Issues with new heating zone

powerade · 26-11-2019 05:09PM #1

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 · 26-11-2019 05:37PM

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 · 26-11-2019 06:21PM

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 · 26-11-2019 06:45PM

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 · 26-11-2019 07:15PM

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 · 26-11-2019 08:10PM

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 · 26-11-2019 09:10PM

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 · 27-11-2019 11:52AM

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 · 27-11-2019 12:04PM

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 · 27-11-2019 01:31PM

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 · 27-11-2019 01:57PM

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 · 27-11-2019 02:11PM

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 · 27-11-2019 02:29PM

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 · 27-11-2019 02:33PM

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 · 27-11-2019 02:41PM

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

John.G · 27-11-2019 03:42PM

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 · 27-11-2019 04:27PM

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 · 29-11-2019 04:23PM

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 · 29-11-2019 05:27PM

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 · 29-11-2019 05:37PM

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 · 29-11-2019 05:39PM

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 · 29-11-2019 06:20PM

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 · 29-11-2019 08:07PM

Cruizer101. Thank you. It looks broadly the same but without the words "Auto" and "Manual. I will give it a go tomorrow &#55357;&#56397;&#55357;&#56397;

K.Flyer · 29-11-2019 08:42PM

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 · 29-11-2019 08:53PM

Thank you so much.

powerade · 01-12-2019 12:05PM

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 · 01-12-2019 12:52PM

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 · 01-12-2019 01:23PM

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 · 01-12-2019 01:32PM

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 · 02-12-2019 11:48AM

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 · 02-12-2019 11:49AM

I meant to address that query to everyone.

Issues with new heating zone

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