CH venting into header

[saveasteading]

I am only replying so that I can click the follow topic button. I've got tbanging and a hot header tank  twice a day.   Probably, we think,  linked to timers and zones switching off.

 

 

Isn't it amazing that there isn't an obvious solution. It's just hot water and pipes.

[marshian]

42 minutes ago, saveasteading said:

I am only replying so that I can click the follow topic button. I've got tbanging and a hot header tank  twice a day.   Probably, we think,  linked to timers and zones switching off.

 

 

Isn't it amazing that there isn't an obvious solution. It's just hot water and pipes.

 

Often very ancient pipes and hot water

 

My house a lot of the underfloor pipes are 42 years old - System was filthy when we bought the house - probably 9 year old inhibitor - bleed a rad and the water came out black indicating a lot of corrosion in the system.

 

It's clean now but I was surprised at the level of muck in the bottom of the last original rad that I cut open when I replaced it

[Mattg4321]

This is still sounding so much like my situation from a few years back. 

I also changed the pump as a first move. 

 

I also then cut the H section out and found it clear. 
 

I removed the mid position valve and found that clear. 
 

I then decided it was very likely the heat exchanger in the boiler as it was unlikely to be anything else stopping good circulation around the primary circuit. Also open vented systems suffer with sludge build up, and I had no magnaclean. 
 

It’s interesting that my boiler is also the same as yours. 
 

You could just replace everything to fix as plumber 3 wants, but seems wrong to me. If I was you then I’d check the ‘H’ section of pipework and if it’s clear I’d be getting the same refurbed heat exchanger that has cured my problem. 
 

Assuming you can find a plumber willing to spend a couple of hours fitting it for you that is. I twisted a mates arm (quite hard it must be said!) £150 for him and £80 for the heat exchanger- which according to him looked new. 

[Peaklander]

Yes that's a good call. I had already looked at the link you sent a few days ago and I can see that they are available next day. So yes, that would be the next step.

Edited January 3 by Peaklander

[Mattg4321]

25 minutes ago, Peaklander said:

Yes that's a good call. I had already looked at the link you sent a few days ago and I can see that they are available next day. So yes, that would be the next step.

There’s no doubt it’s a slight risk. The part could be damaged, perhaps even by plumber upon fitting - who will blame  the part probably. However, if you can find someone sensible to fit it, it’s a risk worth taking imo. 
 

Those boilers are fairly bulletproof otherwise in my experience (had one in my old house for 9 years - was 14 years old in total when I sold - zero problems) and your only other option is new boiler if the heat exchanger is indeed blocked. 

[marshian]

5 minutes ago, Mattg4321 said:

Those boilers are fairly bulletproof otherwise in my experience (had one in my old house for 9 years - was 14 years old in total when I sold - zero problems) and your only other option is new boiler if the heat exchanger is indeed blocked. 

It’s not the only option because it’s clear the HE isn’t totally blocked as OP still gets HW and CH (albeit CH with some pump over into F&E tank)

 

OP hasn’t fitted magna clean yet but in preparation he could put a decent quantity of system cleaner in the circuit and see if that puts any restriction due to magnatite or sludge back into suspension

 

Personally I’m still leaning towards a pump that is over powering the circuit

 

And as @John Carroll has said they aren’t a popular choice amongst gas engineers/plumbers (not sure how the benchmark brand for circulation pumps gets itself into that situation but it seems they have)

 

If @Peaklander gets it resolved I’m hoping I can have the old selectric pump (if it has working speed selector) and I’ll cover the postage

[Mattg4321]

Heat exchanger wasn’t totally blocked on my boiler either. Just about heated the cylinder and got the rads hot for 20 mins or so, then went lukewarm. 
 

The USP3 is a very common pump. It won’t be the sole cause of pumping over on a system configuration and that has never previously pumped over imo. I think it’s pretty well nailed on that there’s some sort of obstruction/blockage on the primary circuit. All only in my opinion obviously. 

Edited January 3 by Mattg4321

[John Carroll]

31 minutes ago, marshian said:

It’s not the only option because it’s clear the HE isn’t totally blocked as OP still gets HW and CH (albeit CH with some pump over into F&E tank)

 

OP hasn’t fitted magna clean yet but in preparation he could put a decent quantity of system cleaner in the circuit and see if that puts any restriction due to magnatite or sludge back into suspension

 

Personally I’m still leaning towards a pump that is over powering the circuit

 

And as @John Carroll has said they aren’t a popular choice amongst gas engineers/plumbers (not sure how the benchmark brand for circulation pumps gets itself into that situation but it seems they have)

 

If @Peaklander gets it resolved I’m hoping I can have the old selectric pump (if it has working speed selector) and I’ll cover the postage

That pump is a relative youngster, PC0945, week 45 2009. My daughters is PC0414, week 14 2004, look at the way its installed! Upright! and still running perfectly, don't know when Grundfos manufactured the cobweb though.

Edited January 3 by John Carroll

[Peaklander]

We fitted a mag clean a few days after the pump. I cleaned it after a week and it did have some gunge and a few steel flecks.

The HE isn’t having any trouble keeping the CH plenty warm enough throughout the day.

As for restrictions, I can understand how one at the tee at the cold feed / H pipe can divert flow up the vent that’s just before it in the flow circuit but I can’t see how a restriction further round the system can do that. 

[Mattg4321]

At a guess, when you get a restriction, the pressure created by the pump causes the water to take the path of least resistance - up the Vent pipe. 

[marshian]

14 minutes ago, Mattg4321 said:

At a guess, when you get a restriction, the pressure created by the pump causes the water to take the path of least resistance - up the Vent pipe. 

 Not disagreeing with you because you are absolutely correct but the same result can be achieved with a pump set to too high a flow for the circuit - the main issue with this thread is no one knows if the situation was the same before the pump was replaced

[Peaklander]

Yes but here the vent is behind the pump, on the other side of the cold feed tee, just along the horizontal pipe in the H. So a restriction there can divert but I’m not so sure of one further along the system.

However we will see. I hope!

 

Edit: just seen the comment by @marshian above. I don’t think it’s been happening for long but something caused the initial problem of air or airlock in the system and lukewarm rads. and that was before the pump change obviously.

Edited January 3 by Peaklander

[John Carroll]

31 minutes ago, Mattg4321 said:

At a guess, when you get a restriction, the pressure created by the pump causes the water to take the path of least resistance - up the Vent pipe. 

 

The PP tests should qualify this, if you assume a present flowrate of ~ 15LPM at 3.7M (CC1) then PP2 will give a flowrate of 11.7LPM at 2.25M and PP1 will give a flowrate of 8.2LPM at only 1.15M. The minimum PP2 head is 1.7M & the minimum PP1 head is 1.0M so even if there is almost a full restriction in the H, there cannot be pumpover (assuming vent ~ 2M above F&E cistern water level) at PP1 and practically speaking no pumpover either on PP2, otherwise the pump is faulty. All will be revealed.

Edited January 3 by John Carroll

[marshian]

2 hours ago, John Carroll said:

 

The PP tests should qualify this, if you assume a present flowrate of ~ 15LPM at 3.7M (CC1) then PP2 will give a flowrate of 11.7LPM at 2.25M and PP1 will give a flowrate of 8.2LPM at only 1.15M. The minimum PP2 head is 1.7M & the minimum PP1 head is 1.0M so even if there is almost a full restriction in the H, there cannot be pumpover (assuming vent ~ 2M above F&E cistern water level) at PP1 and practically speaking no pumpover either on PP2, otherwise the pump is faulty. All will be revealed.

 

It's like a bloody good whodunnit

[Peaklander]

8 hours ago, John Carroll said:

assuming vent ~ 2M above F&E cistern water level

 

The vent pipe bends over just above the header tank. So it's just a few cm above the water level. I don't have a photo but there's not much room to accommodate a rise in the water level in the vent.

[John Carroll]

31 minutes ago, Peaklander said:

 

The vent pipe bends over just above the header tank. So it's just a few cm above the water level. I don't have a photo but there's not much room to accommodate a rise in the water level in the vent.

That changes things a lot because any blockage in the H now only has only to produce a U tube imbalance (differential head) of that "few cm" to get pumpover, reasons are becoming clearer at last.  

The combined vent & cold will almost certainly stop that but would still like to see that vent raised a little, alternatively, as a real combined vent&colf feed doesn't have an vent rising over the level of water in the F&E you can just use the cold feed and cap the vent at the H, (install a thumb vent there instead) BUT the cold feed I think, by the regs must be 22mm or more with no isolation valve, boiler must have o/temp proection as well, which yours has. So you couldn't use the existing cold feed but you could plump the existing vent into the F&E and remove the existing cold feed and install a thumb vent there, (or one of those horrible AAVs), personally, I prefer my type but you just may not be able to rise your vent even say 0.5M?.

 

Edit: Can you post a phot of the F&E cistern + water level, you may be able to lower the level in that considerably to give a little extra head, the level only needs to be 80/100mm, expansion will only rise it another 10/15mm.

Edited January 4 by John Carroll

[John Carroll]

7 hours ago, marshian said:

 

It's like a bloody good whodunnit

Anyone who is interested in PP settings can do their own calcs here, you can just put in your own pump PP settings.

 

 

UPS3 PPs Extract.xlsx

Edited January 4 by John Carroll

[Peaklander]

Sorry about not mentioning the "few cm" before - it's been on my mind and I sat there this morning scratching my head and thought about it again when I saw your reference to 2m. I will go to the house in an hour or so (need to give my parents enough time to get up and going) and post a photo.

 

I can obviously bend the float arm down a bit, in order to lower the water level. The tank is pushed tight against low rafters and there's not much scope to lift the bend on the vent. It must have been a finely balanced set-up and then I came along and changed the pump.

 

Rather than go your combined feed/vent @John Carroll, Plumber #2 wants to remove the header and set-up an expansion vessel with PRV and fill loop. We have discussed it and will do it as long as we just set a very low pressure. I don't want to find any leaks in the pipework. He will re-pipe the H anyway and the vessel will physically go in place of the header but I will examine that H cross-pipe to see what I can see.

 

I'm starting to think that the sequence of events was:

 

1. Lack of corrosion inhibitor and no mag filter, caused some sludge and a little gas to be formed that probably turned into an airlock. This caused the boiler to constantly trip out and in, without getting the radiators to heat.

 

2. Air removed and pump changed and system cleaner and filter added.

 

3. System flushed, sludge removed and all ok except the pump over.

 

4. The new pump has highlighted the lack of tolerance there is with such a low vent to water level differential.

Edited January 4 by Peaklander

[John Carroll]

Do those PP tests anyhow.

[Peaklander]

14 hours ago, marshian said:

Oh that's a good call - I guess they did isolate when the pump was changed or maybe a partial draindown was carried out so no need to close the isolation valves??

 

I changed the pump and I will double-check the valves when I go there this morning.

 

Plumber #2 says that they are very fragile, having sat there for years and they can break when operated.

[marshian]

16 minutes ago, Peaklander said:

 

I changed the pump and I will double-check the valves when I go there this morning.

 

Plumber #2 says that they are very fragile, having sat there for years and they can break when operated.

 

Yes they are - but it's only a few quid to replace them and if you are doing a partial drain down it's the ideal time to swap them out.

 

One of mine wouldn't close when I replaced it (wouldn't fully open either) it did free off with a lot of persuasion but I didn't know that until after replacement - they were both 40 years old which is a pretty good innings I thought

[Peaklander]

Ok some pics plus my father is having some sort of issue which I’m keeping an eye on.

 

This is the first setting and the water flow over.

 

 

This is PP2 with reduced water that sounds worse than it is. That just means I should have looked and not listened.

 

 

 

There is scope to lift the height of the vent.

 

Edit. Obviously the water colour is still not good and it will need a further clean. 

Edited January 4 by Peaklander

[marshian]

OK so pump over can be reduced but even on lowest pump speed/pressure it's still there.

 

@John Carroll for the cheap seats just explain to me how lowering the water level in the F&E tank would help

 

Is it that you lower the level in the F&E Tank and as a result you lower the level in the vent pipe so potentially reduce the opportunity for pump over and you are effectively lowering the overall head - I'm struggling to get my head round it (also my F&E tank when system is running is a few mm below the overflow pipe)

[John Carroll]

1 hour ago, Peaklander said:

Ok some pics plus my father is having some sort of issue which I’m keeping an eye on.

 

This is the first setting and the water flow over.

 

 

This is PP2 with reduced water that sounds worse than it is. That just means I should have looked and not listened.

 

 

 

There is scope to lift the height of the vent.

 

Edit. Obviously the water colour is still not good and it will need a further clean. 

Do the LEDs flash when changing modes/settings, don't know if this is for your particular pump or not but its showing pulsating LEDs in PP or CP mode?

[Peaklander]

Yes the yellow leds flash on those variable speed modes - just needed to catch it right with the phone otherwise they are OFF!

 

I haven't gone to PP1. I will leave until Tuesday and I suspect that Plumber #2 will want to remove the tank as I said. I think I can risk that. Screwfix have the parts ready for me to pick-up.

 

My job will be to bail-out the header although as it's circulating around anyway, perhaps I can let most drain out first and then bung it up.