Raging hot pump, warm rads downstairs, cold rads upstairs

[Space cat]

Oops! You were too quick for my edit.

 

[bobface]

np!

No, it's vertical, pumping downwards to a 3 way DH/CHW valve, which then runs horizontal about a foot and splits vertical to upstairs rads and vertical to downstairs system I guess (can't trace those pipes through the floors!)

The pump makes very little noise (no bangs or knocks), it does feel like water is moving through but its really hard to tell just by feeling pipes. Taking the pump head off there was water in it (a pumps worth I'd say), it does pump all roudn the downstairs rads. Do you think there could be air in the system upstairs in the pipes rather than rads say preventing it pumping water through the air?

What's odd is that if I open the upstairs rads bleed valves water does come out, so it's under pressure. The pump is pumping round the downstairs sytems.

Thanks for the advice and I am clearly a tinkerboy. Combustion chamber lid stays closed mind, dont worry about that!

 

[JohnD]

have you closed all the hot ones yet?

 

[Space cat]

No, it's vertical, pumping downwards to a 3 way DH/CHW valve

If I read that correctly, the pipe from the boiler must be coming up from the ground floor then it turns down through the pump. You have a loop of air trapped in there. The pump might have static water in it but, when it starts up, it pushes that water down until the trapped air comes in - at which point it can pump no more.

If I'm right, that leaves you with a question: How can you get the air out.

 

[JohnD]

cat, he said earlier that it was circulating through the downstairs rads but not the upstairs ones.

Still waiting for him to turn all the hot ones off.

 

[bobface]

I finally got back and turned all the rads off bar the upstairs and shebang, they got hot. Vented a little air that gurgled through. Have started to slowly open a few more and they're staying hot. Will open all again tomorrow and see if th problem is cured or if it's still there

Thanks for the advice, at least its warm tonight!

 

[JohnD]

when balancing, close the lockshield fully, then, when cold, open it half a turn and wait five minutes. Don't move it more than a quarter turn at a time after that either way, just give it a while and see if the flow pipe is "too hot to hold" and the return is "too hot to hold for long"

any lockshield that is wide open can take all the flow, if it's nearer the pump than the others.

p.s. if you have TRVs downstairs they might not be working.

 

[bobface]

Thanks all, it seems to be working well now. Will check balancing.

This might be a stupid question, but re the three way valve, which is a honeywell listed as HW and Domestic heating. The HW end goes off into the unvented cylinder (which on research suggests possibly a Y plan setup?). Is the idea here that the central heating flow is used to heat a tank of water which is the main draw for DHW? How is/is that tank topped up with regular DHW? Now I think about it, the boiler only has one heat exchanger i guess.



Shaun

 

[JohnD]

the boiler supplies primary heat which is pumped to the coil in the cylinder, or to the radiators, or to both.

if there is a fault in the way the 3-port valve works, it is possible for flow to continue going to the cylinder even when it is not needed, and this can mean that insufficient flow is available for the radiators. This is what I call "stealing flow." The same thing can happen if you have a radiator near the pump where the lockshield is open wide enough for it to take so much of the flow that there is not much going round the others. Hence balancing is needed.

The hot water cylinder (not tank) is kept full by admitting cold water to the bottom of the cylinder when hot water is drawn from the top.

Depending on system design, it might be topped up from a tank of cold water, usually in the loft, or direct from the water mains (subject to considerable extra safety precautions)

 

[DP]

OMG
Since when do you touch the PRV to remove air

And why is that not a done thing? If it works, why not? Have done that plenty times and fixed the problem.