Oil boiler in low water pressure location. Pump problem.

[stevef]

Hi, I have an oil boiler in a low water pressure location, ran well for 12 years, now I have a problem. And two questions.
(1) I continually have to bleed air from the pump, can't work out why. Any ideas?
(2) because of this, I am continually running down the pressure, which is already marginal. The input comes straight from the mains - which is a spring on a hill through a Victorian iron pipe.
The red on the pressure gauge of the boiler is 2.5 bar. I will NEVER get 2.5 bar, I dream of 1.5 bar!! Low pressure is a constant worry with the boiler, never have to worry about any of my water being high pressure ever. Cold water upstairs is barely on. Can I just leave my tap from mains on, so that it will continually keep pressure up (to well under 1.5 bar)? Will CH water leak back into drinking water? Is there any other problem leaving water supply to boiler on permanently?
Thank you so much to anyone who can advise.

 

[steadyon]

1. If you leave the water to the boiler on it will replenish the water in the system, taking in Oxygen and leading to rusting of radiators form inside out.
2. Without a fault in the hot water cylinder (if any) water will not pass from the central heating into the drinking water.
3. If your boiler pressure gauge is at 2.5 bar, yet your water supply never reaches that pressure, it suggests you have a problem with the boiler's expansion vessel.
4. If your water mains pressure is less than 1.3 bar, I'd suggest:
4a. Once any boiler problem is fixed, pressurise the boiler as best you can from the mains.
4b. If this pressure is less than 1 bar, get a cheap water pressure pump, something like Toolstation 36395, Put clean water in it, attach to your filling loop and pressurise the system to 1.3 bar.
4c. Renew the inhibitor in the system.

 

[stevef]

1. If you leave the water to the boiler on it will replenish the water in the system, taking in Oxygen and leading to rusting of radiators form inside out.
2. Without a fault in the hot water cylinder (if any) water will not pass from the central heating into the drinking water.
3. If your boiler pressure gauge is at 2.5 bar, yet your water supply never reaches that pressure, it suggests you have a problem with the boiler's expansion vessel.
4. If your water mains pressure is less than 1.3 bar, I'd suggest:
4a. Once any boiler problem is fixed, pressurise the boiler as best you can from the mains.
4b. If this pressure is less than 1 bar, get a cheap water pressure pump, something like Toolstation 36395, Put clean water in it, attach to your filling loop and pressurise the system to 1.3 bar.
4c. Renew the inhibitor in the system.

Thank you for getting back to me.
(1) Thank you for that
(2) I was concerned that when the water pressure was v low, and the water in the system was hot and expanding, it might push out into drinking water, is there a one-way valve?
(3) I must not have been clear, the red line of the boiler gauge is at 2.5, I never ever trouble that mark, that is why I thought leaving the mains on might not be a problem. I barely get 1bar on boiler pressure gauge.
(4b) pressure pump wont work, water supply is a trickle, so it would be pulling at nothing. Long term plan in place - building holding tank half way to spring, pipe has been laid to pumping station between that and the house (lifting water a couple of metre (elevation) from tank, a couple more to house. But system worked fine without that for 12 years when water pressure was even worse (stopped for several months).
Hope that helps explain.

 

[stevef]

Any thoughts on why I need to vent air at the pump every day, sometimes several times?

 

[John.g]

Is the circ pump on the flow or return from the boiler.
where is the expansion vessel connected into the system ie in the flow or return.
what is the make/model and setting of the circ pump
A few pictures will help.

 

[stevef]

Is the circ pump on the flow or return from the boiler.
where is the expansion vessel connected into the system ie in the flow or return.
what is the make/model and setting of the circ pump
A few pictures will help.

Thanks, I'll try to get some pictures, but its so cramped! The boiler is Firebird system 120, and the pump is Grundfos - which is the number for the model? As far as I can see, and its very hard to see, the pump is on the flow from the boiler to the tank. I can't see how the expansion tank is vessel sits, but I can probably download a schematic?

 

[stevef]

Thanks, I'll try to get some pictures, but its so cramped! The boiler is Firebird system 120, and the pump is Grundfos - which is the number for the model? As far as I can see, and its very hard to see, the pump is on the flow from the boiler to the tank. I can't see how the expansion tank is vessel sits, but I can probably download a schematic?

So, if the big orange drum is the expansion vessel, it has a silver coloured flexible pipe that joins above the pump - So I guess it fits in to the flow before the pump.

 

[stevef]

 

[stevef]

 

[SJB060685]

Any plastic pipe in the system?

 

[stevef]

Any plastic pipe in the system?

Nope, can't think of any at all. All copper apart from flexible.

 

[John.g]

Can you confirm that the pump is a "UPS 25 80 130" also very important that you double check that the flexible pipe is attached on the suction side of the pump.
You might also see what setting the pump is on, you should see i 11 & iii on the pump terminal box or maybe 1,2&3.

 

[stevef]

Can you confirm that the pump is a "UPS 25 80 130" also very important that you double check that the flexible pipe is attached on the suction side of the pump.
You might also see what setting the pump is on, you should see i 11 & iii on the pump terminal box or maybe 1,2&3.

Thanks John, the pump says UPS 25-60 130.
There are no obvious flow directions I can see marked on the pump.
But the flexi definitely fits between the boiler and the pump, and I am 90% that all this fits on the flow from the pump to the tank.
I don't know what setting the system ran at for 12 years, the plumber moved it about, but I can def say it is at iii (3) now.
Which I was surprised by, thought it was at 2. I thought I had turned boiler temp down, and speed down, to see if that helped - but obviously if so have put to 3 at some point.
Am sending non-specky son to look at pipes to see if he can confirm flow/return situ - will amend this post if he proves capable. NON- specky son has traced pipes. On the basis that when boiler is on, the flow gets hot first, agrees pump and P vessel sit on flow

 

[steadyon]

1. Because you have a boiler pressure gauge, I am assuming this is a sealed system, either combi or system boiler.
2. The boiler heats the water, which:
2a. For a combi, heats the domestic hot water is a secondary heat exchanger within the boiler.
2b. For a non-combi, heats a coil of pipe within the water stored in your hot water cylinder, thus heating it.
2c. In either case the hot water from the boiler is circulated in the space heating system. (Radiators, under floor).
3. The system need to be pressurised. The normal pressure is around 1.3 bar with the system cold. The pressure should stay at or around this pressure whenever the system is cold. Over time, micro leaks allow the pressure to drop, but it shouldn't need topping up more than once or twice a year.
4. As the system water heats, it expands, and this expansion is accommodated in the expansion vessel (usually red / orange). Depending on the size of your system and the capacity of the expansion vessel heating will result in a slight increase in pressure.
5. If you check the reference example given for the pump you will note that it is not an automatic pump. Rather it can be used to manually raise system pressure to 1.3 bar (or whatever) and then be disconnected. This is only necessary if the mains pressure is insufficient to get the system pressure to an acceptable level.

 

[John.g]

Its quite unusual (impossible??) to get large amounts of air that you seem to be venting each day on a sealed/pressurized system except that there is a bad blockage between the flexible hose and/or where it is attached to the pipework. If it is clear then with the boiler/pump off get some one to watch the pressure gauge and then restart the boiler/pump and you should see the pressure gauge rising a little.
One way or the other I would suggest verifying that the piping/flexy is not blocked right into the E.vessel, it probably will involve system drain down but you have to start somewhere. If you do so, check/set the E.vessel pressure (air end) at 0.75bar and then when filling shut the filling valve at 1.3 bar, this will give ample static head for upstairs rads except you are living in a castle.

 

[stevef]

1. Because you have a boiler pressure gauge, I am assuming this is a sealed system, either combi or system boiler.
2. The boiler heats the water, which:
2a. For a combi, heats the domestic hot water is a secondary heat exchanger within the boiler.
2b. For a non-combi, heats a coil of pipe within the water stored in your hot water cylinder, thus heating it.
2c. In either case the hot water from the boiler is circulated in the space heating system. (Radiators, under floor).
3. The system need to be pressurised. The normal pressure is around 1.3 bar with the system cold. The pressure should stay at or around this pressure whenever the system is cold. Over time, micro leaks allow the pressure to drop, but it shouldn't need topping up more than once or twice a year.
4. As the system water heats, it expands, and this expansion is accommodated in the expansion vessel (usually red / orange). Depending on the size of your system and the capacity of the expansion vessel heating will result in a slight increase in pressure.
5. If you check the reference example given for the pump you will note that it is not an automatic pump. Rather it can be used to manually raise system pressure to 1.3 bar (or whatever) and then be disconnected. This is only necessary if the mains pressure is insufficient to get the system pressure to an acceptable level.

Thanks Steadyon, correct with (1), the system is as 2b. Re (5) you mean the CH/HW pump? I'm confused! Or do you mean an additional pump to get the water pressure from mains higher?

 

[stevef]

Its quite unusual (impossible??) to get large amounts of air that you seem to be venting each day on a sealed/pressurized system except that there is a bad blockage between the flexible hose and/or where it is attached to the pipework. If it is clear then with the boiler/pump off get some one to watch the pressure gauge and then restart the boiler/pump and you should see the pressure gauge rising a little.
One way or the other I would suggest verifying that the piping/flexy is not blocked right into the E.vessel, it probably will involve system drain down but you have to start somewhere. If you do so, check/set the E.vessel pressure (air end) at 0.75bar and then when filling shut the filling valve at 1.3 bar, this will give ample static head for upstairs rads except you are living in a castle.

Thanks John, a very small castle - its a large farmhouse, quite a big system.
The plumber drained and filled the system, which takes a long time with my dribble supply and low pressure. When the system runs, yes, the pressure goes up. I've established that in line with your suggestion.
I will struggle to get 1.3 bar, but I've had the system running fine even when water supply stopped entirely for months. At one point I had to pressurise with 400m hosepipe from "next door", which was fun. But system runs well on much less pressure than I have now.
I too am completely confused how this air is getting into pump. Its why I turned the boiler down, in case (?) boiling water was creating steam buildup. Hey! I'm clutching at straws here!

 

[John.g]

Once the system is topped up then it should only need re pressurizing once/twice a year if no leaks, 1/1.3 bar is quite sufficient to satisfy the static head of a two storey house as its the pump that supplies the circulating force or differential head to force the water around the system so that 6m pump might produce a circulating head of say 2.5/3M on speed 3 with all systems opened up.
I use the PRV (safety valve) on my boiler to vent any air after a drain down, some don't recommend this as it may leak but I have a very clean system with the same PRV for 15 years, if you just turn the knob very slowly anti clockwise this will lift the valve off its seat and release any air, of course a air release valve would be preferable, this is the only part of my system that has to be vented from the top of the boiler otherwise I would be venting air from the rads for days.
I run my boiler at 75C . Presume your boiler flow temp and stat is accurate.
Unlikely that the pump is drawing in air but have you checked the brass pump vent as I think it should have a O ring or suchlike to seal it.
When the system is running have you checked that any of the rads arn't pulling in air when you open their vent screws.
Can't think of anything more obvious right now.

You could consider installing a AAV (automatic Air Vent) on the boiler top but I detest them as they either block up or leak, I would fit a manual bottle vent that you have control over.

 

[stevef]

Once the system is topped up then it should only need re pressurizing once/twice a year if no leaks, 1/1.3 bar is quite sufficient to satisfy the static head of a two storey house as its the pump that supplies the circulating force or differential head to force the water around the system so that 6m pump might produce a circulating head of say 2.5/3M on speed 3 with all systems opened up.
I use the PRV (safety valve) on my boiler to vent any air after a drain down, some don't recommend this as it may leak but I have a very clean system with the same PRV for 15 years, if you just turn the knob very slowly anti clockwise this will lift the valve off its seat and release any air, of course a air release valve would be preferable, this is the only part of my system that has to be vented from the top of the boiler otherwise I would be venting air from the rads for days.
I run my boiler at 75C . Presume your boiler flow temp and stat is accurate.
Unlikely that the pump is drawing in air but have you checked the brass pump vent as I think it should have a O ring or suchlike to seal it.
When the system is running have you checked that any of the rads arn't pulling in air when you open their vent screws.
Can't think of anything more obvious right now.

You could consider installing a AAV (automatic Air Vent) on the boiler top but I detest them as they either block up or leak, I would fit a manual bottle vent that you have control over.

Thank you John, loads to think about here, can you tell me where to find / what to look for with regard to the "brass pump vent" ? presumably this is not just the bleed at the end of the pump ?

 

[John.g]

That's it, in the pump end.

 

[stevef]

That's it, in the pump end.

Ah, no, its got an o ring, and I know its fine because when I open it to vent, I get steam out, not air in! But thanks for the ideas, will take further.

 

[John.g]

I think you will definitely have to vent at the boiler top especially if the flow pipe turns down when it exits the boiler so air is trapped in the boiler top like mine, also a Firebird, which is a heat pack (boiler in a outside metal box) my circ pimp is on the boiler return in a open vented system. Sometimes, the presence of a lot of air results in the hi limit stat locking out the boiler.

 

[stevef]

I think you will definitely have to vent at the boiler top especially if the flow pipe turns down when it exits the boiler so air is trapped in the boiler top like mine, also a Firebird, which is a heat pack (boiler in a outside metal box) my circ pimp is on the boiler return in a open vented system. Sometimes, the presence of a lot of air results in the hi limit stat locking out the boiler.

Sure, but I can't understand why once it is all clear of air, it keep gathering more, and at the pump. It took me a long time to work out the problem with the HW/CH - the pump was spinning in air! What confuses me is that after a dozen years, something has changed, and that something means there is always air in the pump. I feel once I know what has changed, I can resolve it. Plumber spent 6 hours here and never got to the bottom of it!

 

[exedon2]

Reading through all this is what your saying is that you keep having to vent pump but when you do vent it you get steam?
Are you having to re set over heat stat?
Assuming boiler stat is OK steam in pump is probably a circulation problem.

 

[stevef]

Reading through all this is what your saying is that you keep having to vent pump but when you do vent it you get steam?
Are you having to re set over heat stat?
Assuming boiler stat is OK steam in pump is probably a circulation problem.

Thanks for reading through Exedon2. Nope, everything seems fine, all that happens is that the boiler starts, then goes off and stays off. Because the hot water stays in the boiler. Until I vent at the pump. When I have the air and steam out of the pump, and I get dribble of water, the pump works to circulate water, and the hot water to the tank gets warm, the colder water returns, the boiler refires as it should do. A day passes, or less.
Rinse and repeat. At least I have HW now and presumably CH. Its just that I have to give the system a chance to run itself, then give up and vent, and then it seems to work normally. At least herself gets a hot bath without kettles, and I get to live another day. But then it all starts again.

 

[John.g]

Logically. if there is air ingress then some part of the system must be running with negative pressure which might point to a blockage somewhere in the system. I would still prove the E.vessel and associated pipework correct and totally clear.
As a very basic check just remove the plastic cover at the EV air end and press the schrader valve with your finger, air only should come out.
You could also get a bicycle pump and increase the whole system pressure from the EV air end but only by 0.3bar or so as you are reducing its effective volume.

 

[stevef]

Logically. if there is air ingress then some part of the system must be running with negative pressure which might point to a blockage somewhere in the system. I would still prove the E.vessel and associated pipework correct and totally clear.
As a very basic check just remove the plastic cover at the EV air end and press the schrader valve with your finger, air only should come out.
You could also get a bicycle pump and increase the whole system pressure from the EV air end but only by 0.3bar or so as you are reducing its effective volume.

Ok, I'm going to look at that. I'll google some of those words, eg schrader, and that will give me an idea what to look for. This is new ground for me.

 

[John.g]

Its just a car type valve at the air end of the E.vessel.

Regarding the "steam" one must remember that the overtemp stat on the Firebird doesn't operate until ~ 110/113C so as pointed out above the pump could be "lazy" or on the way out but you possibly would see a slow HW cylinder warm up time and slow rad heating.

If the HW coil flow and return pipes have a big temperature difference on HW only then this may indicate poor circulation as well.

 

[stevef]

Its just a car type valve at the air end of the E.vessel.

Regarding the "steam" one must remember that the overtemp stat on the Firebird doesn't operate until ~ 110/113C so as pointed out above the pump could be "lazy" or on the way out but you possibly would see a slow HW cylinder warm up time and slow rad heating.

I think I might have been on those lines when I reduced temp of boiler. Gotcha re valve, I'm going to progress some of these points tomorrow. I've turned the pump down to 2, which is where I thought it was, and retry.

 

[stevef]

I've just thought of something. While I'm trying to fix the problem, I'm not using the timer control unit. I'm just leaving HW on permanently, and using the power to the whole system. Is there a system by which the pump carries on after the timer goes off? To run the heating water around for a while? I can see how this might cause a problem if it can't run any air around to the bleed upstairs by the tank??

 

[John.g]

What you can do is just run the circ pump from a extension lead and plug and vent away (cold) for as long as you like, just latch open manually, any zone valves.

 

[stevef]

What you can do is just run the circ pump from a extension lead and plug and vent away (cold) for as long as you like, just latch open manually, any zone valves.

Right John, I'll do that if (when) I need to. Today water was less than luke, after she had her bath last night. I started today with no bleeding, at pump or anywhere, and it worked fine, could tell immediately I had circulation, and boiler came on and off as you would expect (so HW not stopping in boiler). Wondering if everything I tweaked was irrelevant, just had to purge and purge and purge, and now its there or getting there. One swallow isn't a summer, but I have hope. See what tomorrow brings.

 

[John.g]

Is there anyway you can purge/check for air in the boiler top, I wouldn't be happy that you havn't got a intermittent pump problem unless I could do this via the PRV of whatever.

 

[stevef]

Is there anyway you can purge/check for air in the boiler top, I wouldn't be happy that you havn't got a intermittent pump problem unless I could do this via the PRV of whatever.

I'm away from home until this evening, and then I'll look to see whether there is a way to purge there. I always hear the pump working, it seems to be a question of whether spinning in air or water. It always seems that bleeding the pump fixes the problem for that burn, but air then seems to collect there again - unless there was another sort of pump problem you were thinking of?

 

[stevef]

Is there anyway you can purge/check for air in the boiler top, I wouldn't be happy that you havn't got a intermittent pump problem unless I could do this via the PRV of whatever.

Hi John, back late. But I have run the system again without problem. You asked about way to purge at boiler top. Is this it? And if so, is it obvious what to do with it?