Discuss Inadequate Circulator Pump? in the Central Heating Forum area at PlumbersForums.net
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.
What pump setting? and what are boiler flow/return temps as flow rate can be calculated from this.
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.
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.
Is the hunter stove in use at times for CH,?
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 ?
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?
Can you roughly draw the set up also feed and vent positions
I can do that in the coming days, should I leave the heating running for a couple of hours before I measure that?Have you measured the dT across any of the rads yet?
You can do it anytime after the boiler starts cycling (like now), just take it off one or two, but before the burner cuts out, any idea what the on/off cycle times are now?
No need to wait for balancing just now, the easiest quick test for now is to time say two on/off cycles, and then take the boiler flow and return temps while boiler is firing and as close to burner cut out as possible, ie if burner run time is say 2 mins, take flow&return temps after say 90secs or so and I can calculate the average rad(s) output and temps based on these and the boiler cycle times.
That gives a flow rate of 21LPM and a boiler output of 23kw, also the mid point (mean) temp of each rad is remarkably consistent at ~ 62/63c and probably pretty accurate as the mean of the boiler flow&return is 63C, giving a rads output of ~ 84%, don't see any real reason to balance these rads based on your numbers. 18C is a almost perfect dT IMO. You might just take another cycle time after full system heat up as difficult to see your hose requiring 23kw to maintain 19/20C.
What size are those rads?, I am getting 2.9kw/double rad (assuming "4.5" doubles) based on heat input of 13kw and 3.5kw/double rad based on heat input of 15.73kw (based on cycle time). This gives a average rad deltaT of 8.5C or 10.3C almost double of your values.Thank you for the assistance and calcs with this! Yes for sure I'll re check boiler run times tomorrow they appear too high but I think the stat was just off and back on again.
Upstairs been running for about an hour there on its own. I did a better balance on the rads - each rad has about 5c drop across it. All rad temps pretty much identical at 64c.
4 doubles and 1 single at present. (1 double missing again!)
Boiler outlet temp 74c
Return temp 57c
2.19 run time
1.43 off time
On watching it for 2no cycles the run time dropped by a few seconds which would make sense as the house heat demand/ soak will drop off as it heats up I guess. If running longer would probably go 50/50 or less run time I would say.
What size are those rads?, I am getting 2.9kw/double rad (assuming "4.5" doubles) based on heat input of 13kw and 3.5kw/double rad based on heat input of 15.73kw (based on cycle time). This gives a average rad deltaT of 8.5C or 10.3C almost double of your values.
Can you post the size of burner nozzle fitted to the Firebird.
If the port valves don’t open the pump shouldn’t run
Better to put a bypass rad before the zones as with abv on big pumps they tend to be always open as there normally installed close to the pump
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