Problem with Vaillant 428 and Systemate 2000

[Raymo]

Hi folks, Firstly Id just like to mention that I'm not a plumber and I dont fully understand the techy jargon, so please be patient and I hope someone can help with a problem I've got since a recent boiler change, I have a Gledhill Systemate 2000 in the airing cupboard upstairs and the boiler resides in the untility room downstairs and up until recently had a baxi 100h2plus heat only boiler and all was fine until it died, so I had it replaced it with a Vaillant ecotec plus428 heat only boiler, but on completion the boiler cycles every 1.5 minutes for 30 seconds to keep with the water temerature demand of the systemate. It fires up and the temperature digital display rise really quickly and then shuts off when it reaches its max and then it falls nearly as quick, I have tried resetting the systemate as its meant to learn the setting of the boiler, but to no avail, I spoke to a Gledhill techy who says its to do with the boiler over run facility, I think the plummer has not connected the over run due to the fact the systemate has its own over run facility but he did do a temp feed and apparently it made no difference, so I then spoke the Plumber who installed the Vaillant who says he thinks the 2 units are not compatible, its at this point that my common sense approach attitude is not making sense so I'm turning to some of the specialists on this forum to hopfully enlighten me, many thanks icon_biggrin.gif

 

[Raymo]

 

[twgas]

You say the boiler reaches its max temp, do you mean its set temp?
What temp (in degrees) is it set at and reaching?

 

[mickyg]

I doubt your original boiler needed replacing, just repairing. I would be very wary of what boiler i would connect to a systemate. I would start by downrating the boiler output to around 12kw. 28kw is almost certainly far too much for your system. Also make sure the store pump is on maximum setting.

 

[Raymo]

You say the boiler reaches its max temp, do you mean its set temp?
What temp (in degrees) is it set at and reaching?

Cheers TW, Yes its set temp which i achieve with the dial, HW max is 65Deg and the CH is 75Deg and when the boiler fires up it reaches an indicated 75Deg and shuts off then the numbers start falling approx 2Deg per second until it gets down to say 50Deg and the boiler then fires up again and the temp rises quickly and so the cycle starts again.

 

[Raymo]

I doubt your original boiler needed replacing, just repairing. I would be very wary of what boiler i would connect to a systemate. I would start by downrating the boiler output to around 12kw. 28kw is almost certainly far too much for your system. Also make sure the store pump is on maximum setting.

Thanks Micky, I have been having it repaired for 4yrs and for a new boiler I dont think its acceptable and reading these forums kind of led me to believe the Baxi boilers are crap, well the model I had anyway, as to the KW output, the original was a 30KW boiler so I just got as near to that output as I could, I have a large house with 15 rooms

 

[mickyg]

one of the few benefits of a thermal store is that you can/should use a smaller boiler. The boiler shouldnt be sized to the system but to the thermal store. No thermal store I know of requires 28kw. Downrate the boiler to at least 15kw and see how you go. You can alter it on the D codes D0.

 

[Raymo]

one of the few benefits of a thermal store is that you can/should use a smaller boiler. The boiler shouldnt be sized to the system but to the thermal store. No thermal store I know of requires 28kw. Downrate the boiler to at least 15kw and see how you go. You can alter it on the D codes D0.

Micky any chance you could give me some detailed instructions on how to do this, many thanks

 

[mickyg]

hold the "i" and "+" button together, you will see d0 appear. press "i" again, it will prob display 30 or 28 which is the output. Use "-" button to reduce it to about 12 for now. Hold the "i" button for 5 secs to confirm. Press "i" and "+" again to come out. Make sure the heating temp is maximum, think most you can have is 75, not ideal for thermal store and not ideal for the boiler but thats your best hope.

 

[Raymo]

Right Micky thanks for the info I have done that procedure now, can you tell me what results I should be getting?, also when you say 75Deg is not ideal for the thermal store or the boiler what do you mean by that

 

[GaytonTonner]

The Systemate is a DHW only thermal store. The CH pump and DHW pump are inside the same casing as the store for neat packaging. Treat the Systemate as a high pressure cylinder as far as the boiler is concerned.

1. Heats the thermal store via a large coil.
2. Heats the CH circuit directly, not via the thermal store.

It is in effect like attaching a boiler to a normal indirect cylinder and CH circuit. No different. The setup is the same as a double zone valve system (CH & DHW), except it uses two pumps, not zone valves. The third right hand pump operates when the DHW taps are opened and is separate to the boiler not having any influence to the boiler. The pcb does use this pumps as shunt pump when needed to spread the heat in the store .

This effect will occur when reheating any indirect cylinder with a coil smaller, in kW, than what the boiler can deliver in kW. This is not helped by the boilers control system which is trying to maintain a delta T (temp differential) between the flow and return.

As been suggested have the centre pump in the unit, the DHW pump, on full speed, to get the heat out of the boiler ASAP. See how that works. If no joy, then as been suggested, set the power of the boiler to match the CH of the house.

75C is fine for the Systemate. It learns the power output of the boiler and can operate with a minimum of around 70C. When it know what the boiler is giving out it sets the system to suit. It learns the heat up time of the store. When the stored water drops to around 60-65C the boiler then cuts in. This is to prevent cycling.

 

[Raymo]

Thanks for the reply GT, can you tell me the procedure for setting DHW Pump to max, also you lost me a bit with setting the Boiler to match the CH, how do I find what the CH of the house is, sorry if this is really simple stuff but am a total noob to all this. Oh btw how long will it take for the systemate to learn the output from the boiler or do I neeed to turn it off to reset it etc?

 

[GaytonTonner]

Thanks for the reply GT, can you tell me the procedure for setting DHW Pump to max, also you lost me a bit with setting the Boiler to match the CH, how do I find what the CH of the house is, sorry if this is really simple stuff but am a total noob to all this. Oh btw how long will it take for the systemate to learn the output from the boiler or do I neeed to turn it off to reset it etc?

Look at the centre pump. There is a switch with three settings, 1, 2 and three.

There are a few on-line calculators. Barlo are one and Myson had one. You type in the size of your rooms, etc and it gives the total heat requirements. If it says 15kW then set the boiler to around that level if you can. I am not familiar with your boiler model. Others may help here.

You need to power off the Systemate for a minute or two and switch back on. It will take a day or so to learn.

BTW, pour a can of X-100 in the Systemates top up tank. It is not really required but recommended

 

[Raymo]

Ok I have done all the things suggested so I will wait for the systemate to learn the new settings for the boiler and see if my problem has been resolved, many thanks to all it much appreciated I will keep you posted on the outcome

 

[GaytonTonner]

Ok I have done all the things suggested so I will wait for the systemate to learn the new settings for the boiler and see if my problem has been resolved, many thanks to all it much appreciated I will keep you posted on the outcome

If the cycling stops, you can notch up the boiler power one at a time until the cycling starts again, then drop back a notch until it stops. Then you are on optimum, giving fast reheat.