Plumbing 101: the absolute basics

[Ferdinand]

I have excavated in the filing cabinet, and behind the manifold and - ai caramba! - there exists a pump and even a pressure vessel (so why is it short cycling !),

 

The building spec does not look very impressive by BH standards (conversion was done to 2009 planning permission by previous owners). Floors are 75mm screed containing ufh over 85mm of polyurethane insulation and a slab (membrane somewhere). Walls are (outside-in) Facing brick, 100mm rockwool, 100mm thermalite blocks, and (I am assuming) service cavity then plasterboard. That is the specification on the drawings. Floor area covered by ufh is probably roughly 105 sqm.

 

The approved ufh drawing contains the statement "Mean Water Temperature 30-45 degrees.

 

I make that a wall U-value of 0.26m, and a floor u-value of 0.26.

 

The ufh system is Eco Therm Plus 9, There is 600m of 16mm pipe - I have a total of a little under 400m currently turned on in the flow controllers. At 200mm centres except in the bathroom, where it is at 100mm centres.

 

Out and return temperatures on the manifold thermometers are now 42C and 28C. Presumably if I add in the rooms currently shut off that will narrow a little more.

 

Piccies.

 

The boiler is an 18 month old Bosch Greenstar 42CDi Classic ErP, which should be capable of dealing with anything I can throw at it.

 

 

Wider view

 

 

View of pump and tank. Mixing Valve (?) set to 50 (degrees C?)

 

 

Top of the Pump, was specified as a GrundFoss 15-60.

 

]

 

This one looks to be up to 90W, and to be set to High.

 

 

Ferdinand

 

Edited December 12, 2017 by Ferdinand

[Nickfromwales]

@Ferdinand

Last pic shows pump set to three. Knock it down to 2 and wind the input TMV temp down to 40oC. Leave for 48 hrs to acclimatise and check how it's performing. 50 is way too high. 

Dont confuse your red expansion vessel for a buffer tank, as it's not a buffer and therefore will do nothing towards stopping short cycling. I don't see a 22mm bypass valve anywhere, is there one under the boiler ?

Does the house have rads and UFH or just that manifold and just the one floor of UFH ?

 

[Ferdinand]

3 minutes ago, Nickfromwales said:

@Ferdinand

Last pic shows pump set to three. Knock it down to 2 and wind the input TMV temp down to 40oC. Leave for 48 hrs to acclimatise and check how it's performing. 50 is way too high. 

Dont confuse your red expansion vessel for a buffer tank, as it's not a buffer and therefore will do nothing towards stopping short cycling. I don't see a 22mm bypass valve anywhere, is there one under the boiler ?

Does the house have rads and UFH or just that manifold and just the one floor of UFH ?

 

 

What does a bypass valve do in a ufh system? 

 

This pic at the end is the list of components from the ufh specification drawing. Also a pic of the full drawing.

 

Won't that slow down the flow, which (I thought) was supposed to run at between 1 and 2 on the telltale indicators on the ufh circuits?

 

I hid this in the previous post, which should do that.

Quote

Out and return temperatures on the manifold thermometers are now 42C and 28C. Presumably if I add in the rooms currently shut off that will narrow a little more.

 

Should I put the rest of the system (my office plus a study bedroom plus the utility) on the flow adjusters, which will kick in another 240+m of pipe-run in on 3 lobes on top of the probable 350m I currently have running ie do I need it all on for this exercise?

 

Cheers

 

Ferdinand

 

 

 

 

 

[ProDave]

A bypass valve goes between flow and return as far away from the boiler as you can get it (in the airing cupboard in our case)

 

Normally it is shut.  But if all circuits are shut and there is still a boiler demand, it opens and gives the boiler somewhere to pump to.

 

In practice, the only time it opens is when (note when, not if) the microswitch in one of the motorised valves fails, so it is calling for heat even though the motorised valve is shut

[Jeremy Harris]

Looking carefully at the manifold, it seems that the right-most loop is always on, as it has no actuator, but is fitted with a cap to hold the valve open, so it is acting as the bypass.

[Ferdinand]

Cheers all.

 

So I have now set my flow temp at 40C or just over, the return has dropped to about 28C, but I have dropped the pump to setting 2 to slow the water down so the return temp may be lower and I may be able to reduce the flow temp a little more - boiler can modulate down to 35C flow temp.

 

I have turned all the flow valves full except the conservatory connections that are just stubs.

 

May need to adjust the upstairs radiators in case we are hot or cold.

 

And now it is to wait.

 

Ferdinand

 

 

 

[Ferdinand]

So a day later the flow and return temperatures have stabilised at about 38-40C and 27C, and the thermostat in the hall says it is at a temperature of 18.5-19C.

 

I think I need that thermostat to be at about 20.5C for comfort, but I will give it all another day to stabilise.

[Nickfromwales]

20 hours ago, JSHarris said:

Looking carefully at the manifold, it seems that the right-most loop is always on, as it has no actuator, but is fitted with a cap to hold the valve open, so it is acting as the bypass.

Well spotted. But the strangest thing is it should really be the space where the room stat is . It's a bedroom according to the schematic. 

[Ferdinand]

Returning to the tuning of my ufh system .

 

I have left the system alone for a week, and it is running the house at 19.5-20C (on the manual setting of the stat), with heating coming into all the rooms on the ufh and delivering heat far better than before. That is when the general room thermostat (in the hall) is set to 21C and indicating 20C as the actual temperature reading.  The individual room stats are all set at 25C+ to take them out of the reckoning. It is possible that the room stat is stopping the heating doing its max at the current setting due to hysteris etc, so my first step is to put that up by a jump to see if we can raise the temp with current flow temp etc.

 

The issues now to be addressed are that the room balance is not quite right, and that is not going to be quite enough over Christmas - visitors will like it warmer. Say 22C or 23C. 

 

Am I right that my next steps are?

 

* Juggle moderately adjust flow valves to give a distribution of room temperatures closer to the desired mix eg lounge is too cold, as that is where mum sits.

* Set overall timer - 06:00am to 10pm will be a start.

* Boost overall temperature by a couple of degrees. That may be where there is capacity on current settings, or can I do that by notching up the flow temp by 3-4C while we have visitors?

 

On 13/12/2017 at 13:35, Nickfromwales said:

On 12/12/2017 at 16:46, JSHarris said:

Looking carefully at the manifold, it seems that the right-most loop is always on, as it has no actuator, but is fitted with a cap to hold the valve open, so it is acting as the bypass.

Well spotted. But the strangest thing is it should really be the space where the room stat is . It's a bedroom according to the schematic. 

 

So does that mean that a "bedroom" is always-on or never-on? ie Is the open valve passing water through the loop, or excluding the loop?

 

Cheers for any further comments.

 

Ferdinand

[Jeremy Harris]

It means that the right most circuit is always on.  Whether it is as per the schematic and a bedroom needs to be checked, it's possible that the manifold pipes were not connected in the order shown on the plan.

 

Changing it is easy, just swap the cap on the right most circuit with one of the actuators, whichever circuit you want to act as the bypass and be on all the time.  You may need to change the wiring of this actuator to make sure it's now on the bedroom zone, if you have zone switching.

[Nickfromwales]

The next sensible thing to do is get rid of the rotary mechanical wall thermostats, as they're basically never intended to work with in floor / slab heating. They simply don't respond quick enough. The issue is that you need to set them way over what you need as the undershoot is massive. 

Current customer is awaiting me to return to fit digital controls with 0.5oC hysteresis, about the minimum you'll need for such accurate, multi zone ( space ) heating, and the fine tuning of. 

You may want to increase the manifold flow temp by 2oC and no more, and reassess over the next 48hrs. 

Good to hear the results are starting to come, so at least we're getting somewhere. . 

Trying to balance the loops by closing the flow down per loop will be a royal pita, and you'll literally have to do that at 0.5 lpm increments, adjusted every 48 hrs until you see the change. Personally I'd change the stats and lean on those, the idea being that you can set the flow temp a little higher to get a better response time, and still avoid the under / over shoots. 

Ufh in a non passive house is a tricky beast to tame. 

[PeterW]

Why not swap for the Wunda heads that do both flow and temperature ..??

[Jeremy Harris]

I've just looked at the drawings again, a bit more closely, and found that the orientation of the manifold in the drawing is 180 degrees out compared to the installation photo.  That suggests that the always on bypass loop may really be the bathroom, rather than a bedroom.

[Ferdinand]

16 hours ago, JSHarris said:

I've just looked at the drawings again, a bit more closely, and found that the orientation of the manifold in the drawing is 180 degrees out compared to the installation photo.  That suggests that the always on bypass loop may really be the bathroom, rather than a bedroom.

 

That sounds sensible, as the bathroom is the source of warmth. There is also a towel rail rad, which responds pretty much all the time - but I am guessing that that is plumbed as a bypass on the upstairs rad system.

 

It sounds like the guy who renovated the house did it to follow the ideas of a traditional system.

 

It makes sense, though, in some way as the downstairs bathroom is right in the middle of the house.

 

18 hours ago, Nickfromwales said:

Trying to balance the loops by closing the flow down per loop will be a royal pita, and you'll literally have to do that at 0.5 lpm increments, adjusted every 48 hrs until you see the change. Personally I'd change the stats and lean on those, the idea being that you can set the flow temp a little higher to get a better response time, and still avoid the under / over shoots. 

 

The flows are indicating about 1 lpm for nearly all of them, fully open. Is that low?

 

Well, having whacked up the boiler temp by a couple of degrees yesterday, but leaving the ufh on 24h on Manual, the temperature measured on the hall thermostat is now +1C at 21C not 20C. I will try a bit of crude flow juggling in teh next week.

 

@PeterW Do you have a good source for those Wunda heads? Sound interesting. May need to alter the design of the screw on panel ! What was it you said before - magnets? Presumably that is the type of magnets used for cupboard doors. I have some Howdens ones left, which cost 70p each.

 

Cheers

 

F

Edited December 21, 2017 by Ferdinand

[Nickfromwales]

20 hours ago, PeterW said:

Why not swap for the Wunda heads that do both flow and temperature ..??

Link ?!? ??

[PeterW]

10 hours ago, Nickfromwales said:

Link ?!? ??

 

https://www.wundatrade.co.uk/shop/home/actuator-auto-balancing/

[Nickfromwales]

12 hours ago, PeterW said:

 

https://www.wundatrade.co.uk/shop/home/actuator-auto-balancing/

Ah yes, sorry, thought there was a better one again. That's the ones I fitted last, and put @JSHarris on to. Good bits of kit. 

[MAB]

On 12/12/2017 at 10:26, Vijay said:

Fernox LS-X - great stuff and am surprised it's not been used/mentioned

 

I agree great stuff......Fernox LS-X works well for me:-

https://www.fernox.com/plumbing-consumables/ls-x-external-leak-sealer-50ml

 

Also recommend Loctite 55 pipe sealing cord especially on any threaded fittings which need to end up facing a certain way....as you can tighten up fully and then back off up 45 degrees with no leaks:-

http://www.loctite.co.uk/pipe-sealing-9886.htm

Edited January 29, 2018 by MAB