nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Child Item

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.

Find more posts tagged with

Quick Links

Comments

powerade

The boiler pump was replaced by Worcester Bosch in August this year, not because it was obviously faulty but they wanted to rule it out as a potential cause of the heating problems. I know that doesn't guarantee that it isn't faulty but it is virtually brand new.

John.G

Do you know if the diverter valve was also replaced.
Also sometime can you run a hot tap or combination of hot taps to give you as near as you can to achieve a flow rate of 10/12 LPM, the boiler should run continuously (with no cycling) with a hot water temperature of ~ 45C/40C.

powerade

I dont know if the diverter valve was replaced I'm afraid. WRT the hot water, how can I tell what the flow rate is?

Dtp1979

There’s probably a buildup of sludge/dirt in a tee that’s feeding zone 2. I’ve come across this issue countless times. I’m assuming obvious things like motorised valves opening fully have been checked etc. Good to know the pump is pretty much cleared out. No harm setting the pump to run on max speed too

John.G

Open one of your best flowing hot taps fully into a bucket/dish for exactly one minute and measure it by filling a 1 or 2 litre milk carton/bottle.

powerade

DTP1979, if we assume that a build up of dirt/sludge on a tee that's feeding Zone 2 is a contributing factor, how do I resolve it? I don't think that sludge is a general issue as the water out of all of the radiators, except the bathroom in Zone 1, is clear. I can see in the manual that there are four options for constant pump pressure and the default factory setting is 4. I am a little nervous of going into the menu settings but I will have to have a look.

powerade

I have checked the positioning of the flow and return pipes with the manual and they appear to be correct. These are the new pipes that were fitted when the zones were configured. There are also three copper pipes coming out of the bottom of the boiler, two of which appear to connect to the mains water and the third appears to be the gas supply pipe.

John.G

I was trying to get a online users manual for you boiler... Coule you please post the exact name/model of your boiler as shown on your printed manual.

Re pump setting of 4 this probably indicates a constant head of 4M, you said earlier that the original ABV setting was 0.1 or 1M, it's surprising that you were getting any real flow through the heating system at this setting as there should have been a huge short circuit through the ABV resulting in anti cycling. It is also unusual to have a pump set to constant pressure v/vis fixed speed/constant curve as the ABV will by pass water continuously in constant pressure mode so has tho be set up knowing the actual pump curve, if the pump curves are shown it would be interesting if you could scan and post them.

powerade

That's very kind of you John. I have attempted to attach three images but we will see if they post. I was looking at the curve chart as I had seen a post on the screwfix board on how to determine the appropriate ABV setting from this chart.

John.G

Don't know what make/model ABV you have got but using the Honeywell DU145 as a guide then a setting of 0.42 will give a constant/minimum flow rate of 5 LPM and a setting of 0.4 will give > 11 LPM so this setting is very important to give required minimum flow but not excessive flow. That pump setting of CP4 will give up to 20 LPM flow before the head starts falling. If you can post the ABV particulars then very good, if not, I would not set it below 0.4, possibly 0.42 is a reasonable setting.

Apoligies, CP4 setting is a constant 3M head so suggest ABV setting of ~ 0.35.

powerade

I don't know if my setting is at 4 but I know that is the default. I can't see any details on the ABV but it looks like a BiWorld ABV - 22mm.

rightjob!

Never mind the thermostats,are all the rads scalding when both zones are on?
Is the boiler short cycling?
Take all the trv heads off,close the bypass valve fully turn the heating on for an hour.are the rads roasting?

powerade

I wouldn't say that any of the radiators are evetr scalding. It does not appear to short cycle when both zones are on. I removed all of the TRV heads a couple of days ago.so I will try your suggestion tomorrow to close the bypass valve and run both zones for an hour.

John.G

I think I've found the e manual (couldn't attach as too large). It shows a (integral) by pass valve so you should be reasonably OK in shutting off the ABV, when it is shut just ensure that its not faulty and passing by feeling its outlet, even though you said its on a short piece of piping it should stay far cooler than the flow pipe temperature.
I couldn't find any reference to the CH minimum kw, it does say that the HW minimum kw is 7.14 input = ~ 6.0kw output so I presume that the minimum CH output is similar at ~ 6kw.

Thinking there about zone2 which has two roomstats….a dial type which you think is hard wired to the boiler and a digital which is wired to the zone valve, there could be a mismatch/conflict there, normally you have timer, roomstat, zone valve, boiler enable (by the zone valve end switch) but the digital roomstat may only be controlling the zone valve with the end switch not connected and the dial roomstat may only be controlling the boiler enable.
Before the zoning was fitted it would be correct to go timer, roonstat, boiler enable.
You might carry out a simple test to prove/disprove this. With zone1 off and zone2 on and dial roomstat at minimum see does zone2 motorized valve actuator light up and see if the boiler also fires up, if it doesn't then turn up the dial roomstat and see if the boiler starts up.

For anyone's interest here is a link to the e manual; just google "installation commissioning and servicing instructions wall hung rsf gas fired condensing boiler greenstar i erp" and then select the first PDF file of the same name.

powerade

I have set the ABV to 0 and turned on bith heating zones. There is demand for heat in both zones but the Zone 1 valve dies not appear to have opened, I.e. the actuator light is not illuminated. However, the radiators in both zones appear to be heating up, with the exception of the one in the kitchen.The pipe from the bypass valve to the return is equally as hot as the flow pipe. Should the ABV be set at 0.5 to close it?

John.G

Yes, set to the highest index to close it.
Have you read my edited post #105, it might be interesting to carry out after this present test.

powerade

Zone 2 radiators are belting out heat but the temperature is still slow to climb. The radiators in Zone 1 are not heating equally, e.g. the kitchen radiator and living tmroom radiators were extremely slow to heat.

John.G

The now shut ABV (at 0.5) should give both zones the best possible chance of heat up and the pipe from it to the return should be slowly getting cooler.

powerade

Hi John. I had tested this before and the results were as follows:
1. If the manual dial is set @ a temperature less than the digital thermostat, the manual dial will control the boiler, e.g. digital thermostat set at 32 degrees, manual dial set at 18 degrees, boiler will knock off at 18 degrees
2. If the manual dial is set higher than the digital thermostat, the digital thermostat will control the valve/boiler.
I will test it again later jyst to be absolutely sure but I am reasonably confident that these controls are working as expected.

powerade

I turned off the heating, reset the ABV to 0
5 and turned the heating back on. The temperature soared to 72 degrees, and then went into a rapid anti cycle. It took quite some time to get back up to 65 degrees whereas it got there pretty quickly when the ABV was set at 0. The actuator light for Zone 1 is still off. The pipe from the bypass valve to the return pipe is equally as hot as the flow pipe. The pressure is ever so slightly higher than I have previously noticed it to be (around 1.6). The radiators are very hot in both zones, except the kitchen radiator. The boiler has not cycled, apart from when I changed the ABV setting but the temperature has still only increased by 1 degree in an hour in Zone 2 compared with 2 degrees in Zone 1. That is slow for Zone 1 but it go off to a very slow start when the ABV was set at 0.

John.G

powerade wrote: »

Hi John. I had tested this before and the results were as follows:
1. If the manual dial is set @ a temperature less than the digital thermostat, the manual dial will control the boiler, e.g. digital thermostat set at 32 degrees, manual dial set at 18 degrees, boiler will knock off at 18 degrees
2. If the manual dial is set higher than the digital thermostat, the digital thermostat will control the valve/boiler.
I will test it again later jyst to be absolutely sure but I am reasonably confident that these controls are working as expected.

So you are quite happy that the lower setting on either will close the zone valve (indicator light off) and switch off the boiler?, this means that the dial roomstat is not hard wired to the boiler but is wired in series with the digital roomstat to the zone valve and the zone valve end switch then enables the boiler on/off, technically OK but a bit strange to have two roomstats actuating one zone valve.

John.G

powerade wrote: »

I turned off the heating, reset the ABV to 0
5 and turned the heating back on. The temperature soared to 72 degrees, and then went into a rapid anti cycle. It took quite some time to get back up to 65 degrees whereas it got there pretty quickly when the ABV was set at 0. The actuator light for Zone 1 is still off. The pipe from the bypass valve to the return pipe is equally as hot as the flow pipe. The pressure is ever so slightly higher than I have previously noticed it to be (around 1.6). The radiators are very hot in both zones, except the kitchen radiator. The boiler has not cycled, apart from when I changed the ABV setting but the temperature has still only increased by 1 degree in an hour in Zone 2 compared with 2 degrees in Zone 1. That is slow for Zone 1 but it go off to a very slow start when the ABV was set at 0.

It's strange that zone1 actuator light is off but the zone is still heating up, I can only conclude that the reason for the continued hot by pass pipe is radiation IF the ABV is holding tight.

powerade

The actuator light is off if I have the ABV fully open or closed. In relation to the dual thermostat functionality, I will check again when the heating has cooled down a bit. I am also going to test both zones for one hour again with the ABV fully closed to see if that speeds up Zone 2. I have attached a photo of the pipes & wiring of the thermistats.

John.G

powerade wrote: »

The actuator light is off if I have the ABV fully open or closed. In relation to the dual thermostat functionality, I will check again when the heating has cooled down a bit. I am also going to test both zones for one hour again with the ABV fully closed to see if that speeds up Zone 2. I have attached a photo of the pipes & wiring of the thermistats.

The plot thickens, a ABV is normally a two port valve and would be connected BETWEEN the flow and return, the valve shown is a 3 port and is inserted in the flow pipe, it looks like some form of pressure mixing valve, IMO the flow line should be un restricted so I just don't know how this works, normally a valve inserted like this would be a mixing valve and would be thermostatic.
As you look at your photo above showing flow and return horizontally (I know they are vertical but I cant post your picture showing that ) and pretending the "ABV" is a inverted T so the direction of flow is from left to right and the leg of the T attaches to the short pipe joining the return pipe.....can you say where that arrow is stamped, it on the left or the right (or on the leg) and which direction it is pointing in and we might be able to figure something out.
Also its name, I know you gave it in a previous post.

K.Flyer

John.G wrote: »

The plot thickens, a ABV is normally a two port valve and would be connected BETWEEN the flow and return, the valve shown is a 3 port and is inserted in the flow pipe, it looks like some form of pressure mixing valve, IMO the flow line should be un restricted so I just don't know how this works, normally a valve inserted like this would be a mixing valve and would be thermostatic.
As you look at your photo above showing flow and return horizontally (I know they are vertical but I cant post your picture showing that ) and pretending the "ABV" is a inverted T so the direction of flow is from left to right and the leg of the T attaches to the short pipe joining the return pipe.....can you say where that arrow is stamped, it on the left or the right (or on the leg) and which direction it is pointing in and we might be able to figure something out.
Also its name, I know you gave it in a previous post.

That's a fairly standard two port right angled abv.
Its connected to a piece of pipe coming from the (left) branch on a 3/4" compression "T".
The inlet of the abv is from the underside off that left "T".
So if plumbed correctly, the flow is along the pipe towards the zone valves with the abv before them.

rightjob!

John.G wrote: »

The plot thickens, a ABV is normally a two port valve and would be connected BETWEEN the flow and return, the valve shown is a 3 port and is inserted in the flow pipe, it looks like some form of pressure mixing valve, IMO the flow line should be un restricted so I just don't know how this works, normally a valve inserted like this would be a mixing valve and would be thermostatic.
As you look at your photo above showing flow and return horizontally (I know they are vertical but I cant post your picture showing that ) and pretending the "ABV" is a inverted T so the direction of flow is from left to right and the leg of the T attaches to the short pipe joining the return pipe.....can you say where that arrow is stamped, it on the left or the right (or on the leg) and which direction it is pointing in and we might be able to figure something out.
Also its name, I know you gave it in a previous post.

Thats a bog standard Bi World auto by pass

powerade

I have attached a photo of the bypass that shows the directional arrow. The actuator light on the zone 1 valve does not come on now, regardless of the setting of the ABV. That worries me a bit. The radiators definitely get warmer with the ABV closed and the rate of temperature increase started to improve a little in Zone 1. However, it completly slowed down when the system went into a waiting status, fired up, went into a waiting status again and then a rapid cycle, all of which lasted about 10 minutes. This was repeated 15 minutes later.

John.G

Here ia another bog standard 2 port...http://www.toplinegreenes.ie/plumbing-heating/plumbing/pipe-fittings/valves/biworld/automatic-bypass-valve-22mm

powerade

Yes, I'm pretty sure that's the one .

John.G

Thanks to all, I thought looking at the first photo, that it was a 3 way valve.