Any Heating engineers / plumbers on Briskoda - Hot water issue

[mannyo]

Help..

 

My hot water is only getting luke warm at best. The below maybe a bit all over the place but they are as I think this through.

 

Setup info:

 

Grant Oil fired boiler, with two pipes in/out leading to airing cupboard.

In the airing cupboard the boiler output is fed into an electronic switch that operates between hot water and heating.

Pump is a Grundfos Super Selectric.

 

Whats happening, I think is all down to air but how can I bleed this thing.

 

Switch on heating, you can hear the switch change over, get gurgling sound through pipes which stabilises. Radiators get lovely and hot quiet quickly, however one radiator in the system is always getting air trapped and requires regular bleeding to keep it clear of air.

 

Electronic changeover is working because when on hot water the radiators remain cold, and get hot when switched to heating.

 

This evening I bled the radiators to check no air, then switched the heating (not hot water yet) on. Gurgling through pipes, let it run for 15mins, switched it off. Radiators all hot. Now bled this single radiator again, and trapped air released.

 

Is there anyway I can bleed all the air from the system without it running as its apparent must be a lot of air in it currently.

 

Both me and next door, farm cottage semis have the same system design and both have the same issue with exactly the same radiator always getting air. Been like it since I moved in six years ago, just bleed the radiator every week in winter. Property is rented, so trying the usual before getting the landlord involved.

Edited 9 October, 2016 by mannyo

[Rustynuts]

The problem is either air being pulled down an open vent pipe, or chemical reactions going in in the system which is producing gas (not air) in the system. The first option is the usual cause.

 

Essentially, if the cold feed and vent from the header tank are piped in incorrectly then it means the pump sucks air down the vent into the system.  Unless you have a sealed system, that is, in which case are you topping up the pressure when you bleed the radiators?

 

Edit: Or it might be the other way round and it's pulling oxygenated water down the cold feed and squirting water up the open vent.

Edited 9 October, 2016 by Rustynuts

[GentleGiant]

This was my thought as well; if you constantly have trapped air, it has to be getting in from somewhere. Another culprit might be the pump, check the seals to see if they feel damp, remember metal expands when hot, however we had a Grundfos system that ran flawlessly for many years..

 

Identical systems with identical issues sounds more like a install cockup though.

[mannyo]

its an open as opposed to sealed system, the pipework in the airing cupboard is an intricate piece of work. Access to half of it is impossible, tiny cupboard loads of pipes/wiring all squeezed into such a tiny space.

 

I've just finished repeatedly cycling between heating and hot water removing yet more air. Now seems quieter so running the system for 20mins on hot water to see if I get hot or luke warm water.

 

I've tried each of the three pump speeds, on the fast one it sounds a whole lot worse than number 1.

[Rustynuts]

Sometimes it happens that the system works fine on 1 or 2, but putting it up to 3 means it sucks air in. I'd try it on the lower speeds.

Can you take a pic of the pipework & pump etc.?

Edited 9 October, 2016 by Rustynuts

[mannyo]

Pics coming up, although the pipework is all over the place.

[mannyo]

Some pics, stupid iPhone has rotated them. Floor is right, ceiling is left.

Edited 9 October, 2016 by mannyo

[mac11irl]

I was hope youd say floor was left....

that would be

a - awesome

b - probably the problem...

[Rustynuts]

I take it the motorised valve has 3 pipes going to and from it?

[mannyo]

Yes

 

One closest is the heating, then the feed from boiler, by back wall is hot water. I dont know if the pump is pushing or pulling, maybe you can tell by the picture in which case the water flow will be the opposite of the annotated picture.

 

There are two pipes to the bottom of the pump, one thin and one thick that head up into the roof space. Not sure whats on the end but it would seem odd to have that on the inlet which is what makes me think the pump is pulling water from the top down.

Edited 9 October, 2016 by mannyo

[Rustynuts]

Well, from a purists point of view.

 

The cold feed and vent from the header tank are just below the pump, and join the pipe horizontally. This means that any air in the system can't rise up the pipe and vent out. If they joined vertically then air would tend to rise up the vent. Also the cold feed and vent should be the other way round so that the suction of the pump acts on the cold feed rather than the vent, which would minimise the chance of air being pulled in (the cold feed is the smaller 15mm pipe and the vent is the 22mm pipe).

 

I'm also not a fan of the pump fitted vertically and then both DHW and CH dropping back down again. It means that air will tend to rise up to where there's a high point with no means of natural venting. With a bit of thought and half a day with a proper plumber, that could've been designed much better. As it is now then it's going to be a fiar old chew to repipe by the look of things.

[Robjon]

Yes - in one of the pictures I can just make out V4073A, which is a Honeywell 3 port valve.

 

Mannyo - I think i can see a manual air bleed on the top of the pipe to the right of the 3 port valve.

Apologies if you already have - but have you bled air out from this air bleed?

 

Disclaimer - I am not a heating engineer/plumber

[mannyo]

Well, from a purists point of view.

 

The cold feed and vent from the header tank are just below the pump, and join the pipe horizontally. This means that any air in the system can't rise up the pipe and vent out. If they joined vertically then air would tend to rise up the vent. Also the cold feed and vent should be the other way round so that the suction of the pump acts on the cold feed rather than the vent, which would minimise the chance of air being pulled in (the cold feed is the smaller 15mm pipe and the vent is the 22mm pipe).

 

I'm also not a fan of the pump fitted vertically and then both DHW and CH dropping back down again. It means that air will tend to rise up to where there's a high point with no means of natural venting. With a bit of thought and half a day with a proper plumber, that could've been designed much better. As it is now then it's going to be a fiar old chew to repipe by the look of things.

 

 

So looking at that picture is pump running bottom to top or top to bottom? Just curious, its obviously been done badly as the air has no way to get out until I bleed the thing.

 

I'll just keep going as before, the heating will be switched on in a couple of weeks so I'll once again be bleeding air out weekly from the single radiator that gets air. 

[mannyo]

Yes - in one of the pictures I can just make out V4073A, which is a Honeywell 3 port valve.

 

Mannyo - I think i can see a manual air bleed on the top of the pipe to the right of the 3 port valve.

Apologies if you already have - but have you bled air out from this air bleed?

 

Disclaimer - I am not a heating engineer/plumber

 

I dare not touch anything in that cupboard for fear of creating a leak. the system already has a leak from the upper pump valve as the crusty green gives the game away. Also the pipes heading to the header tanks in the loft have green running down them.

[Rustynuts]

So looking at that picture is pump running bottom to top or top to bottom? Just curious, its obviously been done badly as the air has no way to get out until I bleed the thing.

 

I'll just keep going as before, the heating will be switched on in a couple of weeks so I'll once again be bleeding air out weekly from the single radiator that gets air. 

Looking at that picture and installation, I'm presuming the pump runs bottom to top. However, if you look on the side of the base of the pump there'll be an arrow indicating direction of flow. Like on this picture...

 

[mannyo]

Gotcha,

 

So the thinner of those two pipes below the pump should be the one where the escapes from, and the thicker one is there to supply water to the system. I therefore guess that the end of that vent pipe is higher than the header tank otherwise water will flow out the end of the vent.

 

The heating installation from what I can gather was done in both cottages near 16 years ago when the entire house was remodelled internally, the boiler was replaced in about 2009 (I moved in in 2010) although not sure if anything else was done at that time.

 

To think there used to be a nice big Range and inglenook fireplace, all ripped out and now there is a wood burner where the fireplace was and where the range was is now a door to the downstairs loo and boiler and the now front entrance.

[Rustynuts]

The thinner pipe should be closest to the pump, and the thicker one should be further away from the pump. That way as any air comes along the flow pipe towards the pump, the air will go up the vent and be replaced by water coming in through the cold fee. At least it would if the vent pipe was tee'd in vertically. As it stands there the air just goes straight past the vent and back into the pump to be recirculated round again. No self venting possible.