oil boiler cycling

[frpcraig]

Thanks lameplumber ,yes I have a new engineer booked in for next week.
What do you think an efficient cycling time is?
Thanks

 

[lame plumber]

if you mean how long to warm rads 10 mins reasonable and then your boiler should cycle on and off as required, and it will take however long it takes to cycle on and off, but obviosly not on off on off every minute or so.

 

[frpcraig]

I just want a rough idea lameplumber.
!0 mins off 10 mins on , 20 mins /30 mins etc.
A ballpark would be good,
I have read an oil burner comes to max eff, after 18 mins??
Thanks,

 

[lame plumber]

it will take at least 10 mins to reach peak efficiency as a boiler with correct flue temps etc, but then of course it will cycle on and off as req by need to heat return temp of water. best advice to you is to stop reading and trying to comprehend oil and burner manuals and just refer to the owners operating guide.

 

[dontknowitall]

Is there a by-pass fitted?

Thanks again,
Look please stop shouting at me and telling me I am an idiot.
You don't know my background.
....

I wasn't!!! If there is no by-pass fitted then it might short cycle. If there is a by-pass fitted then it could just be a case of adjusting the gate valve.

 

[peteheat]

Thanks for the replies.
Bunker the rads both upstairs and downstairs all heat up to temp in 20 mins,

About right.

If I turn the boiler stat down it comes up to temp quicker then short cycles, if I turn up the boiler stat it takes a bit longer to get to temp then short cycles.

Reads exactly the opposite to what I would expect, what controls your boiler firing?

If I go from a 0.65 to a 0.4 I will reduce my gph by 37% rather than halving it as you mentioned.
Riellos spec sheet for my burner says you can run between a 0.4 and a 0.65 nozzle with the same pump pressure.

Riello manufactured the burner not the boiler, it is the boiler manufacturer who spends the big money on R & D to ensure the correct burner, nozzle and settings are used to achieve the most efficient performance.

Lame plumber, if you re-read my posts I have always used a registered engineer, hence my issues!.

Peteheat, thanks again for your comments.
As mentioned I will get a stack temp ,co2 etc analysis done for sure.
What I object to is paying hundreds of pounds a year for an engineer not to service my boiler properly.

Far as I know from earlier posts I'm probably one of the most expensive service engineers who posts here, allowing for currency exchange rates I would be charging circa £100.00 for an oil boiler service.

I want my customers back again next year so if there is a problem with a job I do I want to know about it, I understand most who post here have a similar policy.

With respect I suggest you use a new service engineer / technician preferably one with a plumbing back ground.


I am quite capable off scraping crap off the inside of my boiler if the engineer doesn't
I have found nozzle containers that vary from 0.4 to 0.65 in the case of my boiler.

The burner can use nozzles in that range, that does not mean they suit the boiler in fact .65 is only part of the nozzle data.

I think my'engineer' has put bigger nozzles in over the years to combat the inefficient coked up chamber.
Best, thanks for your reply,
The boiler is sited in the downstairs toilet with a rad in it.No underground pipes
Most of the rads are singles and little.
I have no need to run the hw tank and the rads at the same time.
Cheers
Craig

You mention in a later post that it is now taking a continuous 80 minutes to achieve the same temperature the larger nozzle achieved in 20 minutes, the basic maths should be telling you all the advice you received was correct, you are using more oil with the smaller nozzle.

To answer your last question, the cycle time should be directly related to the heat loss of the building.

Nobody is calling you stupid we are trying to help by posting a few lines (I touch type with one finger) after we have completed a fairly hard days work, it is not always possible to trouble shoot a boiler problem without being in front of it.

Sorry I can't be of more help.

 

[frpcraig]

Thanks everyone, I have put the original nozzle back in the burner and promise to stop fiddling!
dontknowitall, I have found another manual red valve in the bathroom. It was wide open.
When I close it the boiler gets very hot then shuts down. There doesn't appear to be any short cycling when the valve is shut.
The boiler water temp stays hot for ages.
If I open the valve the boiler water temp (in the boiler tank) loses heat at the rate of 15 degrees celsius in 3 mins!
Is this the bypass valve you talked of?
Thanks
Craig

 

[Best]

Is this a red headed valve (probably a gate valve?) at a copper cylinder?
If so, then could be there to balance the flow through the heating coil.

 

[frpcraig]

Thanks Best, it is a red headed valve ,it is in the hw tank area.
One connection to it goes up into the loft, one connection seems to connect to the top of the hw cylinder and the ( a smaller pipe) goes to the hot water tap in the bathroom sink???
I may be wrong but that's what it looks like.
I've done some more tests and with the valve open the boiler gets up to temp then cycles often at about 70 degrees according to the boilerstat.
When I fully close it the boiler tank temp hits 95 degrees but does not short cycle.
Any ideas??
Cheers
Craig
If I turn the valve shut the boiler tank temp gets up to 90 degrees

 

[frpcraig]

When I say the tank temp hits 90 degrees I mean the top , the bottom is 70 degrees if that helps??

 

[SimonG]

You mean the cylinder?

 

[frpcraig]

No the boiler water tank.
I have the hot water cylinder shut off.
Cheers Simon.

 

[peteheat]

Thanks Best, it is a red headed valve ,it is in the hw tank area.
One connection to it goes up into the loft, one connection seems to connect to the top of the hw cylinder and the ( a smaller pipe) goes to the hot water tap in the bathroom sink???
I may be wrong but that's what it looks like.
I've done some more tests and with the valve open the boiler gets up to temp then cycles often at about 70 degrees according to the boilerstat.
When I fully close it the boiler tank temp hits 95 degrees but does not short cycle.
Any ideas??
Cheers
Craig
If I turn the valve shut the boiler tank temp gets up to 90 degrees

My reading of the above may appear crazy (not aimed at you Craig) is it possible that the hot water supply to the sink is being taken from the heating circuit?

Without a few photos or preferably standing in front of the installation I can't figure out if the gate valve is meant to be restricting the expansion from the heating or the cylinder (both no no's).

Craig would you mind uploading a few photos?

 

[frpcraig]

Hiya Pete,
There is another red tap (call that one no. 1) on another pipe near the hw tank near the red tap we are on about (call this one no.2).
If I turn no.1 tap on then the hw tank heats up on the ch and hw setting on the programmer as well as the rads .
If I put the ch and hw setting on the programmer and close the red tap (no. 1)then the heating is on but the tank does not heat.
This tap is on a pipe which connects directly to the top of the hot water cylinder and then goes to multiple junctions ?
If I put the programmer to hw only the the rads don't heat but the boiler gets to temp before the hwc is at temp.
Please tell me what area of pics you need and I'll put them up (with instructions)
Thanks again
Craig

 

[frpcraig]

If it helps pete..................
We only ever had hot water from the taps when the I turn on the no.1 tap (from the cylinder).
When I crack open the no.2 valve a bit we get warm water out of the bathroom tap (not hot)

 

[lame plumber]

best advice is just get a decent engineer in to look at your system, no one has any idea what valve does what unless you can see or trace them back so
giving advice like this is pointless.

 

[peteheat]

Much better the two valves are serving different purposes, I have to agree with lame plumber the best advice will be from the person standing in front of the system, turning on and off valves will never prove to be a safe efficient way to control your heating system.

Heating controls play a big a part in the efficiency and comfort levels that can be achieved from any boiler, a big advantage is anything you do now can be part of a full upgrade of your heating system so no money is wasted.

There are good engineers out there you were unlucky with the last one doesn't mean we are all the same, best to ensure the next one is a heating contractor who does more than just service boilers, sadly the trade is being broken up into different segments specialising in parts of the overall trade.

 

[SimonG]

Failing that you can always let the tyres down, that will stop the boiler cycling.

Just a bit of levity, pictures or professional me thinks.

 

[frpcraig]

I've cracked the mystery tap open a fraction and the boiler comes up to temp and doesn't keep cycling on and off. The boiler retains it's heat rather than plummeting as it did when the valve was wide open.
Must be a crude way to control the return temp.
Anyway as suggested I'll leave it alone till someone who knows what there doing has a look.
While i'm here............
I am trying to balance the rads (safe for me to attempt???)
I have followed instructions and have managed to get somewhere near a ten degree drop.
To get this drop on some of the rads the lockshield is barely cracked open , does that sound normal??
Ta,

 

[peteheat]

Hi Craig,

The purpose behind balancing the radiators is to ensure an even distribution of the heat around the system, it is not unusual for the rads nearest the boiler to be hotter than the rads at the end of the circuit, by closing the valve you push the heat to the next radiator, this process is only needed if you have some cooler normal rads on the system.

It is safe as the worst you can do is switch off the radiators the fun part may be getting them back to where they were, to make it easier use your notepad and pen, count the turns it takes to close the valve, make a note of it and open the valve up to say within one turn of the original position, if the heat drops too much open it back to where it was.

One of the best ways to regulate the heat in each room would be to discuss fitting thermostatic radiator valves with your engineer when he arrives.

 

[SJB6]

First off I agree with what some have said here, despite what mechanical engineering experience you might have setting up these burners to run smoothly, effectively, efficiently and safely requires someone fully qualified and experienced, by no means should they be tinkered with by someone half educated, regardless of how basic the concept appears to them.

All boilers require regular servicing and maintaining if there to run efficiently and safely, and on older boilers like that they should really be serviced every six months.
Efficiency is roughly 8% less to every 3mm of soot build up (you do the math)
With regards to the nozzle, like some have said reducing it's size is not going to make a difference. With the size of your system a .6 gallons an hour sounds about right but any professional engineer would be looking at the boiler manufacturers booklet (and if you don't have it then download it) and then checking the required size nozzle and settings for the burner for power output your boiler requires. These burners have to be set up accurately or you will have problems.

With regards to the cycling it could be a few things.
Starting With boiler:
. Any soot at bottom of flue indicates a flue problem, you could have a partially blocked flue retaining more heat within the boiler (servicing every two years means thats a strong possibility). Flue gases would eventually escape up the flue, the temperature would fall and the boiler ignites again.
.A faulty boiler stat is just as likely, set to cut power to burner when 60-65 degrees C is reached but is cutting out at 50 for example.
. It has been colder recently and when colder air is forced in for the combution process sometimes the flame is brighter and might burn a little hotter.
It doesn't sound like a problem with the burner because I would expect lockout, certainly not coming on and off every 3 minutes.
Inside house causes:
. An old pump on its last legs could be struggling to pump the heat away from the boiler quick enough.
. Air locks or partial air locks can cause the same problem, much like a system filled with black iron oxide (sludge) would as well, when the pump is circulating it will act as a magnet and suck in any sludge causing a restiction in flow and in turn heat away from the boiler.

Those are what spring to mind initially but like I and others have said these things are NOT toys and only someone who understands these things 110% and then some should be working on them.

 

[frpcraig]

Thanks guys,
An engineer called today to check out the boiler.
All good at that end thankfully.
Things mentioned.....
The 2 red taps ............
1 shuts off the feed to all the hot water taps, so told to leave open.
The other stops the hw tank heating, so told to leave open.
On my system I'm told the hw tank has to heat up whether you want hot water or not.
It all works fine but the boiler still cycles every few mins.
The chap suggested a cylinder stat may help.
when I switch the programmer to ch it shows ch and hw.
The rads get hot and the tank gets hot at the top half.
Am I right in thinking that the coil is in the bottom (cold) part of the tank and cooling the return temps so the boiler comes on again even when the rads are hot enough??
In light of this where on the tank should the stat be fitted?
At the moment the temp of the water in the actual boiler is dropping 12 degrees c in 3 mins after it switches off which seems a lot even in an old house, and cycling the boiler.
Cheers
Craig

 

[SJB6]

Hi.

This is just to enlighten you a little on your system but you must call an engineer out to undertake any remideal work.

1.You should have 1 gate valve (red tap) on the cold fill from the hot water header tank to the hot water cylinder, this is to isolate the cylinder should it ever need to be drained down. There should never be any sort of gate valve on the heating circuit that will block off the vent for safety reasons.
2. From what you have just said your system is an old gravity hot water and pumped central heating, camrays were a thing from 20-30 years ago at a time when most systems were like yours. The boiler cycling is because of that sort of system, it always happens as long as the programmer is calling for hot water and when the programmer is calling for CH you will see the HW light on as well, thats how those systems are wired.
This can only be fixed by either having an engineer install the correct zone valve on the hot water return from coil with a cylinder stat to prevent boiler cycling or converting to a fully pumped system with thermostatic contol (which is what it should be)

When you take into consideration the age of your boiler and the fact that at best I wouldn't expect any more than 80-85% Net efficiency I strongly suggest you think about a complete system upgrade.

I've enlightened you on the cause of your issue so now is the time to contact a compitent engineer and discuss what your going to do. All I've said here is to inform you of the issue, I am not advising or suggesting you carry out any work yourself.

 

[frpcraig]

Thanks for taking the time to explain my system SJB6.
There is no way I can afford a whole new system in the next couple of years unfortunately.
Would you mind answering a couple of questions for me?
Does a fully pumped system mean the system would then be more pressurized?
I have been told that while my system is and old design as you mentioned it was quite a safe system with regards to pressure?
The reason I'm asking is that as I can't afford a new system I was wondering if going the fully pumped route would be massively more expensive than adding a zone valve and a tank stat.
I was kind of hoping I could get the guy back who checked out my boiler to put a tank stat on and the zone valve you mentioned as it sounds cheaper than going fully pumped, and would at least be an improvement would it not??
Cheers
Craig

 

[SJB6]

Hi.

Converting to a fully pumped system means that both heating and hot water would be pumped, as it stands your heating is pumped and your hot water is gravity. When they are both fully pumped they would be thermostatically controlled, meaning once desired temperature is reached the boiler would shut down, preventing any cycling, which you have now. With regards to pressure your system is safe now just not thermostatically controlled, when pumps are used they do cause a slight incease in pressure but nothing to worry about, it's just the pump forcing heated water around the system.
Converting to fully pumped will be more expensive than just zone valve and stat because more wiring will be needed as well as pipework will need to be re-done so not to block off safety vent and/or get air entraitment (sludge).
Personally I think you should have a good engineer install the zone valve and stat now, that would atleast give you thermostatic control and prevent boiler cycling (won't improve boiler Net efficiency, just decrease the amount of fuel your boiler burns), then when you can afford an upgraded system (new boiler, oil tank, fully pumped heating system with thermostatic control etc) consult with a good engineer then (look into government boiler replacement schemes, you might find something your eligable for)

Side note : There are open vented and sealed boiler systems, both with their advantages and disadvantages, ask your engineer to explain further.