Thanks @Spectric really appreciate your insights. It’s a big learning curve for me, but fun! I understand that the system was installed by ADM plumbing based in Stoke. I’ve spoken with the engineer who suggested he had installed the system. I was after the system design but he suggested that it hadn’t been designed, he made it up on site. Now, I could be wrong but I understand that any system installed in 2021 had to be designed to ensure that the boiler had a temperature no higher than 60C? With full heat loss calculations for each room to size the rads / underfloor properly. I’m intending to get him over in a couple of weeks to service the system and walk me through it. I’d like to get the best understanding of it beforehand to know what to ask him.
Central Heating system help
- Thread starter deema
- Start date
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As I said what you need is a simple line diagram of your system showing flow paths, control valves and all the components plus having another simple diagram of the so called boiler logic which is the control path from a thermostat to give a demand signal, each zone should have it's own ability to request heat from the boiler. Your pipe work is notthe best I have seen but it is definately not the worst and the pipe insulation makes it look worse than it is, it looks like 22mm insulation has been used on a 15mm pipe down at the bottom and hence the large corner crease.
With all condensing boilers the return flow temperature will determine if the boiler goes into condensing mode, this is quite a complex area of the design because if it is a replacement boiler using existing radiators then they may not be large enough to run at ideal temperatures.
The important thing to understand from the design aspect is Delta T, this is simply the difference in the average temperature between the central heating water flow temperature and your room temperature. For example, 20°C is classed as average room temperature so if the average flow temperature in the heating pipework is 70° C then your Delta T value is calculated as 70° C – 20° C = 50°C or Delta 50 which is the current value. So why does this mater, well when you size radiators it is this Delta T value which is used to get the right one for a given sized room, if you look at a chart of radiators all the heat outputs will be given for a Delta T value which is now T50. If you are not using this value for Delta you have to use correction factors which in simple terms means as you reduce flow temperature you increase radiator size so a 1Kw rad based on T50 becomes a 750 Watt rad if you use T40 & vica versa.
So the guy can do the design on site, he will just split the property into zones, measure the size of the rooms and a few other factors like size of windows and determine how much heat is required for that room, also taking into account the usage so bedrooms run cooler and this gives the sizes of radiators needed and total gives the boiler size, gone are the days of just fit a boiler you know is big enough and control the temperature by opening windows !
To give you an idea of what I mean by a basic diagram this is what I knocked up in Excel before I got a 2D cad package and it just makes things clear. As I live in a bungalow no zoning is needed for the heating.
With all condensing boilers the return flow temperature will determine if the boiler goes into condensing mode, this is quite a complex area of the design because if it is a replacement boiler using existing radiators then they may not be large enough to run at ideal temperatures.
The important thing to understand from the design aspect is Delta T, this is simply the difference in the average temperature between the central heating water flow temperature and your room temperature. For example, 20°C is classed as average room temperature so if the average flow temperature in the heating pipework is 70° C then your Delta T value is calculated as 70° C – 20° C = 50°C or Delta 50 which is the current value. So why does this mater, well when you size radiators it is this Delta T value which is used to get the right one for a given sized room, if you look at a chart of radiators all the heat outputs will be given for a Delta T value which is now T50. If you are not using this value for Delta you have to use correction factors which in simple terms means as you reduce flow temperature you increase radiator size so a 1Kw rad based on T50 becomes a 750 Watt rad if you use T40 & vica versa.
So the guy can do the design on site, he will just split the property into zones, measure the size of the rooms and a few other factors like size of windows and determine how much heat is required for that room, also taking into account the usage so bedrooms run cooler and this gives the sizes of radiators needed and total gives the boiler size, gone are the days of just fit a boiler you know is big enough and control the temperature by opening windows !
To give you an idea of what I mean by a basic diagram this is what I knocked up in Excel before I got a 2D cad package and it just makes things clear. As I live in a bungalow no zoning is needed for the heating.
Stuart Moffat
Established Member
In Excel Roy? That’s some spreadsheet!
Yes Excel can be pushed beyond spreadsheets, not the easiest if compared to something like Qcad but with the ability to " Send to Back " and "Bring to the Front " you can be quiet creative.
Spectric, Impressed on two counts!
RogerS
Established Member
+1
And here is the wiring
Powerpoint is pretty good for drawings too
Deema,
Do you have any heated towel rails in bathrooms?
Looking at the pipe layout photo you appear to have an additional heating circuit.
Is the underfloor heating manifold some distance from the cylinder cupboard?
Is it possible that the flow through Pump D is actually opposite to your arrows?
In which case the gate valve A is merely there to assist with filling and venting the system (as previously mentioned who still uses gate valves)
Do you have any heated towel rails in bathrooms?
Looking at the pipe layout photo you appear to have an additional heating circuit.
Is the underfloor heating manifold some distance from the cylinder cupboard?
Is it possible that the flow through Pump D is actually opposite to your arrows?
In which case the gate valve A is merely there to assist with filling and venting the system (as previously mentioned who still uses gate valves)
That extra pump, it looks like another smart pump with digital display. Have you tried to see when it powers up, could it be providing a hot water supply for the UFH pump due to the distance ? It looks like it is fed by the other pump which would be really odd via that gate valve at the top and whatever it is supplying that bottom pipe from that odd pump looks to be 28mm ? you then have two returns from where coming back to the pump inlet so it really makes little sense unless there is other pipework not shown, ie below the boards or elswhere.
Seascaper
Established Member
Hello,
Looking at the installation this is a very unprofessional installation, possibly by a trainee. Suggest you contact the house builder, check to see they were qualified or had any experience installing plumbing,
Regards
I don't think @deema means brand new, just new to him and with new houses most house builders will have changed name, declared bankruptcy or just vanished.
nolly47
Established Member
Under floor heating
A = the pump for under floor heat manifold
B = 4 port proportional mixing valve
c = I think is motorized valve can’t see it all
I = the circuit thermostat’s
H = flow rate gauges
Flow water enters valve B from F is then mixed with manifold return water E blended water exits through G surplus unrequired water exits through D and returns to boiler. The under-floor heating will have been setup by the installer, without design details there is not a lot you can do.
The radiators that don’t working properly are the all on the same circuit ground or first floor?
If you turn the motorized valves 1,2,3 off then see what gets hot, which pipe is the return from the cylinder
A = the pump for under floor heat manifold
B = 4 port proportional mixing valve
c = I think is motorized valve can’t see it all
I = the circuit thermostat’s
H = flow rate gauges
Flow water enters valve B from F is then mixed with manifold return water E blended water exits through G surplus unrequired water exits through D and returns to boiler. The under-floor heating will have been setup by the installer, without design details there is not a lot you can do.
The radiators that don’t working properly are the all on the same circuit ground or first floor?
If you turn the motorized valves 1,2,3 off then see what gets hot, which pipe is the return from the cylinder
It’s a house that was renovated about 2 years ago, the central heating system was allegedly totally replaced. I’m really interested why you feel it’s appalling? This isn’t an area I profess to have any knowledge about to determine what’s good and poor. Any pointers would be really helpful
Having seen many instalations then this does not stand out as appalling, what makes it look worse is the pipe insulation which is badly fitting and looks the wrong size. I would not have used gate valves as they are cheap and nasty, ball valves are much better and unless you use pre formed insulation like these then it is not always easy to get a tidy job.
https://www.bes.co.uk/insulation-90-bend-15mm-dia-x-25mm-wall-pack-of-2-16709/
https://www.bes.co.uk/insulation-90-bend-15mm-dia-x-25mm-wall-pack-of-2-16709/
@nolly47 The rads that don’t work are on both circuits, or upstairs and downstairs. They are random, it not in one particular area of the house.
I will do a bit of experimenting to find out what circuit is on what return.
One thing I can’t work out and I don’t think has been answered is how you balance the UFH with rad circuits. I’m assuming that the balance valve with no demand from the UFH to top up is a straight return offering little back pressure. If this is the case then it will starve water from any rad circuits open?
I will do a bit of experimenting to find out what circuit is on what return.
One thing I can’t work out and I don’t think has been answered is how you balance the UFH with rad circuits. I’m assuming that the balance valve with no demand from the UFH to top up is a straight return offering little back pressure. If this is the case then it will starve water from any rad circuits open?
The ball valve is just a ball with a lever and requires 90° movement to shut and they do not have a tendency to seize. The gate valve is a screw device that raises and lowers a slide which jam and that tin handle will just rotate if too much force is applied trying to move one.
UFH uses water at a much lower temperature and flow unlike the radiators which will have constant flow. The UFH only tops up the hot via the mixer when needed and does not continously circulate hot water like a radiator, so balance the rads with no UFH.
The underfloor heating circuit is pump driven and it is taken that the pump will produce enough flow to comfortably move water around the entirety of the underfloor heating.
The individual underfloor circuits are regulated via the small flow rate site glass type gauges on the upper rail. Slightly lifting the red locking ring will allow these to turn which will increase or decrease flow around the circuit. Be warned if you keep turning eventually the site glass piece will unscrew and water will leak freely!
In general we look for all the circuits to have even flow and if there are numbers on the gauges I would suggest the water should be just over 1 on each gauge, this would usually represent a flow of 1.2 mps (meters per second)
The radiator circuit is also pump driven with all the rads balanced across their circuit.
In terms of UFH starving the radiators this will not happen as both circuits are pump driven.
The mixing valve attached to the underfloor heating is there to protect the underfloor heating and also the structure of the floor. It's job is to prevent radiator heat (60 - 80 degree c) water flowing into the floor loops. It does this by always allowing a small amount of the cold returning water (from the floor loops) to be mixed with the flow hot water entering the UFH pump in order to maintain a lower set temperature.
Most UFH systems also have a secondary safety thermostat attached to the flow pipe which would cut the electric supply to the UFH pump if the mixer develops a fault and the flow temperature exceeds a certain value (E.G. 50 degrees C) This will prevent possible major damage from thermal shock of the floor screed which can happen if its heated too quickly and too hot.
In short the radiator circuit is what is known as a Variable Temperature Circuit and the underfloor heating is known as a Constant Temperature Circuit.
In terms of random Rads not working this is likely to be local to the radiators and my first check would be stuck pins within the thermostatic heads.
To check remove the TRV head and press the pin in gently but firmly with a flat disc like thing. it will only travel a maximum of a few millimetres and should freely press in and then return out when released. If its stuck down then gently pull up with pliers but remember no more than 4mm maximum travel.
Second thought would be sludge in the system, more noticeable when some radiators seem to get only warm in cold rooms or have cold spots in the middle. This may need attention from a professional to clean and flush the system, neither cheap nor quick if done properly, but can restore system performance and reportedly decrease fuel usage by circa 20%.
If the system is seemingly suffering from sludge and your a confident diy'er then start by draining it and refilling with the addition of some system cleaner (check screwfix etc) run it for at least 24 hours with the cleaner in then shutting down rads which work properly (usually upstairs as the sludge falls to the bottom of the system) trying to force flow through any stubborn rads.
After a day or two empty the system out and if a wet vac is available disconnect each rad and hoover all water out of them and the low level pipework.
Refill and add inhibitor (screwfix etc) check for leaks and hopefully you will have cleared any sludge, and restored flow.
Finally the reason plumbers hate gate valves is quite simply they don't hold water, when shut they will still allow water to pass through where as ball valves will not.
