Boiler control/ Home set up

gorwanvfr

Have a question about the central heating system in my home. A few details of the system set up. Oil fired boiler Firebird Enviromax condensing boiler, fitted out in the garage (approx 60 feet from the house). 300L stainless steel tank twin coil as there is a solar panel fitted. Only one thermostat fitted in the system and that’s on the boiler it’s self. The boiler is feeding 30 rads and 40 sq metres of under floor heating, the under floor heating is feed off a mixer valve and has it’s own circulating pump (Gunfos). When the heat is switched on everything is fine the house heats up within 15 minutes and the under floor is up to temp within an hour or so. The boiler is in condensing mode judging by the vapour plume and the water dripping from the drain.
Now for the question, the boiler is constantly switching on and off on its thermostat which is set to 55oC. It appears that the boiler jacket temp is reaching 55oC turns off the burner the circulating pump continues to run and with in 3 to 4 minutes the water temp drops to 52oC / 53oC and the burner turns back on with in a minute or two the water temp is back up to 55oC and again the burner turns off. The burner continues like this for as long as the heat is turned on. I’m guessing that this cannot be mechanically good for the burner never mind efficient. Is there any thing I can do to improve my system and stop the constant cycling? If I was to fit a room thermostat cant see how it would improve things as the room would never get up to the 21oC trigger point of the stat and so the boiler thermostat would still be in control???
Any thoughts or help very much well come.

cmsp.plumber

a condensing boiler works on 20'C flow/return difference. a standard boiler is 10'C. your boiler is short cycling, ie coming on off on off. a room stat wood not sort ur problem. i would suggest getting firebird out to have a look at it. the pump running is fine its just 2 get rid of the heat from the boiler, it protects the boiler basically

gorwanvfr

cmsp.plumber wrote: »

a condensing boiler works on 20'C flow/return difference. a standard boiler is 10'C. your boiler is short cycling, ie coming on off on off. a room stat wood not sort ur problem. i would suggest getting firebird out to have a look at it. the pump running is fine its just 2 get rid of the heat from the boiler, it protects the boiler basically

Thanks for the reply. The boiler is brand new only fitted 3 months ago. according to the info I go my hands on and the info from the plumber the boiler is sized for the heat load on it. Really don't want to get him back as I feel he is not really up to speed with condensing boilers. would changing the size or speed of the circulating pump help me out?

cmsp.plumber

is the boiler temp a digital display? can u see that at 52'C it comes back on?

gorwanvfr

Just using an infa-red temp gun on the inlet and outlet pipes.

cmsp.plumber

ok and on the hotter of the 2 pipes its 52'C? if so contact firebird.

gorwanvfr

Just so I don't give you the wrong info as regards temps and timings I'll take a note of everything tomorrow when the heat it running. Would really like to sort it out once and for all. The reason for the new boiler was to cut down on the oil usage put the new boiler is running the same as the old standard boiler. Thanks for the help so far

Pete67

It sounds like the boiler is operating correctly - ie controlling the flow temp to around 55C which is the thermostat setting. If the heat load is low, then the boiler will only fire for a short period at a time, and the pump should continue to run when the burner cycles off. When the heat load is higher (colder weather) then it will fire for longer periods. If the boiler is oversized it may be possible to reduce the output of the burner by changing the nozzle size.

For a heating system of the size you describe, it is unusual that there are no controls installed. At a minimum I would expect that the heating is zoned into living and sleeping areas, with seperate room thermostats and timers for each zone, and TRVs on the rads in rooms without a room stat. Also the UFH should have controls to modulate the water temperature going to the floor slab - it should be much less than the boiler flow temp.

gorwanvfr

Morning gents, started the boiler this morning and took a few readings. the water temp was 10'C at the start it took 35 minutes to get the water up to 60'C at which point the thermostat cut the boiler out. the boiler remained off for 20 seconds and then fired again, ran for 3 minutes and then off, Started again after 40 seconds ran for 2 and a half minutes then off for 40 seconds ran again for 2 and a half minutes. the 40 seconds off 2 and a half minutes on this cycle continued until I switched off the heating.
The underfloor heating only has a mixing valve that looks like a TRV. the temperature on the supply and return lines on the underfloor heat read 60'C and 40'C the floor itself is running at 22'C.
The original heating system was installed in the house when we purchased it. since them the underloor heating was installed and the new boiler fitted. Don't mind speeding some money on making the system work correctly or better but don't want to throw money away either.
I worked out the heat loading from the rads and the underfloor heating using info from the net and it worked out at 38Kw.
Believe the boiler is 44Kw.
The boiler maintained a 20'C differenial between supply and return while it was running. the system pressure was 1Bar when the system started and went to 2 Bar once the system was up to temperature.
Hope I'm giving you enough info.

gorwanvfr

Any ideas or comments??

Lisawully

Hello, I am new to the Forum, I have a slightly different boiler problem. I have a Firebird Boiler installed since the end of November and the problem I have is the Photocell or magic eye is clogging with soot and the boiler stops firing up. I have to clean the photocell once a week minimum and sometimes more often, it is a real pain in the neck, has anyone out there a more permanent fix to the problem.

Thanks & regards

gorwanvfr

Lisawully wrote: »

Hello, I am new to the Forum, I have a slightly different boiler problem. I have a Firebird Boiler installed since the end of November and the problem I have is the Photocell or magic eye is clogging with soot and the boiler stops firing up. I have to clean the photocell once a week minimum and sometimes more often, it is a real pain in the neck, has anyone out there a more permanent fix to the problem.

Thanks & regards

For fear of some people jumping all over my post here goes, to me it sounds like your burner is over fuelling which is causing the build up of soot. When I say over fuelling it may be the right amount of fuel but not enough air (wrong fuel air ratio) is there any smoke out the exhaust when the unit is running? If yes have a look at the air adjustment plate on the side of the burner. Would recommend you get a registered boiler tech to look at it. hope it helps

Lisawully

Thank you gorwanvfr, I will have this investigated, appreciate the quick reply.