Reverse circulation

[nivek]

I have recently re located the cylinder cupboard (new cylinder) also adding a small radiator at the top of the stairs to the heating circuit , The pump had to be relocated as well. It was under the flooring boards in a bedroom, the pipe work has been extended by about 1 mtr and is still under flooring but accessible from a cupboard on the ground floor, this has been re plumbed using new 22 mm copper pipes, all the normal rules have been applied (vent and drain).

Now the big BUT the system appears to be working normally but cant quite put my finger on that facts it not. things I have noticed
1. In the morning after the whole system has been off all night (cold state) on firing up the the heating the boiler will ignite and will run for an estimated 3-4 mins before shutting down, room stat is still calling for heat, pump running, rads will very slowly start to warm, after about 6-8 mins the boiler will re fire and will run for about 6 mins before shutting down once again, rads still not up to heat, pump still running, *** my diagnosis of this is the boiler stat is shutting the boiler down until pump has removed the heat from the boiler hence the re fire but why?**

2. With C/H off and D/H on (programmer) the cylinder heats up nicely however it then seems to reverse flow through the return heating up the rads, obviously not as fast as a properly working C/H system ** Haven't really a diagnosis on this one at present**

3. This has happened only twice. With both C/H & D/H on call the cylinder (d/h) seems to take preference over C/H even though cylinder is up to temp. (this bit I find strange) one of the tests i carried out after altering where the rad return was plumbed in case it was a simple case of it being to close to the D/H return (which is first in line) this had no effect. with the D/H up to temp (programmer D/H waiting for call) thus leaving the C/H to take full discharge from the boiler around the system the rads will only heat up properly if the Programmer D/W is turned off. ** m diagnosis would be the operation of the 3 port motor valve , this seems to do what it should when it should.

The electrical system has also been rewired (Yplan)

A comment I made to a colleague was it seems like there is more resistance from the D/H return to the boiler than the other way around the return (reverse).

 

[GasmanxxxR1]

Is the cylinder still the last return before the boiler?, sounds like you have air in the system too

 

[nivek]

Not sure our terminology is matching here, I have always referred to to what I think you are referring to as the first return

the cylinder is the first return back to the boiler and is only an estimated 6-12 inches from the boiler itself. Obviously the flow come directly out of the divert-er valve.

 

[SimonG]

Air in system and youve stuffed up the pipework to allow reverse circulation.

 

[nivek]

thanks for the comments air in the system I can take on board but cant agree with the pipe stuff up, this was carefully worked out prior to any swap outs and had been thoroughly inspected for any mistakes. I anticipated a reply may come back like this so can now declare that a fully qualified (for 60 years) has also crawled over the system and cannot find any plumbing anomalies, the only reason he has not got the the bottom of this is down to cost.

 

[kris]

Its easy to vent air out when refilling but remember the cold feed is on the return so by filling up from the return it leaves a pocket of air near the motorized valve unless you manually open the zone valves to allow a full fill free of air, but depending on the pipe layout youl still get air, especially bleed the pump.

 

[nivek]

Yep thanks for any comment received, I feel a reverse fill hose bleed coming on. A job for Tuesday I think.

 

[nivek]

Just for the record I have thanked commenters,

 

[kris]

Over the years I've seen some crazy ways of removing air locks and mains water manual fills to clear the air locks using hoses etc and never died a winter yet lol.