Inadequate Circulator Pump?

[John.g]

Be interesting to see how this pump performs, you may as well clean that mag. filter as well after any flushing etc.

 

[ShaunCorbs]

Thanks for that, am I right in thinking those figures may relate to

25mm inlet
80mm pump vane?

If so yes that would make sense as old units are 15mm inlet and 60mm vanes

Yes 25mm bore 8m head

 

[ShaunCorbs]

Could you freeze one side and adjust the pipe/ pump valve sages draining down ?

 

[JC22024]

Could you freeze one side and adjust the pipe/ pump valve sages draining down ?

Yes probably could freeze it except I don't have any of that equipment!

It's easy enough to drain down anyway I suppose. stopcock for header tank easily reachable at trap door. Pop hose on boiler and let it run. If I don't crack the bleed screws on the rads most of them tend to stay full anyway.

New pump dispatched today by 24hr service so should have it tomorrow and will tackle replacement Friday night probably need to pick up some 28mm olives too.

 

[John.g]

Upstairs has been running on its own tonight for a couple hours. 2 double rads hot and bathroom tall single hot.

On time = 1.5 mins. Off time= 4 mins 45 secs.

Return temp 43c

View attachment 67200
View attachment 67201

Again on the small upstairs zone I can get all rads warm. But when I balance first 2 correctly the rest fall off cold even with valves fully open.

It's on the larger downstairs circuit that the return temp never rises above 25c even after hours of running.

Is the boiler firing or not with that temp of 89.5C?.

 

[JC22024]

Is the boiler firing or not with that temp of 89.5C?

Those temps were taken whilst the heating was running can't remember exactly if the boiler was firing at that exact moment but the temp would be fairly consistent in any case.

 

[John.g]

I think the max boiler setpoint temp on that boiler is 75C or maybe just 80C max?. Can you ensure that the pump is pumping away from the boiler and what is the power showing there, it looks like 13W? What is the boiler stat set to? there is a 28mm? copper elbow under the boiler stat, is that the vent?.

 

[JC22024]

I think the max boiler setpoint temp on that boiler is 75C or maybe just 80C max?. Can you ensure that the pump is pumping away from the boiler and what is the power showing there, it looks like 13W? What is the boiler stat set to? there is a 28mm? copper elbow under the boiler stat, is that the vent?.

Yes pump is on outlet and arrow pointing away from boiler.

Not sure why the reading appeared so high yesterday. After upstairs running a few hours checked now and boiler outlet high 70s. yes open vent at top rear right.

Ps just thinking I did actually turn boiler stat down since last night!

 

[John.g]

Thanks, that very high temp of 89C might cause the pump to cavitate and cause circulation problems, might try a SP of ~ 70C for tomorrow and see what the pump power is. Can you see what that power reading was above, looks like 13W to me.

 

[JC22024]

Thanks, that very high temp of 89C might cause the pump to cavitate and cause circulation problems, might try a SP of ~ 70C for tomorrow and see what the pump power is. Can you see what that power reading was above, looks like 13W to me.

Thanks yes I was wondering the same thing last night and turned the temp down a little. Will turn down some more too to hit 70 as you suggest.

The wilo pump is still in there and I'll likely just put the Trident pump in next so can't see the pump power readings any more at the moment.

 

[John.g]

OK thanks again, can see tomorrow what the 70C does, if anything, you will soon know as the boiler dT will decrease if the pump is circulating more.

 

[JC22024]

OK thanks again, can see tomorrow what the 70C does, if anything, you will soon know as the boiler dT will decrease if the pump is circulating more.

Thanks I did turn it down more this morning and ran for 1.5 hrs before I left for work on downstairs zone. Didn't appear to make a difference on the rads not heating decently. Indeed they felt cooler. But will be sure to test this with new pump also incase the boiler is actually boiling the water at high settings! Which it could well be too adding to problems.

 

[John.g]

Presume boiler only ran continuously for 20 minutes or so and then started cycling??.

 

[JC22024]

Presume boiler only ran continuously for 20 minutes or so and then started cycling??.

Correct yes. I did get the olives etc this morning and DHL delivered new pump. So I'll fit it tonight when home from work, refill and properly time the boiler start up run time on GF zone. And see if the rads perform better. Fingers crossed!

 

[JC22024]

System draining down, this is the water coming out (I believe the system shouldn't have blockages. Water is always clean coming out)

 

[JC22024]

Pretty good difference comparing pump to pump opening

 

[John.g]

Is there much of a build up on the Wilo impeller vanes??. or is that the Alpha?.

 

[ShaunCorbs]

Note it will be brown / black this is normal

 

[John.g]

Here's mine, after 18 years, ready to be reinstalled when my smart pump packs up.

 

[John.g]

The impeller on JCs old (alpha/wilo) looks as if it has been in contact with something metallic as it seems a bit chewed up.

 

[JC22024]

The impeller on JCs old (alpha/wilo) looks as if it has been in contact with something metallic as it seems a bit chewed up.

I tried to split the Grundfos but it was the motor coming apart! So didn't want to break it altogether.

From what I can see the old vane looks OK?

 

[JC22024]

PS regards fitting new pump could the gate valves I have be considered a restriction?



They narrow to 15mm or so at pump inlet. Maybe this is nothing to worry about but If there may be a better way of connecting it let me know.

 

[ShaunCorbs]

No there all the same sorry to say you can pipe straight to the pump but then there’s no valves

 

[JC22024]

Well the new pump appears to be working very well.

Boiler only on 20 mins and already can audibly hear the pipes clicking as they heat up in far room of house! Radiator that never heated is already heating up evenly.

Will let it fully warm up for next hour or so and see how it's doing but appears very promising

 

[John.g]

What pump setting? and what are boiler flow/return temps as flow rate can be calculated from this.

 

[JC22024]

What pump setting? and what are boiler flow/return temps as flow rate can be calculated from this.

Setting 3, I'll let it run a little longer then record temps. Boiler should be putting out 26kw approx as that is the nozzle and settings I have it at.

 

[John.g]

While its running, pop up to the attic and look for any movement in the F&E tank, hold a "glass" of water with the vent immersed in it and see if any water is being drawn in, also, later, get someone to stop/start the boiler/pump and watch for any pump over or tank surging when the pump starts or stops. IMO 6M on that capacity pump would be more than adequate and 5M would probably fit the bill as well as its so big that it will run like a constant pressure pump on any one of those settings.

What is the Boiler SP.

 

[JC22024]

While its running, pop up to the attic and look for any movement in the F&E tank, hold a "glass" of water with the vent immersed in it and see if any water is being drawn in, also, later, get someone to stop/start the boiler/pump and watch for any pump over or tank surging when the pump starts or stops. IMO 6M on that capacity pump would be more than adequate and 5M would probably fit the bill as well as its so big that it will run like a constant pressure pump on any one of those settings.

What is the Boiler SP.

There are 3no vents up there. Tested all 3x and no water being drawn in. 1 of them slightly bobbed the water up and down a little but did not suck it in just slight movement of water. And one tiny bubble came out of it. I presume that's the one that comes from the boiler. The other 2 I know 1 comes from a large hunter stove and the other not sure maybe redundant from back boiler fire / range cooker that both were done away with years ago.

 

[JC22024]

What does boiler SP refer to?

Here are temps now

ALL downstairs rads toasty now.

 

[JC22024]

I have a theory here of what was happening.

The pump was always undersized. However with the old boiler it was just about functional and balancing still wasn't right but "good enough"

New condensing boiler definitely made it lie down dead pressure wise. I believe the new boiler is harder to pump water through the jacket. Maybe due to heat exchanger etc.

Additionally, when the water flow was well down the new boiler was getting up to temp too fast and too high. Also cavitating the pump for good measure. There were times I could hear the boiler boiling the water.

 

[John.g]

Boiler SP is the boiler thermostat setpoint, I would dial that down another 2 divisions to give ~ SP of 75C.
Your flow/return temps above of 81.1/47.8 = dT of 33.3C and with a boiler output of 26kw = flowrate of 11.2 LPM so still a big resistance somewhere IMO as ~ 3/3.5M head should easily give you that flow rate.
The resistance of that boiler Hx is negligible like all oil fired boilers, where the Hx is basically a box full of water, its only 0.19mbar, a fraction of a meter.

If the Alpha (or any 6M) pump was operating correctly the you would have still got 9.6LPM, the new pump will give the same 9.6LPM at 6M (speed2)

 

[John.g]

Is the hunter stove in use at times for CH,?

 

[ShaunCorbs]

I have a theory here of what was happening.

The pump was always undersized. However with the old boiler it was just about functional and balancing still wasn't right but "good enough"

New condensing boiler definitely made it lie down dead pressure wise. I believe the new boiler is harder to pump water through the jacket. Maybe due to heat exchanger etc.

Additionally, when the water flow was well down the new boiler was getting up to temp too fast and too high. Also cavitating the pump for good measure. There were times I could hear the boiler boiling the water.

Probably working on gravity circulation as well / helping hand now around 60 won’t work as much so more strain on an undersized pump so I guess your happy now ?

 

[JC22024]

Is the hunter stove in use at times for CH,?

Literally never. Lit at Christmas once every 2 years. Should use it more!! Or move it into a room where it will actually get used. (Im dining room) it is a big one - 32kw or something total.

Probably working on gravity circulation as well / helping hand now around 60 won’t work as much so more strain on an undersized pump so I guess your happy now ?

Yes amazed at the difference and the house definitely needed this size of pump. Thanks for the recommendations there of 25 / 80!

All rads were hot tonight. I could probably jet boiler back down to 20kw but will run it into Jan this way anyway before deciding. House never had such good heating as right now. Lived here all my life so I know the heating system very well and how the house feels. This is amazing now.

I did also turn boiler stat down a couple notches as suggested by John as rads were almost scalding.

Not sure how John's calcs are determined above, wouldn't ambient temperatures and actual room temperatures severely influence any such calculation? I think its all running very good now.

Header tank doesn't appear to be doing anything stupid but left trap door off and will monitor. Also need to replenish inhibitor now I drained it out.

Will clean mag filter every week now for foreseeable until I see it totally clean. I do get very slight buildup after it was installed so I suppose its doing a great job at capturing anything in this old system.

 

[John.g]

Will explain general calcs tomorrow which you might find interesting.

Re d/stairs, are some of the lock shield valves throttled in and have all got TRVs fitted?