Raging hot pump, warm rads downstairs, cold rads upstairs

[bobface]

Hi,

I have a baxi boiler on a sealed system in a three story house. Boiler on ground floor, pump and gubbins on middle floor, rad pipes up and down from middle floor. I recently whipped a radiator off downstairs (remodelled kitchen) by draining the system enough to remove the rad, and refilling via the filling loop to 1bar at cold.

Before this the boiler has turning on and off very frequently (it would run for say 45 seconds before clicking off and back on again) but all the rads were hot. Now after this the boiler is still doing what it was, but the top floor rads are cold. On investigation the pump is getting incredibly hot, hot water is coming out of the three way valve for CH (or at least the pipes are hot!) and then the pipe work splits up and down for the rads in the house. The pipes going up get progressively colder to cold about two feet above the split, and the upstairs rads are cold. If i vent a little water from an upstairs rad the warm water will move up the pipe.

What I'm not sure about is (a lot of things, CH newb!) but

a) raging pump is bad, but it spins freely (it's not fouled, impeller is clean), not sure if it's actually running at speed tho when it's on (not really noisy, can hear rumbling and pipes feel like water is moving) (speed 3). It's a Grundfos 15/60. I dont have another to compare noise levels. Could the pump be what's causing the boiler to switch off, or vica versa, is a boiler fault causing the pump not to run enough? The raging hot pump is definitely not normal, it's not noisy, no banging. I dont think there's air in the system, there's none in the pump. Maybe it's just worn out and wont push water upstairs?

b) Have a buggered the balancing? I removed one downstairs rad a while back (shut locksheild and other end valves) and the system was fine (despite the cycling boiler). The weekend job was cutting back the pipes.

c) Have I buggered the refilling process?

d) something else i've done that's likely ruined my system?

The little lever on the three way valve doesn't do anything when I pull it across, it doesn't feel attached at all. I dont think this is a problem, certainly i think the valve is behaving as per the boilers instructions.

I appreciate there probably isn't enough information here, again, apologies, heating newb

Shaun

 

[bobface]

maybe 1 bar when cold is too low for a three story house? I stupidly didn't take a reading before popping the rad off.

 

[Space cat]

One bar will lift a column of water about 10 metres. How high are your floors?

 

[bobface]

Well the pump is in the middle, puming up and down, splits shortly after the 3 way valve. Floors are 2.5 metres high, so it pumps three rads up 2 metres and round, 5 rads on the same floor and 4 downstairs and round 2.5 meters

 

[JohnD]

the top floor rads are cold.

turn off all the hot rads and see if the cold ones then warm up. If so you need to revisit the balancing.

make sure that the primary circulation is not all getting stolen by the cylinder or any bypass.

do all the rads bleed successfully?

did you get any sediment out when you removed that rad?

The 1bar guage will be on the boiler, so it's 10m up from there, not from where the pump is. If water squirts out of the highest radiators when you bleed them, then the pressure is not the problem.

 

[bobface]

okay, i turned off all the middle floor rads and it didn't help, but i'll try the all off. Rads bleed fine, i think all the rest are fine (will recheck).

I'm not sure I know how to answer the second question but will see if it makes sense when i'm back in front of it.

As to sediment, not really, bit of sludgy crap but mostly water + inhibiter i guess. pump is clean as a whistle, upstairs rad water is cleanyyellow.

 

[bobface]

the pressure gauge is by the expansion tank which is in the same airing cupboard as the pump (and the giant unvented water cyclinder for dhw). I guess you're right, water does come out of the upstairs rads at a decent pressure.

Okay - so this would indicate a problem pumping? I'll shut all the downstairs rads and see if the pump will push water around upstairs.

 

[zanwan]

By the sounds of it you have air trapped in the system. It was working fine before you drained down, problems only started since working on system. Since you have probably already bled the rads, the only other area air will likely be trapped is in the boiler itself.

Take of the boiler cover. Look for the pump. Turn the screw slightly to release any trapped air in the pump. You'll get a bit of water come out, which could be very hot so be careful.

Next follow the pipes just as they leave the pump, you'l see a red and black round mechanism. turn this (the red bit) i think its anti-clockwise, it only turns one way, this will purge water and any air from the system via the overflow pipe, just a couple of turns, you should hear water "gurgling" as it exits, indicating air in the system.

Now refill back to 1.5 bar if you need to. Start up heating, give it a few mins. This should hopefully sort the problem out for you.

 

[HERTS P&D]

Next follow the pipes just as they leave the pump, you'l see a red and black round mechanism. turn this (the red bit) i think its anti-clockwise, it only turns one way, this will purge water and any air from the system via the overflow pipe, just a couple of turns, you should hear water "gurgling" as it exits, indicating air in the system.

OMG
Since when do you touch the PRV to remove air

Andy

 

[zanwan]

Next follow the pipes just as they leave the pump, you'l see a red and black round mechanism. turn this (the red bit) i think its anti-clockwise, it only turns one way, this will purge water and any air from the system via the overflow pipe, just a couple of turns, you should hear water "gurgling" as it exits, indicating air in the system.

OMG
Since when do you touch the PRV to remove air

Andy

Listen i've done this several times in recent weeks and each time its solved the problem of rads not heating up/no flow in system.

You may advise an expensive powerflush, and a new combination boiler and advise them your mate needs to also build them a new boiler room. But i prefer to get the job done in an honest manner without riping the customer off. Working with a very honest and admirable heating engineer over the past couple of weeks, i'm learning just how boilers work and how easily 80% of the faults can be fixed without poor customers having to fork out stupid prices.

 

[HERTS P&D]

But i prefer to get the job done in an honest manner without riping the customer off.

You should not be taking the cover off the boiler! You are not Gas Safe!

Andy

 

[JohnD]

if you open the PRV, isn't it then prone to leak in future?

 

[Space cat]

This argument is largely academic ---

Boiler on ground floor, pump and gubbins on middle floor --

The pump is nowhere near the boiler.

The problem is almost certainly trapped air and, given the noise that the pump's making - added to the fact that it's running red hot - that's where I'd be looking. A centrifugal pump is designed to pump water, not air. If it's sitting in an air pocket, it'll sound wrong, it'll get very hot (no cooling water) and it won't do much pumping. Bobface, is your pump sitting in a horizontal pipe run?

 

[bobface]

I have checked for air in the pump (there wasn't any). I've had the pump head off to check it's fine. My boiler does have some kind of pressure or air release thing on the front (i can't remember, will check later).

I dont think it's air - i have water all round all round the system, no noises and bangs, and water peeing out the top rads open bleed valves. I guess it might still be.

Is it normal practice to split the pump output up and down if the CH pump is mounted on a middle floor?

 

[bobface]

The raging hot nature of the pump - that's not normal is it?