oil fired boiler, flow direction wrong?

[Red One]

Hi.
I am just about to drain down and flush my pressurised oil fired home heating system which is situated in my garage (adding a TF1 filter and fresh inhibitor as well.).
After looking at the whole system and trying to plan the job out, I am suspicious of a few things that I have seen, and just wanted to ask for some opinions.

1. The pump is mounted 'upside down'. Ie, the writing on the pump is 180 degrees upside down. I don't know if this is just the pump, or the actual pump casing that it connects to (I understand the casing is directional?), because the actual electric pump could technically be bolted on in 4 different directions? I have attached a photo to see if anyone can tell. (excuse the mess, I am going to tidy this up when draining the system)

2. on the radiators, the return pipes heat up before the feed pipes. (although this is not the case in 1 or 2 of the 16 radiators)

3. There is a constant drip from the Automatic air release valve mounted on a length of 15mm pipe above the pump. I read somewhere if the valve is place above a pump drawing water away from the valve, it can draw in air causing issues? (see pics)

The two 28mm water feed pipes connect top left side and bottom left side of my Warmflow 90/120 oil boiler as you are looking at it. (see pic)
Currently when fired up, the top pipe heats first, the lower pipe after a longer period of time, indicating the flow is from top pipe through pump and into the ground , returning cold to bottom pipe and into boiler. Does this sound right? Is there protocol that the top most pipe would be the hot feed, and the lower pipe the cold return? Unfortunately, I cannot find the installation details for this boiler.

Should the pump be pumping hot water away from the boiler, or cold water into the boiler?

I am also suspicious, because I checked the radiators in the house, and most of them seem to be heating on the return end first, then the supply control valve end. I have no TRVs fitted, just the basic twist and turn valve caps. Of course, the original plumber may have just put the plastic caps the wrong way round on the rads as the brass fittings look identical on the feed and return ends

Is it possible for the heating to have worked for this many years with water circulating the wrong way round? I am also a bit baffled how this would be the case when I have 3 motorised valves (2 heating zones and hot water), because logic would suggest to me that its impossible for the system to flow the wrong way or these motorised valves would not work, given they are connected to the feed only?
I would like sort this all out if it turns out the water is circulating the wrong way round. Would I see any improvements, or indeed if the current flow is wrong, what issues should be apparent?
I take it IF the flow is wrong, then reversing the pump direction would 'cure' the problem?

 

[oilboffin]

God almighty I'd rip all that pipework out and renew it and the pump takes water away from the boiler.Bob

 

[Pauli11]

.

 

[Red One]

Thanks for that, but why? Other than being dirty, its been there 16 years without any issue other than what I am querying above. The rusting and dirt are from the constant dripping of the Automatic air valve above the pump, dripping down the piping but there are no leaks from the system piping itself. (I have the replacement air valve here ready to fit when I drain the system down. Im not after an oil painting, this is out in the garage, what would the benefit in 'ripping' out the piping be other than to have shiny copper?
Have you anything you can add to my query?

Read more: https://www.diynot.com/diy/threads/oil-fired-boiler-flow-direction-wrong.520464/#ixzz5jCwwEXMk

 

[oilhead]

Apart from making it look nicer, there is no reason why you should not leave it as it is. A pump on the flow should take hot water away from the boiler. A pump on the return will pump cold water into the boiler which results in hot water leaving the boiler. Top flow and bottom return is correct, and if it works then the pump body must be the right way round. It matters not about the writing being upside down. If the valves on the radiators are the same except for the difference between lockshield caps or knobs, then nothing is wrong. Swap the knobs if it annoys you. An auto air vent above the pump is not the best place, especially on the suction side as the lower pressure can allow the pump to draw in air by allowing the float to fall. Blanking the fitting off and putting the AAV in another place on the flow may be of benefit.

 

[ianmcd]

just close the cap on the AAV

 

[Red One]

Thanks Oilhead. My intention is to strip off all the old insulation and give all the pipework a good clean down anyway as part of the flushing of the system I am going to do. The pipework itself is sound. I am going to fit a TF1 Omega filter also and a new 18 litre expansion vessel and pressure release valve, and I might replace the water pump for a more modern one such as the Wilo Yonos Pico (only because I can get a new one for about £65 which is about half price). The Wilo Smart 25/6 in the pics is about 7 years old now although functions flawlessly, a replacement along with the other work should keep issues at bay for a few years. The Reillo RDS burner had a new jet and oil pump fitted recently, so fitting a new AAV, water pump, exp vessel and TF1 filter , along with a good flush out and new inhibitor should hopefully have the system functioning well for a few years yet. The complete system is 16 years old, and I suspect it has only been flushed out once in that time! The rads are all quite hot, but I suspect could do with balancing etc. I also fitted a new 18ltr potable expansion vessel to the hot water tank last weekend as I suspect the one in place had failed. Even if not its the original and has been there 16 years. Ive read that the vessels should be replaced every 5 years.

I also take your point about the AAV location, as what you have said tallies with what I read elsewhere, in that the pump could be 'pulling' air in through the AAV due to the AAV being on the suction side. I'll look at possible places to relocate somewhere after the pump.
Thinking also about the flow direction, it does seem more likely that its ok as you say. Also, the heating system has 3 motorised valves (Zone 1 Bedrooms, Zone 2 rest of house, Zone 3 Hot water). I presume these only work in one direction and the flow was in the opposite direction, the valves wouldn't function properly?

Anyhow , thanks for your advice.

 

[Red One]

just close the cap on the AAV

Its a plastic cap, and I have it closed but I also ripped the plastic threads in the process hence the leak. Just on that point, because I noticed my new AAV has a plastic cap also, if this is closed shut, how does the air escape?

 

[ianmcd]

they are there really for when you drain and fill the boiler, yes they are supposed to be left open to remove any air that accumulates, but they leak for fun , I never leave them open , but what do I know

 

[Red One]

I see. So best left closed then. Wish I had have bought one with a brass cap then.

 

[Red One]

Thinking about the relocation of the AAV. There is not a lot of surplus piping around my boiler, particularly after the pump. Only about a foot or so before the pipe disappears underground and back to the house. There is more vertical piping than horizontal. Looking at the existing and proposed diagram below, would my proposed location for a new AAV work, and would it be worth the effort relocating it to there? Obviously the inlet for the proposed AAV piping from the 28mm feed pipework would be lower than the highest point in the system, but by running the 15mm piping up above the hot feed from the boiler as in the diagram, would that work??

 

[JimCrow]

Leave the AAV where it is, the highest point on the pipework.

better with this,https://www.screwfix.com/p/compress...VsDLTCh1vTwbtEAQYASABEgJhQPD_BwE&gclsrc=aw.ds

 

[Red One]

interesting, thank you Jim. I take it the benefit being, even though the air vent is on the 'pulling' side of the pump, air won't get in due to the airtight seal. Then just release when wanting to bleed air after a service or flush?

 

[ianmcd]

your pic wont work, leave it where it is and either screw the cap down or as advised fit a manual vent, either will have the same result if it was me I would just screw the dust cap down, if you dont have a cap it is the same as a car tyre valve so nick one off the car

 

[MeldrewsMate]

Just a word of caution.
You started this thread by proposing to fit a TF1 filter. If you propose to install the TF1 on the return leg to the boiler then you MUST ensure that the pressure relief valve (safety valve) is located between the boiler and ANY valve or isolator....your many photos haven't shown it's present location.
If you imagine closing every valve on the system, then lighting the boiler, the pressure relief valve must be able to discharge the boiling water and steam generated in it...so no valve between boiler and PRV.

On the subject of zone valves and wrong circulation direction, if it were wrong and they were Honeywell or Drayton valves you would hear a bang every time the final one shuts; rotary shoe valves are more forgiving (Satchwell, Danfoss), but in all honesty it sounds and looks like the flow direction has been correct all those years. Radiators don't care which way the water flows, and as said previously, just swap the knobs over if it bothers you. Having said that, my experience is that the system runs quieter when the balancing valve is on the radiator exit, so read up on system balancing and do that after your other work is completed - a properly balanced system is a joy compared to the alternative!

MM