Issues with new heating zone

Wearb

K.Flyer wrote: »

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.

Are some of them also installed to give a minimum return temperature to the boiler to prevent thermal shock?

powerade

WRT the ABV, I closed the valve fully,I.e. just lpast the 0.5 setting and turned on Zone 1at 9.28am. All of the pipes were cold at this point. The flow temperature started at 32 degrees and rose to 59 degrees by 9.35. At this point the flow pipe was very warm, the horizontal bypass pipe was also very warm (not quite as warm as the flow) and the return pipe was cold.By 9:37 the return pipe was getting warm and the flow temperature was up to 66. Since then the flow temperature moved between 66 and 65 degrees but it has not cycled. At 10:12 the horizontal and return pipes are scalding and the return pipe is marginally cooler. The room stat has risen from 13.6 to 16.6, set point is 18.
The max output is set at 24kw. My very simplistic understanding of the operation of the system is as follows:
Heating starts up and belts out water that should eventually reach the set flow temperature of 65 degrees. The water flows into each of the radiators (not sure if this happens sequentially), the radiators start to warm up and dissipate heat. At some point the water returns to the boiler and the boiler measures the return temperature. If the return temperature is higher than the boiler is expecting (not sure how that is calculated), the boiler output is 》the combined radiator output and the boiler will modulate down, subject to a lower limit of 7kw. If 7kw is still not low enough the bypass should kick in. That is what logically makes sense to me. If it is that simplistic and everything is working as expected then the boiler, in theory, should never cycle. Am I on the right track here?
In Zone 1, if all 5 radiators are fully on, the output is around 9.5kw. The boiler should be able to modulate down to that level of output without needing the bypass. If I turn off a couple of radiators, however, and reduce the output to 《7kw, Zone 1 will behave exactly the same as Zone 2.
Given that the horizontal pipe heats up almost at the same time as the flow pipe, with the ABV closed, is that just latent heat or actual water?
Just to continue with my simple logic, given that the radiator KW output in Zone 2 will always be 《7kw, should a correctly working bypass manage the deficit between the boiler and radiator output and prevent anti cycling?
In Zone 2 the flow temperature climbs up to 69 degrees and then the system shut down & anti cycling starts. Is that temperature rising because the system cannot balance the boiler and radiator output, for whatever reason ?
I am sorry for all of these questions but, if I have a basic understanding of the logic if what should be happening, it is a lot easier to interpret what is actually happening.

powerade

rightjob! wrote: »

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

The boiler only shoots up and down when Zone 2 is on (or less than 5 radiators in Zone 1). The manual dial stat is set to max, the digital room stat is typically set between 21 and 22 degrees. The actuator light on the Zone 2 valve and the red demand lights on the boiler remain illuminated when the temperature starts to rise.

John.G

The by pass is only there to dissipate heat from the boiler when it shuts down and also in some cases, as wearb pointed out, to maintain a minimum flow through the boiler as TRvs shut in but in your case the boiler has a internal by pass which should maintain this minimum flow. As no mention of pump overrun is mentioned then presumably this boiler does not need to dissipate the heat. With the external by pass the heat is simply dissipated in the pipework due to radiation and is very little so even though your thinking is logical it really wouldn,t help in any significant way to help reduce the boiler cycling at reduced load and might actually make it worse as you could be introducing very hot water to the return which, when mixed with the far cooler return water from the rads will result in a far higher temperature than desirable and this is why it is so important that the ABV is tight. There is no return temperature sensor on this boiler, it modulates down when the flow temperature approaches the set point and if/when it exceeds this setpoint by ~ 5C, it shuts down. It is quite normal for a boiler to cycle when the heat requirement is < the minimum boiler output but WB do seem to have a "probem" with this. Its a bit ironical but there are still gas boilers running that have no modulation and seem to work away OK.

You now have the boiler at 25KW output? so when its recycling what is the lowest flow temperature? if its not more than 10 to 12 deg lower than the setpoint then you should be reasonably happy, oil fired boilers spend their whole lifetime operating in cycling mode and the flow temperature will rise/fall by this margin during each cycle. Obviously, it would be nice if gas boilers didn't cycle and some like Vokera can modulate down to ~ 2 kw.

K.Flyer

The bypass valve does not react to temperature or heat outputs, it reacts to back pressure and flow rates.
If the connecting pipe from the bypass to the return is "scalding hot" and your #2 zone is still open and stat calling for heat, and heating space not satisfied, then you have a circulation issue.
Things to check;
1- Fault with bypass valve.
2- Fault with zone valve not opening fully.
3- Incorrectly set lock shield valves.
4- TRVs set too low.
5- Obstruction in pipework circuit.

powerade

John, thank you so much for your patience, it is much appreciated. I have a few final questions and then I am going to leave it to my plumber and Worcester Bosch. Hopefully my next post will be the solution
1. Should my boiler modulate?
2. When demand is 《7KW, is that what drives the flow temperature up?
3. How does the boiler know that it needs to modulate up or down if the return temperature is not measured
4. When the system shuts down the bypass kicks in to dissipate the extra heat, right? Given that I have seen multiple shut downs precede a rapid anti cycle, is it the case that the system will keep shutting down until the temperature has reached the desired level ?
5. What is the point of the rapid anti cycle if the shut downs and by pass are lowering the temperature.
That's it for now and thanks again.

John.G

1. Yes, and it does, if you mean should it cycle, then yes, it should and does, sort of.

2. The heat input to the boiler is greater than the heat being emitted by the rads, this excess heat has to go somewhere so it continues to heat up the water.

3.Because it only uses the flow temperature as the measurement, at full firing the heat input is far greater than the rad output so the water continues to heat up and as the temperature approaches its set point then the boiler gas flow is reduced (modulating) until the setpoint temperature and the (flow) temperatures are the same. It will stay at this steady firing rate until say one zone is shut off, the temperature will again start to rise and the firing rate will reduce until the flow temperature matches the set point, and vica versa, if another zone is opened the flow temperature will reduce and the boiler will increase its firing rate until the flow temperature and the set point are again equal.
All boilers use this as the main controlling sensor but some also use the return temperature as a controlling influence as well.

4, The system will only shut down if all zone valves shut. if the flow temperature rises ~ 5C above its setpoint then the burner only will stop firing, the circulation pump will continue to run until the flow temperature again reaches its set point, at which time the boiler burner will refire and if its minimum output is higher than the rads output it will again shut down when the temperature is 5C above its setpoint, the anti rapid cycle time (in theory anyhow) should just give a 3 minute delay before the next cycle commences but again in theory this should only happen if there are two consecutive (on/off) cycles within this 3 minute period.

5. That is the $60,000 question. As I said previously if the drop in temperature is 10 to 12C consistently, then I would be quite happy with this but apparently its not doing this now?? and when you lowered the max output to 12 kw, was it ok and was it OK at 16kw. ALL the posts that I have also read re WB boilers would suggest that this is at least a partial solution to the problem. Also don't get fobbed off by WB saying that the boiler should not cycle, I will repeat what I've said before, my relations 20 kw Vokera often servicing one zone with only 3 rads cycles on/off without a bother, when I next visit I will check to see how low the flow temperature gets during this cycling.

Note: The by pass doesn,t or shouldn't operate during this cycling period at all, its only if the whole system shuts down that the by pass comes into play really, with your boiler the only by pass in play is its internal one and this does nothing when the whole system shuts down as apparently there is no pump overrun.

powerade

Thank you again John. I just want to ensure that I am using the correct terminology. When I use the term modulate I mean is the boiler adjusting its KW output because the flow temperature is greater than the set point. Given that there is a maximum and minimum output KW setting, I assumed that was the case. ls that what is happening when the boiler gas flow is reduced?
If the temperature rises to 5 degrees or more above the set point, is that because the system cannot modulate any more, i.e. it is down to the lowest KW output and that's still greater than the radiator demand? That's when the burner stops firing (status 204) and that is what I have been referring to as a system shutdown. Typically there will be two followed by a rapid anti cycle. The system is basically paused to try to reduce the flow temperature, right ?
When I lowered the maximum KW output to 16.1 and 12 when I was just running Zone 2, the boiler constantly had a 204 status and there were sometimes 3 or 4 204's before the anti rapid cycle. The rate of temperature increase, however, appeared to be unaffected. I really wasn't expecting that result .....Given that one of the functions of the bypass is to dissipate heat, it sounds like this was working less effectively when I lowered the KW output. I am sure that there is no connection but I'm just putting it out there. Just to be absolutely sure that I have understood some of your previous comments about the by pass function, am I correct in saying that the by pass should dissipate heat when the boiler status is 204.?

powerade

K.Flyer wrote: »

The bypass valve does not react to temperature or heat outputs, it reacts to back pressure and flow rates.
If the connecting pipe from the bypass to the return is "scalding hot" and your #2 zone is still open and stat calling for heat, and heating space not satisfied, then you have a circulation issue.
Things to check;
1- Fault with bypass valve.
2- Fault with zone valve not opening fully.
3- Incorrectly set lock shield valves.
4- TRVs set too low.
5- Obstruction in pipework circuit.

Thank you. All of the TRV's have been removed so we can rule no 4 out. How can I tell if the lockshields are incorrectly set? Is that a balancing issue?

John.G

Yes, you are correct re modulation.... then "If the temperature rises to 5 degrees or more above the set point, is that because the system cannot modulate any more, i.e. it is down to the lowest KW output and that's still greater than the radiator demand? That's when the burner stops firing (status 204)"

Status 204 is system waiting, primary flow temperature greater than set point temperature. The burner shuts down but the circ pump keeps running until the primary flow temperature reaches the set point temperature, this is NOT system shutdown, the burner should then come back on fairly rapidly because the rads are cooling the water down

"and that is what I have been referring to as a system shutdown. Typically there will be two followed by a rapid anti cycle. The system is basically paused to try to reduce the flow temperature, right ?"
I presume you are saying that there are 2 two system waitings followed by a rapid anti cycle? the system waiting should really cool the system down (via the rads). Here is my complete answer again from one of the posts.

4, The system will only shut down if all zone valves shut. if the flow temperature rises ~ 5C above its setpoint then the burner only will stop firing, the circulation pump will continue to run until the flow temperature again reaches its set point, at which time the boiler burner will refire and if its minimum output is higher than the rads output it will again shut down when the temperature is 5C above its setpoint, the anti rapid cycle time (in theory anyhow) should just give a 3 minute delay before the next cycle commences but again in theory this should only happen if there are two consecutive (on/off) cycles within this 3 minute period.

"The rate of temperature increase, however, appeared to be unaffected. I really wasn't expecting that result .....Given that one of the functions of the bypass is to dissipate heat, it sounds like this was working less effectively when I lowered the KW output."

What do you mean by the rate of temperature increase, however seems to be unaffected.? The function of the by pass (as I stated previously) should only operate when the whole system shuts down IE all zone valves shut but no effect with this boiler since no pump overrun.

Now can you please do the following tests on zone 2 only and calling for heat in all 3 cases.

1. Set max output to 25kw and just tell me what is the lowest flow temperature during the cycling/anticycling. (Don't need any other information)

2. Set max output to 16kw and just tell me what is the lowest flow temperature during the cycling/anticycling. (Don't need any other information)

3. Set max output to 12kw and just tell me what is the lowest flow temperature during the cycling/anticycling. (Don't need any other information)

powerade

There were two reasons why I started this thread as follows;
1. The temperature is Zone 2 is very slow to increase and it can take hours to get it to the set temperature
2. The boiler, after a short period of time, will pause (system waiting) and cycle resulting in the radiators cooling off if I am running Zone 2 on its own. . This, in all likelihood, is contributing to issue no 1.

The rate of temperature increase that I referred to in my previous post is the rate of Zone 2 temperature increase.

I will let you know the results of the tests that you have advised me to carry out.

K.Flyer

K.Flyer wrote: »

The bypass valve does not react to temperature or heat outputs, it reacts to back pressure and flow rates.
If the connecting pipe from the bypass to the return is "scalding hot" and your #2 zone is still open and stat calling for heat, and heating space not satisfied, then you have a circulation issue.
Things to check;
1- Fault with bypass valve.
2- Fault with zone valve not opening fully.
3- Incorrectly set lock shield valves.
4- TRVs set too low.
5- Obstruction in pipework circuit.

powerade wrote: »

Thank you. All of the TRV's have been removed so we can rule no 4 out. How can I tell if the lockshields are incorrectly set? Is that a balancing issue?

Yes they are used for balancing the system.
You could start by rotating each one a full turn anti-clockwise to increase the flow through the radiators.
A simple exercise, but just to see if that changes anything.

powerade

John, before I test Zone 2 again, can you let me know if you want me to leave the ABV closed?

John.G

Yes, thanks.

powerade

Okay. Just to advise of a new scenario that I have not seen before but it may or may not be relevant. I have just been running Zone 1 this morning with a stat temperature of 18 degrees. I heard the boiler come on as the Zone 2 start time kicked I. I immediately turned Zone 2 off and a few seconds after I saw the blue demand light for Zone 1 come on. I checked the boiler status and it was 202. I then checked the flow temperature and it was 29 degrees. By the time I got my phone it was down to 27 and it settled at 25 (photos attached). The boiler fired and the temperature started to climb. It was not running at 24KW, to the best of my knowledge, judging by the noise of the boiler but by the time that the flow temperature had reached 44 degrees it was pretty noisy again. I'm not looking for feedback, I just wanted to mention it as it might throw up some new clues.

I Am The Law

powerade wrote: »

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.

Is this how your system is piped OP?

powerade

K.Flyer wrote: »

The bypass valve does not react to temperature or heat outputs, it reacts to back pressure and flow rates.
If the connecting pipe from the bypass to the return is "scalding hot" and your #2 zone is still open and stat calling for heat, and heating space not satisfied, then you have a circulation issue.
Things to check;
1- Fault with bypass valve.
2- Fault with zone valve not opening fully.
3- Incorrectly set lock shield valves.
4- TRVs set too low.
5- Obstruction in pipework circuit.

Can I just ask a quick question regarding the lockshield valves. When the heating was split into two zones, the plumber replaced all of the TRV's and the lockshield valves. I tried to turn a couple of then in Zone 2 and they were extremely difficult to turn in either direction. I did manage to open two of them by approx one turn and, almost immediately, I could feel a difference in the radiator temperature. Is there any harm in opening them any further?

John.G

Was on another mission to relation's house and she kindly let me take a few readings off the above boiler which has a max output of 20 kw with a minimum output ~ 5.4 kw and a anti cycle time of 3 minutes.
One zone has 3 rads on it so I carried out the test with 2 rads of combined output of ~ 3.5 kw.
This boiler has a total hysteresis of 10C...cut in = SP-5C & cut out = SP+5c.
I set it to 70C so cut in = 65C & cut out = 75C.
From cold (two rads, 3.5kw). The temperature climbed to 71C in ~ 8 minutes and then over the next 5 or 6 minutes climbed to its cut out (burner off) temperature of 75C. The temperature then fell to 61C in ~ 3 to4 min, the burner then refired and in 30 secs or so climbed to 72C and then again over the next ~ 4 mins it reached its cut out temp of 75C. It did this consistently while I watched 4 cycles.
So the average flow temperature over these periods was a excellent 68C.

The temperature difference between the Flow & return was 10C/13C.

John.G

powerade wrote: »

Can I just ask a quick question regarding the lockshield valves. When the heating was split into two zones, the plumber replaced all of the TRV's and the lockshield valves. I tried to turn a couple of then in Zone 2 and they were extremely difficult to turn in either direction. I did manage to open two of them by approx one turn and, almost immediately, I could feel a difference in the radiator temperature. Is there any harm in opening them any further?

I must confess I thought that they were all fully open, maybe your plumber throttled them in a few days ago, to adjust/open/close you sometimes have to remove the plastic cover and use a adjustable spanner, it should be ~ 3 full turns from closed to open, I would suggest closing them fully, then reopen fully ~ 3 turns and leave them like this + all TRVs fully open (Zone2, the cold one) you will then also be able,IMO, to carry out more meaningful cycling tests.

powerade

Thank you, I will do that.

powerade

John, thank you so much for doing that. It was very kind. I must confess that I think I am starting to lose the plot with this. Earlier today I put a temperature and humidity gauge from a weather station pack on top of the manual dial thermostat in Zone 2 to see if it recorded the same room temperature as the digital thermostst. There was only .2 of a degree in it so I was, therefore, comfortable with the accuracy of the digital thermostat.The broadband went down around 5, at which point Zone 2 was 22.2 degrees and it came back on at 7:15. At 9pm Zone 2 was displaying a temperature of 22 but the weather station was displaying 21.4 degrees. Zone 2 had definitely cooled down so I did not trust the reading on the digital thermostat. I reset the temperature using the Amber App to 23.5 and both the digital stat and weather station temperatures increased by the same amount in the last hour. Which starting point do I believe, however? On top of that the boiler cycled with both zones on and I have never seen that before. What on earth is going on .......

John.G

I'm afraid I don't know, you may see some difference now if/when you open all the lock shields & TRVs in zone 2, you can then just use the room stat(s) to control the temperature and see how you get on, don't know what the state of play with zone 1 is, if its heating up OK maybe leave well enough alone. If the boiler doesn,t cycle with both zones on then, apart from your own observations re heat up times, this would indicate that zone 2 is now outputting to its full capacity.
You might also just sit back and let the system run away for a few days and just use the roomstats in both zones to control the house temperature, after all, that's what they are for. I am not a big fan of using roomstats & TRVs in the one zone even though I suppose there is some logic/merit in it.

K.Flyer

powerade wrote: »

Can I just ask a quick question regarding the lockshield valves. When the heating was split into two zones, the plumber replaced all of the TRV's and the lockshield valves. I tried to turn a couple of then in Zone 2 and they were extremely difficult to turn in either direction. I did manage to open two of them by approx one turn and, almost immediately, I could feel a difference in the radiator temperature. Is there any harm in opening them any further?

Open all of them fully for now, and starting from cold, compare how each of them heat up when you turn on zone 2 heating only.
At the same time checking the pipe from the by-pass valve to see if it is getting as hot as usual.

powerade

By way of background, Zone 2 is a self contained appartment which I rent through AIRBNB plus one bedroom in my living area. My current guest messaged me this evening to say that she was cold but I was seeing a thermostat temperature of 22 degrees. So, I have to get on top if this.

K.Flyer

Everyone has their own definition of cold.
I've met people who would be using the heating almost all year round, they just prefer higher temperatures indoors.

John.G

K.Flyer wrote: »

Open all of them fully for now, and starting from cold, compare how each of them heat up when you turn on zone 2 heating only.
At the same time checking the pipe from the by-pass valve to see if it is getting as hot as usual.

The pump on this boiler is set at 3M constant pressure so there should be a relatively constant by pass of ~ 5 LPM if the ABV is set to say 0.25, which theoretically added to the zone flowrate shouldn't affect the temperature rise through the boiler for any given heat input but in practice due to pipe friction losses the actual radiator flowrate will tend to fall and because of the ongoing problems with zone 2 rad output and boiler cycling it may be better to ensure that there is no by pass and get as big as possible a flow through the rads.

powerade

K.Flyer wrote: »

Everyone has their own definition of cold.
I've met people who would be using the heating almost all year round, they just prefer higher temperatures indoors.

Yes, that is very true and sometimes I think that people assume that the place is cold just because the radiators are cold.

K.Flyer

John.G wrote: »

The pump on this boiler is set at 3M constant pressure so there should be a relatively constant by pass of ~ 5 LPM if the ABV is set to say 0.25, which theoretically added to the zone flowrate shouldn't affect the temperature rise through the boiler for any given heat input but in practice due to pipe friction losses the actual radiator flowrate will tend to fall and because of the ongoing problems with zone 2 rad output and boiler cycling it may be better to ensure that there is no by pass and get as big as possible a flow through the rads.

Which is why I suggested opening all off the lock shield valves fully and start from there.
If the zone is plumbed and balanced correctly then the bypass should remain closed during normal operation.

powerade

I have just closed and reopened the lock shield valves by three turns. The valve on the towel rail felt fully open after three turns the the valves on all of the other radiators felt like they could turn quite a bit further. Should I keep turning them or leave them as is? Also, I have the ABV fully closed. Is that right?

K.Flyer

powerade wrote: »

I have just closed and reopened the lock shield valves by three turns. The valve on the towel rail felt fully open after three turns the the valves on all of the other radiators felt like they could turn quite a bit further. Should I keep turning them or leave them as is? Also, I have the ABV fully closed. Is that right?

Open them all fully, it's the only place to start.
The towel rail can be left approx midway open.
Check from a cold start if all the radiators heat up fully at the approximately the same time and how quickly and see how it all interacts with the zone stat and your boiler.