Issues with new heating zone

powerade

My heating was spilt into two zones in May this year. Immediately after the zoning work was completed I noticed that the water temperature on the boiler was constantly cycling up and down when Zone 2 was on, even though the set heating temperature had not been reached. I raised this issue with my plumber but he claimed it was perfectly normal. In the last two months I have found that Zone 2 takes hours to heat up ( 4 hours today to rise from 14.8 to 21 degrees). I suspect this has something to do with the fact that the water temperature is constantly climbing up and down so the radiators get warm and then cool off again. During this time the pilot light is constantly on. I have a Worcester Bosch Combi boiler which has been serviced regularly and a Worcester Bosch engineer recently checked it. Zone 2 is extremely well insulated and it tended to get too warm very quickly, prior to the zoning work. My plumber claims that he has no clue as to what is causing this problem and that it has nothing to do with the zoning work. That may well be the case but something is causing the radiator temperature to constantly rise and fall and I would be extremely grateful if anyone can offer me any advice as to what might be causing this issue.

John.G

How many rads are on Zone2?
Is zone1 heating up OK and how many rads are on this.
Can you hear the boiler modulating down.

powerade

John.G wrote: »

How many rads are on Zone2?
Is zone1 heating up OK and how many rads are on this.
Can you hear the boiler modulating down.

There are four radiators in Zone 2. Zone 1 heats up perfectly, there are five radiators in Zone 1. I can't hear the boiler modulating down but I can hear it firing up when it starts to cycle back up. I can also hear a click when it hits 64/65 degrees when it is modulating down.

John.G

You might watch zone2 valve and make sure its not opening/closing before the setpoint temp is reached due to some fault with the room stat or wiring or some fault in the actuator itself. If it remains open then it may be something to do with the circulating flow through this zone and as there is no problem with the circulating flow through zone1 then it again might point to a fault in zone2 motorised valve although if the boiler is firing up on this zone only then the valve actuator is probably opening fully to call in the boiler on the end switch, one would think that the valve shaft would also then open with the actuator, if your handy you could remove the actuator head, open the valve manually and switch in this zone and see what happens.

powerade

I'm not handy in the plumbing department at at all, unfortunately. The yellow light appears to stay on all of the time when there is demand for heat so that would appear to indicate that the valve is open. I did wonder about the wiring as there are two thermostats right beside each other in Zone 2, a digital and a dial thermostat. The dial thermostat is hard wired to the boiler (I think) and the digital communicates via Wi-Fi. If the dial thermostat is set lower than the digital thermostat, that will control the boiler. If the dial thermostat is set higher than the digital thermostat the digital thermostat will control the boiler. I hope that makes sense. They are all EPH controls.

John.G

The actuator light staying on would be a reasonable indication that the valve remains opened so are the rads themselves not getting uniformly hot from top to bottom (air?) because even if the boiler is cycling frequently the flow temperatures to the rads won't change by more that 10C as I think modulating gas boilers cut in is Setpoint -5C and cut out is setpoint +5C. You probably have bled the rads of any air anyway?.
I don't know what boiler output you have but assuming 30kw with a min output of 6kw then it shouldn't cycle a awful lot as those 4 rads if heating up properly are emitting at least 4 to 6 kw.

powerade

I have bled the radiators and checked that all of the TRV's are connected properly. I have a Worcester Bosch Greenstar Combi boiler, 3 years old. Thank you so much for helping me out on this.

serox_21

First I would try like bellow.

- make sure zone 1 is fully turned off.
- fully open all TRVs in zone 2 (or remove the heads)
- set both thermostats from zone 2 to 23-24 degrees or higher
Expect all radiators in zone 2 to be hot.
Radiators should stay hot and boiler running at set temperature for a good period of time.

If radiators don't stay hot then start with thermostats(both should call for heat).

Zone valve 2 should be opened .A possible fault is when valve is powered but won't open(stuck). I had a similar problem in the past.
To test this manually open zone2 valve and put the heating on for zone1 only . zone2 radiators should get hot as well.

powerade

Hi and thank you for your advice which I will try in the next few minutes. In the event that the radiators do not get hot as expected and/or the boiler temperature is cycling what should I do with the thermostats?

powerade

I set both thermostats to 25 degrees. The room temoerature was 20.8 degrees. All of the TRV's were fully open and Zone 1 was turned off. The radiators started to heat up but, as per usual, the boiler temperature started to cycle after 20 minutes. The temperature dipped to 59 degrees and it appears to dip further with every subsequent cycle. I could feel the radiators cooling slightly but the level of cool off will increase as the boiler temperature dips lower and appears to hover at the lower temperature for longe before firing up and starting to climb again.. The yellow light was on all of the time. The room temperature increased by 1 degree in an hour which is what I have experienced, as an average, over the last two months. So, I'm not sure what to do next🤔🤔

John.G

What is the set point temp of the boiler,??. If its cutting out before it reaches the set point then its probably a circulation problem causing the deltaT (temp rise through the boiler) to be too great, some gas boilers will cut out if this reaches 30C I think but I don,t know if this should flag a alarm or not, anyway what is the set point temperature??

powerade

The set temperature is 65 degrees. The boiler will settle at this temperature for around the first 15 to 20 minutes of operation. It will then climb to between 69 to 71 degrees and then fall off to anything as low as 28 degrees. The average fall off temperature is around 54 degrees. The boiler will then sound like it is firing up, the temperature will settle at 65 degrees for a while and then cycle again.

serox_21

Can you also try
- manually open zone 2 valve and turn on only zone1 heating(motorized valves should have a lever, move it to manually opened position).
This should allow hot water to flow to both zones (even if zone2 is not calling for heat)and heat full house. Zone 2 radiators should be hot for the same period of time zone1 is running(zone2 valve should not have the light on).

If this works there might be a problem with thermostats or zone2 valve restricting the flow.

John.G

powerade wrote: »

The set temperature is 65 degrees. The boiler will settle at this temperature for around the first 15 to 20 minutes of operation. It will then climb to between 69 to 71 degrees and then fall off to anything as low as 28 degrees. The average fall off temperature is around 54 degrees. The boiler will then sound like it is firing up, the temperature will settle at 65 degrees for a while and then cycle again.

Its operating OK for the first 20 minutes, after that then the boiler minimum output must be higher than the radiators heat output so the temperature will rise to SP+5, 65+5, or 70C and the boiler will cut out. It should then, normally cut back in at SP-5, 65-5, or 60C but its obviously not doing that and the only logical answer that I can think of is that the ant cycling time is set way too long, don't know if this is adjustable or not but I have seen anti cycle times of 3 mins or so which is fine. Just because the demand is a little lower (for whatever reason) than the boiler minimum output shouldn't cause that huge boiler off time.

powerade

Thank you so much. I will try that this evening as I have to pop out for a while.

John.G

You say Zone1 is working OK, do you know if the boiler ever cycles when getting the zone up to the room stat set temp because if it doesn't then I would say it's definitely got something to do with the anti cycling time on Zone2 as the boiler does cut out.

powerade

I have, occasionally, noticed it if the stat temperature is set to 22 degrees and the actual temperature is around 21 to 21.5 degrees. The drop does not go below 58 degrees. I have not seen this happen, however, in the last few weeks. A further point to note is that if both zones are on, the boiler will not, generally, cycle until demand has been satisfied in Zone 1 but Zone 2 is still just as slow to heat.

powerade

I have just turned Zone 1 on and tried to manually turn Zone 2 on, as suggested, by moving the metal lever on the top of the Zone 2 actuator to the same position as the same lever on the zone 1 actuator. However, it will not lock in that position and keeps moving back to the off position. Am I doing this correctly or is there another lever?

powerade

A further observation on this. I am running both zones together. Zone 1 temperature had to increase by 1 degree to satisfy demand. While Zone 1 increased by 1 degree, Zone 2 only increased by .2 of a degree. The boiler ran steadily at 65 degrees when both zones were running together. When demand was satisfied in Zone 1, the boiler temperature started to cycle. Zone 2 room temperature is continuing to crawl upwards and I think that the digital thermostat is reading the temperature correctly as the room does not feel warm. The radiators in Zone 2 are heating up and cooling off marginally. What I really don't understand is why the temperature would be so slow to rise in Zone 2 when the boiler temperature is not cycling, I.e. when both zones are running together. I know that I will have to get a new plumber as the guy who did the zoning work has no interest in getting to the bottom of this issue but I would really like to have some inkling as to what is causing this issue, before I engage someone new.

cruizer101

Normally you have to move the lever across and push it up a bit into a locking slot to stop it springing back.
You can see the locking slot in this one, I'd imaging there is something similar on yours.
http://www.freeheatingadvice.com/wp-content/uploads/2018/04/Honeywell_motorised_valve_manual_lever.jpg

Dtp1979

Haven’t read the thread except for the first post but I’d say it’s dirt in the upstairs zone and a buildup of heat too quick. As an old old old engineer once said, it’s like trying to force an elephant into a rabbit hole

powerade

Thank you for your comment. It is a bungalow and the system has been flushed a couple of times in the last two years as some of the radiators were moved. Would that not mean that the system should be fairly clean? There is an automatic bypass which is set to 0 1 (max setting is 1). Does that have an impact on the build up of heat?

powerade

Cruizer101. Thank you. It looks broadly the same but without the words "Auto" and "Manual. I will give it a go tomorrow ����

K.Flyer

powerade wrote: »

Thank you for your comment. It is a bungalow and the system has been flushed a couple of times in the last two years as some of the radiators were moved. Would that not mean that the system should be fairly clean? There is an automatic bypass which is set to 0 1 (max setting is 1). Does that have an impact on the build up of heat?

While reading the thread before I got to this post I was thinking of an incorrectly located or set Auto By-Pass, a faulty zone valve, or the lock shield valves on zone 2 rads closed down too much.

Let the system cool right down, only turn on zone 2, check the by pass valve to see if you can feel hot water passing through it.
If heat passes through valve with zone 2 only, but not with zone 1 on, open each of your lock shield valves on zone 2 half a turn anti-clockwise.
Let system cool down and check again.

powerade

Thank you so much.

powerade

At 10:14 this morning I turned the heating on in Zone 1 and manually turned on Zone 2. The radiators in Zone 2 warmed up and I don't think that the boiler cycled. By 10:40, Zone 1 temperature increased from 16.8 to 18 degrees at which point demand was satisfied. The starting temperature in Zone 2 was 19 and this had only increased to 19. 4 degrees by 10:40, I.e. an increase of .4 of a degree. This is consistent with what I have previously experienced when Zone 2 is on auto which is an average temperature increase of 1 degree in an hour.
A further observation in relation to the boiler cycling is that boiler cycled quite a lot yesterday when both zones were on but only Zone 1 was demanding heat.. The only configuration change was that I lowered the TRV setting to 3 on the hall and one of the bedroom radiators. Both of these radiators are in Zone 1.
I am going to look at the by-pass next. There is a copper pipe connected horizontally to the by-pass and this connects to a vertical pipe that runs up through the ceiling and splits into two pipes down though the floor. Is it the horizontal pipe that I should be checking? It's quite warm right now.

K.Flyer

powerade wrote: »

I am going to look at the by-pass next. There is a copper pipe connected horizontally to the by-pass and this connects to a vertical pipe that runs up through the ceiling and splits into two pipes down though the floor. Is it the horizontal pipe that I should be checking? It's quite warm right now.

My suggestion is to check the outlet pipe on the by pass for heat when starting the system from cold and only running zone two.
There is usually a direction arrow on the by pass valve, find it and establish which is in and out.
When running any zone the by pass should not open allowing hot water to pass through it.

powerade

I have just turned Zone 2 on. There is not water coming through the copper pipe that is attached to the Zone 2 valve and the horizontal copper pipe attached to the by-pass. I can't see and my directional arrows.The vertical pipe that connects to the horizontal by-pass pipe is also starting to get warm. I can also feel some heat in the top of the horizontal pipe that connects to the Zone 1 valve. I hope that makes sense.

powerade

There is no visible change in the room the Zone temperature yet but the boiler has just starte to cycle and the temperature is slowly falling.

powerade

K.Flyer,Putting the by-pass to one side for the moment, it would appear that the boiler cycles when Zone 1 is on if any if the TRV's are not fully open. This slows the heating diwn but not on the same scale as Zone 2. Would anyone know why this is? Also, I have just bled the radiator in the bathroom (Zone 1, second time in 2 months) and black oily water came out after the air. Should the water not be clear?

powerade

I meant to address that query to everyone.

K.Flyer

What settings have you got your valves at?
If they are too low they could be shutting down too soon and not satisfying zone heat requirements.
Turn them up full for a while and compare results.
Sometimes you get a little bit of black water. But if draining a 500ml sample shows water quite dark / black your system is contaminated and should be cleaned out and treated for better efficiency.

powerade

All of the TRV's are set at 5 with the exception of the hall and one bedroom radiator which are turned off and one bedroom radiator is set at 3. The TRV'S in the two rooms with the digital thermostats are always fully open. Zone 1 will not cycle, to the best of my knowledge, if all of the TRV's are fully open. Zone 2 appears to cycle regardless as to whether all of the TRV's are fully open. At the risk of asking a stupid question, what is happening when the boiler cycles and what triggers it? The temperature rises to between 69 and 71 degrees so something must be driving it up. Something then kicks in to lower the temperature but I would expect it to drop and settle around 65 degrees. That's not the case, however, and I have seen it drop to as low as 28 degrees. Thank you so much for your help with this.

John.G

How long does it take the temperature to fall to - 28C before boiler fires up again?...can you time it please.o

powerade

That degree of fall off is not the norm and I don't know how I can replicate it. From memory, however, I would say no more than 2 to 3 minutes.

John.G

I don't know the anti cycling logic of that particular boiler but I think 5 mins off time might be reasonable to assume, one would then expect the boiler to fire up and increase it's temperature to - 75c before cut or and another 5 min off time, IF this is the case then one would not expect the temperature to fall to 28c in 5 minutes except that the boiler is not reaching 75c each time it re fires.

powerade

Thank you for your post.The temperature never reaches 75 degrees, the normal maximum is 69 to 71 degrees. The boiler is set at 65 degrees and I think that the standard cycle is +- 5 degrees, based on an earlier post. I have spoken to Worcester Bosch and they do not believe that it should be cycling, I.e. it should be purring along at 65 degrees. Instead it is up and down and the constant noise from the boiler is ridiculous. Plus the heating is inefficient and impractical in Zone 2. So, what I would like to understand is why it is cycling and what needs to be done to stop it cycling.

John.G

It will only purr along at - 65c if it's maximum turndown is greater thanks the radiator output, if the radiators emit 5 kw and the boiler minum output is 6 kw the it has to cycle, period. Remember a oil fired boiler has a fixed output my own 20kw boiler might cycle 2 min on 4 min off when the cylinder coil demand might be only 2kw when the cylinder is nearly up to temperature.

You could shut off say 2 rads in zone1 which will force the boiler to cycle with just this zone1 on and see if you have the same problems.

powerade

Thanks John. So, if I have understood you correctly, if the combined output of the radiators is less than the minimum output of the boiler, it will cycle. It was interesting that you mentioned your oil fired boiler asI had noticed that my Dad's boiler was constantly coming on and off but it didn't appear to impact the heat of the radiators. So, in my case, if I have all of my radiators on and all of the TRV's open it should be unlikely for the boiler to cycle. If I turn radiators off and/or lower the TRV settings, I am reducing the radiator KW output and the boiler is likely to start cycling, at some point. Am I on the right track as that makes sense to me in the context of what I have observed. I will run a few more tests today.

Given that Zone 2 is smaller in terms of KW output than Zone 1, I can now understand why it is cycling after around 15/20 minutes. Can I just ask a few more questions on this, if I may:
1. Is the boiler output fixed or variable (WB 25i Greenstar Combi)
2. There is a TRV on the radiator in the room with the digital thermostat in Zone 2. The TRV is always open but I am wondering if it might close the valve to the radiator which might help to explain why this room is taking so long to heat up
3. How can I tell if the boiler is cycling as expected, e.g. the temperature drops to anything less than 60 degrees which is outside of the minus 5 degree range. Thanks again for your help

powerade

John.G. I just watched the boiler cycle with only Zone 1 on. At 9:16 the temperature rose to 70 degrees. It then fell rapidly to 59 degrees. By 9:20 it had fallen to 51 ddegrees. The boiler then fired up, the temperature rose rapidly to 62 and then back down to 60 (9:21). It is now 9:28 and the boiler is settled at 65 degrees, for now.

John.G

The reason that it has settled down is because the radiator output or demand is higher than the minimum output of the boiler if you now shut down say 2 rads in zone1 then the boiler should cycle.
Z take some readings then over a number of cycles.

Yes the heating output of the boiler can be reduced without affecting the heat output to hot water (showering etc) and it
May help but even though the output may be reduced (range rating) the min output will still remain the same, for example if you reduced the output from say 24kw to 10kw then the minimum output will remain unchanged so you can still get cycling. I don't have domestic gas boiler experience but you may be able to access this function from a user accessible menu. Someone on here may be able to assist.

Try removing a TRV head off one of the rads on zone 2.

Dtp1979

Still sounds like dirt to me and possibly the rads are undersized upstairs

powerade

Cheers John. If it is dirt in the system, do I just need to get the system flushed? I replaced all of the radiators in the house when I moved in 7 years ago and the plumber re-assessed the BTU when the combi boiler was installed three years ago so I think I should be ok on radiator size but worth checking again.

John.G

I didn't suggest dirt in the system did you shut off
Two rads more in zone 1 to get the boiler to cycles and take Agee readings for a few cycles + times off and on

Let’s keep this simple as I’m a simple man.

Remove the heads of the trvs on zone 2 to see how things work with no mechanical restrictions, if you find the boiler is still short cycling you than have to determine why, so you get somebody in to look at your pipework and controls.

If you find it works then refit all the valves bar 1 which can be called your bypass rad, if you find this works for you then have your auto bypass checked or leave the valve off.

John.G

Gary, surely a gas boiler can cycle and still supply a reasonable flow & return temp just like a vokera vision 20S that I think I mentioned previously, there seems to be some percularity about this particular boiler's cycle/anti cycling that we migjht e able to fathom out, one shouldn't have to make your system fit the boiler.

powerade

I returned off two radiators in Zone 1 and the boiler cycled almist immediately. It took 4 minutes for the boiler to fire up and then the temperature climbed rapidly to 71 degrees and then straight back down to 60. It appears to be cycling every 4/5 minutes and it has not settled at any point at 65 degrees. (16:21, 16:26 and 16:31)Also, it has consumed 1/2 unit of gas to heat 2 radiators in 30 minutes. That is comparable with the consumption to heat the whole house in the same time period.
I would love to keep this simple Gary but I have a feeling that there are a few contributing factors. The zoning work was only completed in May of this year and the plumber who installed the pipework and controls is adamant that everything is working as expected. If I don't have some kind of handle on the issues, I could waste an awful.lot of time and money on another plumber. So, I am extremely grateful for everyone's input and advice.
It would appear that the boiler is cycling, as John suggested, because the combined radiator output is less than the boiler minimum output and that would explain why the cycling has only become an issue after the heating was spilt into two zones. Prior to that I would have been running most of the radiators in the house.
I am going to leave Zone 2 off today. Tomorrow I will remove the TRV head from the radiator in the room with the digital thermostat and I will monitor the temperature in this room and the bedroom in Zone 2 to see if the two rooms are heating at the same rate.
With the two radiators back on in Zone 1 now, the boiler is purring along at 65 degrees and it sounds a lot less labored than it did with just the two radiators on . It will cycle but I think it was taking about 30 minutes yesterday for it to cycle with four radiators on compared to the 4/5 minutes with just two radiators on.

John.G

John.G wrote: »

Gary, surely a gas boiler can cycle and still supply a reasonable flow & return temp just like a vokera vision 20S that I think I mentioned previously, there seems to be some percularity about this particular boiler's cycle/anti cycling that we migjht e able to fathom out, one shouldn't have to make your system fit the boiler.

I like to start at the beginning and work from there.

You can’t put a elephant in to a rabbit hutch:cool:

If the boiler is set for whole house heat and hot water requirement which you then push in to a circuit that has a alternating mechanical restriction then it’s not unusual to see what the op has on a small circuit, a bypass rad would be required on every zone with trvs or a very good auto bypass before the zone valves but before I do anything I would want to prove to myself that the zone works.

I Am The Law

Can you confirm that the Flow from and Return to the boiler have not been swapped by mistake when first installed?

powerade

How would I check that?