Bosch Condens 5000W Hydronic Heating Boiler Questions & Answers

I have found previously with some heaters if the water flow is lacking in volume the heater will cut in and out. A common cause of this in a house water supply is if debris has come through thewater supplandlocked t flow control wase in showerheds etc. It may be the cas with your heating circut?

Have had exactly the same issues for years with our unit. Has never worked properly. Hydronic heating aspect is fine, but tap hot water fails intermittently with the unit overheating and shutting itself down. Have replaced the heat transfer plate 3 times which seems to resolve the issue for a while. Bosch customer service useless. No interest in assisting. Having it removed next week and replaced with a non-Bosch system. Absolute waste of money.

Hi Martin - did you find out what the problem was? I'm having the exact same thing...

Mine is plugged into an every day power point (outdoor obviously). So you would have to just go outside and just plug it into your portable generator.

Thanks Derrick, I’ve tried that but the issue I have is I am getting a flame error, which I think is due to a grounding issue, as the generator is not earth while the boiler is. Does anyone with enough knowledge has any advice how to overcome this issue. Thanks Thanks

Are you still running the original pump? There was a known problem which was fixed for us by replacement under guarantee.

Hi Grant. Thanks for your quick response. Yes, this is the original pump. According to the Bosch Guarantee that I have, there is only a 12 month warranty on the parts (other than the heat exchanger - which is 5 years). The unit is now 3 years and 4 months old. Of course, if there was a known issue with the pump, maybe this is covered under some sort of extended warranty. As an interim measure, I have turned the water temperature down, so the unit keeps running for a much longer part of the day. As I noted in my original message, it sees that the start-up after being idle for a number of hours during the warmer part of the day seems to be most problematic in terms of the malfunction. I guess if it is actually the pump, it will just get progressively worse over time. Also, I thought that the best efficiency would be achieved with a boiler water outlet temperature towards the hotter end of the scale, but I have not tried to confirm this.

Hi As an update, I have noticed that the pressure indicated at the boiler was quite low (right on the margin of the lower red zone, about 0.5 Bar). I was fooled into thinking the boiler fill and pressure reducing valve (a Caleffi 553540, I believe - without an external pressure gauge) indicated the actual pressure on the settings dial, but it is actually just the approximate set pressure. Even though it was set to 1.5 Bar, it was only delivering about 0.5 bar. I have now ordered a pressure gauge to fit to this valve! I might need to strip the Caleffi and give the internals a clean. Anyway, the boiler is now back up to about 1.7 Bar, and I will see if this fixes the issue. I have increased the set temperature back to what it was when the problems were occurring, so I am only looking at one variable at a time.

To close this out, the boiler has been running fine since resolving the low pressure issue. I do now have the pressure gauge fitted on the downstream side of the pressure reducing valve. In this position, the gauge shows me the minimum boiler pressure as it is upstream of the anti backflow valve. The pressure reducing valve was disassembled and "exercised" at the time I fitted the pressure gauge. However, the setting dial still reads about 0.5 Bar higher than the actual set pressure, which is 1.5 Bar, based on the new pressure gauge reading and the reading of the pressure gauge in the boiler. The boiler/system pressure varies from 1.5 Bar (cold) to about 2.2 Bar (hot, 68°C). Yes, there may be a bit of air in the upper floor radiators, although I did bleed them a month ago. For reference, I do not have any leakage in my system, as the cold pressure is maintaining 1.5 Bar even though the upstream (of the pressure reducing valve) water supply isolating valve is turned off. I would only open this upstream isolating valve in the case that I notice that the boiler minimum pressure has dropped.

Hi, my hydronic heating is working ok but, it causes intermittently humming and loud noise, which I think the water pump is not working properly. it's only just over 3 years old unit, what a shame for Bosch such a good brand. The service guy came in today also confirm the same thing, hopefully it's going to be replaced under warranty.

If your pressure has dropped to 0 bar, I would get a plumber to come and see why. Ours had that problem and the installer replaced a faulty pump under warranty. How much did your system cost? It's seem false economy to make that investment and not get any return in the form of heating.

Hi Derek, we're sorry to hear about the difficulties that you're facing with your unit. The lost pressure could indicate a fault in the system rather than the hydronic heater. As Grant has suggested, we highly recommend that you get in touch with an approved service agent so that the system can be checked. Please get in touch with our friendly team at 1300 30 70 37 any time between 7:30am and 6:00pm (AEST) during the week to arrange assistance from one our consultants and be connected to an approved agent.

I don't know. But if you are scientifically/mathematically minded it could be worked out. Main point is that the bouiler works off gas, or at least ours does. I understand that gas is more expensive than electricity right now. So not sure if Bosch makes a hydronic system heater powered by electricity. I think the advantage of gas is that it is instant. Best I can do. I have seen something just today saying that the cheapest way to heat our houses right now is with reverse cycle air conditioners, especially if they can be powered by rooftop solar.

Hi Amy I had Fosters Hydronic heaters Melbourne put in my Heat pump as I live in an area with only electricity and I needed a system to heat the water for the floor heating which was economical and worked sand they were the only ones who came up with a solution. Before I had a slow combustion stove but we went through 2 ton a wood a month at $300 a ton whereas my electricity bill is only and extra $120.00 a month

We use Foster Hydronic Heating in Melbourne [www.hydronic.com.au & 03 9569 9559. They did not install our system [we are the second owners of our house] but they service the system.

Hi Peter, thanks for your question. Please be advised that we have Bosch accredited specialists that can install a Bosch Hydronic Heating System for you. In Victoria, we have Foster Hydronic Heating, Nissl Eichert, and Hydrotherm. All of them should be able to provide you with an obligations-free quote. If you require further information, please don't hesitate to get in touch with us at 1300 30 70 37. It's toll-free and our team is available from 7:30am to 6:00pm (AEST) Monday to Friday.

Hi Peter I had Foster Hydronic Heating Melbourne install my system as I needed a rather large system to heat the water to go through the floors and they were the only ones who had the answers

i have already bed the air out also. :)

Hi Peter, thank you for taking the time to write your request. Unfortunately, the unit that we sell in Australia is unique to our market and is the not the same as the Condens 5000W sold in Denmark. We understand where the confusion may have come from due to the similar names however the specific unit you have is not sold in the Australian market and we would not have an appropriate English manual for it. We would recommend getting in touch with your local Bosch customer service team. Their details can be found on their site here: external link .

Thanks for the reply Robert, Can you confirm if the user manual for the boiler in Australia is ref: 6 720 646 195a (2010/11) The ref on the installation manual we have is 6 720 860037 (2016/07)DK I am looking for this DK manual in English. Thanks Peter

Hi Peter, we can confirm that the installation and servicing manual for the Bosch Condens 5000W (ZSB18-2A) has the reference number 6 720 646 195a (2010/11). Please be advised the Australian boiler is a very different unit from the Condens 5000W sold in Denmark. You will need to contact your local Bosch customer service team to see if they can help you with your request as we do not have the product information you are after.