Do that anyhow but I think that MPV is knackered.
Open vented system, No HW, CH works fine, BAXI 80HE boiler shows Dry Fire after every restart
- Thread starter fandyman
- Start date
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I've got TRV valves on all rads. When they are all switched off (set to 0) then the pump shows 32W in the A position.
As for B to A I just did that and it is similar behaviour - it goes from 45W to 32 (if all rads' TRVs are on 0 or to about 42W if at least one rad TRV valve is fully open - set to 5). I also hear a bang about mid way through the turn and the valve is forced straight to A from about mid position. Just realised the pipes banging sound is the same sound I always used to hear when I tried to turn down the TRVs from higher setting to about 1.5. It was always banging on all TRVs around the 1.5 mark in the same way I heard it from the 3 port valve on that video.
As for B to A I just did that and it is similar behaviour - it goes from 45W to 32 (if all rads' TRVs are on 0 or to about 42W if at least one rad TRV valve is fully open - set to 5). I also hear a bang about mid way through the turn and the valve is forced straight to A from about mid position. Just realised the pipes banging sound is the same sound I always used to hear when I tried to turn down the TRVs from higher setting to about 1.5. It was always banging on all TRVs around the 1.5 mark in the same way I heard it from the 3 port valve on that video.
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When you are controlling the room temperatures by TRVs you should have a ABV, (automatic bypass valve) installed that will start opening when the TRVs throttle right down, Have you got any roomstat installed anywhere? That pump setting CCIII which is over 6M should not be required, as a interm measure I would suggest changing to CCII at 3.0M, it can allways be changed to CP2 at 4.5M, when/if required,
Honeywell used to have a great name, not so much now I think, installer friends of mine now use EPH but you won't go too far wrong replacing like with like.
The 45watt on HW only shows anyhow that the cylinder coil is not blocked.
If you don't want to install a ABV, you could leave one towel rad or a small rad with the TRV set to 5 (full open) and throttle the lockshield valve to ~ 1 turn open, this will act as a permanent By pass
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What's the probability this thresd will get to 10 pages?
Andy
Andy
D
Deleted member 267285
Was just thinking 7 pages for a seemingly easy fault. I suppose if people keep answering and so does the OP, it may well reach in excess of that!
No room stat - just TRVs.
I will try changing the pump to CCII and look into the ABV.
Many thanks for all that info - helped a lot understanding the system.
If I had read your very post properly where you said in very second paragraph that "when i crank up the termostats on the radiators and boiler kicks in I can feel the pipe is hot on both side of the A and B piping" I should have realized that you were referring to TRVs and might then have copped on to the fact that there is no roomstat installed once the pump power was changing, did you tell the heating engineers that there was no room stat(s) installed?, otherwise they may not have asked?, maybe that's a bit surprising in itself.
Its also surprising that the system was installed without at least one roomstat as its very wasteful of energy not to mention constant boiler cycling of the boiler although your boiler Dry Fire protection acted as a very very crude "conrol" with all TRVs closed but of course this then led to conclusions that it was probably a boiler problem.
You should consider getting a roomstat installed, I run my CH in that manner, I have 10 rads, 8, TRVd, two, non TRVd, in a combined dining/sitting room where the digital roonstat is installed so have a very reasonable system as I get pinpoint control of the rooms where we spend most of the day and quite acceptable control of the others. mine is a S plan.
At the end of the day though, you should still be able to run that system with HW only selected but maybe not out of the woods yet, but hopefully the new MPV will cure that.
Its also surprising that the system was installed without at least one roomstat as its very wasteful of energy not to mention constant boiler cycling of the boiler although your boiler Dry Fire protection acted as a very very crude "conrol" with all TRVs closed but of course this then led to conclusions that it was probably a boiler problem.
You should consider getting a roomstat installed, I run my CH in that manner, I have 10 rads, 8, TRVd, two, non TRVd, in a combined dining/sitting room where the digital roonstat is installed so have a very reasonable system as I get pinpoint control of the rooms where we spend most of the day and quite acceptable control of the others. mine is a S plan.
At the end of the day though, you should still be able to run that system with HW only selected but maybe not out of the woods yet, but hopefully the new MPV will cure that.
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I though AB referred to 3 port valve
Well noted.
Me thinks the ball is in the wrong park as to what is being looked at.
Hi @Johntheo5, Thanks for your comment.
I was referring to the 3 port valve there.
I am new in this house - moved in 1 year ago.
The only other component that looked like room stat (I always thought is not functioning as assumed not powered and a leftover from previous system) is this one attached in the hallway.
Could this play a role in it?
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It most certainly could and should. Open up (to 5) a few rad TRVs, turn that roomstat down to 10C, boost or programme CH only ON, check that pump/boiler not on, turn up the roomstat until it cliks on, check pump/boiler running.
Consider going to an S plan if looking at replacing the MID.
As suggested though - I would recommend you get someone in that is experienced with these types of system to get it to a base line so everything in known and understood. Given the way a CH system controls etc chain together, then chasing one problem after another could have you running around in circles, as one issue can sometimes seem to cause a problem in another especially if it's intermittent.
I did that test and yes the roomstat turns off the boiler if TRVs set to 5 and I turn the room stat down to 10C. I then turned it up to 22C again and the boiler switched on. After that I had to turn the TRV down to 0 from 5 and again to 5 and observed the boiler firing again. I checked the CH pump after the test and it was showing 19W (I listened to your advise and change it to CCII which seems to be working fine for now).
@Madrab Just spoke to a heating engineer over a messenger re the Y plan vs the S plan and he told me this (without seeing my set up yet):
"... I don't believe there's any main differences between an S plan and a Y plan cause they both got pros and cons between them. With S plan you will need 2 valves so you have 2 chances of either of these valves going faulty. You will probably need a bypass for either this boiler or a next boiler. That will also have component on it that can go faulty, get blocked up, be set up incorrectly etc. The Y plan itself is just basically a one zone valve so you do not need a bypass for this. There's pros and cons between the two - for me whatever you've got you stick with it. Obviously the main difference would be wiring - if they are wired up right they normally work forever the way they should. System wise it's a problem for both so if the system is dirty and got debris in it or sludge or something in it that is foreign (not water) they will both be an issue. You do need a clean system free from debris and sludge..."
What do you say - is he right or wrong?
What is the advantage of S plan?
Do I need a bypass with S plan if the pump is not operated by the boiler (pipe overrun)?
"... I don't believe there's any main differences between an S plan and a Y plan cause they both got pros and cons between them. With S plan you will need 2 valves so you have 2 chances of either of these valves going faulty. You will probably need a bypass for either this boiler or a next boiler. That will also have component on it that can go faulty, get blocked up, be set up incorrectly etc. The Y plan itself is just basically a one zone valve so you do not need a bypass for this. There's pros and cons between the two - for me whatever you've got you stick with it. Obviously the main difference would be wiring - if they are wired up right they normally work forever the way they should. System wise it's a problem for both so if the system is dirty and got debris in it or sludge or something in it that is foreign (not water) they will both be an issue. You do need a clean system free from debris and sludge..."
What do you say - is he right or wrong?
What is the advantage of S plan?
Do I need a bypass with S plan if the pump is not operated by the boiler (pipe overrun)?
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