Saunier Duval Semia F21 Boiler Failure: Troubleshooting Start-Up, Heating & Hot Water Issues

Hello

I have a problem with the boiler as in the topic. It started when the boiler stopped turning on, i.e. it made an attempt in accordance with the diagram on page 23 of the appendix, but after the third unsuccessful attempt, it gave up, signaling it by the flashing red diode signaling the failure. This was the case during the attempt to start the central heating and hot water. Both the reset and the shutdown did not bring any changes, but until then, because when the next attempt was made, he started working and worked properly for almost a day. Unfortunately, it now works in such a way that when it is turned on, it starts up, heats both in the central heating circuit and domestic hot water, but only until the set central heating temperature or until the domestic hot water is turned off, and then it goes into failure mode. Another inclusion and the whole cycle repeats itself. What seems important to me during the transition from the operating mode (yellow LED) to the failure mode, you can hear a characteristic knock, but I suspect that it is caused by the protection on the gas valve. The only question is, what could it be caused by? Voltage loss on the valve? Rather not, since after turning on the hot water, it heats up until the water is turned off, regardless of whether I turn the water off after 30 seconds. Is after a minute.

In Krakow, ul. Kamionka 8 you have the Saunier Duval service. It's worth calling and making an appointment, Mr. Piotr will help you.

Thank you for your answer and I think I will have to do that, because it is gas. On the other hand, as probably everyone here, I wanted to avoid a situation when a service technician comes and exchanges something, because he thinks that this is the reason, but it does not bring any results, then he takes the cash and the man is still with the broken boiler. I have only problems with this boiler and it was recommended to me by a friend who deals with plumbing and gas on a daily basis. Well, my mistake is that I trusted him and did not check the opinions about this boiler on the Internet before and they are bad. The effect that after a year the rotor of the rotating assembly was worn and water leaked. The service for replacing the pump shouted PLN 700 and I replaced it for PLN 150 and it works until today. By the way, how can a new (service) engine for the boiler cost PLN 320, and the rotating unit itself also PLN 320, in the same company? After all, this is something strange? It is also a phenomenon that if someone wanted to assemble the boiler from (new) parts, how much could he buy new boilers, three for this money? Electronics PLN 700, pump PLN 600, gas unit PLN 700, expansion tank PLN 500 total PLN 2500, and where is the rest? I am a passionate electronics engineer and I know very well that you can replace, for example, a given module with a new one and at the same time not work hard and have money from it, but you can repair a given module. Yes, you need to work more, but you can also earn more, and the customer will be more satisfied, because he will pay half or less, depending on the complexity of the defect and the value of the components mentioned.

The problem was solved not cheaply, because for PLN 800 with the exchange, the only question was for how long and the cause was the gas mechanism.



The one in the photo was removed from the boiler and in a moment I will check where the problem is. Seizure, stepper motor or maybe some more prosaic reason like an electromagnet, what the service technician suggested? By the way, I do not understand this policy, that when one element of the whole fails, everything must be replaced, because when the relay in the car is lost, the entire board of relays is replaced immediately? Or, when the stepper motor fails, the entire throttle is replaced immediately? For security reasons, this cannot be explained, but I don't want to dwell on it anymore.

It's been a while now, you looked inside what was the cause? Interesting because parts for each boiler are a huge expense.

I just consciously chose the boiler myself and after 5 years it works properly. However, I have a few filters plus a softener at the water inlet and a coarse filter for what. I filled the central heating system with softened water and I fill it with water if it drops off the pressure.
After a year of commissioning, the stepper motor started to make noise from modulation and I heard that this type is there and after replacement it will make noise anyway. Indeed, after some time, the new one started knocking and it has been knocking for 4 years.

I must admit honestly that I have not yet approached this gas mechanism due to the lack of time and willingness, but when I do, I will not fail to share the information about what caused it.

Hello to the electrode. I have a Saunier Duval Thenomak C 24 E stove, and I think I have the same problem with the gas mechanism. The electrodes heat up and the stove does not start. I don't know yet how much it will cost me if within eight hundred cents it's a nightmare. Do you already know what was the cause of the gas mechanism failure? I hope you can fix it yourself.

Welcome back . The problem is solved, the cost is PLN 250. The symptoms led to the valve, however this was a misdiagnosis. The valve is in very good condition. Somehow, the fuse at the thermostat between the valve and the meter blocked the gas supply. Why? It is not known. Next time, before calling the service, I will check if the gas reaches the stove. The most important thing is that the stove is working (knock on), the cost is PLN 250, including the review, and I learned something more.
Thanks for the helpful articles.

Late because late, but I answer ...
The reason turned out to be trivial, the mechanism simply crashed. It's hard to say how and where it is, because after dismantling and inspection, I put it back together and it works (checked in a different boiler). It is a pity and I regret that, instead of looking for the cause or causes, they are limited to replacing the entire modules, which is associated with high costs for the user.
Someone will say safety, etc., but for the user's safety, is the entire engine in the car replaced immediately, or is it just what it takes for the engine to be operational again? It is such a digression, but returning to the topic, it once again turned out that what was "broken and replaced" turned out to be functional differently and could be brought back to life at a low cost.

As a service technician, I have repaired the motherboard more than once, but I have installed a gas valve that freezes ... once it did not open, the second time it may not close ....

And what does the Semia, Semia C24 and Semia F21 training manual say about this?





This is why the mechanism has two gas safety solenoid valves so that, in the event of a failure, the second one takes over its functions, which is clearly described by the manufacturer when diagnosing the failure. A new valve can also get jammed at any time and in any position, because it is only a mechanical part.
Aside from the mechanical part, in such a bathroom stove as PG 6, once installed quite commonly in blocks for heating water in both bathrooms and kitchens, there was no security. It was enough that the spire in the water unit was seized and instead of retracting after the water pressure dropped under the membrane, it did not do it, and then ... And then the stove, instead of going out, was burning until it boiled water and boom. However, I do not remember any meches replacing the entire water unit with a new one then? Not only that, there were also those who treated the needles with grease that would "slip".
Well, the old times were different and the approach to everything was different, which does not mean that it was better, because there are no jokes with gas and electricity, and you should be aware of what and how you do it.

Moderated By piracik:

I treat the advice as harmful.
The fact that there are two valves does not mean that it is possible to use a gas unit with one faulty valve.

Not on the topic, but I was called to the board and I do not intentionally write back to bok(_at_)elektroda.pl, but here.

Moderated by piracik:
"I treat the advice as harmful.
The fact that there are two valves does not mean that you can use a gas unit with one faulty valve. "

Sorry, but where did I write that one of the valves of the gas unit is out of order and that I use it in this condition? It was out of order, but this does not exclude its further use after repair (hanging up). Since the manufacturer takes this fact into account in his training manual for boiler service technicians and does not suggest replacing the entire gas unit with a new one, I apologize, but where do I present the harmful content? I repeated the words after the producer and nowhere did I write what and how to unscrew, unscrew, etc. to hang it up. Equally, 80% of the content posted here on the forum could be considered harmful, because I do not think that everyone has, for example, SEP qualifications, and yet they are not forbidden to rummage in electrical and electronic devices where the supply voltage can lead to death and write about it on forum?

You have mistaken repairing with diagnostics. The training materials teach how to make sure that the problem is in the gas unit. In order not to replace the working one with a new one.
If the valve has crashed, it means that it is out of order. These are the first signs of trouble. You have a wish, mount it to a friend and stay awake at night because maybe sirens will wail somewhere.

Hello. Recently, I noticed drops from the stove. I have located where the water is dripping. Someone can tell why and what is this element of the furnace?

@ Przemo_n3
It is a 3d valve body

Thanks for the info, I can see that it will be a big expense .... 700 PLN valve

The author of the theme "Amador" is right, most things can be fixed, you just need to have the appropriate knowledge, skills, practice and abilities.
I like this comparison:

Amador wrote:

Someone will say safety, etc., but for the user's safety, is the entire engine in the car replaced immediately, or is it just what it takes for the engine to be operational again?