Adding UFH to Y plan (radiators removed)

[doesitmatter]

Hey guys, tried searching for an answer but couldnt find one, so thought I'd post. Be gentle!

I'm in a bungalow with a Y plan system and a heat only boiler (Potterton Profile 40E). The cylinder is now mains pressure as I added solar thermal.
Recently, I insulated my floors, removed the radiators and added UFH. And now it's time to do the plumbing work!

The two drawings show what I am moving from and to but I am trying to work out what I need to do and where the additional 2 port vale needs to go (initial thoughts were before the UFH pump) because I was told just to tee off from the boiler (where I suggested) and move to S plan in the future, as the Y plan would work for now (plus the pump overrun would dump water into the hot water tank, which is fine with me.)
However, the more I read, the most confused I'm getting because ideally the system pump would be before the UFH pump? However, it's currently next to the cylinder.
Plus - and please forgive my ignorance - the plan was be the cap off the removed radiator system pipes but if I connected them, although it's inefficient due to pipe length, would that solve the pump issue and I could keep the Y plan? Or have I just vomited nonsense?

I will get a heating engineer a friend knows to get the work done but if I can get everything together and make their life easier, I can get it all done asap....ie-before winter bites!

 

[Exedon]

First you shouldn't have a pressurised cylinder on a Y plan unless you have a 2 port on hot water side as well.
On your proposed drawing you either need to connect underfloor after main pump or move pump .
The pump on underfloor manifold is just for circulating the underfloor.

 

[Madrab]

+1 - if you have a Y plan, the unvented cylinder must be protected by it's own 2 port valve controlled by the HL stat, to safeguard against runaway overheating (when the 3 port powers down the spring moves the valve to HW(B) open). Whoever installed your unvented should have known this as they should have been qualified to do the work and the install then notified/SCert to BC.

No reason though not to use another 2 port to control the UFH.

If all the other system pump would be doing is running the primary circuit to the cylinder then I wouldn't think there would be a huge impact as the cylinder coil wouldn't have a huge throughput demand when both are calling, may depend on effective length of pipe if excessive. That may of course be defined by how large the UFH system is too and how it's pump is set. The ideal would have been feeding the UFH where the main CH pipes branched out after the cylinder.

 

[doesitmatter]

Thanks both. Really appreciate your response, v kind to be so quick to respond too.

In terms of moving the pump or rerouting the UFH, eeep. I did initially think about having the manifold just after the cylinder but was advised it wasnt needed so went for the easier option of sticking it in the garage. Moving the pump would probably be easier and sadly, this is exactly what I feared.
Expected I'd have to use another 2 port for the UFH. Always nice to get confirmation though.

Erm, panic mode on the unvented cylinder! It's something that I definitely expected them to know! Thanks for that knowledge. Sigh.....

Btw, small UFH as it's a tiny house. 100m, 60m, 70m and 78m pipes for 4 zones.

 

[doesitmatter]

Just thinking last night, I could just extend the CH flow back through the loft and into the UFH system, then tap into the return and add a zone valve, (as Madrab suggested) right? It's not that efficient a use of pipework but would surely work...?

And if so, I presume I could just do with it with a 22mm PEX pipe for the flow? (as that would make life a little easier)

 

[Madrab]

Erm, panic mode on the unvented cylinder

Don't need to panic as the system has multiple fail safes but if it is on a Y Plan then there must be 2 port valve protecting the cylinder. Time to call the installers. That and confirm with them that the install was notified and you have sign off from the LA. Also check that the benchmark has been completed, if not then you need that done. You mention it's also solar, is that connect to V tubes etc? Did the same guys who installed the UV do the solar too? That requires another set of quals and proper sign off.

If you don't move the pump @ the cylinder and all it is feeding is the cylinder then you may just need to balance the HW supply (adjust the pump speed) when the UFH is calling just to ensure you have enough flow to the coil to ensure ample recovery times without robbing too much from the UFH when both are in demand.

The 2 port for the UFH would traditionally be in the flow before the pump/manifold however it is piped.

 

[doesitmatter]

@Madrab. sorry, my post on my phone didn't send. Also, I you've gone into detail, so understand if you're fed up with replying to me and have other. easier to work with posters to message instead!

It is connected to the V tubes, yes. Only the upper part of the cylinder is heated via the solar coil. Sorry if I'm being dumb but you said 'installed the UV' but I didnt understand what 'UV' was. If 'UF' (underfloor), I installed it.
The solar and change to unvented is MCS certified and one tick box on the paperwork states it follows Building Regs. Would an expansion vessel and overflow tank remedy the lack of port? Btw, I know many have issues with MCS.....I do sort of work in construction but in policy. No skills here!

Sorry to ask for clarification on something you may have already answered but I didnt understand, but if I connect the radiator flow and return to the UFH flow and return instead (as I don't have radiators anymore), and don't include a 2 port valve, would it simply operate as a direct replacement for the rads on a Y plan system? I rarely really need heating and HW at the same time.
Or, as your last line states, I would still need to put a 2 port vale before the pump/manifold.

 

[Madrab]

Not an issue @doesitmatter

Unvented Cylinder - UV

Putting a 2 port upstream of the UFH just allows you a bit more control over the boiler/zone via a thermostat, the thermostat controls the valve and the valve controls the boiler and the pump. That being said you could control the pump and boiler through a live switching stat and wiring centre. If you plumb it into the flow and return where the rads were removed then yes it should be controlled by the 3 port.

MCS is fine for the solar side of things and is a quality assurance program and a competent persons scheme but it doesn't supersede the requirement to have any installation notified to the LA and BC. An MCS installer can self certify and I believe that an MCS sign off is required for GS/AS heat pumps/PV/ST but the install still needs BC sign off. An MCS installer cannot sign off a UV install unless they have an unvented qualification too and that is also a separate sign off.

 

[doesitmatter]

Thanks all, especially @Madrab, I managed to get it connected up plumbing wise, and the pressure appears to be holding.

I did have a subsequent question though about the electrical connection as despite saying they do 'emergency' appointments, I cannot get a heating engineer or electrician out for love nor money,

I have a Heatmiser UH8 box with LS and LR connections (Boiler Enable and End Switch) and Heatmiser told me that to connect it up to use my room stats, I needed a NO/NC relay which connects the UH8 the 3 port valve, which I cant get right now or find someone to do/test the installation. Therefore, I just need to run it as one zone......so.....any guidance on how I do that with the UH8 (which I assume is needed to turn the pump on?)

Fwiw, the existing thermostat for the now removed radiators goes to the CH on at a British Gas programmer and Switched live to the Zone Valve's white wire, if that's any help....

 

[Madrab]

To be honest, it all sounds like its getting very complicated, then there's more things to go wrong. You may be easier just converting the system to an S plan. That removes the requirement for an off signal etc and simplifies the wiring.

The UH8 then controls the UFH zones through the stats to the actuators, the UFH pump & switch to the boiler and then use the rad (zone8) output switch from the UH8 to control the HW 2 port, that 2 port SL then runs back to the boiler and main pump for the cylinder.

 

[doesitmatter]

To be honest, it all sounds like its getting very complicated, then there's more things to go wrong. You may be easier just converting the system to an S plan. That removes the requirement for an off signal etc and simplifies the wiring.

The UH8 then controls the UFH zones through the stats to the actuators, the UFH pump & switch to the boiler and then use the rad (zone8) output switch from the UH8 to control the HW 2 port, that 2 port SL then runs back to the boiler and main pump for the cylinder.

I know you're correct but I am where I am and just needing to get the heating on.

I also need to get the solar guy back to check his work and if he has messed up and needs to rectify, he will make an S plan very easy, as I can just install my own valve on the UH8.

 

[Madrab]

Converting what you have to an S plan would be really quick and simple. If you have done plumbing work then taking out a mid pos valve and adding in 2x2 ports would be dead easy, especially if you already have to add a 2 port to the primary. Jury rigging Y plan wiring is a real PIA due to the way the way it works with the 3 port and the various signals it needs to work correctly.

Presumably the system is already wired through a programmer and receives the correct signals at the moment for the 3 port/boiler/pump etc so all you need to do is send a switch to the UH8 , to turn the UFH systems on when required?
What thermostat do you currently have or are you looking to take a SL from the programmer when it's calling for CH to activate the UFH?

 

[doesitmatter]

Well, all done and we had 40 minutes of heat.....until the boiler packed up! Sigh!

So that I can help anyone else, if you have a Y plan, mid position valve this is how you get it to work on a Heatmiser UH8 wiring centre.

You need an SPDT relay with a NO connection (no NC needed).
UH8 -
LS goes to live in your non UH8 wiring centre.
LR goes to one end of the Relay's coil.
Earth to earth.

Wire the other side of the Relay's coil to neutral at the wiring centre (non-UH8).
Wire the Relay's COM port to Live in the wiring centre (non-UH8)..
A cable runs from the Relay's NO to the white wire in the three port valve, so when you call for heat, white is energized and A on the valve opens..

On a three port valve, a spring returns the port to hot water, so you don't need a NC connection to close the port.

Now to work out what the hell happened to my boiler....it's a positive pressure boiler and the fan has stopped, so now I (someone) needs to work out whether it's the fan or the pressure switch.

Huge thanks to @Madrab, who gave me the confidence and also the reprimand to go S plan, which is of course the best option!

 

[picasso]

I haven't followed your wiring description but it does not sound right also the three port does not return to hot water after demand , three ports stay in the last position they where in when demand has stopped.

 

[flameport]

three ports stay in the last position they where in when demand has stopped.

They will stay at CH only if that is the last option selected, a position which has the motor powered continuously to waste electricity and shorten the life of the motor. That only lasts until HW is selected again.
Otherwise it will return to HW only.

Y plan is obsolete, and as mentioned above should be replaced with S plan where extra zones or an unvented cylinder is added.
No new system should be installed using Y plan.