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l have a conventional vented fully pumped system from an oil-fired boiler on the ground floor. HW tank is in the 1st floor airing cupboard along with the pump and 3-port valve. 22mm vent pipe rises through the airing cupboard up to the F&E tank in the loft where it rises some 600mm before dropping back to the tank. HW feed tees off the rising vent pipe in the airing cupboard through an air separator then to the pump inlet with the cold feed in between. All was working fine until a recent pump failure. This was duly replaced but then found there was a degree of pumping over even on the pumps lowest speed. It is the correct pump for the installation. Rectified this by re-routing the cold feed into the vent pipe approx. 250mm above the air separator. Cleaned out the air separator and pipework to pump while at it. BUT, now have occasional flow stoppage around the CH circuit? Programmer and 3-port valve/controller all checked OK. Local heating engineer scratching his head as is one of his colleagues who he brought along for a 2nd opinion. Would be very grateful for any suggestions as to where o go from here....
 
First thoughts on an open system on oil or gas is would it be suitable to have it a sealed system.
 
Nervous about converting to a sealed system as the CH has microbore pipework and is 38 years old. As for the pump, the old one was a fixed speed Wilo, not sure of the model. The new pump is a 3 speed Grundfos UPS2 15-50/60. House has 14 rads but usually only 8 in use now with just 2 of us in the house.
 
Nervous about converting to a sealed system as the CH has microbore pipework and is 38 years old. As for the pump, the old one was a fixed speed Wilo, not sure of the model. The new pump is a 3 speed Grundfos UPS2 15-50/60. House has 14 rads but usually only 8 in use now with just 2 of us in the house.
look it worked before, so thats what needs fault finding ...not altering ...aww I will have a look later centralheatking
 
Nervous about converting to a sealed system as the CH has microbore pipework and is 38 years old. As for the pump, the old one was a fixed speed Wilo, not sure of the model. The new pump is a 3 speed Grundfos UPS2 15-50/60. House has 14 rads but usually only 8 in use now with just 2 of us in the house.
In my opinion as an old very experienced fart ....

if your system is 38 years old and has been a good friend until this new pump...then on the dont fix what is not broken principle
I would look very seriously atbthe pump. Who says its ok ?
its obviously not ! centralheatking
 
Re "combined cold feed and vent" that you now have. Originally you had a air separator with 3 pipes?, the inlet at one side, the vent from the top & the outlet to the pump with the cold feed in between the vent & pump?.. Now after this modification, I presume you still have a 3 pipe set up as above, the only difference is now that the cold feed is teed in to the separator vent but the separator outlet pipe is still going to the pump, is this correct?. I am just wondering if the mod is somehow allowing air to be drawn into the pump suction.
I have a combined cold feed & vent system from first install 42 years ago but no air separator, the cold feed is teed directly into the vent which passes up (and then over) adjacent to the F&E tank.

The UPS2 was pumping over even at fixed speed 1 so you teed (as above) in the cold feed to the vent, this cured the pump over but you now have a occasional problem with the CH. Did you try fixed speed 2 or even 3 after this.
Now this suggestion is at odds to what I just said above but you might consider just changing over the pump setting to (proportional pressure) PP 3, this is even a lower setting than the fixed speed 1 but worth a try. You just press and hold the button for > 5 secs to get a flashing green LED and then select PP3 and see how it goes. (page 7 of 16, in attachment).
Of course as stated above you could have a pump problem, if under warranty, you can get a new one and just change the pump heads. I have a Wilo Yonis Pico 1-6 which is working very well on PP control with 10 rads.
 

Attachments

  • Grundfos UPS2.pdf
    7.2 MB · Views: 18
That's a very good point but which pump?
I work on the complicated is easy and simple is hard principle in my plumbing and heating design business. So keep your new pump it cost plenty I expect, just stick an adjustable valve just beyond it
like a gate valve and make the pump behave according to what you want and how the old Wilo did ...you can then dick around with the gate to achieve happyness centralheatking
 
Re "combined cold feed and vent" that you now have. Originally you had a air separator with 3 pipes?, the inlet at one side, the vent from the top & the outlet to the pump with the cold feed in between the vent & pump?.. Now after this modification, I presume you still have a 3 pipe set up as above, the only difference is now that the cold feed is teed in to the separator vent but the separator outlet pipe is still going to the pump, is this correct?. I am just wondering if the mod is somehow allowing air to be drawn into the pump suction.
I have a combined cold feed & vent system from first install 42 years ago but no air separator, the cold feed is teed directly into the vent which passes up (and then over) adjacent to the F&E tank.

The UPS2 was pumping over even at fixed speed 1 so you teed (as above) in the cold feed to the vent, this cured the pump over but you now have a occasional problem with the CH. Did you try fixed speed 2 or even 3 after this.
Now this suggestion is at odds to what I just said above but you might consider just changing over the pump setting to (proportional pressure) PP 3, this is even a lower setting than the fixed speed 1 but worth a try. You just press and hold the button for > 5 secs to get a flashing green LED and then select PP3 and see how it goes. (page 7 of 16, in attachment).
Of course as stated above you could have a pump problem, if under warranty, you can get a new one and just change the pump heads. I have a Wilo Yonis Pico 1-6 which is working very well on PP control with 10 rads.
 
Re "combined cold feed and vent" that you now have. Originally you had a air separator with 3 pipes?, the inlet at one side, the vent from the top & the outlet to the pump with the cold feed in between the vent & pump?.. Now after this modification, I presume you still have a 3 pipe set up as above, the only difference is now that the cold feed is teed in to the separator vent but the separator outlet pipe is still going to the pump, is this correct?. I am just wondering if the mod is somehow allowing air to be drawn into the pump suction.
I have a combined cold feed & vent system from first install 42 years ago but no air separator, the cold feed is teed directly into the vent which passes up (and then over) adjacent to the F&E tank.

The UPS2 was pumping over even at fixed speed 1 so you teed (as above) in the cold feed to the vent, this cured the pump over but you now have a occasional problem with the CH. Did you try fixed speed 2 or even 3 after this.
Now this suggestion is at odds to what I just said above but you might consider just changing over the pump setting to (proportional pressure) PP 3, this is even a lower setting than the fixed speed 1 but worth a try. You just press and hold the button for > 5 secs to get a flashing green LED and then select PP3 and see how it goes. (page 7 of 16, in attachment).
Of course as stated above you could have a pump problem, if under warranty, you can get a new one and just change the pump heads. I have a Wilo Yonis Pico 1-6 which is working very well on PP control with 10 rads.
Note your suggestion re switching pump to PP3 but was also thinking of cleaning out the pipework again twixt air separator and pump as there's some magnetic activity here. Would it be worth getting rid of the air separator while at it and tee straight into the vent pipe from the pump? You could be right about air being drawn in....
 
Note your suggestion re switching pump to PP3 but was also thinking of cleaning out the pipework again twixt air separator and pump as there's some magnetic activity here. Would it be worth getting rid of the air separator while at it and tee straight into the vent pipe from the pump? You could be right about air being drawn in..
yup simplify the whole set up , then you reduce the variable problems ...centralheatking
 
Your original pump over problem was probably due to the fact that the UPS2 pump (>6m pump @ speed3 and still a 4M pump @speed1) was more powerful than the one it replaced, speed1 on the ups2 is probably more powerful than speed2 on your old pump).

However that's history now and you must deal with what you have.
You "now have occasional flow stoppage around the CH circuit", how was this manifesting itself, was it colder rads or boiler short cycling or tripping on Hi limit stat? or whatever.

I would first check for any blockages in view of the magnetic activity, also remove the pump and/or pump head and check for blockages in the pump casing ports and in the pump impeller itself. Depending on what you find then you may then decide to get rid of the air separator, I just don't like the idea of the cold feed teeing into the separator vent even though it stopped the pump over.
As a interim measure if you are happy that the pump isolation valves are holding, why not just remove the pump head and inspect the ports & impeller and flush out from both sides. Dare I say it, ensure that the replacement pump has been installed properly and is pumping in the "right" direction.
 
Your original pump over problem was probably due to the fact that the UPS2 pump (>6m pump @ speed3 and still a 4M pump @speed1) was more powerful than the one it replaced, speed1 on the ups2 is probably more powerful than speed2 on your old pump).

However that's history now and you must deal with what you have.
You "now have occasional flow stoppage around the CH circuit", how was this manifesting itself, was it colder rads or boiler short cycling or tripping on Hi limit stat? or whatever.

I would first check for any blockages in view of the magnetic activity, also remove the pump and/or pump head and check for blockages in the pump casing ports and in the pump impeller itself. Depending on what you find then you may then decide to get rid of the air separator, I just don't like the idea of the cold feed teeing into the separator vent even though it stopped the pump over.
As a interim measure if you are happy that the pump isolation valves are holding, why not just remove the pump head and inspect the ports & impeller and flush out from both sides. Dare I say it, ensure that the replacement pump has been installed properly and is pumping in the "right" direction.
As for the occasional flow stop round the CH circuit, all will be working perfectly well for a few hours then the flow would just stop. I can restart by switching off the CH, switching on the HW circuit then switching the CH back on again - air somewhere around the 3-port valve? Interestingly, there were no CH flow problems when the cold feed was between pump and air separator. After your very helpful comments, now thinking about piping cold back to where it was, get rid of the air separator and then deal with the pump pressure if the pump over returns. On setting one, the pump over was approx. o.5l per min so not a great rate. Could well be sorted by your earlier suggestion of dropping down to one of the PP settings.
 
I hope you havn,t got some problem with the 3 port valve, a bit suspicious.
The UPS2 is a poor choice when using PP control as the three settings are too close together, the max (PP3) setting is 3.0M but in a 6 M pump should really have 4 or 5 settings up to 5.5m to give you the required flow when all systems are open, for example I have my PP setting (Wilo) at 4.0M (up to PP 6.0 M available) to give me that required flow, it then ramps down with the throttling of the TRVs. You may have a low resistance system so why not just change over now to PP3 and see how you get on?, you will soon know if all the rads arn't heating up.
That pump over of "only" 0.5 LPM will very quickly corrode your system and shouldn't be tolerated under any circumstances.
I know I'm repeating myself but be happy that the pump is pumping in the right direction first.
 
I hope you havn,t got some problem with the 3 port valve, a bit suspicious.
The UPS2 is a poor choice when using PP control as the three settings are too close together, the max (PP3) setting is 3.0M but in a 6 M pump should really have 4 or 5 settings up to 5.5m to give you the required flow when all systems are open, for example I have my PP setting (Wilo) at 4.0M (up to PP 6.0 M available) to give me that required flow, it then ramps down with the throttling of the TRVs. You may have a low resistance system so why not just change over now to PP3 and see how you get on?, you will soon know if all the rads arn't heating up.
That pump over of "only" 0.5 LPM will very quickly corrode your system and shouldn't be tolerated under any circumstances.
I know I'm repeating myself but be happy that the pump is pumping in the right direction first.
Pump is the correct way round and the 3 port valve is a new one fitted recently when the cold feed was switched to the vent pipe. As for a low resistance system, the central heating circuit is microbore and the hot water is a combination of 22mm and 28mm. One thing I have noticed with the current problem of the CH flow stopping is that it seems to occur after approx. 5 hrs each time. I then need to switch off the CH and run the hot water circuit only for a few minutes. If I then switch on the CH again the flow resumes. Build up of air over the 5 hrs possibly via the air separator? As mentioned previously this problem didn't occur when the cold feed was between the pump and air separator but then of course I had the pump over problem.....
 
As for the occasional flow stop round the CH circuit, all will be working perfectly well for a few hours then the flow would just stop.
There are several reasons why the flow could stop:
1. The room stat has reached temperature
2. The programmer has turned CH Off
3. The boiler has been turned off by the limit stat to prevent overheating
4. The pump has stopped
5. The 3 port valve has moved to HW only.

Assuming you have already checked 1, 2 and 3, that leaves 4 and 5.

4 is easy to check: the pump light will go out. You can also hear the pump working if you put the point of a screwdriver against the pump and hold the handle against you ear.

5 can be checked by moving the lever of the 3 port valve from Auto to Man. If there is resistance and the lever moves back to Auto when released, the valve is in the HW position. If the lever is loose in the slot, the valve is in either mid or CH position.
 
Pump is the correct way round and the 3 port valve is a new one fitted recently when the cold feed was switched to the vent pipe. As for a low resistance system, the central heating circuit is microbore and the hot water is a combination of 22mm and 28mm. One thing I have noticed with the current problem of the CH flow stopping is that it seems to occur after approx. 5 hrs each time. I then need to switch off the CH and run the hot water circuit only for a few minutes. If I then switch on the CH again the flow resumes. Build up of air over the 5 hrs possibly via the air separator? As mentioned previously this problem didn't occur when the cold feed was between the pump and air separator but then of course I had the pump over problem...

The 5 points raised above are well worth considering, point 3 can probably be ruled out though as you would have had to reset the Hi lmit stat manually at the boiler.
Your own suggestion of air build up is another one as the pump might start losing suction after a number of hours, then you clear it by c/o to HW which gives the pump a easier flow path?.

What alerts you to the CH flow stopping?.

Re the system resistance, the reason I ask if that if you do change the cold feed to its original position then you will probably have to go to pump PP setting PP3 which on the UPS2 is "weak" and may not supply enough flow to satisfy both CH&HW together and you may as well try it out now before changing any pipework.
 
The 5 points raised above are well worth considering, point 3 can probably be ruled out though as you would have had to reset the Hi lmit stat manually at the boiler.
Your own suggestion of air build up is another one as the pump might start losing suction after a number of hours, then you clear it by c/o to HW which gives the pump a easier flow path?.

What alerts you to the CH flow stopping?.

Re the system resistance, the reason I ask if that if you do change the cold feed to its original position then you will probably have to go to pump PP setting PP3 which on the UPS2 is "weak" and may not supply enough flow to satisfy both CH&HW together and you may as well try it out now before changing any pipework.
Checked all of your 5 of points and no problems there. The alert for the stopped CH flow comes simply from all the rads cooling when the rooms are still cooling for heat usually after around 5 or so hrs which, as mentioned previously, I then clear by c/o to HW for a few minutes. One point I did forget to mention originally, when the cold feed was in the original position (no problems with CH flow then), was the pump over only occurred when the HW circuit (less resistance) was switched in either with or without CH. Too high pump pressure even on 1? I'll try your suggestion of PP3 later this afternoon and report back although I'll only be able to determine if there's enough pressure to push the water around both CH and HW. If it works do I then revert to the original cold feed position and hope that the reduced pressure stops the pump over? Many thanks for taking an interest in my conundrum, very much appreciated.
 
22mm vent pipe rises through the airing cupboard up to the F&E tank in the loft where it rises some 600mm before dropping back to the tank.
1. What is the distance between the water level in the tank and highest point of the vent pipe (i.e top of the bend)?

2. How deep is the water in the tank when boiler is running?
 
Checked all of your 5 of points and no problems there. The alert for the stopped CH flow comes simply from all the rads cooling when the rooms are still cooling for heat usually after around 5 or so hrs which, as mentioned previously, I then clear by c/o to HW for a few minutes. One point I did forget to mention originally, when the cold feed was in the original position (no problems with CH flow then), was the pump over only occurred when the HW circuit (less resistance) was switched in either with or without CH. Too high pump pressure even on 1? I'll try your suggestion of PP3 later this afternoon and report back although I'll only be able to determine if there's enough pressure to push the water around both CH and HW. If it works do I then revert to the original cold feed position and hope that the reduced pressure stops the pump over? Many thanks for taking an interest in my conundrum, very much appreciated.

The reduced pressure should stop that pump over, I have attached a S.sheet which I made for a friend of mine who is (still) considering the UPS 2 as a replacement and I did it on two different assumptions based on speed 1, the first assumes a flowrate of 15LPM@3M, this would fall to 12LPM@1,92M on PP3, the second assumes [email protected], this would fall to [email protected] on PP3.
You can all ways go to a lower PP setting if you still have pump over.
 

Attachments

  • Grundfos UPS 2 PP3 Calculations.zip
    10.4 KB · Views: 8
The reduced pressure should stop that pump over, I have attached a S.sheet which I made for a friend of mine who is (still) considering the UPS 2 as a replacement and I did it on two different assumptions based on speed 1, the first assumes a flowrate of 15LPM@3M, this would fall to 12LPM@1,92M on PP3, the second assumes [email protected], this would fall to [email protected] on PP3.
You can all ways go to a lower PP setting if you still have pump over.
 
OK, I've now tried the PP3 setting and as you suspected there doesn't appear to be enough pressure to satisfy both CH and HW. Fine on CH only but rads cool off when HW switched in. Once HW up to temp, rads warm up again. This of course doesn't take into account any recent furring up of the pipe section from air separator to pump. As for your other questions, the distance from water level in tank to top of bend in vent pipe is 700mm and water depth in tank when hot is 180mm
 
Yes, I thought that might happen all right. You are sort of caught between a rock & a hard place now. Your problems were triggered by installing the UPS 2 pump, don't know what the old pump was, ie a 5M or 6M and its speed setting but in general F.speed 1 on a ups 2 would run at a higher head than speed 2 on a 5M pump at the same flow rate so maybe you were running on borderline pump over with the old pump. I was a bit surprised to see pump over before you modified the feed/vent as the feed was probably very close to the vent take off and is a very accepted way of doing things.
You might consider just running the CH alone with pump on PP3 and see what happens after that 5 hour period with special attention to points 1,2,4&5 raised by doitmyself above. If still no problems then you might consider installing a balancing valve on the cylinder coil outlet to give more flow to the rads when both HW&CW are on together and let the pump setting at PP3 with no plumbing changes.
You might take the pump or pump head off and check for blockages etc by back flushing etc.
You could replace the pump with one with higher PP settings like mine but its still strange to say the least that you can't run with the UPS 2 on F.speed 1 without incurring that CH problem.
I think you will have to try and identify why the rads are going cold after 5 hours.

Can't think of anything else just now.
 
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Yes, I thought that might happen all right. You are sort of caught between a rock & a hard place now. Your problems were triggered by installing the UPS 2 pump, don't know what the old pump was, ie a 5M or 6M and its speed setting but in general F.speed 1 on a ups 2 would run at a higher head than speed 2 on a 5M pump at the same flow rate so maybe you were running on borderline pump over with the old pump. I was a bit surprised to see pump over before you modified the feed/vent as the feed was probably very close to the vent take off and is a very accepted way of doing things.
You might consider just running the CH alone with pump on PP3 and see what happens after that 5 hour period with special attention to points 1,2,4&5 raised by doitmyself above. If still no problems then you might consider installing a balancing valve on the cylinder coil outlet to give more flow to the rads when both HW&CW are on together and let the pump setting at PP3 with no plumbing changes.
You might take the pump or pump head off and check for blockages etc by back flushing etc.
You could replace the pump with one with higher PP settings like mine but its still strange to say the least that you can't run with the UPS 2 on F.speed 1 without incurring that CH problem.
I think you will have to try and identify why the rads are going cold after 5 hours.

Can't think of anything else just now.
Thanks again for all your thoughts. Think I'll start by dismantling the pipework between air separator and pump, all within close proximity to each other, and check they're completely clear. Think I'll also reinstate the cold feed to the pump side of the vent (only a couple of inches). That'll sort the CH problem. Will then see if pump over returns on pump setting 1. If it does then I can get by using the immersion for hot water temporarily while I reconsider the pump &/or fit a balancing valve in the HW circuit.
 
As for your other questions, the distance from water level in tank to top of bend in vent pipe is 700mm and water depth in tank when hot is 180mm
They were my questions; but that's not important. The important thing is they are acceptable distances and shouldn't give rise to pumping over.

I agree with John.g that you need a balancing valve in the HW circuit (they are usually fitted on the return).

1. Do you know if the system has been balanced?
2. Do you have TRVs on the rads? If so, turn them all to max and see if you still have the problem.
 
They were my questions; but that's not important. The important thing is they are acceptable distances and shouldn't give rise to pumping over.

I agree with John.g that you need a balancing valve in the HW circuit (they are usually fitted on the return).

1. Do you know if the system has been balanced?
2. Do you have TRVs on the rads? If so, turn them all to max and see if you still have the problem.
Yep, I have TRV's on all the rads and I have tried flat out. There's no problem as far as the CH is concerned so long as the cold feed is twixt vent pipe and air separator BUT, this then introduces the pump over problem which occurs when the lower resistance HW circuit comes in. If it's still a problem after I've checked the pipework is clean and I've moved the cold feed back to its original location then as you and John have suggested, I'll look at fitting a balancing valve. The return from the coil in the HW cylinder is easily accessible.
 

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