Inadequate Circulator Pump?

[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?

 

[JC22024]

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?

I fitted quality liquid Drayton TRV valves throughout house a few years back. Except for the rooms which have the digital stat. (Living room GF and master bed FF)

Many of the radiators (+50%) are new Myson also. Each time I decorated a room I renewed the rad too.

Yes lockshields are in roughly balanced but will balance it correctly over holidays now.

I wonder do I need a bypass valve now too as I can hear noise in water flow upstairs due to bigger pump. Not terrible but noticable. As the house would heat up and TRvs shut could get worse.

 

[John.g]

You can reduce to sped2 which is a 6M setting which should reduce noise as the TRVs will be opened more and apart from that a interesting exercise to see if all the rads would still get hot.

 

[ShaunCorbs]

Would just let the system run for a few weeks before messing anymore with it eg let it settle etc

 

[John.g]

Calculations for boiler flow rate etc.
Flowrate (LPM) = (boiler output (KW) X 860) / (boiler dT X 60)
LPM = 26 X 860/33.3/60, 11.2 LPM. (boiler dT, 81.1-47.8, 33.3C)
The above calculation need no other input(s).

Re rad outputs, all modern rads are sized based on a "50 Deg" basis which is the mean rad temp-the required room temp (generally taken as 20C). the mean rad temperature is the (flow temp+the return temp)/2. In your case above IF the rad(s) flow and return temps are 81.1/47.8 then the mean rad temp is, (81.1+47.8)/2, 64.5C, if the room temp is 20C then you effectively have a 64.5-20, "44.5 Deg" rad so it will emit 86% of a "50 Deg" rad (44.5/50)^1.3 X 100, (86% of its rated output.)
However, because the huge dT means the boiler has to be run at almost full flow temp available, 80C. to obtain this performance, if you reduce the boiler temp to 70C then there will be a marked reduction in the rad(s) output.
You might measure the dT across a few of your rads sometime as I am amazed at the very poor flow rate with a 8M head and 28MM flow&return piping. I have a 20kw firebird with 10 rads and the flow rate is 16LPM based on the boiler dT of 18C, this flowrate is achieved at a pump head of 3.5M. I have 22mm piping. If I installed a 8M pump then my flowrate would be , 16*sqroot(8/3.5), 24LPM which is what I expected to see from your system at least. Even one rad, with fully open valves will flow 4/5LPM so I am wondering if your TRV's are somehow restricting the flow through the rads, you might remove the actuators from 3 or 4 of them and check that the pins are fully out.

However, you do have a comfortably heated house for the first time in your life so well done.

 

[JC22024]

Thanks for comments above! I did try the pump on setting 2 and all rads appear to be heating about the same including the furtherest one.

Over the holidays I will get time to try properly balancing the rads and see if setting 2 is enough when they are set at 11c drop.

I did clean the mag filter again and noted more buildup than normal. Note it is new install mag too. Probably because the water is now actually circulating properly! I did order more X800 cleaner so will use that again now the water is going through all rads just to make sure all is clear and should dissolve any rust buildup which may exist.

The overflow for the heating header tank dropped into the water tank for the house. This meant any time it overflowed etc it dumped rusty chemical laden water into where you brush your teeth from!! So I redirected that overflow pipe this morning so it discharges externally and not into the other tank anymore.

Whilst in there I noted the main tank ballcock is dribbling constantly so I'm going to go get a new one today and install tonight. That means both ball cocks will be new.

Now for the bad news- noticed the water level in the heating tank is indeed rising. When switched on and overflowing. However I believe this system has done this for years too 🙄 and I think it is coming from the stove circuit which is teed in just before the circulator. I will do more testing to be sure and for now maybe add 2no full bore 28mm ball valves on those pipes to shut them off.

The stove is connected to heating in the boiler room. Then loops up into attic, into gravity rad and drops down into stove. Trouble is I do not believe there is a link to the header tank to that stove circuit. It relies on atmospheric pressure to fill with water from boiler room. Maybe another outlet teed into that circuit from header tank would balance it and stop the water head being pulled down into the boiler room which is what I believe is happening but need to test more.

It didn't happen the first night because there was probably still air in the stove circuit which slowly vented out and filled and the problem re-surfaced. Literally!!

This house used to also pump water up out of the overflow vent but was cured years ago by moving the circulator pump to the boiler outlet side VS where it was pumping into boiler casing from return.