HELP: F&E tank overflow when boiler comes on

stooge · 04-01-2022 06:40PM #1

Hi,

Bit of advice or help needed. Long post below (TLDR version -> looking for advice on troubleshooting F&E overflow issue)

SETUP:

Three sources of heating rads:

Firebird Oil boiler in garage
Oil Stanley Range in kitchen
Solid fuel Stanley Stove with back boiler in Living room

CWS tank and F&E tank in attic.

Bungalow with approx 25 rads

Hot water cylinder with immersion

PROBLEM

Over the last year I had noticed a small drip from overflow pipe outside. Then, when we used the Firebird boiler to heat the house, a gush of water would come from the overflow. I suspected something with the ballcock. I took off the ballcock float/ball and it was full of water and obviously F&E tank had been filling up more than it should. Easy fix I thought....replaced the float, checked there was no leak from the valve and off I went...... BUT

Next time I used the Firebird to heat the house the overflow started leaking again. This time (and ever since) the F&E tank filled so quickly the overflow couldnt get rid of the water quickly enough and the water spilled out onto the rafters and plasterboard underneath (Disaster!). Not too much water but still not good.

The quick expansion only happens when the garage boiler is used. Does not occur when the oil range in the kitchen is used to heat the rads (Stove is not strong enough to heat all rads so I dont think this comes into the equation)

STEPS TAKEN SO FAR

Replaced faulty ballcock float
Turned off cold feed to hot cyclinder (to check if there was an issue with a leak in the cyclinder)
Turned down pump setting on garage boiler

I'm at a loss and the only thing I can do now is have a drip tray under the F&E tank to provide extra protection when it overflows.

Any advice, before I get someone in...?

Thanks all

Stooge

John.G · 04-01-2022 07:47PM

Presume only using the firebird alone when this occurs?, are there any non return valves or isolating valves on the two solid fuel stoves?, how many coils does the HW cylinder have?. can you see where the cold feed joins the system or systems.

What make of pump have you in the garage and what setting is it on now, does this pump only serve the Firebird and do the other two systems have their own circ pumps?.

stooge · 05-01-2022 01:26AM

https://www.boards.ie/discussion/comment/118417805#Comment_118417805

Hi John, thanks for the interest and all the questions! :-)

Will try to answer as best I can.

- yes, happens when only firebird is on (also happened when we had stove and firebird on at same time)

- 1 coil in the cylinder as far as I know

- cold feeds i have access to and can see where it comes from and can turn off

-grunfoss (spelling?) Pump beside the firebird in the garage. Only serves that and no other. Currently set at low/1 (was at high/3)

Cheers

Irish Steve · 05-01-2022 12:55PM

From the description you're giving, if the level in the header tank is rising as rapidly as you're suggesting, while it might seem to be a strange response, I would suspect that there is some significant air trapped somewhere in the system that's expanding when the boiler is lit. The Air could have originated from the time when the faulty float was allowing extra water into the system, so there was a regular supply of fresh water into the header tank.

The overflow not being able to clear the extra inflow is a bit strange, is there any chance that there is a partial obstruction of some sort in the pipe, which is restricting the flow rate that can be achieved?

What level is in the tank when the system is cold? It doesn't need to be full in the same way as a cold storage tank would be, depending on the capacity of the system, which sound like it's quite large (25 rads mentioned) if the level is too high when cold, it will expand and reach the overflow as part of normal operation even if there is no air in the system. If it's only a small (10 gallon) size tank, it's very possible that you only need 2 or 3 inches in the bottom of the tank when cold for things to work without problems, and when the heat comes on, it could well rise several inches as the temperature of the system rises, and if the level goes above the overflow, so some water lost, the lost water will be replaced the next time the system cools, and this will perpetuate the addition of fresh water, with the potential for that water giving off a little air the first time it's heated.

Are there any automatic air bleed valves on the system, and if there are, have they been checked to make sure that they're open, and not furred up with lime scale as a result of a lot of fresh water getting into the system over time.

John.G · 05-01-2022 01:18PM

https://www.boards.ie/discussion/comment/118419397#Comment_118419397

Can you see the exact Grundfos pump you have, it may be a UPS3? and was this a replacement pump installed relatively recently?

Can you also see where the cold feed to the Firebird is located.

Wearb · 05-01-2022 02:02PM

I know you said that you turned off feed to cylinder; what level is the expansion tank in relation to domestic water tank?

stooge · 05-01-2022 02:53PM

https://www.boards.ie/discussion/comment/118420577#Comment_118420577

You may be on to something in terms of air in the system. Have had to bleed rads quite often and we have one Rad in the hall which seems to be on the way out (not heating up fully, no air coming out when bled). Maybe a blockage with this?

Overflow pipe -> No obstruction that I can see. The water does flow out of it easily enough, it's just that the level rises so quickly it can't get rid of it all.

Tank level -> About 4 inches of water in the tank normally (just less than 1/2 full). Could try reducing this by bending the float arm down a bit?

Air bleed valves -> not sure, where would they be normally? I assume you dont mean the ones on the rads.

Thanks!

stooge · 05-01-2022 02:54PM

https://www.boards.ie/discussion/comment/118420963#Comment_118420963

The F&E tank is on teh same platform as the CWS tank.

i.e. lowest level of both is the same but highest water level of F&E is lower than CWS. Both CWS and F&E tanks are well above the hot water cylinder obviously.

Wearb · 05-01-2022 03:10PM

https://www.boards.ie/discussion/comment/118421270#Comment_118421270

In that case you need to rule out a leak in the cylinder coil. You cannot be certain that the feed valve to cylinder is fully closing.

Best way to check would be to leave a wash hand basin hot tap running a bit and then turn off feed to cylinder. This assuming that said tap is fed from cylinder without any pump aid. The tap should stop. Make sure all other taps are also off during this test.

Even testing like this will not give certain results because if coil is leaking, there might be enough flow either way through it to frustrate the test. Surest way would be to have a plumber pressure test coil.

Are the Overflow pipes from both attic tanks combined at any point?

stooge · 05-01-2022 03:11PM

20220105_133013b.jpg

20220105_133035.jpg

Grundfos UPS 25-50 130. No work done on the pump or boiler in a while.

Uploaded a couple of pics above of pump and boiler

Boiler return pipe shown in the picture below.

Inked20220105_135746_LI_b.jpg

NOTE: the pipework may be very confusing on first look (With four heating methods (including immersion) and a rainwater harvesting system (not in use at the moment), but I think I have a good handle on what everything is at this stage!

Irish Steve · 05-01-2022 04:48PM

OK, looking at the boiler photo, I'd be tempted at this stage to replace the elbow to the left of the orange thermostat with a T fitting, capable of taking an air vent fitting similar to https://www.screwfix.ie/p/bottle-air-vent-3-8/76650 (no connections with screwfix, but it's a handy link to explain what I mean) so that if there's any air in the boiler, it will be automatically released, as there looks to be no easy escape path for trapped air at the moment, as the discharge goes down from that elbow to floor level.

If there's air in the boiler, when the boiler fires, it is very possible that it is expanding significantly, that would provide the sort of flow scenario you have described.

Another way to check for air would be to (carefully) twist the red valve top on the pressure safety valve that's to the right of the orange thermostat before the boiler is fired, if there is air in the system, it would escape as that valve is opened. Open it slowly, and don't open it if the system is hot, as you may get water splash out of the valve.

John.G · 05-01-2022 05:43PM

Back to basics again,

When the F&E tank is overflowing is water coming out of the Firebird vent, assuming you have 3 separate vents??. It must be getting water from somewhere else to overflow continuously if the ballcock is up and makeup shut because ~ 120 litres of water will only expand by around 2.5 litres or so, as pointed out above, air is a possibility, I vent by firebird with the PRV valve on the top of the boiler as well.

Can you point out exactly on the (a) photo exactly where the cold feed tees into the system

The minimum setting on that selectric pump certainly shouldn't cause any pump over problems as the head is so low, I'm surprised it can actually circulate adequate water through all the rads. It is only producing 2.3/2M head if the required flow rate is 0.8/0.9m3/hr.

I feel you have a partial blockage somewhere that is causing the water to pump up to the F&E tank.

stooge · 05-01-2022 09:18PM

https://www.boards.ie/discussion/comment/118421411#Comment_118421411

Going to try this again tomorrow (I had tried turning off the cold feed to the hot water cylinder to see if the F&E level would drop)

The coil worries me a lot to be honest...House is about 15/16 years old and we have a very limescaley water supply with no descaling system. Would be afraid to open the HWC and see what it is like inside!!

BTW -> Overflow pipes from CWS and F&E are combined in a T fitting. I always thought this was poor design, in case there was flow from both? but I dont think I'm getting an overflow from CWS at the same time?

stooge · 05-01-2022 09:22PM

https://www.boards.ie/discussion/comment/118422095#Comment_118422095

Going to look into this aspect a lot more (i.e. air venting). We are continually bleeding air from rads. I'm not sure if that is because air is getting in somewhere, or because the system is constantly getting fresh water from somewhere).

I might hold off on replacing the elbow for now and see if there are any other places to vent. Thanks for the tip on the pressure safety valve -> so this is a possible way of venting air in the boiler?

stooge · 05-01-2022 09:33PM

https://www.boards.ie/discussion/comment/118422344#Comment_118422344

Back to basics? I think I'm nearly going beyond my basic level!! 😀 (I know what you mean though)

On your first question -> There is no water coming out near the boiler and I dont think there is anywhere for it to come out?

My understanding of the feeds for the boiler is shown on the picture below:

20220105_133013.jpg

Maybe you mean where is the cold feed into the whole system? If so, it is the top right blue arrow/copper pipe in the picture below.

The red arrow is the hot water from the boiler to HWC. The bottom blue arrow is the cold feed/return back to boiler.

Inked20220105_135737_LIb.jpg

Partial blockage is my hope at the moment (worst case is leak in cylinder coil). I am going to replace the faulty rad we have and see if that helps. Although it does nto entirely explain why the issue only happens when the boiler is on and not the stove or range. Maybe because the boiler has a higher capacity to heat more rads, or stronger pump?

stooge · 05-01-2022 09:35PM

Sorry for all the separate posts guys, but I just want to say a huge thanks to you all for the advice and help. I'm not there yet but I definitely have some avenues to explore, whereas previously I think I was running out of road! 👍️

John.G · 05-01-2022 10:48PM

The cold feed is the pipe from the F&E tank that tees into the system or systems, its sole purpose is to make up for any slight leaks or any air that is vented from the system, the water in this pipe is balanced by the water in the vent pipe or pipes, if there is a partial blockage in this (cold feed) pipe then you can get pump over from the vent for a few seconds which normally might only happen when the circ pump starts and stops, this in turn can introduce air into the system hence all the required venting, someone would have to be in the attic to watch for this.

If it is the top blue 1/2" pipe in the photo, can you see where it joins (teed into) the system, is it teed into the other blue arrowed pipe or does it go through the floor and join the system lower down.?

I can assure you that the Firebird Grundfos pump on setting 1 is not the cause of the problem.

What you might just check is that none of the other two pumps are running at any time that the Firebird is running on its own.

There are normally non return valves (NRVs) fitted in all three systems to prevent backflow, the flow and return pipes on the two stoves should be cold/cool with firebird only in service.

What purpose does the pipe stat on the Firebird flow pipe serve?.

There are two coils in that cylinder, which is which??, the left hand one has what looks like another cold feed teed into the cylinder return.

stooge · 05-01-2022 11:29PM

https://www.boards.ie/discussion/comment/118423935#Comment_118423935

Ah ok, I understand you now. The cold feed from the F&E tank is actually the thin pipe that joins with the bottom left return cold pipe from the hot water tank (hope I am explaining that ok) The top right pipe that I highlighted in blue is the cold feed from the main cws tank into the hot water system.

I have set up a blink indoor wireless camera (motion activated) in the attic beside the tank for the next time I put the boiler on and see the issue. hopefully will be able to show what exactly is happening.

The pipe stat on the boiler pipe I presume shuts off the boiler when the heat of the water is high enough ie.. no point reheating already hot water? I thought this was a common enough feature?

I think the hot water tank hshould have three coils in total (for the three heat sources?)

The left hand coil I think is for stove (the pipe with green on it is the hot water from solid fuel stove). Right hand coil I then presume is for the boiler. The final coil is actually in around the back for the Stanley range.

John.G · 06-01-2022 12:14AM

OK then, things are getting a bit clearer now.

The cold feed is teed into the stove return which will possibly balance the stove system but both the firebird and the range should have their own cold feed teed in somewhere to balance their own systems so can't see that system, as is, working correctly.

Can you post a picture tomorrow of the F&E tank with presumably 3 separate vents?, I can then suggest a cold feed tee in for the firebird that may work, also the cold feed should be teed into the range cylinder coil (like the stove), this may then work (but no guarantees) and stop the activity in the F&E tank.

How many rads will the firebird heat with the pump at its present setting?.

The firebird has its own boiler stat to stop/start the burner, the pipe stat is there for another reason, maybe its a pump overrun when the boiler shuts down to avoid overheat and the hi limit stat locking out the boiler.

stooge · 06-01-2022 10:36AM

https://www.boards.ie/discussion/comment/118424440#Comment_118424440

The F&E has only one overflow pipe and only one cold feed out (the one that you see teeing into the stove). There are no other outlets.

There is one cold feed in also with the ball cock.

See the picture below from the blink camera I have set up. Also shows the normal water level and room for expansion

Screenshot_20220106-092104_Blinkb.jpg

Havent checked how many rads the firebird heats on the low setting, but will do that now and report back.

Have you any recommendations on temp settings for the boiler stat and pipe stat?

I turned on the boiler (pump at lowest setting) and after about 5mins the level in the tank has gone up to the overflow (see below). Water is NOT comings from the overflow so it must be entering fromt he cold feed at the bottom.

overflow.jpg

EDIT: For clarity I should mention that the feed outlet from the F&E tank is about 2-3 cm above the bottom of the tank. I just drew the black circle on the picture above to illustrate a pipe. It is not in that exact location in the picture.

Irish Steve · 06-01-2022 11:52AM

going back to air trapped, the picture a couple of messages ago of the hot water tank has an air release at the top of the heating coil on the right, and that's the sort of air release that I'd be expecting to be on the output pipe of the Firebird, to ensure that there's no air trapped in the boiler.

John.G · 06-01-2022 12:36PM

Does the overflow from the F&E tank keep over flowing while the pump is running ie is the water constantly flowing into the tray that you made tp pipe it away? If so, then water has to be replacing the water going to drain. OR is the level just reaching the overflow without actually constantly overflowing?. I would tie up the ballcock and watch for a few cycles because if the water isn't being drained off then the level will return to "normal" with pump off.

The "overflow from the heating system" is actually the "Vent" from all three systems.

There is no vent on the boiler, if you very slowly turn the knob on top of the PRV (safety valve) very slowly anticlockwise then this will crack open the PRV and release any air then water, the valve will reclose once you let go of the knob, I use this after any drain down of my system. Hold a container under it while venting or better again stick a bit of 1/2" pipe in the vent.

Have a look at the setting on that pipe stat and carefully note it. I would expect it set to ~ 90/95C. I have my boiler stat set to 75C which is a fairly reasonable, so count the number of divisions from either end that this set to or/and post a close up photo of both.

stooge · 06-01-2022 12:50PM

https://www.boards.ie/discussion/comment/118425775#Comment_118425775

I turned this air release (one on the top of the heating coil input on the right) but didnt see or hear any air coming out. I did however turn the release beside the boiler which you had recommended in your last message and two quite big puffs of air came out before some water.

Irish Steve · 06-01-2022 01:37PM

https://www.boards.ie/discussion/comment/118426143#Comment_118426143

The air release on the tank should be fully automatic as long as the small cap on the valve is not tightened down, that's the beauty of them, they just do what they're there for. The fact that you got air from the firebird safety valve tends to confirm the thinking of air in the boiler expanding when the boiler is first lit, causing the level rise, and getting air out of it makes worth considering putting an automatic air valve on that line out of the boiler.

Good luck with the resolution, it's certainly not the normal run of the mill fault that is more common.

stooge · 06-01-2022 02:42PM

guys, thanks very much for your help, advice and replies. Between the venting of air at the boiler and the coil, and the setting of the pipe and boiler stat I think we might have cracked it or at least narrowed down the issue.

I have just put the boiler on and can see water expanding in the F&E but not now causing overflow, rads all heating (apart from the one problem rad that needs replacing (will isolate this). So, system seems to be operating ok for now. Still need to figure out how the air is coming in, but at least my attic is dry (for now!) 👍️ Thanks again.

John.G · 06-01-2022 02:46PM

What were the Boiler stat and the pipe stat settings?

What are they now?

stooge · 06-01-2022 02:51PM

https://www.boards.ie/discussion/comment/118426911#Comment_118426911

Boiler stat was 65C, now 75C

Pipe Stat was 70C, now 90C

John.G · 06-01-2022 03:00PM

To check that the boiler stat is actually starting/stopping the boiler normally would suggest just turning it (boilerstat) to minimum and see that the burner cuts out and then return it to75C.

stooge · 06-01-2022 03:38PM

spoke too soon, happened again 😪 i.e. Boiler had been on for ~10/15mins, F&E filled up very quickly, overflow pipe kicked in but couldnt get rid quickly enough and tank overflowed onto attic (approx ~1ltr water).

John.G · 06-01-2022 03:45PM

OK, carry out that test as per post#28 just in case the boiler stat is knackered and the pipe stat is used instead.

Then measure the F&E tank lengthXwidth and the height from the normal cold level to the overflow outlet to make sure it can accomodate the expansion volume.

Irish Steve · 06-01-2022 04:48PM

Seems to me that there may be a lot more air around the system, and it's going to be trouble until it's all out.

It will take time, I think every radiator is going to have to be checked again, then the boiler again, the result you get will determine how to proceed from here.

HELP: F&E tank overflow when boiler comes on

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