Inadequate Circulator Pump?

[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.

 

[John.g]

Its nigh impossible to make any comment on your set up without at least a schematic to show how the two systems are integrated and how recirculation through one system is prevented with either system in use, the potential for very dangerous conditions exist if these systems are not properly installed, I would strongly advise not to use the stove until problems addressed.

 

[JC22024]

Yes I plumbed the stove in about 5 years ago. It is absolutely safe I made sure of that hence why I wanted to do it myself. Eg, large capacity gravity rad which was sized per manual to soak away the heat if fhe power went out in use and heating not circulating. In conjunction with high and low pipe stats and a thermostatic damper on the stoce which at that time was special order. (Now it is legal requirement as I understand it and all new stoves should come with it.

But... here is an update. When I changed the ball cock in heating tank I noted it was too high. Set about 2 inches below the outlet.

So the new ball cock heating tank level is only a couple inches above the outlet to allow for expansion.

So that was yet another error in the system.

But the main error it appears when I thought about it is the actual vent pipe itself. This house has the old school heating plumbing whereby if you wanted hot water it switched the boiler on and no pump hence it raised up the pipe and fell back down warming the cylinder coil.

That is a 22mm pipe which goes from the boiler and loops over and down into the hot press. With a 15mm vent pipe teed off that mid point and above heating tank.

Years ago when I was upgrading the controls in the house I may have made an error of judgement I fitted a cylinder stat and control valve to the hotpress 22mm pipe.

I was thinking about this and did a test there by turning on hot water to permanent on (I normally use economy 7 electric on immersion heater all year around) and switch heating on and off.

Bingo- now the heating tank water level stays AOK doesn't rise. Sits at correct level. Could be speaking too soon but before I opened that it was pumping up and out the overflow then filling back up again a little when shut down. Now it stays level. Will it creep up still? Time will tell.

I guess this is just how the house was plumbed and I need to remove that valve, the only downside being that there will always be a degree of hot water from normal space heating running but that's OK.

 

[JC22024]

So just to make this clearer, I belive the expansion tank puking out water has been a long term problem. The overflow is out the back of the house and I'm usually never out there. But I recall before seeing it putting bursts of water out of the pipe and thinking "I need to look at that" but never did.

After the old boiler burst and working on system in recent weeks I noticed the high water level in the heating expansion tank. And thought must be ball valve. I renewed that and lowered the water level.

But it wasn't the ball cock. It was the fact that one end of the 22mm vent / feed pipe was effectively capped in the hot press.

So in that state when you turn the heating on and all is bled properly the lower feed pipe in the header tank backfeeds water and rises the level in the tank until it overflows a couple litres out the overflow pipe.

Now with the hot press valve overrode/ powered on this does not happen. There must be a small head in the water, perhaps intentional that travels down into the HW cylinder when the system is operating. And since it couldn't go that route through the cylinder it was instead being pushed up into the header tank.

So I'll leave the HW valve permanently on for a few days and report back If heating tank water level / puking issues are now resolved.

Space heating is superb Pump on setting 2. Overflow from heating tank also now bypassing the drinking water tank. And I did renew the second ball cock in the main loft tank today as it was actually constantly leaking.

 

[ShaunCorbs]

Can you roughly draw the set up also feed and vent positions

 

[JC22024]

Can you roughly draw the set up also feed and vent positions

Yes I will in coming days and will post. Will monitor heating tank and see if this went away also.

If it doesn't next step for me will be to temporarily cap the stove pipes in boiler room to remove it from equation.

 

[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.

 

[ShaunCorbs]

might just be metal expanding on first heat up

 

[JC22024]

might just be metal expanding on first heat up

It's actually the flame, the second it fires up I can hear it shuddering and popping for a few seconds. Say around 10 seconds then it goes solid burn no popping or hesitation thereafter.

On reading up on tiger loops and single line oil systems they do appear to be a good idea anyway to ensure maximum efficiency and eliminate any potential for air bubbles at the nozzle which I suspect is the problem. There may be tiny air bubbles in the oil line then as it sits overnight these go up near the pump and it has to clear them when first firing up.

And no need to bleed oil line either if the tank runs out of oil.

 

[JC22024]

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.

Great explanation thanks for that I will not bother with an ABV in this instance it should be aok without it unless trv noise is a problem but does not appear to be even with the house up a 24c this evening.

 

[John.g]

TRV noise (or lack of) has always been a bit of a mystery to me, I have used them for years and have never had a problem with noise, I have now replaced almost all, apart from one Myson, as the plastic heads were getting a bit brittle after 10/12 years or so, I have replaced them with EPH and all of them are/and always have been installed horizontally on the rad returns. Some makes seem more prone to noisy operation, your's must also be "noise free" as the pump on setting1 is still producing 5M.

 

[JC22024]

Getting some progress on boiler room. Insulating pipes now, there is a pair of 22mm pipes very close together. For those I'll slice the insulation with a razor so both layers fit around the pipes. Is there a better way to do that? Kind of want all the insulation the same VS using a wrap.




All pipes will be fully lagged. Then on the small radiator in here I'll keep turned on low. And fit a frost stat inside this room which will override the downstairs zone. That should protect the whole system from getting frozen. (Both internal room stats also have set back temp settings and frost stat if turned on standby)

New fire ceiling going in and will paint floor to finish the boiler room.