Question regarding connecting underfloor heating to existing system

[Steve2381]

Hello all

Well.. after a rogue builder left us in chaos... I am trying to pick up the pieces with zero funds...:banghead:

Underfloor heating manifold + pump is install and pressurised (has been for weeks) downstairs (about 3 metres directly below the boiler cupboard). That went in fine.

I have run a 22mm copper down from the airing cupboard (where the Performa System HE boiler and megaflow CL170 are installed).

My plan... correct me if I am wrong!....

Connect the 22mm copper to the boiler flow, somewhere where it splits into the existing electric heating and hot water valves.
This new 22mm feed then goes through a new 2 port 22mm valve and onto the underfloor heating manifold flow port.

The return port from the manifold, I planned to tap into the 22mm ground floor radiators return which passes right by the manifold. I established it was the return by letting the system go cold and then firing up the rads.... out of the two 22mm pipes, the one that got hot first would be the flow from the boiler. Therefore the other is return.
Is it OK to share the short 3 metre 22mm return run back up to the airing cupboard with the rads? They would connect together in the airing cupboard anyway before returning to the boiler.

The underfloor heating pump will be wired to run when the underfloor heating stat calls and also fire the boiler (I am a sparky - that bit is easy).

Another question. Getting in the airing cupboard now is madly tight. Would it be OK to tap off the boiler flow and fit the electric valve for the underfloor heating downstairs by the manifold instead? That will be about 3/4 metres away from the boiler at most. Getting the valve in the airing cupboard is going to be hell. Also, I imagine its best to have the valve below the point you tee off the boiler flow pipe and that may prove impossible in the cupboard.

Any other tips? I know to run it up slowly over a few days - increasing 5 deg a day or so from a start of 35 deg.

Thanks for any advice
Steve

 

[Howsie]

Welcome Steve!

I'd take a step or two back if I were you. Do you know if this rogue builder has specified and fitted the UFH pipes correctly?

 

[Steve2381]

Hi Howsie... I fitted the underfloor heating and the system came from a company who sent the required pipe/manifold etc - measured from the floor plan. I know it went in as it should. I pressurised it while he screeded and its held pressure fine.
We deleted several large radiators during the build so I think the system can cope OK (its a big boiler). Anyway... no funds to replace that!
I have been involved with many underfloor heating systems, I just have never actually connected them to the system before - so I was checking my limited knowledge (and yes.. little knowledge is dangerous!).

My real questions is whether its OK to have the 2 port control valve 3 metres away from the boiler (can't see why not) and if it is OK to share the ground floor return pipe (which is the same floor as the underfloor heating). There are only 3 other radiators on the ground floor using that 22mm return pipe anyway.

Thanks

 

[Howsie]

It should be but without seeing the system that comes with the usual caveats.

 

[Howsie]

If it isn't, you can always re plumb.

 

[Steve2381]

Ha... My thinking as well

Attached is an appallingly quick diagram if it helps.
My main worry is the water returning from the underfloor manifold will backflow around the ground floor radiator system if they are not on.

 

[Howsie]

You'll be fine.

 

[steadyon]

I'm no expert on UFH, but thought they normally ran at much lower temperatures than CH radiators. Is there a blending valve in with the manifold / UFH zone valve set up. If not your UFH temperature may well be too high.

 

[Steve2381]

I am no expert either Steadyon...

The manifold has its own blending thermostat and pump. It says in the installation manual to connect directly to the boiler flow/return and control the underfloor temps with the blending stat.

My super basic diagram doesn't include the blending stat. The manifold came pre-assembled with the blend valve, pump etc all fitted.

 

[dancinplumba]

dont forget your bypass which should be before all valves

 

[Steve2381]

Err... bypass? No bypass on my pretty plumbing diagram that came with the manifold.
This is a underfloor manifold added to an existing working system... won't their be a bypass on the existing system. I suppose it depends on what it bypasses!
Where does that go?

 

[Whn1]

There is a built in bypass I believe but it's very small bore, if I can remember correctly.

 

[dancinplumba]

you need one between F an R pipes on boiler, ignore the fact there is one in boiler, it is inadequate.
When ALL valves closed where does heated water go ?

 

[Steve2381]

Err.. where ever it has for the last 5 years! So adding a manifold to the boiler means I need a bypass, even though the system has worked fine as it is without one so far?
There is absolutely no way I can get to the flow and return under the boiler (hence the connection the the flow pipe at a different location. The Megaflow has been mounted directly under the boiler blocking access to the pipes out of the boiler totally (yes - stupid but not by me).

The boiler is a Potterton Performa System HE. It does have an internal bypass, so I expect the original plumber is relying on that

 

[Whn1]

They will work with the internal bypass but what dancin is saying is its reccomended/a lot better for your boiler to have an automatic bypass fitted before the first motorised valve. You have to access this point anyway to tap in for the primary flow to your manifold.

 

[Steve2381]

OK. Yes I can 'just' reach the flow where it leaves the boiler and splits to the original hot water and central heating valve. However, as I cannot access the return at all (totally hidden from view), I am not going to be able to connect the other side of the loop.
I only just managed to fiddle a new 22mm out of the airing cupboard down to the manifold to get me a new separate flow pipe for the under floor manifold.

I suppose you could jump across between the flow before it enters the under floor heating valve and then tee into the return pipe downstairs? (see attached updated sketch).

What is inside a bypass valve anyway? I am assuming a simple temperature controlled valve that lets water over a certain temp through. What temp would this valve normally be set at?

OK.. Edit post: Its a pressure valve then ... set to 0.2bar.

 

[Steve2381]

Ever wish you hadn't started something?

OK.. all in.. working sort of fine. Fitted a bypass - just in case. Underfloor heating was on and away (set low) last night.

This morning... one of the flow meters on the manifold is stuck down (a light tap doesn't free it). Any ideas?

Also, and slightly more concerning is the boiler is now humming (sounds like a light airplane) when the central heating is selected (the radiators). Any ideas on that?

 

[Howsie]

Change the flow meter or use pipe thermometers to get the balance right.

Boilers usually hum a little.

 

[Steve2381]

OK. De-pressurised the manifold - TINY bit of crap stuck in the flow meter.

What should the bypass be set at? Its factory set at 0.2 (which doesn't seem very high). I have moved it to 0.4 and possibly imagining things.... but it sounds quieter.

Any suggestions?

OK EDIT...

The humming from the boiler is getting louder and louder. What the hell is that.
Only seems to do it on the central heating

 

[Howsie]

Bypass depends on the installation setup.

Boiler could have air in it or could be going wrong. Who knows...

 

[Steve2381]

Well its a vibration of some sort. I thought slowing up the underfloor heating pump may help... and I thought it did for a while.
But then the hum inside the boiler slowly returns over 5 minutes... getting louder and louder. Instantly stops when you turn off the central heating on the programmer.

Is the small black knob built into the top of the boiler pump a manual or automatic air valve? Although surely the noise would be on the hot water as well if it was air.

This is turning into a really bad week

 

[Steve2381]

OK. Just to keep the thread updated (why I hear you ask!)

Slowed the underfloor heating pump to speed 2. Noise seems to have slowly disappeared. Not going to say its gone, but currently.... running quiet.

Fingers crossed. Thanks for all the advice guys

 

[Howsie]

Sounds like the UFH is pumping against the boiler. Have you connected them the right way around?

 

[Steve2381]

Yep - pump on manifold is correct. All works fine. Underfloor heating is working fine.
Its just every so often... sounds like a light airplane passing over. Certainly coming from the boiler and doesn't sound like the pump to me.

I have set the bypass valve I installed to 0.5. Quite high I expect, but set lower than that seems to make it worse. There is one in the boiler apparently anyway.

The underfloor heating pump is currently running set on speed 2. There is no speed adjustment (that I can see) on the boiler pump - not that I would change it.
I thought perhaps the underfloor pump was interfering with the boiler pump - making it noisy. The underfloor heating seems to work fine on speed 2, so I don't think that is an issue.

All radiators are bled, so not sure what the noise is.

Its all running now - and quiet. Has been for the last half hour. Perhaps it is just air?

 

[Steve2381]

Mmm... its run all afternoon just fine. Then tonight when the CH came on, it sounded like a Boeing coming in to land. The 'hum' just got louder and louder.

No hot water issues (that I can see). Radiators are lovely and hot. Underfloor manifold/floor seems to be working fine.

Blocked heat exchanger? Perhaps draining down has dislodged some crap in the pipes (I did flush through the pipes as best I could - fairly brown but not sludgy). I was going to put inhibitor in the CH system, but not until I know its all working fine.

Anywhere else muck could be trapped, and is this something I can do... or after all my efforts, am I going to have to admit defeat and borrow money for a plumber?

Edit... Is Fernox boiler silencer concentrate (the one you add via a rad vent with a mastic gun) any good?
Fernox stuff is usually quality. Wondered if this was worth a shot.

 

[Mike Jackson]

Any boiler silencer is rubbish. It will only mask a problem, not cure it.

 

[Steve2381]

I thought it might be. Couldn't see how it would fix any kind of issue properly.

 

[thompsonbrown]

you can find out the correct lay out by looking at your boiler,cylinder and ufh manufactures guide. personally i would get someone qualified locally in, to commission system properly you have decent equipment at your house and manufacturers wont repair equipment without it being registered with them, regardless of fault.

 

[Steve2381]

I am going to get someone out next week. Its running totally fine today.
I will get the system flushed, boiler serviced and inhibitor put in.

 

[thompsonbrown]

sounds like a plan. just a couple of points. the bypass you fitted is purely protection for the system eg. if you had the boiler set to hot water only and the cylinder reached temp turning off the hot water zone valve, the boiler would still run and be purely reliant on the boilers built in bypass. also with the noise you keep hearing in the system this could be air still trapped in the ufh pipe-work. worth increasing the flow rates up one zone at a time to see if any air is trapped. lastly i would fit a gate valve on the rtn line from the cylinder this will help to balance the system when you are calling for heating and hot water, little things like air vents on the flow feeding the cylinder you probably are aware of. another good tip more for your bathrooms than any thing else, is to take the cold supply to the bathrooms from the 3bar reducing valve feeding the cylinder. you should see a brass nut with a blanking plate where this can be done. hope this helps and wish you all the best with your new house.

R.Brown

 

[thompsonbrown]

forget the cold feed from the cylinder prv. just released that its not a new build and you've had your bathrooms fitted more than likely over 5 years. guess ill have to start reading post throughly from now on. take care matey.

 

[Mike Jackson]

It is not recommended under Part L to fit balancing valves (Gate valves. ballofix, lockshields) to cylinders any more. Best practice is to allow as much heat as possible to get to the cylinder to achieve a rapid heat up. What's the point of having a super duper high efficiency coil and then throttling it down. With modern control systems the hot water can be timed to come on half an hour before the heating requirements and have no detrimental effect on the heating.

 

[thompsonbrown]

i thought part l only covered new installations.

 

[Mike Jackson]

The building regulations cover any work done.

 

[thompsonbrown]

i might have this wrong but i always thought that part l was legal requirements in new buildings and only best guidance on any changes to existing systems due to financial and practical restraints. im not 100% though. I mean they change reg's so many times without thinking about the practical and financial implications, that when they revert back to the old system it makes you wonder how considered these changes are. I can understand with health and safety issues to a point, but even this has been changed back and forward so many times over the last few years. A good example of this would be the change of the regs regarding electrical consumer units, such as every mcb circuit must be protected by rcd with 30ma trip. 16th edition regs 2004. sounded great, until the finally realized that when a light bulb blows, it would trip the consumer unit and given most light are only used when its dark, you can see the potential problems. lots of old people hurt trying to get down the stairs in the pitch black to try to reset their consumer unit. There were even deaths (no joke). ironic that probably more people died through these new safety regs than would have occurred if the changes were not implemented. regs were quickly watered down and in a lot of cases changed back. now with the latest 17th edition being twice the size of previous editions such as 12 and 13 there is no clear definition of what is right or wrong. terminology like "functional provision", "Best practice" and "future proof" is just wording banded together with supplements and amendments attached to try and make sense of what it was they were trying to achieve. Electricians trying there best with what they know whilst reading the latest amendments on which consumer unit to fit in which house, most times falling back onto best guess. Split load units with 1, 2 , and 3rcd with installer using best practical options most of the time to choose which way to go. options that include installing stair lighting based on nothing other than the age of the current owner and the latest amendment to fall through his door. installing a non rcd circuit to the boiler room for a audible, wired-up EN 50291 monoxide alarms that may or may not be installed in years to come "future proof". its a real joke check out the amount of amendments in the 17th edition regs. who could forget the changes the 16th edition made for plumbers with having to cross bond all pipework in bathrooms and with trv to be fitted as standard had to cross bond between the pipe and the rad.(looked great in a £20.000 bathroom ) especially that we had to buy the earth clamps with the blue safety tag due to it being classed as a damp environment. then having to run a 6mm earth back to the consumer unit and a separate 10mm earth and 10mm t+e if you were fitting a electrical shower.this all happening while the electrician was cross bonding bathroom lighting circuits back to the switch then back to the box leaving a nice yellow warning sticker on the new lighting just installed. All regulations back in 2005 now scraped or amended. £4000 Hips and chaps certificates you needed just to sell your house... all scrapped. part p 2005 competent person definition changed 2013 to save Electrical Safety Council £61.3million and a promise from the government to look into placing health warning stickers on all diy sold electrical sockets.
i know i went a little long winded in replying to your post regarding, part l existing dwellings. but with all the blunders and all the changes made to building regs since 2005, The ongoing fight between the gas safety trust and the Electrical Safety Council over rights to control Part J of the Building Regulations. the overlap between the HSE and Department for Communities and Local Government over the safety of local Building Control, through in "gas safe" supposable looking after the register of approved fitters of the registered competent persons officially 32% of fitters do not comply with part p have been tarnished with not knowing what forms are to be filled in for local building control. when you look at all the bureaucracy electricians and heating engineers have to deal with i'm surprised its not higher.