HVAC Questions? Ask an HVAC Expert for Answers ASAP
Good morning, welcome to the Technical section in JustAnswer; my name is ***** ***** I will help you today.It sounds like the installer has not configured the boiler to use an external heat demand. Do you have a room thermostat?_____If you receive a phone call offer, please ignore it - these are system generated and outside my control. My understanding is that you won't be charged if there's no phone call.
OK. It's certainly relevant that you have UFH, because that potentially requires an extra connection to a wiring centre.The conventional configuration for a heating system like yours is for the heat demand from all zones to converge electrically at a wiring centre, and the demand from a hot water storage vessel (if you have one), and the demand from the UFH system.Your radiators thermostats - are they wireless, or simply acting locally on the valve tp open/close it?
Regarding the noise, without wishing to be a doom-monger, sometimes these noises can't be solved. I have one customer whose Vaillant boiler had everything single part replaced, except for the casing, over a period of 18 months, because it was making a droning noise. In the end Vaillant gave up and replaced the boiler as a unit, which didn't make the noise. Nobody (outside Vaillant) will ever know the cause.Did the noise start within the warranty period?
Is your plumbing guy the person who installed the boiler?_____Going back to your original problem, which isn't solved, do you want guidance with that?
OK. What your describing is a control issue. It might not be a problem with one of your thermostats, but you can't eliminate anything until the fault is found and fixed.This is the kind of problem that I solve day in day out. As I said at the beginning, if the installer didn't configure the boiler to use an external thermostat then it will default to the behaviour that you're describing. I correct at least one of these a month during the winter season. But you have an electrician coming on Friday so between the two of them I would hope they can get it right.
The electrician won't know, unless he happens to be Gas Safe registered too, but a decent heating engineer should know, and Gas Safe engineer who doesn't know should get themselves the appropriate Vaillant training.This is one of the most sophisticated domestic boilers on the market, with a plethora of test modes and configuration parameters. The installer needs to follow the manufacturer's detailed installation instructions - there's no quick summary that I can give you. If I could, I would.
The electrician won't know, unless he happens to be Gas Safe registered too, but a decent heating engineer should know, and Gas Safe engineer who doesn't know should get themselves the appropriate Vaillant training.This is one of the most sophisticated domestic boilers on the market, with a plethora of test modes and configuration parameters. The installer needs to follow the manufacturer's detailed installation instructions - there's no quick summary that I can give you. If I could, I would.On top of that, you have a complex installation with multiple zones, and UFH. It's not an installation I would necessarily expect to get right myself, first time, so I would test extensively before handing over to the customer.
The MZV that has been latched open must also have been disabled electrically, unless it’s faulty. The purpose of the MZV is two-fold:
1. To prevent heat circulation into the UFH zones when there’s no demand. As you say, this reduces wasted energy.
2. To provide an electrically independent (of other zones) heating demand to the boiler.
The reason you were given for latching it open seems fallacious to me.
Thanks for your rating :-)
Answering your questions one at a time...Q: ...we have hopefully a Vaillant Engineer my plumber knows coming on Monday to check the configuration of the boiler.A: I'm relieved to hear that!Q: I need your further advice on the Zone Valve issue. You are right that the U/F ZV is not connected and was latched open on the instructions of someone from Honeywell (Residio) Technical after there was a problem with the U/F manifolds not receiving water (I think because maybe the ZV was not being told to open). He told us that there was no need for a ZV because the individual U/F valve heads effectively cut off the water flow and therefore presented that circuit with a "dead end" so water would not flow very far up it. This does not appear to be the case as I think the manifolds have a by-pass so when all heads are closed they still get a hot water feed. In that case we need a zone valve to cut it off don't we?A: Yes, quite so. If you have a bypass downstream of the MZV then there would be insufficient control of heat flow to meet the current Building Regulations.Q: I wonder if you have any experience of Evohome U/F controls and can comment?|A: Yes I do , so yes I can comment.Q: I don't see why, if the U/F controller turns on the boiler and C/H pump why it cannot also open the U/F circuit ZV?A: Firstly, I would prefer to say that the controller "presents a heating demand", not that it "turns on" things like the boiler and/or pump. owint to the boiler's pump overrun function, and the potential presence of a MZV, the controller might fail to turn on the boiler through no fault of its own. I know it sounds pedantic, but sometimes the wrong wording can lead analysis in the wrong direction. Q: Seemingly that's what the separate Hot Water, Piped heating and Towel Rail controllers do? I am asking the same question of Honeywell's support people but they have not been terribly good at solving my issues up to now so I am hoping you or a colleague may have an insight to offer.A: My answer to that is the Honeywell has not been paid to take a look at the big picture with your system, so they will probably revert to script and make the standard assumptions. Your system is quite complex, and not many people will be prepared to think about it without attending.
This isn't necessarily an Evohome issue; as I've said, each zone should present its heating demand to the wiring centre, and from there you should have one connection to the boiler. The conventional way to electrically isolate each zone, and to save energy, is to use a MZV for each zone. (There is an exception in single zone systems where a 3-port MZV can be used effectively.) There are other ways to achieve these two goals, but most people find those ways to be more complicated and more expensive.You need one person to take charge of determining the best means in your system to achieve these two goals. So far, you've had two engineers attend, and taken advice from Honeywell, and from me, but nobody is actually achieving anything. I strongly suspect the Vaillant engineer will focus solely on the boiler. I don't want to sound like I'm scolding, because that isn't my intent, but you need someone to do what the original installer should have done, which is to integrate all of your zones, wire things up correctly, test the arse off everything to make sure it works, and then (and only then) hand over to you with an explanation of how it works. If that person does anything unconventional with the wiring or control methods, then it needs documenting prior to that handover. That's what any good professional would do.I'm not saying that you can't DIY, but you have an uphill struggle in terms not yet knowing what you need to know, how much you don't know, and learning a lot very quickly. On top of that your system is about as complex as a domestic system can get without it being a small-scale industrial installation.____I'll do my best again to answer your specific questions...Q: was Evohome tech correct in saying don’t use ZV and if not what is the proper (actually any) way of introducing the required control of the u/f system under the present setup.A: I doubt it, but please recap concisely what the Evohome proposal was.Q: There is a wiring centre next to the boiler (2 actually) but as I said it’s unclear how the u/f controller connects to it - how ideally in your view should it be set up?A: So far I've seen no reason not to do things conventionally.Q: There is no obvious Evohome installer here that I would trust...A: Whereabouts in the UK are you?
Erratum: "(a) working the system" in my previous post should have been "(a) wiring the system".
Unfortunately I'm not close to Torquay; I would have enjoyed knocking your system into shape!In principle I'm happy to guide you and to keep answering your questions. I don't like being mercenary, but the reality is that I have to earn a living and I'm not being paid much for this topic. What would you think of the idea that you have a one month subscription? Then I believe you can keep asking new questions for no extra fee (but please check my facts on that). That way you have access to a resource (me) and I also get something out of it. You can direct a question to me specifically and the system will prevent other experts leaping in to answer.
That sounds like a good plan - I should have suggested waiting until after Monday, which was my intention.
A thought has circled back to me from Saturday - I wanted to mention OpenTherm, but in one of my posts I asked what Honeywell were proposing and was waiting to see if they had mentioned it.
It’s possible that somehow has attempted to use the OpenTherm interface to control the boiler from the Evohome UFH controller. IMHO that would be problematic, because implementations can differ between manufacturers, so it’s not reliable. It will be interesting to hear what the Vaillant engineer finds.
I really don't think this is a question of asking different people or companies what needs doing - you'll get one opinion for each person you ask. You just need to follow the Evohome installation instructions.Which Evohome products do you actually have?
Do you have the HCE80, and/or the R8810?
If you're going to do the installation, the following online course will help you:http://youlearn.honeywelluk.com/index.php
Er, that was the wrong page. Try this one:https://youlearn.honeywelluk.com/course/evohome
OK. I understand the reason given, but I disagree with that person's logic.If the concept of treating the UFH system as providing a heat demand is upheld, then the problem melts away. What you've ended up with is a bad design that has been half-implemented.It's conventional for the UFH controller to power the pump on the manifold, not for the MZV external to the manifold to do it. The MZV simply opens the flow to it's "zone", and when open it presents the electrically decoupled heating demand to the boiler.If someone wanted to use the MZV to power the UFH pump, for whatever bizarre design they had in mind, then they should have installed one MZV per UFH manifold, which is an option that's still open to you. However, the simply solution is to disconnect the MZV orange wire from the UFH pump, and connect it to the same terminal as the other orange wires from the other MZVs. And to use the UFH controller in the way that all other UFH controllers are used.Do you have just one UFH controller for both of the manifolds?
Nearly. I'd like to get you to stop thinking about pumps. It's leading your thinking in the wrong direction.Conceptually, the UFH manifold and everything on it, including the pump, is one component. The UFH controller is part of that component, and manages the pump, the actuators for the loop valves, and accepts inputs from the roomstats in the UFH zones. Whether or not the UFH pump runs should be down to the relevant UFH controller.You're probably about to ask id the UFH pump should run when the zone valve for that manifold is closed, and why would it. The answer is yes, and the reason is because it's designed to do that. The UFH pump is there to circulate water within the UFH loops. That's all. Nothing else. When all of the UFH zone room thermostats are satisfied, the controller should then turn off the UFH pump. If it wants to. That it's business. It doesn't matter.Separate to all of that, the UFH controller is capable of presenting a call for heat from a heat source. The UFH controller doesn't know or care what that heat source is, or whether or not there's a pump - that's none of its business.Again, this basic design concept has been chopped up into bits and then badly implemented in your system.So, the call for heat from any UFH controller should be treated exactly the same as any call for heat from any conventional room thermostat. It doesn't matter how many calls you have, or where the calls come from. The call from the UFH controller should power open the respective MZV. The switched live from the MZV is the final stage in the process of presenting a heating demand to the boiler. Again, it doesn't matter how many potential demands there are from MZVs, or indeed where they actually come from - the boiler neither knows nor cares.Does this make sense?
I’m not feeling frustration at all, but I’m sympathetic to yours.
I don’t trust what your electrician is reporting. Honeywell’s answer depends on the question he posed, and if he doesn’t under stand underfloor heating then he could easily have posed the wrong question, or wrongly described the system, or led their thinking.
I’ll remind myself of the controller wiring at lunchtime, and I should be able to tell you exactly what should connected to what.
Morning!I'm probably going to backtrack here, because with new understanding (since my previous post) I can actually see that a MZV isn't essential. As you say, the Honeywell schematics are lamentable, but before I get too far into that, and the backtracking, could I ask you the following?1. What is the model number of the room sensors (aka room thermostats) that you have?2. Do you have one room sensor per UFH zone?3. What is the model number of the wireless receiver?(Please note that I'll be out for a chunk of today, but will check in here when I get back.)
Good evening, I’ve been out for most of the last two days, so I haven’t. I’ll be at my desk tomorrow morning if you could wait until then.
I can’t see an answer to Q3 - the wireless receiver. Do you have one?
OK. I imagine that you one per HCE80, plus one for the Evohome hub. Assuming (which is always risky) that the switched lives from the BDR91s all converge at the wiring centre, and between them all present the heating demand to the boiler, then that makes sense.However, you still have the original symptom of the boiler cycling on and off with no apparent demand, which brings me back to the boiler configuration.This is probably a good time to draw a schematic of your system, to show what's connected to what.
Hello, to recap the problems...1) The boiler was firing too often;2) The boiler was very noisy;3) The system configuration is undocumented and might be wrong.I believe that (1) has been fixed. I'm not sure about (2) - is that still an issue? Regarding (3), I have a hunch that the HCE80s and BDR91s between them aren't connected and/or paired correctly, but I don't think we can do any more without a schematic diagram that shows what's connected to what. Then I can look at that and tell you if I think something needs correcting.
Yes - a block diagram would be spiffing. Even an incomplete one, as long as it's clear what's certain and what's uncertain.To re-iterate: I don't need to know how it ought to be wired. What's missing is how it is actually wired.
Acknowledged. I'm probably going to struggle to find time to look over it until later tomorrow afternoon, but if you don't hear from me before Thursday morning then by all means give me a prod.
Good afternoon!I hadn't, so thank you for the prod. I will look this afternoon.
I've spoken to them in the past, but not very recently. They were helpful enough, as far as I recall.I have printed out your schematic so that I make notes on it, so will get back to you ASAP.