Inadequate Circulator Pump?

[John.g]

Have you measured the dT across any of the rads yet?

 

[JC22024]

Have you measured the dT across any of the rads yet?

I can do that in the coming days, should I leave the heating running for a couple of hours before I measure that?

 

[John.g]

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?

 

[JC22024]

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?

We are away this evening so I'll turn it on tomorrow when I get home, time etc and report back.

What I did not earlier was a 20c difference in the boiler feed and return temps. I think this is fairly optimal(?) On speed 2 after it had been running for an hour or so

 

[ShaunCorbs]

Yes 20 is spot on for the boiler

 

[John.g]

That's more like what I would have expected alright as it means that the flowrate is actually, 26*860/60/20, 18.6LPM, which makes more sense with a pump running with a constant head of 6M.

 

[JC22024]

How to calculate the

After you have worked out the heat requirement for your room (AEL's easy-to-use BTU calculator will help you do this), how can you check that the radiator you have chosen will provide enough heat output? There is a simple calculation to check if the radiator will provide sufficient heat output...

www.buildingservicesindex.co.uk

Should I be waiting until the radiators are balanced before taking the above readings? Or for now, prior to proper balancing taking place just shoot the centre of the rad for an average temp across the ground floor?

 

[John.g]

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.

 

[JC22024]

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.

Yes I'll do that this evening and mark current return / feed temps on the rads on the GF plan.

Then will balance later this week. Will clean the mag filter each day - more so to use the dosing capacity to get the new 2L of X800 into the system. Then after boxing day I'll drain and flush the whole system for final time and add inhibitor

 

[JC22024]

OK, heat has been on for a few hours downstairs zone only. It was at the 19.5c digital stat setting in living room so I think was likely OFF for a while before I got to testing it.

Hence readings may have been when it was warming up again :

72c out
54 return
7.5 mins run tune
1 min off time

Note I just took a temp reading at top middle of each rad. Then the last one which was always cold flow and return temps too.

Hasn't been balanced properly yet but appears decent spread all the same. (I had just balanced by hand feel last week) Pump on speed setting two still.

Bedroom 2 rad is off as room being refurbished at moment. I will get a new double Myson rad and liquid Drayton TRV for it this spring.

Utility will be Knocked down this summer so it's rad is off possibly for good.

 

[John.g]

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.

 

[JC22024]

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.

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.

 

[JC22024]

Since the first 2L of X800 cleaner was wasted due to no water circulation and drained I added another 1.5L tonight.

I'll let that run for a few days and add the last .5L just before draining.

The mag filter is collecting black sludge. A day of running it has about 5mm coating on it. Again this system was never fitted with a filter so I expect this will drop off as I monitor and clean it.

The cleaner is probably moving the stuff around and the mag grabbing it. Ill monitor and clean the magnet until such times as it remains clean for a week or more run time.

It is a Grant Mag One 28mm filter, really well designed bit of kit,. Just a minute or two to shut off, drain, clean and bleed again.

They are definitely highly effective wish it was fitted sooner.

 

[John.g]

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.

 

[JC22024]

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.

The rads are all glossy white so was hard to get accurate temps on them. Whilst 5 was about the average a couple were nearer 10 maybe depending on what exact spot I took the reading.

2 of them are 4 ft Myson double Finned (belt out the heat)



2 other doubles are older none finned 6 foots. And a tall vertical single radiator in bathroom.

The boiler has a 0.65gph nozzle at present.



Pipes also run down an unheated cubbyhole, they are lagged but probably lose some heat there too.

 

[JC22024]

Happy New Year to all! I did get the rising CH expansion tank issue resolved. I fitted 28m ball valves on the stove pipes in the boiler room which shut it off from the system when not in use. This is 100% fine as it is only lit once in a blue moon and only by me so I know to open the yellow levers before lighting it. And for avoidance of doubt I will fit a warning notice on the stove to instruct same.

I reduced the pumps speed setting to 1 and the house still heats 100% fine that way. I am currently progressing the painting of the boiler room and will be fitting new pipe lagging in there too.

I do wonder now should I fit an automatic bypass valve?

A reminder is this house had no TRVs and was all one zone with no stats.

Now it is split into 2no zones and TRVs are fitted to all rads except the 2no In the rooms with the stats.

I wonder that now if one of the 2no 2 port zone valves fails to open the pump will be running with no where for the pressure to go. Since it is no longer a smart pump either.

As a safety factor, to reduce stress on pump / boiler and in order to reduce noise of TRVs when the others start to shut I think it would be a good idea(?) There is no such device on this system at present automatic or otherwise but then at the time that wouldn't have been a consideration with no TRVs etc.

I could install an automatic bypass valve between the 22mm upstairs zone pipes about 2m pipe distance from the boiler. After pump and before boiler return and where there are no zone valves yet to stop flow around the bypass loop.

If anyone here thinks that would be a good idea I may go ahead and order a quality ABV by Honeywell or similar and get it installed which would complete this project.

 

[JC22024]

Or is it a case you should only install an ABV if you are experiencing issues such as excess noise from TRVs which I am not experiencing at present.

 

[ShaunCorbs]

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

 

[JC22024]

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

Thanks for that and yes fair point. My system is using the microswitches so probably not an issue. I guess a gate valve I'm conjunction with the abv would provide additional control. But with the big pump being so efficient on speed 1 I don't hear any trv valves making excess noise so I'll just monitor and if its not broke don't fix it!!

Being in the boiler room alot the past couple of days I did notice that on the first startup of the day there is a faint popping noise heard inside the burner. I think the new boiler would benefit from a Tiger Loop. I'll order the correct all metal internal type and vent it externally per instructions.

 

[John.g]

Oil fired boilers in general do not need ABVs as the Hx holds 20/25 litres of water which acts as a buffer so when the boiler+ pump cuts out, the water temperature (from a target temp of say 70C) will not rise > 90C/95C, a long way from the hi limit lockout of 113C. Gas boilers have a Hx content of only a few litres and this is why they have a timed pump overrun after all zone valves shut, the water then has no where to go so need a ABV.