UFH mixing valve not restricting heat to floor

[oz-plumber]

Gee Pal,

You're a hard nut to please!

You've done all the work yourself, altered the configuration of your heating system, added UFH and then you have a problem and you blame it on the equipment.

You have had a thermostatic repair kit supplied free of charge and then you admit to probably stuffing up the first one and now the second one.

You have had the supplier of the heating equipment offer you a full refund on the mixing assembly if the one you have is faulty.

What do you expect?
A complete replacement without them checking if the unit you installed is faulty?

As far as I can tell you are getting as good a treatment, if not better treatment, than some of us in the trade get.

I would say that you are now in the position to pay someone who has experience in heating systems to check the system over.

There's obviously a problem somewhere, but after replacing 2 thermostatic sensors and now wanting to replace the mixing block, it would seem less likely that there is equipment failure

 

[Dtwone]

yep, I may seem hard to please and I understand the suppliers position but I'm also quite technically minded and not overly impressed by their attitude in providing any level of technical support, they basically told me they never have problems with their mixing valves and to contact the manufacturer, they don't seem to know their own products very well - Unlike the RWC tech guy who was very helpful and confirmed my understanding of the operation of the valve and stat. It's hardly demanding to expect some level of customer support beyond a list of parts supplied.
I think I've explained and covered everything in my system to you guys on here and thanks for the responses, it's confirmed my thoughts and reassured me I've not overlooked something fairly obvious.
If you'd like to see the fruits of the rest of my efforts, pics attached. This is my biggest project yet and has taken me 18 months of evenings and weekends but I'm very pleased with the result and so are building control.

 

[ShaunCorbs]

One major problem and I would be worried about is that flue is very dangerous and needs turning off

 

[Dtwone]

been onto RWC again, like one of you suggested they also think restricting the flow controllers right down is worth a try.
Maybe the Grundfoss pump in the kit is just too powerful (even on low setting) for a smaller setup? It is used on the manifolds with many more loops but he thinks it's possible it's just overwhelming the return from the floor with the flow rate I've had it set at.
He's also asked for pics of my whole system to take a look over which was very good of him, now that's what I call good service and a company I'd recommend to anyone.

 

[Dtwone]

One major problem and I would be worried about is that flue is very dangerous and needs turning off

it's a bit deceptive in the picture but it's within the Gas Safe general requirements and also the manufacturer specific requirements for distance from wall, below opening window and from roof line and roof windows, this was installed by a gas safe engineer too.

 

[ShaunCorbs]

it's a bit deceptive but it's within the Gas Safe general requirements and also the manufacturer specific requirements for distance from wall, below opening window and from roof line and roof windows, this was installed by a gas safe engineer too.

What boiler is it ?

 

[Dtwone]

potterton suprima 60 non condensing

 

[ShaunCorbs]

So it's a min of 1m away from the window/wall?

 

[Dtwone]

So it's a min of 1m away from the window/wall?

yeah, 3 maybe 4 roof tile lengths and its a very low pitch 12.5 degree roof so not much length of tile lost in the incline, fitter was not initially sure so actually called Gas Safe to get his interpretation of the diagrams confirmed, it's close to max length of that flue allowed on that boiler with the elbows included but it actually ran better emissions when tested than the original short straight flue did - go figure that?

 

[ShaunCorbs]

I would say it's too close

 

[Dtwone]

I would say it's too close

I'm not questionning the the requirements but it's actually further away from opening windows (both horizontally and vertically) than the old horizontal flue was when the house was newly built, silly house layout with the flue going out of the back wall rather than a side alley.

 

[Dtwone]

well, as a follow up to my call today RWC technical have replied via email and OK'd my install from my description and photos, their advice is to try restricting the zone actuators and then get a new valve body so hopefully I'll get to the bottom of this soon.
Thanks again for all your suggestions, I'll let you know the outcome.

 

[Ric2013]

Thanks again for all your suggestions, I'll let you know the outcome.

I for one will be interested to hear back from you.

 

[Dtwone]

I for one will be interested to hear back from you.

Well its not an over specced pump, with both actuators almost shut off it shot up from 17 degrees to 65 on the manifold input within 10 minutes 🙁 new mixing valve it is then, you never know perhaps I dropped an olive into it?

 

[Dtwone]

Well I think I've sussed it, I removed the valve to watch the stat react to hot water from the side connection, the stat didn't move at all so I removed the control tap and then the stat and Spring, I then reassembled with no spring and repeated. Still no movement of the stat, and then I realised the stat didn't recess further than flush with the tap base which means no return flow can mix into the inlet through the stat to the pump.
Basically the drilling in the valve body the stat recesses into isn't machined far enough to allow the stat to open!
This also explains why when I wound the tap into the minimum position, if not when it was factory assembled, the stat pin was crushed into the wax body so it appeared damaged when I compared it to a new one.
Pictures uploaded show how the stat plastic surround is flush with the brass body of the tap face when the tap is screwed in, I'll mail the info and pics to RWC but I'm pretty sure it's a manufacturing defect, typical when this is the first time I've used or seen one.

 

[Ric2013]

I've never had to take one apart, so can't comment, but I like your investigative approach... let's hope you're right.

 

[Dtwone]

Well it's sorted, just before Christmas I bought a new RWC mixing valve.
So it was the valve that was faulty but not in the way I had thought.
Turns out the brass tap mechanism that was fitted to the original unit is incompatible with the main casting and thermostat!
Basically the new tap has a different rear face that essentially makes it shallower and allows the water to flow and the stat to open. I couldn't resist so took the new one apart to investigate!
In the images attached you can see the new assembled unit at room temp with the stat very slightly open from the tap face, i.e. allowing a small flow of returned cooled water from under the floor. The old unit is jammed shut at any temp.
In fact as I'd discovered before, the old unit doesn't allow the stat to move at all, and worse than that as the tap face extends as you dial the temp down it crushes the stat pin into the wax and damages the stat!
The interesting thing is that I've carefully measured all of the new casting and it is identical to the old one so it's only the new tap that is different.
In the new year I'll ask RWC what is going on, because I'm interested to know what has happened here as the valves have the same part no??
The retailer was pretty poor, basically they only supply a whole kit with this valve and pump, so I'd have to pay packaging to return, £250 for a new valve and inferior pump or over 500 for a new kit and then wait weeks for a warranty claim. In the end (and actually suggested by the retailer - cheek) I bought a new valve for £100 from a different supplier to get it in a couple of days and took the cost myself. Bit annoyed and won't be recommending them to anyone soon.
Bottom line is there was nothing wrong with my self-install, it was a really odd, hard to diagnose fault with the mixing valve so I thought I'd share the detail.
I now have a steady 45 degree flow and a very happy cat lying on the new floor 🙂

New unit slightly open to return flow at room temp:

New tap has the protruding ring, but shallower main base surround

At initial low temp the input thermometer reads what I'd expect now, at about 42 on the knob it runs at a steady 45 regardless of other demand on the boiler

 

[Ric2013]

So, it was equipment failure after all, not an installation error. Good good, glad you got it sorted. Unfortunately most things seem to be built and sold with low margins and this is the sort of sheight that we end up with.

As an aside, I know a plumber who insists the reason a TRV he installed won't allow any hot water through on any setting is that the customer puts her open-shelved TV stand in front of it, thus restricting airflow. I've seen it, I think it's a faulty TRV, as I don't think the shelf can possibly restrict airflow by any meaningful measure, but he was trying to train me so I just nodded politely. The lesson I learnt was to always blow through TRVs I'm about to install and check they are all roughly in calibration with one another, then they should all work about the same as one another. But on the production line, this would cost a few extra pence, which means that by the time it gets to the user, that's another £5 or so. So, sadly...

Going back to UFH, I used a different supplier and was very pleased with the quality of some of the components, and thought others were pants. Only reason I bought the kit was that it was easier to argue potential problems if I had used a kit, rather than make it up myself. I did suggest improvements to the firm, giving them some potentially valuable(?) feedback on what I liked and disliked (it was about 50/50), but they didn't seem that interested (I certainly never heard back) or even that knowledgeable about their products.

 

[JonnyF]

Hi. Only just skimmed the thread but this seems exactly the same issue I’m having with a Polypipe 4 port set up and pretty poor technical support from them. Would there be any chance I could speak to you on the phone please rather than send messages back and forth? Thank you