Issues with new heating zone

powerade · 10-12-2019 6:29pm

Sorry, I thought I responded to this earlier. The max output is 24 kw. When the boiler cut out this morning, Zone 1 temperature was 19.5 (thermostat set to 25 degrees) and Zone 2 temperature was 19.8 (thermostat set to 21 degrees). So yes, it is difficult to understand why it would cut out and why the temperature dipped to 48 degrees

John.G · 10-12-2019 7:28pm

powerade wrote: »

Sorry, I thought I responded to this earlier. The max output is 24 kw. When the boiler cut out this morning, Zone 1 temperature was 19.5 (thermostat set to 25 degrees) and Zone 2 temperature was 19.8 (thermostat set to 21 degrees). So yes, it is difficult to understand why it would cut out and why the temperature dipped to 48 degrees

Maybe the answer lies in a previous post #136....

"There were two consecutive system waiting periods which amounted to 8 minutes followed by one anti rapid cycle which was 2 to 3 minutes so the total off time was approx 11 minutes. 15 minutes later the temperature went up to 69 degrees again and the 11 minute off cycle kicked off again."

a waiting period is the time it takes the flow temperature to fall to its setpoint so one would expect the boiler to fire up again so did you mean that there was one waiting period of 4 minutes followed by another waiting period of 4 minutes (amounting to 8 minutes) without any boiler firing ? and did the first waiting period go off and was it immediately followed by another waiting period
of 4 minutes?. What I am trying (badly) to say is why do you get two waiting periods with nothing happening in between??. The only reason I can see is that the flow temperature had fallen to its set point (waiting time) before the 5 minute anti rapid cycle time had elapsed so another anti rapid cycle time was called for.

I still think you should be able to tune that boiler, maybe by reducing the anti cycle time to 2 to 3 minutes (if allowed) and see what happens, also maybe later try reducing the max output to say 12kw although it goes against the grain.

powerade · 10-12-2019 9:11pm

After the first waiting period the boiler fires up, the ch demands heat and the temperature shoots up to 69 degrees. This all happens in seconds. Then a second waiting period kicks off and the temperature drops to 60/61. Then it goes into a rapid anti cycle and that is when the temperature can really start to fall. I hate to say it but this pattern is not consistently repeated but I don't know if that has anything to do with messing around with the ABV setting.
I had an interesting visit from my plumber this evening. He confirmed that the radiators were not underspeced in Zone 2, that the Zone 1 valve was working fine, in spite of the LED not working, all heating controls were working fine and there is no dirt in the system. He balanced the system and flipped and cleaned the filter. He had no clue, however, about the Zone 2 heating issue or what was driving the rapid anti cycle. He did think, however, that the boiler was faulty as he witnessed the Zone 2 temperature rise issue and he is going to speak to WB tomorrow. I'm not convinced as all of the major boiler parts have been replaced but it won't do any harm. I couldnt really understand his explabation of the role of the ABV but said that he always sets it at .38. He offered no advice on TRVs in the context of the current heating issues.I also asked him about the pump head setting, the best I could get was that it shouldn't be set at 4. He was rushing to get off.
I am going to change the maximum CH output setting, as you suggest and I will see if I can reduce the anti cycle time.

John.G · 10-12-2019 11:07pm

That's a very detailed explanation, sorry for all the questions but after that second period of waiting does/did the boiler fire up again and shoot up to 69C and then go into anti rapid cycle or did it go straight from the second period of waiting onto anti rapid cycle?.

Re ABV, Generally speaking the ABV was set up to dissipate residual heat that build up in a heat exchanger when the boiler shuts down, not used much in oil boilers as the Hx in these which are basically a "box" contain 20 to 30 litres of water which will soak up the residual heat and won't cause a huge rise in temperature. A gas boiler Hx will only contain a few litres of water and are often made of aluminium so it was/is common practice each time the boiler cuts out to keep the circ pump running (pump overrun) for a couple of minutes, this, in itself is useless with the advent of zone valves and that is where the ABV comes in. Again traditionally circ pumps were fixed speed (constant curve) pumps that will have the highest head when pumping against a closed circuit and when the zone valve(s) or TRVs start opening then the pump head will start reducing. Bearing this in mind it was relatively easy to set up the ABV to only pass water when all the circuits were closed but once anyone opened then the ABV will close off. However because a lot of pumps are now run in constant pressure mode (like yours) then the ABV will have to be set up to by pass a fixed quantity of water continuously. Some gas boiler have a internal by pass (like yours) and generally don't need a ABV, some now also have have a stainless steel Hx and may not have a internal by pass and no pump overrun/ABV. It is also common practice to use one rad, say a towel rad without a TRV and with the flow connected upstream of any zone vave to act as a constant by pass and no ABV is fitted.
I know your ABV is on a very short piece of pipe but you said I think that even when you set it at index o.45 (4.5M) that the horizontal pipe was still roasting so ther is just a slight suspicion that this ABV is passing, you might check this out again if you get your heat scanner fixed.

Anyhow we are getting more and more info which is a good thing and most interesting.

powerade · 10-12-2019 11:30pm

I am so glad that you are finding this interesting as I am intrigued but also incredibly frustrated. In answer to your question, the boiler did not fire up after the second waiting period. It went straight into rapid anti cycle. Then the boiler fired up and the CH started to demand heat.
When my plumber completed the zoning work he did not install the ABV. When I reported the cycling issue to him back in May of this year he came back out, said that he had forgotten to do something and when I looked in the old hot press I could see that he had installed sonething else as it protruded out beyond the actuators. That transpired to be the ABV. Given that it was an afterthought, I wouldn't be surprised if it was faulty. Thank you for the ABV explanation which I will digest in the morning.

John.G · 11-12-2019 12:49am

Saw this somewhere else re anti cycling.

If two on/off cycles take place within the anti cycle set time then the boiler will stay off for the anti cycle set time.

So it will be interesting to see what this set time is.

powerade · 11-12-2019 11:55am

I still do not get the role of the ABV in the current configuration of my system as there is one in the boiler, there is the one that was fitted by the plumber and, up until yesterday evening, every radiator was a bypass as all of the TRV heads were removed. The plumber put a few of them back on in Zone 1 last night. He also drained the water out of the radiator in the kitchen. Was that something to do with balancing the system?
Anyway, I have been familiarizing myself a bit more with the manual and I had a look at all of the items on the info menu. Item I2 shows the "appliance previous operational status" which was displayed as d4 Temperature Fault. From page 67 of the manual, the description of this code is "Primary flow temperature rising too fast". There are a number of checks listed which include the pressure, air in the system and circulation within the heating system. I have no idea if this is of any significance but I noticed that the pressure is at 1.5 today wirh the heating off but it is normally at 1.0. Also I checked the Air Purge Mode setting (2.2C) and it is OFF.
Finally, I lowered the max CH output to 16KW (lowest possible setting is 13) and turned on Zone 1. It took 20 minutes to reach flow temperature which is a good bit slower than usual and, consequently, the Zone took longer to heat up. It was only on for one hour and it did not cycle.
I am going to lower the max output again to 13KW, keep an eye on the pressure and I want to measure the return temperature.
Should I change the Air Purge setting and is there a air purge routine that I should run, just in case?

powerade · 11-12-2019 12:31pm

Just a few more observations. I put a bit if tape on the flow and return pipes ( see photos) and measured the temperature. The flow temp was 29.3 and the return was 30.6. The flow temperature as per the boiler was 58. The bypass pipe is scalding and there appears to be no change in the pressure.

John.G · 11-12-2019 12:31pm

I'll come back to the ABV role later. I would not change the air purge setting, this may be to do with the boiler furnace air purging before and after firing (and has nothing to do with air in your system) so leave it as is. Re air in your system, just crack open the air vents on the rads and see if you get any air out, a small hiss is no problem, then reclose when water comes out. Once all the air is got rid of its unlikely to return as you have a sealed system. You may have to vent the rads for a bit longer since the kitchen one was drained down.
RE 1.5 bar vs 1.0 bar previously, you should see a flexible hose for topping up purposes adjacent to the pressure gauge, there should be a valve at both ends of these and should be closed, post a pic if not sure. The plumber will have topped up the system after draining down the rad as well so might account for that 1.5 bar.

Table 39
I would check item item 2.3b Anti cycle function (3 to 45 mins) it defaults to 5 min, if it is showing this 5 mins I would suggest reducing it to 3.0

Also item 2.3c Anti cycle temp hysteresis but purely for interest, do not adjust, just note the setting.

The reason for the "Primary flow temperature rising too fast" is probably because with one zone only in service the boiler was firing at full output of 25 kw which you have now reduced to 16kw, it's up to yourself but I would be inclined to let it at 15/16kw in conjunction with reducing the anti cycle time to 3 mins and then try the system on zone2 only and see how it responds.

John.G · 11-12-2019 12:35pm

I.m afraid that thermal gun you have is pretty useless, just check the temperature on the flow pipe close to where it comes out of the boiler, if its not within 10c of the displayed flow temp, forget it.

powerade · 11-12-2019 1:12pm

Interesting because the plumber used it last night. I am running Zone 2 right now with the max output down to 12. I was mistaken earlier, you can set it as low as 7. The plumber changed the anti cycle time to 3 minutes last night.
With the max output set at 16kw, Zone 1 temperature increased by 3.1 degrees in 52 minutes and consumed .83 units of gas. With the max output set at 12kw, Zone 1 temperature increased by 1.8 degrees in 52 minutes and consumed .77 units of gas. So, the lower setting made it considerably slower to heat up but consumer almost the same amount of gas. Baffling......

powerade · 11-12-2019 1:14pm

The anti cycle temperature setting is 6.

John.G · 11-12-2019 2:22pm

The gas consumption @ the 16 kw setting was 0.83 m3/h and @ the 12 kw setting was 0.77 m3/h... an increase of 7.79%
assuming initial zone temp @ 15C in both cases then after 52 minutes @ 16 kw gave a zone temp of 18.1c & @ 12 kw gave a zone temp of 16.8c.... an increase of 7.7%. You will probably find in practice that the lower power rating will give a very small benefit in fuel economy as it will be running longer with a lower return temp but practically speaking no difference.....what you require is a reasonably quick warm up AND when either zone is satisfied, as consistently a flow temperature as possible while the boiler is cycling. If you find that the 12 Kw gives you the best compromise then fine but you will have to bring the zones in earlier to achieve the set point temp, I would suggest incrementally increasing the max output to ~ 15kw and see how these changes (inc 3 min a.cycle) time deal with zone2.

ABV: Yes, it would seem that there was/is no need to have one in your system as it doesn't mention pump overrun in the manual and the boiler also has its own by pass, possibly to maintain a minimum flow through the boiler when TRV's are closing in. IF a ABV is required/requested by the boiler manufacturer then, in lieu, you cannot use any radiator(s) that are fitted with TRVs or are zone controlled as in both cases they can shut off the circulating flow completely but as I suggested, a rad without a TRV that has its flow piped upstream of any zone valves will provide a permanent path for the circulating water as long as the pump is running even with zone valves and TRVs shut, a towel rad is often utilised for this purpose as you will generally have a wet towel and the weeks washing draped around it and you are not wasting any real energy.
In respect of the ABV fitted in your system, I would suggest, shutting it off completely, even beyond its max setting (clockwise, I think) and then, in the morning as soon as the boiler fires up, keep your hand on the return side of the ABV, this should remain relatively cool even when the flow pipe is roasting, if it seems to be heating up as fast as the flow pipe then its passing/faulty which would be a bit surprising as I reckon that it would have been new. If it is passing, then because you have no idea really how much, get your plumber to renew it even if not required now, you can just leave it shut off and in the event of installing a new boiler sometime down the road which does need a ABV, you have it already in place.

I Am The Law · 11-12-2019 7:43pm

OP Can I ask you to check the copper pipe shown in Photo1 and state which pipe it's connected to in Photo2?

powerade · 11-12-2019 8:43pm

It is connected to the return pipe in photo 2.

I Am The Law · 11-12-2019 8:54pm

Well IMO that's the problem, according to the manual thats the flow from your boiler.

The first problem is it means the bypass valve is the wrong way around and short circuiting the flow and return, causing cycling and so on.

BDI · 11-12-2019 8:58pm

I’m not reading all that thread, and seems too complicated with all the ideas and heat guns.

Is the room stat in a drafty area or hot to cold area.
If you turn it off does the boiler turn off and does it turn back on when you turn it up again. If you run one zone at a time does only the things that are supposed to work, work?

Is zone two running a heating circuit and hot water cylinder?

Probably faulty wiring job seen as it’s done when the zone valves were added or zone two is leaking so badly into the hot water cylinder that it takes 4 hours to heat it up then when you turn on the tap it needs another 4 hours.

I wouldn’t know without looking at it and have no interest in looking at it or reading the thread to be honest I’m a bit tired but it looks very over complicated.

powerade · 11-12-2019 9:47pm

I Am The Law wrote: »

Well IMO that's the problem, according to the manual thats the flow from your boiler.

The first problem is it means the bypass valve is the wrong way around and short circuiting the flow and return, causing cycling and so on.

Let me answer your question in a different way. The short horizontal pipe is connected to the flow pipe on the left and the return pipe on the right. The directional arrow on the ABV points from the flow to the return. The plumber was here again this evening and he checked all of the configuration.

John.G · 11-12-2019 9:57pm

Did he have anything to say about the ABV?. How is your system performing now if in cycling mode?

powerade · 11-12-2019 10:01pm

BDI wrote: »

I’m not reading all that thread, and seems too complicated with all the ideas and heat guns.

Is the room stat in a drafty area or hot to cold area.
If you turn it off does the boiler turn off and does it turn back on when you turn it up again. If you run one zone at a time does only the things that are supposed to work, work?

Is zone two running a heating circuit and hot water cylinder?

Probably faulty wiring job seen as it’s done when the zone valves were added or zone two is leaking so badly into the hot water cylinder that it takes 4 hours to heat it up then when you turn on the tap it needs another 4 hours.

I wouldn’t know without looking at it and have no interest in looking at it or reading the thread to be honest I’m a bit tired but it looks very over complicated.

It shouldn't be complicated IMO, but I don't have a solution so it clearly is complicated.
I don't have a hot water cylinder and the room stat is located in a draught free. internal corner. The room stat is working as expected and turns the boiler on/off.The problem is mainly with Zone 2, slow to heat and constant anti cycling but it can also happen in Zone 1 if I turn radiators off or lower TzrV settings.

powerade · 11-12-2019 10:10pm

John, I tested Zone 2 this afternoon with the max KW output set to 16.1. No real change in the rate of temperature increase but the shut downs and rapid anti cycles were almost constant after 25 minutes. My plumber has contacted Worcester Bosch and I am hoping to hear back from him tomorrow. In the meantime, I am continuing to look for information on Google as there are numerous posts from people with similar issues, specifically with Worcester Bosch Greenstar boilers but, as I mentioned before, I have yet to find one with a definitive solution. I'm going to make a You Tube video if we ever crack this

John.G · 11-12-2019 10:20pm

Very good and is the flow temperature consistent and not falling too low?? remember no matter what solution you come up with.... the boiler will have to cycle on low heat demand, period. Standing back a bit I would insist that either that ABV is renewed or thrown away and a gate valve put in its place because IF it is passing excessively then you are kicking the proverbial up a mountain, I,m amazed your plumber hasn't zoned in on this, its no good going to WB without having the hardware right first.

It's also possible that a bit of crap is trapped in the ABV so he can check for that presuming he can split it open.

Don't bother with google, you will be able to charge them when you tell them how you fixed the problem.

powerade · 11-12-2019 10:42pm

He only called out because of my persistence. I know that he won't do anything with the ABV no matter how insistent I am and, given that I still don't fully understand how the ABV should be operating, it would be very difficult to present him with a convincing argument to check and/or replace it. If I close it fully and the horizontal.pipe heats up shortly after the heating is turned on, is that definitive proof that it is not working as expected? He will, in all likelihood, say that it's not causing any problems so I really need to understand how the ABV can be causing or contributing to the heating problems. The temperature drops have not been below 55 degrees today, btw.

rightjob! · 11-12-2019 11:00pm

Its not the by pass valve,are both stats set to max when the boiler shoots up and down in temperature?
Are you sure the zone valves arent closed when this is happening?
Its that or else sludge in the system

John.G · 12-12-2019 2:20am

powerade wrote: »

He only called out because of my persistence. I know that he won't do anything with the ABV no matter how insistent I am and, given that I still don't fully understand how the ABV should be operating, it would be very difficult to present him with a convincing argument to check and/or replace it. If I close it fully and the horizontal.pipe heats up shortly after the heating is turned on, is that definitive proof that it is not working as expected? He will, in all likelihood, say that it's not causing any problems so I really need to understand how the ABV can be causing or contributing to the heating problems. The temperature drops have not been below 55 degrees today, btw.

You don't need to know how a ABV works, all you need to know, despite some rather one or two daft comment(s) stating "its not the bypass" is that when you WANT no bypass that you will get it, otherwise, you may as well just stick that piece of pipe to just "short circuit" the flow & return OR install a gate valve to give no by pass or whatever.

12-12-2019 9:18am

John.G wrote: »

You don't need to know how a ABV works, all you need to know, despite some rather one or two daft comment(s) stating "its not the bypass" is that when you WANT no bypass that you will get it, otherwise, you may as well just stick that piece of pipe to just "short circuit" the flow & return OR install a gate valve to give no by pass or whatever.

John how many gas boilers have you commissioned or repaired? I ask because your giving advice on the characteristics of a gas boiler and deciding other posters views are daft.

You have posted some comments that I don’t agree with as they don’t match my own findings but I’m not attacking your views.

Also please don’t call posters daft or I’ll have to put my moderator hat on.

K.Flyer · 12-12-2019 10:42am

powerade wrote: »

I still don't fully understand how the ABV should be operating.

In simple terms it is a spring loaded valve in which you can adjust the load on the spring.
You set the load on the spring so that the valve remains closed during normal heating / hot water circuit operation and should only open when there is back pressure from all the zone valves having closed or all the trv valves having closed, in other words, when there is nowhere else for the water being pumped around circuits to go.
If on a particular circuit it cannot be adjusted to stay closed during normal operation and radiators are not heating correctly, then the radiator lock shield valves on that circuit need to be checked to ensure that they are opened sufficiently and the system is balanced.
If the bypass remains open with little to no back pressure from the circuit, then the by pass may be faulty or is being held open from debris in the heating system.

John.G · 12-12-2019 10:51am

gary71 wrote: »

John how many gas boilers have you commissioned or repaired? I ask because your giving advice on the characteristics of a gas boiler and deciding other posters views are daft.

You have posted some comments that I don’t agree with as they don’t match my own findings but I’m not attacking your views.

Also please don’t call posters daft or I’ll have to put my moderator hat on.

Gary,

It certainly wasn't my intent to call anyone daft and apoligies if I gave that impression, I thought the comment( s) was "daft" but ONLY in the context that the OP has repeatedly stated that the ABV is faulty. Personally, I wouldn't take the slightest umbrage if someone called one of my statements daft, I would certainly either agree or defend it robustly.

Re boiler experience: I had over 40 years experience in the running and maintenance of oil fired boilers. I was involved in the conversion of a number of 50 MW oil fired boilers to enable them to burn either oil only or natural gas only or Natural gas + Biogas and the subsequent maintenance of these boilers including all the control/safety devices involved in the burner control/management.

May I ask why do you agree that the by pass isn't a problem?.

John.G · 12-12-2019 11:02am

powerade wrote: »

He only called out because of my persistence. I know that he won't do anything with the ABV no matter how insistent I am and, given that I still don't fully understand how the ABV should be operating, it would be very difficult to present him with a convincing argument to check and/or replace it. If I close it fully and the horizontal.pipe heats up shortly after the heating is turned on, is that definitive proof that it is not working as expected? He will, in all likelihood, say that it's not causing any problems so I really need to understand how the ABV can be causing or contributing to the heating problems. The temperature drops have not been below 55 degrees today, btw.

The proof is that the boiler circulating pump is configured to give a constant head (pressure) of 3M and if you have the ABV setting at anything higher than 0.35 which is 0.35 bar or 3.5M then the ABV is shut and should not pass any water through it.
If your plumber doesn't accept this and you are quite sure that it is passing even when fully shut (index 0.5 or higher) then get another plumber to change it or fit a gate valve, period, otherwise IMO you will never be able to fine tune your system.

12-12-2019 11:46am

John.G wrote: »

Gary,

It certainly wasn't my intent to call anyone daft and apoligies if I gave that impression, I thought the comment( s) was "daft" but ONLY in the context that the OP has repeatedly stated that the ABV is faulty. Personally, I wouldn't take the slightest umbrage if someone called one of my statements daft, I would certainly either agree or defend it robustly.

Re boiler experience: I had over 40 years experience in the running and maintenance of oil fired boilers. I was involved in the conversion of a number of 50 MW oil fired boilers to enable them to burn either oil only or natural gas only or Natural gas + Biogas and the subsequent maintenance of these boilers including all the control/safety devices involved in the burner control/management.

May I ask why do you agree that the by pass isn't a problem?.

Truth be told this post has become far to complex for me so I’m staying out of it I have a far more simple approach

but to answer your question it’s not unusual to see gas boiler act in this way and I would be surprised if it was the bypass but everyday is a learning day.

Issues with new heating zone

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