T connection on return flow of central heating

[ab0apm]

Hi all.

I'm after a quick bit of reassurance that the plumbing work I have just had completed is up to scratch.

I have an open vented central heating system with hot water cylinder in an S plan plus arrangement - 2 central heat zones (one old, one just added for extension).

The second central heating zone has just been added and the return flow T'ed into the return flow to the boiler just before re-entering the boiler. The T junction is arranged however such that the 2 return flows (from the old system and the new extension heating) enter the T connection from directly opposite directions and then both have to find find their way down the leg at 90 degrees.

Being and Engineer (but not one with a good knowledge of plumbing and pipework) this would not appear to be the best way of going about things as the 2 flows are directed directly at one another and will cause a turbulent flow effect (basically pushing against each other) before they find their way around the corner.

This all might be perfectly acceptable in the world of central heating plumbing but I'd be interested to get the advise of others on this forum.

Many thanks!!

 

[Best]

Could you post a photo of all the pipework at the connected area?
I am thinking it is ok

 

[Chalked]

It's fine on an s plan.
Loving the " engineer " terminology. Connecting in a return flow!

 

[SimonG]

It's fine, it's not exactly niagara falls inside central heating pipework.

 

[Riley]

Sounds reasonable what does your engineering senses tell you is weong

 

[tolly]

not quite sure what a return flow is but the cylinder return should be the last tee before it goes back to the boiler.

Also you say the boiler is open vented? If its a heat only boiler with external pump you need to have tee'd into the flow after the pump.

 

[tolly]

not quite sure what a return flow is but the cylinder return should be the last tee before it goes back to the boiler.

Also you say the boiler is open vented? If its a heat only boiler with external pump you need to have tee'd into the flow after the pump.

 

[steadyon]

I wouldn't worry about the "fighting" tee junction. But you might like to check you don't get radiators coming on when hot water only is demanded. The last return connection before the boiler should be the hot water connection.

 

[magicno1]

Reverse circulation is going to occur
Return needs to be connected back before the hwc return!

 

[magicno1]

Reverse circulation is going to occur
Return needs to be connected back before the hwc return!

 

[magicno1]

http://www.hertsboilers.co.uk/tech/backflow.jpg

 

[ab0apm]

Thanks for your various replies. To answer one of the first queries my thought was that best practice might be for 2 incoming flows to meet at 90degress in the T connection - like a slip road joining a main road as opposed to traffic meeting head on! Consensus seems to be however that what has been done is ok.

On the reverse circulation issue the new zone is an UFH circuit with a 2 port valve on the supply which i have been told should mean reverse circulation shouldnt be an issue be an issue. Worst case it would be the return flow pipe from the UFH manifold that would heat up.

Next issue:

Plumber wanted T the feed to UFH zone off directly after the boiler before the existing pump set! I've told them it has to be after the pumpset and they're going to do it that way but they're not happy - saying they normally connect off after the boiler and it is fine.

Speaking to the UFH supplier they have backed me up and said it should be after the existing pump set. Although the UFH manifold has its own pump it is not design to be pulling the water from the boiler so you wouldn't get the full output from the UFH and the pumps life would be dramatically shortened. So although it might just about work this is not how it should be done!

Is my plumber slightly confused by what they're doing (being polite) or do some UFH pumps work like this and it is just the system I have chosen that is a bit different?

Thanks again all

 

[oz-plumber]

Re: Pump location - sound like the heating plumbers are correct from your description.

You never want a pump pulling water through another pump unless they are in series.

If you tee it off after the existing pump, when that pump is not in operation you will be pulling water through that pump. When the other pump is in operation it will be pushing heating water through the UFH manifold.

If you have multiple pumps on a system for separate zones ( like you have) the pumps should be pulling water through the boiler,. eg, the boiler should be on the suction side of each pump.

Post some pics of what you have installed.

 

[ab0apm]

I've added some diagrams below of what the UFH company have advised with regards to install and what the plumber wanted to do.


UFH company advised it should be done that way to ensure flow to UFH system is adequate as UFH pump is designed for the UFH circuit but not to be pumping from the boiler. As central heating system pump will pump when boiler fires it will just be pumping through the by pass valve if installed as plumber wanted when HW and CH not calling but UFH is.


Plumber simply says this is how he normally does it.


Any comments appreciated.

 

[ab0apm]

And just to be clear the way the controls are wired the boiler and main pump will always fire when the UFH calls for heat so there wouldn't be a case where the UFH pump is trying to draw water through the stationary main pump.

Thanks

 

[Chalked]

Bottom drawing won't work, as the flow is on the negative side of the pump. Return is fine.

 

[ab0apm]

Thanks for confirming. Plumber says bottom layout is what is always does!

Think it might appear to be working where he has done it before but it will be relying on pump in the manifold to do a job it isn't meant to. So UFH heat output isn't going to be what it should be and the manifold pump would probably die early.

Anyway I've said I want it done like layout 1 much to his annoyance.

 

[ab0apm]

Thanks for confirming. Plumber says bottom layout is what is always does!

Think it might appear to be working where he has done it before but it will be relying on pump in the manifold to do a job it isn't meant to. So UFH heat output isn't going to be what it should be and the manifold pump would probably die early.

Anyway I've said I want it done like layout 1 much to his annoyance.

 

[Chalked]

He might have done it before on a system boiler , or combi. ( the pump is in the boiler) that would work fine.

But on your system will cause all shirts if circulation problems. Good job you noticed. It will need altering to after the main pump.

 

[magicno1]

Are there any proper tradesman left????