CH & HW system upgrading
 

I wonder if anyone might have some familiarity with Vaillant heating systems?


I had a new EcoTec 418 Pure installed last March, on my open vented system to then find it only had one boiler output temperature setting. Wanting the HW hot, I had to set it to 75C, but since then for CH it has tended to run flat out then off, with not much modulation - so not a very efficient way to run. This was using a Sunvic SDM 1901 three port, separate timeclock and mechanical room and cylinder stats.



This past week, I have ripped out timeclock, both stats and replaced them with a new fancy Vaillant control system. A VR65 (Control Unit) linked to the boiler via an ebus and a VRC 407F, which connects wirelessly to the boiler module and module also connect wirelessly to an outdoor sensor, so the boiler output can auto-compensate for anticipated heat loss. It is also supposed to allow HW temperature to be set independent of CW. 407 is a combined LCD display, room temperature sensor, clock and has all the means to adjust the setup.



CH is working spot on, boiler output is now modulating its output perfectly as it is supposed to and generally its output temperature is well within the condensing range.


I have set HW to 70c via the 407, but it never achieves it, the best it seems able to manage is around 50C - it just never gets there so demand never cuts off.


I have tried adjusting the boilers settings via its own LCD, to set it so it knows it is working with a mid- position 3-port, that allowed it to enable CH setting and HW setting for output temperatures, I set both to max. 75C CH and 60C HW, but HW cylinder still only manages around 50C.


Odd that the 407 allows 70C for HW, but the boiler HW max flow is only allowed to be set at a max of 60C.. Unless this particular setting in the boiler was only intended for when it was a combi version of the boiler?



I have three times emailed Vaillant to ask if the VR65 + VRC407F + ECOfit 418 + SDM 1901 were compatible with each other, before buying - they replied three times saying nothing more than that my VR65 + VRC470F were superseded by the VR66 + VRC700. They gave no clues about any possible compatibility issues at all.


When the HW desired is set higher than the around 50C it can achieve, the boiler will be cycling constantly trying to achieve it. So HW boost never switches off. Adjust the desired to somewhere less than 50C and boost manages it and turns off just fine, but we want hotter HW than nearly 50C.

Harry try posting in the plumbing section on here

https://www.diynot.com/diy/

Thanks, but I am still trying to get my head around its problems, I have just found another issue, with the Legionaire system program. It is supposed to ignore the set temperature for the HW cylinder, to heat the HW even hotter to kill any bacteria in the cylinder. It seems to be running the boiler flat out to do that, but above a certain temperature (of the cylinder I assume), it begins cycling the valve and passing boiler heat to the CH circuit when there is no demand. So I'm pretty sure it is not controlling the valve actuator quite as it should. Very confused..

Don't talk to me about boilers :mad:
Ours has been nowt but trouble since end of October. Having to get Baxi out for a third visit tomorrow. End of Oct we had no heating or hw, started a boiler repair plan with them, just as well we did. They came next day and fitted £300 worth of parts, loads of leaks and a dead pcb. Been ok until before Xmas, when hw started playing up. Had them out on 7th Jan , engineer replaced electrodes and said we needed to get a chemical flush on ch system, as there was dirt in system. Tues night no hw at all, called Baxi again and was told they wouldn't come out again until system had been flushed. I asked for them to come and do it and I would pay the fee as it not included in care plan. No was the answer, they only repair and service, dont do that. Had to call 3 gas fitters before someone agreed to do it. After it was done, STILL no hw. Apparently its the diverter valve at fault. So although the system did need cleaning, the Baxi engineer was talking cack that this was the cause of the fault. So yet another day of disturbed work tomorrow. Dont buy Baxi boilers folks, they are s$€/e.mad:End of rant

I look after my own system, though I did get a Vaillant agent to do the basic install of the new boiler last March.



If your system needed flushing, obviously it has been lacking inhibitor for a while. My system was installed in the mid 1980's and has never needed flushing, though I gave it a good flush anyway, as I was adding TRV's all round, before the new boiler was fitted.


I also had a filter to the return pipe added as a precaution. Boiler passages are much smaller these days, so easily blocked with debris. I have checked the filter a few times since and a minimal amount of debris has come out each time, but it proves it is doing its job.

with filters a lot of manufacturers insist on them now with inhibitor for warranty purposes, in fact the strength is often tested at the annual inspection for warranty

i had a Baxi. Biggest pile of rubbish ever. Replaced with a Vailant over 10 years ago which has never missed a beat. Never had to top it up either although thats probably more to do with the excellent guy who fitted it all.

Not just me tben. This particular model has now been discontinued. according to the local fitter. If we have to replace it at any stage, we will go with Valiant or Worcester Bosch

Harry. That passing of the boiler heat to the CH circuit sounds like it might be the temperature sensor. The sensor could be sending an OVERHEAT signal to the circuit board. As a safety feature the board would open the diverter valve to get rid of what it thinks is excessive heat in the boiler.

It's not demand opening the valve, but maybe just a faulty sensor signal.

Could be why the temperature to kill the bacteria will never be achieved.



Colvert.

Turns out diverter was fine, but the flow cartridge was the cause of the fault