UFH constantly calling boiler

CAF80ST

Hello, 

I am new here and wondering if anyone is able to offer me some advice please. 

We have wet UFH throughout the entirety of our property (ground floor). In the summer we were very concerned by the amount we were paying for Gas (hikes aside), this was circa £700 per month (for each of May, June, July) although there was absolutely no heating on, no other appliances using gas, no leak.

Room temperatures are controlled by thermostats, of which these were all set to Frost Protection (ie 'off' unless the temperature dropped below 16 degrees, unlikely in the summer). It was during this time I noticed the boiler would fire up perhaps every 20 minutes and stay on for 10 minutes. This happened all day and all night. I also noticed when this happened the pump attached to the UFH manifold was also running when the boiler was being called, (with 3 lights ignited on the manifold indicating Power, Boiler, Valve,) even though there was no call for heat to any rooms/zones. 

We contacted an independent plumber and electrician of our findings who also agreed this was happening, and it was explained from a plumbing aspect why this is happening. As I understand the manifold calls the boiler to ensure the hot water is hot and ready when it does eventually need it. The water will then cool down, and the manifold will call the boiler again to reheat it, so on so forth. We have a large joule hot water cylinder which should hold its temperature for a long time, that's presuming the UFH system is even connected to this?. The plumber and electrician were a little baffled as to why the manifold is almost constantly calling and firing up the boiler in such a short space of time. An interim 'off' switch was wired up to the manifold so we could turn off the manifold in its entirety (which also completely shut down the thermostats) for the remainder of August this year - and what a difference (not only to our eardrums) to the gas bill. We had gone from £700 per summer month to £112!

Alas, it is now winter, the manifold for the UFH is once again back on and the same thing is happening. The boiler is being called all day long and all night, waking me at 3:20am this morning of which I came downstairs to check and again no rooms/zones were calling as they hadn't dropped below 16 degrees.
The heating for individual room/zones thermostats are now set for 2 hours in the morning, and 2 hours in the evening, however as mentioned the boiler is being called all the time. We have received another gas bill for £840. I am sure this is the reason for it, the constant calling and firing up of the boiler, although I am not that well informed to understand why, what we can do to stop this, or if something has been installed/wired wrong? The installation company have been little to no help, hence the independent plumber and electrician, however both admitted it's not really their speciality and view as above. 

Any help and advice would be greatly appreciated. Apologies in advance for any incorrect terminology.  

Thank you

Krakkkers

UFH? isn't that long life milk?

CAF80ST

 Sorry, Under Floor Heating

Rodders53

Something is wired and/or set up wrong.  You need a plumber and/or electrician who is familiar with such UFH systems to sort it out.  DO NOT call back the last people who obviously arrived on horseback.

Do your own due diligence and research the subject of UFH and controls and how they are supposed to work.

You'll need to identify makes and models of ALL the component parts to find and read the manuals.

Room Stats - conventional or Day and Nigh/Setback? for UFH)

Other controls (UFH timer on/off other zones and HW timers).

Zone valves for UFH and Central Heating Rads and Hot Water cylinder.

Some say UFH is on 24/7 with Day/night setback stats (set back circa 4-5 degrees lower than daytime comfort)...

If no UFH room is calling for heat then the UFH manifold pump will be pushing into a dead short if running (it ought to stop under control of the UFH wiring/control centre though!).  Although here may exist a 'UFH bypass loop' to allow for the minutes it takes for UFH zone valve actuators to open a floor loop when a room stat calls for heat.

My gut is suggesting a stuck microswitch in one of the main valves for HW / UFH / CH (other rooms) that is calling for heat 24/7 or - perhaps in the UFH control/wiring centre.  Such faults are 'bread and butter' issues for decent, qualified, techs to resolve.

molerat

My gut is suggesting a stuck microswitch in one of the main valves for HW / UFH / CH (other rooms) that is calling for heat 24/7 or - perhaps in the UFH control/wiring centre.  Such faults are 'bread and butter' issues for decent, qualified, techs to resolve.

This.  The thing that actually calls for heat is the zone valve, not the timer, thermostat or anything else.  Could be the valve is stuck open as the system is using gas / getting hot.

My son had a similar problem with his standard heating, boiler overheating and all sorts of problems.  BG called out several times and the only problem could be the boiler according to them.  Took someone with a bit of common sense and logical diagnosis skills - AKA me -  to figure out it was a microswitch in the zone valve stuck on made.

Rodders53

molerat said:
Took someone with a bit of common sense and logical diagnosis skills - AKA me -  to figure out it was a microswitch in the zone valve stuck on made.

Drayton ZA5 valves by any chance (or the BG-labelled equivalent)?   
Changed some switches on the late in-Laws system (me being too mean to get a new head).   They seemed to mechanically stick rather than electrically weld in the call for heat position.

Rodders53

NB For information, MY UFH pump is fired up by the (Drayton, I think) wiring control centre it is wired from. 
A 'Boiler' demand from that control centre goes to the UFH (Honeywell) valve motor to open whose microswitch signals my Kerosene Boiler (with internal pump) to operate once open.

So my suspicion falls more on that control centre than any other place... but I could well be wrong.

alan_d

Rodders53 said:

Something is wired and/or set up wrong.  You need a plumber and/or electrician who is familiar with such UFH systems to sort it out.  DO NOT call back the last people who obviously arrived on horseback.

Agree.
I have installed UFH systems in 3 houses, they are not difficult to control or diagnose, and shouldn't be demanding the boiler to fire unless the zone actually needs heating.

And this, is simply not true:

As I understand the manifold calls the boiler to ensure the hot water is hot and ready when it does eventually need it. The water will then cool down, and the manifold will call the boiler again to reheat it, so on so forth.

You need someone out who can properly test, diagnose and fix it.
The switch installed by the previous cowboy was a bodge to cover up a fault they couldn't diagnose.
Bear in mind that it's possible this system had never worked properly from day 1 due to the original installer screwing up some part of the wiring or config, i've seen that before also.

nadsat

As others say it could be a faulty zone valve switch.

One other thing occurs to me and that is the hot water - is that on all the time as on some systems it will keep cycling local heating as well as keeping the tank hot. 

daveyjp

I noticed this at my parents property a few years ago.  The boiler was providing heat to the UFH in the middle of summer.

All down to a faulty room stat in the bedroom they don't use often.

All the stats have all failed and have been replaced since they had the system installed.