Connecting underfloor heating to a combi part 1

[@yensabi]

First time I ever saw close coupled tee's done like this I thought WTF is going on here....that was about 10 years ago , I then found a guy called Andrew Millward who is really clued up on these systems and has a great you tube channel of his own , I learned a lot from him and now fit these systems all the time whenever possible and my preferred boiler is a Viessmann as you can set these up perfectly to match your system design.... Cheers 👍

[@andrewmillwardwatford9410]

Thanks for your praise.....

[@Razz60]

Loving your videos mate

[@griffithsheating]

🤘 😎

[@YMNS86]

One of the few videos which shows how it’s done properly. Really good video. What I can’t get my head around is how to size the pump for the rads after the cct. Will it not interfere with the boiler’s own pump modulation unless you use the same pump which is in the boiler?

[@griffithsheating]

Cheets mate 😎 just size the 2nd pump to suit your index circuit. The hydronic gods will take care of all the other stuff. The worst that happens is that you get a bit of distortion. I.e. the boiler is running at 55 degrees but your flow temperature out of the secondary circuit is 50 degrees as it's pulling in return water through the CCT and lowering the flow temp.

[@YMNS86]

@@griffithsheating hello mate, just got round to doing this on my system. I was wondering where you would wire the additional pump for the rads after fitting the cct. if I wire it to come on when the zone valve for the rads opens, then it'll run when just the UFH is calling for heat, since they share the same switched live to the boiler. but if I wire to the switched live from the thermostat to the rads, it'll come on before the rads zone valve has opened. I've got a bypass radiator to dissipate heat though so I could have the pump before the branch to this and the zone valve controlled rad circuit. what do you think? sorry for bending your ear on this, do you think I should use a relay?

[@griffithsheating]

@@YMNS86 yep ideally you’ll need relays. I had the same problem. I can’t remember what I did to get around it I think I did something by taking the heads off the zone valve and using them as a pseudo relay of sorts……I really can’t remember….but it worked🤔🤨🧐

[@HarvinderSingh-ni2hq]

Hi mate, great video. Just trying to get my head around this. I recently done my own ufh and connected it up to my combi - Vaillant eco tec. I added an external automatic bypass and it all seems to work but not sure if it’s running correctly. I’m finding the temp rises pretty quick and the egg timer symbol comes up. Would this solve this issue?

[@griffithsheating]

Yeah it likely will cycle set up like that. Do you have any radiators on the combi or all underfloor?

[@HarvinderSingh-ni2hq]

@@griffithsheating yes, 7 rads and most of downstairs on UFH

[@griffithsheating]

@@HarvinderSingh-ni2hq My preference is to always hydraulically separate pumps. Though the way you've done it which is technically incorrect will probably work acceptably on a smallish system - it's how almost all plumbers will connect ufh to a combi and not give it a second thought. You could definitely make the boiler run better and more consistently with a CCT under it.

[@HarvinderSingh-ni2hq]

@@griffithsheating cheers mate. I will give this a go 🤞🏽👍🏽

[@andrewmillwardwatford9410]

Great to see this good practice becoming the new norm. Hydraulic seperation becomes necessary when running at low boiler flow temperature. If your using normal on off controls it may not be so important. Are you running at a reduced flow temperature ?

[@griffithsheating]

Well the job has been a bit of a nightmare for the client to be honest. They've been well and truly rinsed by the concrete contractors who sold them the underfloor system. Once the dust settles from the building work they'll be going full weather comp with a mixed circuit for the UFH.

[@andrewmillwardwatford9410]

@@griffithsheating great move

[@julianhawker7672]

Is there a rule of min/max distance between CCT? Rest of it all makes sense to me. Very useful video for me. I'm largely service/repair for many years now but just come across a similar job that I think would benefit from CCT and want to be sure of my facts before speaking with the householder . Cheers. 👍

[@griffithsheating]

yeah there are some rules of thumb. The close coupled tees must not be more than 4 x the diameter of the pipe apart. Flow out of the cct to the system should be atleast 4 x the pipe diameter before the first bend and the return into the cct is 8 x diameter before first bend. Only important one really on a small domestic system is 4 x diameter between the ccts.

[@julianhawker7672]

@@griffithsheating Thanks, that very helpful. Cheers.

[@jacbisgood2221]

Nice work. I do have a couple of questions though. 1. Would you need to install non-returns on the 2 circuits to stop one drawing back from the other? 2. Does the ufh manifold pump draw flow from the cct's? I would have thought that it only circulates around the loops?

[@griffithsheating]

Shouldn't have to put check valves I as it will draw from the CCT bit you could if you wanted I suppose. The ufh manifold pump will draw from the new primaries. Not all types of manifold will though. 👍

[@tsw4437]

Hello I am in process of installing water underfloor heating. As part of the project the engineer is also moving the boiler from kichen to garage. My question is when the project completed what kind of certificate and documentation should I get for the underfloor heating installation and for moving the boiler for my future record. Can you please list out what should I get from the company on completion please. Thanks,

[@brendanfisher2528]

looking forward to the next video... your jobs sound aloy like mine.. customer calls as other plumber charged a fortune and did nothing.. they I have to go and pick up the pieces

[@griffithsheating]

Yep. Alway the last man in the door and leaving with the least money 💸

[@Purebeltersteve]

With the close coupled tees, does the pumps not steal the water to the boiler if that makes sense. I think that would cause overheating issues, or am i talking rubbish lol

[@griffithsheating]

It's one of those things that when you see it for the first time you can't quite wrap your head around but It's just essentially a mini low loss header on its side.

[@waynenixon729]

Doesn't the water take the path of lowest resistance straight through the T's and back to the boiler? (Primary circuit) Unless there is a pump on the radiator circuit and underfloor (Secondary circuit's) Because radiators and underfloor require different flow temperatures.. Would a blended underfloor circuit with some return water not be more efficient? Great channel by the way 👍

[@griffithsheating]

@@waynenixon729 yep there are additional pumps on the secondary side. There is a blender at the manifold. I'd have liked to weather compensate it all with a mixer and vaillant controls but the budget had been syphoned off by the time I'd got to the job.

[@waynenixon729]

@@griffithsheating Could you show how the wiring works on programmers to thermostats to 2 port valves to boiler. 3 ports are as you know a bit different. How the power goes through from the programmer from the fused spur. 2 port on the grey always live. Signal from the programmer to the thermostat to the 2 port on the brown switching over the micro switch opening the valve. Sending power from the grey down the orange to switch on the boiler. I'm a bit unsure on hot water priority? Smart stats are good but do you think the boiler manufacturers controls are the best to fit?

[@griffithsheating]

@@waynenixon729 if it was my job I'd have had it all running on manufacturers controls. 2 weather comped circuits with the ufh circuit on a an esbe mixer and ditch the blender at the manifold. Having spoken to the customers they're up for eventually replacing the boiler for a V200 with all the bells and whistles. As it is I've just got 2 Billy basic programmable room stats running the show. The heating one runs the zone valve and the ufh one is just switching the pump because for the £6k they paid for that manifold the controls were extra 😒

[@jay96lfc]

What would pump speeds be set to in the boiler and on the rad and underfloor circuit? Just curious

[@griffithsheating]

The system is a bit of a lash up. Massively oversized circs in some places and then in others we've got multiple rads running off a long 10mm run. So the technical answer is whatever setting works...

[@normanboyes4983]

Really interesting video and you inherited a bit of a poisoned chalice there. I do not like blaming the consumer (because ‘I is one’ )- but a little bit more thought in terms of planning ‘the bones’ of the project rather than the colour of the kitchen would have paid dividends. Screaming out for a V200W, but you have to work with what you have got. Thanks for posting.

[@griffithsheating]

For What they paid the bloke who put the ufh down they could have had a v200 and a mixer AND the ufh system from me 😭

[@HarryMasters-hd3pn]

Spend all that money then leave old boiler in, typical.

[@randomcamerajunk6977]

LoL bro you didn't even use uni strut and rubber lined Munson's in the 'plant room' take some pride ffs