Viessmann Outdoor Reset Question

zoulas

I have a Viessmann VR1 with Vitotronic 100 KW10B control. The unit works very well but the outdoor reset is not working. The boiler runs at 170 degrees all the time. The Adj High is set for 167 degrees. The reset slope is set to 1.2. The WWSD is set to 70 degrees. There seems to be something overriding the reset function and I cannot seem to figure it out. DHW is via indirect. Unit was installed by authorized dealer do I would like to think they know what they are doing. I have provided some pictures of the control. Switch S6-6 is set to on (outdoor reset enabled) . This is a really important function that I would like to get working. Many Thanks

ChasMan

Check the obvious. What's the minimum temp set to?

zoulas

This is the only mention of minimum temperature in the manual. My setting is OFF.
Minimum boiler water temperature selection
S7.7 in the OFF position - 113o F (45o C)
S7.7 in the ON position - 131o F (55o C)

ChasMan

Well, your outdoor sensor is wired, IMO poorly. Are you using the 5K sensor supplied with the control? It may be acting up. Also, what thermostat control and or indoor sensor are you using?

ChasMan

I am asking because in reading the manual, the principal and operation changes depending on the indoor control. It works together on that 0-10vdc circuit to adjust the temperature. I am not familiar with this control at all though Now that I read the manual it appears you can't see what temperature outside or inside the boiler thinks it is to reduce the water temperature so you have to troubleshoot it with a meter. When was this introduced? 1975?

zoulas

I have 4 Honeywell thermostats connected to 4 zone valves. The outdoor sensor is two wires (non polarized) so not sure how it could be wired poorly. This is the one that came with the control. Although switch S6-7 is set to on, there is nothing wired to the A1 Auxiliary input.

ChasMan

Those little NTC thermistor circuits can be sensitive to interference and for long runs, IMO they should be two twisted pairs surrounded by a foil shield which gets grounded when it enters the boiler and be kept away from 120v wiring as much as possible. The control, if they did it right, is sending power through that circuit and measuring the current coming through to determine the resistance of the thermistor and using that resistance value to measure the outdoor temperature. So it is fairly noise sensitive. Since I did not program it I have no idea how sensitive it is so I err on the side of caution. But heck, just use LVT. Anyhow, That's why I mentioned the wiring since it is at about the minimum standard I guess which is what the manual calls for as long as it never gets near 120V circuits which is impossible since it runs into the boiler about three inches away from the pump relays. I am still trying to find out how to troubleshoot that thing. Also working on my own boiler at the moment. Hopefully someone more familiar with it will chime in.

zoulas

The outdoor reset wire is zip-tied to the bx going to the circulator pump. Not sure if the circulator pump runs on 120v or not, not sure if the bx offers enough shielding to prevent interference .

ChasMan

Well, that's where experience comes into play. The x factor. A lot of things work fine even if they are not done in an ideal way. It's the reason there is so much flakey software. Ok, the circulators do run at 120v and the flex acts as an antenna not a shield since it is grounded at both ends. I am not saying that is your issue. Do you have a volt meter? The manual goes through basic no heat issues but then it delves into test points. Its the low voltage ones you want to check as well as the resistance values for the outdoor thermistor. But I would not suggest poking around with the power on much if you are not used to doing it.

ChasMan

Out of curiosity, what is your outdoor temp. The manual says the curve kicks in a temps. Below 37 degrees. And wit the differential between your low and high limit you don't have huge range.

zoulas

Are we looking at the same manual? The outdoor reset seems to work at all temps below the WWSD. See enclosed pic. Also, there is no mention in the manual about a low limit, only an adjustable high limit. BTW, yesterday 40 degrees outside, and when the boiler was providing heat, it boiler water was 170. I am also attaching the manual pdf.

zoulas

ChasMan

No, not exactly. I had one for the KW0A / KW10B combined. You appear to have it set up so it should work. I would start by checking the outdoor sensor. If it is shorted or open it will assume it is -4 out. That would give you a fixed temperature.

ChasMan

I found that reference to 37 degrees F again. It is on page 11 under the description of the summer mode switch in the third paragraph. You have it in the summer / winter position which seems correct however. It is weird they put that there.

ChasMan

It also appears you have two perhaps three boiler water temperature sensors. One feeding the temperature gauge, one feeding the FHL safety, and one connected to the control. It is possible the control is seeing a different temperature than the gauge. Just a thought. Wouldn't have killed them to add a 2 line LCD to this thing would it.

ChasMan

Just trying to take a detailed look at the S6 Dip switches. From the photo you posted, it is a little unclear but S6 is on the top right of the control. (Top left of your picture) It has seven switches. The manual numbers the switches left to right 7,6,5,4,3,2,1 so that would be bottom to top of the image you posted. And the manual show the down position to be ON which would be to the right on your picture.

So you have
S6 - 1 OFF
S6 - 2 OFF
S6 - 3 OFF
S6 - 4 OFF
S6 - 5 ON
S6 - 6 OFF
S6 - 7 ON
At least going by the pictures and the manual. That obviously will not work. Need a clearer picture of those dip switches.

zoulas

Although Viessmann makes a great boiler, their implementation of outdoor reset is lacking. The authorized service man said to get it working they must install a pump relay. The Viessmann manual and docs seems to state that the functionality is built in. This is not the case. ChasMan, thanks for your help.

ChasMan

I think that control is a little older but it has all the features needed. It does have built in pump relays. I think the issue is that the circ pump relay runs all the time for constant circ. Switch s6-3 will stop that. I have a very similar control to yours except it has a scheduler and lcd readout. It is a beautiful thing when you get it hooked up right.

zoulas

My understanding is that the Vitotronic 100 is a single boiler control, while the model 200 and 300 are multi boiler controls that also work with radiant heating (which I don't have.) The Vitotronic 100 (what I have) is still a current model on the Viessmann web site.

ChasMan

Yes, it is current but I think it is an older design. They have a lot of stuff in Europe that they do not bring over. And oil has gone the way of the dodo pretty much. You would be better served with a Tekmar 260 but at this point it wouldn't get you much more than you already have except for room temp influence and a readout so you can see what the outside temp is and the target boiler temp etc.

gennady

Check fuse F3

ChasMan

I love the symptom for blown F3, continuous burner call. I imagine that would produce this banging up against the ahl all the time right? That's too easy of a fix . I really like this control. Wish it had indoor feedback, appears to be very well made.

HomerJSmith

I haven't worked on this model Viessmann boiler, but as I remember they have an override switch that eliminates the slope and parallel shift settings and defers to the AHL. If the AHL is set at 167 deg, it will run at 167 deg all the time and ignore the outdoor reset.

zoulas

I have gone through the manual 25x and I am not seeing such a setting.

zoulas

Boiler tech called viessmann and was told I need a relay installed to separately control the zone valves. The conclusion was that the indoor thermostats and the outdoor reset are both trying to control the boiler.

ChasMan

The override is the manual / auto on the front panel. In your picture, that is set correctly for outdoor reset.

ChasMan

The only additional relay needed is one to provide priority zone closure on the zone valve controller if you are using priority. Pump power on the zone valve controller should come from the system pump power on the kw10. The dhw pump can be hooked up to the kw10b directly. Otherwise, post purge won't work. Additional relays can be added for isolation but there is no way your thermostats can affect the boiler water temperature no matter how bad your wiring is.

ChasMan

So, just to clarify, you should have a zone valve controller with one channel for each zone valve plus an extra unused priority zone. So you have four zone valves running a single pump, you need a six zone valve controller because nobody makes a five. If you are not doing priority you can use a four but I would still suggest a six in case you want priority for the indirect. You have to run a hot/ neutral / ground constant power plus an additional hot wire to the zone valve controller from the kw10 system pump. The transformer will connect to the constant power source. The switched power source from the kw10 will connect to the NO pump contact. The rest depends on priority. I would suggest a TACO zone valve controller because others have tried to simplify things by hardwiring the transformer to the power which is not ideal for you.

ChasMan

Also, if you hook it up any other way, you will lose the low temp protection functionality of KW10 which is essential if you do not have a bypass.
Edit to add, you will lose post purge on the heating circuit with this because when the call for heat is lost on the zone valve controller. Even that could be fixed with a couple of relays but it shouldn't be necessary. On my controller post purge for dhw and system both alternate the system and dhw pumps. So dumb. I would need a PLC to deal with that mess. Ahhh, the French.

ChasMan

Can I ask, what kind of radiation do you have? Baseboard fin tube or what?

zoulas

Hot water baseboard. I do use dhw priority, i guess this is why the need for the relay?? Also post purge on hearing side is disabled as per the tech it would "dead head" with zone valves closed. Dhw purge is enabled as there is no zone valves.

ChasMan

Yep, it would deadhead, if not wired properly and enabled. The zone valve controllers can prevent the deadheading allowing you to leave it enabled and it will only pump if there is a heat call but that's fairly if not entirely useless. You need another relay, pair of them actually to open a zone valve when there is no heat call. That would let the freeze protection work as well. Oh, the fun. Also, don't forget to check the fuses because they do not shut off the control. They throw it into limp modes. F3 in particular turns off outdoor reset. The main fuse on the front panel turns on both heating pumps when it blows. That's for freeze protection. With fintube you will need hotter water at some point unless you have a boatload of it.

HomerJSmith

zoulas, From the manual--"Override switch
The front mounted override switch H when in the up position
h, turns the boiler pump on and enables stage 1
and 2 call for heat. The boiler operates on the adjustable
high limit temperature.
When the override switch H is in the down position a,
the system is in normal operation."

The top rocker switch is the override switch. The picture show the override switch in the down position. Push it to the top position and see if that solves your problem.

I don't like viessmann boilers. I'm not saying they're no good, they're great, just over engineered. That's German engineering for you.

https://www.viessmann.ca/content/dam/vi-brands/CA/pdfs/doc/v100/vitotronic_100-kw10bis.pdf/_jcr_content/renditions/original.media_file.inline.file/vitotronic_100-kw10bis.pdf

HomerJSmith

As I recall, the slope is set based upon the type of heat emitters the boiler services. Low temp (infloor), medium (Radiators), hi (fin tube baseboard). The higher you go up the slope the hotter the supply water.