopped working. Although I don't know the likelihood, the problem could be a failed check valve. I don't see how else you could get cold water bypassing the heaters after previously working.