Pump overrun is killing my heating!

[Milleniumaire]

Righto, I'll answer what I can just now.

1. One is a heating pump, another is a Cylinder charging pump, and normally another is a secondry circualtion pump (the one that moves the hot water for taps round the taps in the likes of a hotel so the hot waters always near the taps) Basically if your system heats then its at the right setting for you.

Ah, so circulation pump refers to a pump used to circulate hot water, rather than central heating. That makes sense and explains why the "Circulation Pump" Time-programme doesn't do anything on my system. I see on the schema diagram the circulation pump would be wired to R4 and I have nothing in R4.

So, a cylinder charging pump is an additional pump that pushes water to the cylinder, and the circulation pump takes the hot water from the cylinder and pushes it around the house to the taps.

So, the new Grundfos pump on my system is an external "heating" pump.

2. Thats something Im going to pass onto technical to have a look at, mine does the exact same, Im 99% sure its the relay opening and closing to control an electronic mixing valve, but I assume it should be able to be stopped when a mixing valve is not in use, pretty annoying, although taking the VR10 sensor off the pipe (the one on the heating flow) stops the clicking after a few moments which makes me think it is a mizer relay.

My boiler and cylinder etc. are all located in the garage, which is below the master bedroom. I can't hear the VR 71 clicking unless I'm in the garage and its not so much the noise that worries me as the fact that it is constant and therefore could potentially "fail" in time (maybe)! As you say, if it isn't doing anything why can't it be stopped. Unfortunately, since having the LLH and external pump installed this does result in more noise that can be heard more easily in our bedroom. Previously, we could just about hear the boiler when it was on, but it is now very noticeable, but we are getting used to it.

The installer left the pump on speed 3 (the default I believe) and I have now turned it down to speed 1. I have wondered if this is potentially a conflict with the internal boiler pump, which is on the default d.19 setting of 2. I have read in some forums that it should be on 3, so the internal boiler pump works at speed 2 all the time. d.0 = 37, which affects the heating speed, so I think hot water and heating speed will always be 2, whereas pre ignition and overrun speed will be 1?[/QUOTE]

3b. depends on the coil rating of the cylinder, if the cylinder coil is rated at 15kw then not much use having the boiler run at 37kw, would have it a bit higher than cylinder coil rating just to keep the recovery time faster.

I've attached the Vaillant uniSTOR 260 manual, but it doesn't appear to say anywhere what the coil rating is. The graph on page 5 implies the heat input to the cylinder can vary between 12 and 38 kW, but not sure how that is possible, but if 37kW is possible (the maximum output of the boiler) then I guess d.77 is correctly set at 37kW?

7. You almost certainly dont have a buffer cylinder, a buffer cyl is not for hot water, its like a store for heating water, be interesing to know what your System Diagram number is under that same config menu?

The System Diagram number is set to 2. As none of the schema diagrams in the VRC 700 Schema Diagrams manual matched my system, Vaillant sent me another one, which is much closer, although it shows multiple zone pumps and mixer valves, which mine doesn't have, just the one external system pump and the way that is wired is still potentially an issue that I'm waiting for Vaillant to resolve. I have attached a copy of the supplied schema diagram.

8. They can be found on the confiiguration menu under the info for each zone. They only actually take effect if you have electronic mixing valves on the system, but they are required to be fitted for the system to work regardless.

My installer couldn't get the system to work and then realised after speaking to Vaillant, it was because he hadn't included ANY of the supplied temperature sensors! I did prompt him by asking what they were for and why were they supplied if they weren't needed!

What make/model/size is your DHW cylinder? heat up times will vary considerably depending on the installation and cylinder fitted but with a little more info we could maybe tweak it to suit

It is a Vaillant uniSTOR 260, installed 10 years ago along with the boiler. How time flies, I still consider the boiler to be almost new as it only feels like it was installed a few years ago! I've attached the uniSTOR manual.

hopefully that clears up a few of the questions, on my old laptop so its a pain typing into, anything else just ask and I'll get back when I can get onto the other computer

Thanks, that has been very useful. As I said, I'm really keen to learn as much as I can about the system and to be sure it is configured correctly.

Feel free to check my VRC 700 settings and let me know if you see any that obviously need to be changed. I've attached an XML file, which I had to zip up so it could be uploaded, and if you open this in the free Microsoft XML Notepad software that you can download from here, then you will see all the relevant settings in a menu type structure.

 

[Harry Bloomfield]

Wild suggestion and possibly wrong - Your config file shows you have it set to heat the water in the cylinder to 55C, it shows what I think is the actual temperature in the cylinder as 60C....

My 700 very accurately controls my cylinder temperature, when on it never overshoots. Might your sensor have been somehow misplaced? Might it not be seeing the proper increasing temperature of the cylinder as it is being heated, so it goes into a long cycle of giving priority to heating the cylinder?

My sensor is pushed between the insulation and the copper of the tank, where my original tank stat fitted. It reheats my (open vented) cylinder in around 20 to 30 minutes.

 

[Milleniumaire]

Wild suggestion and possibly wrong - Your config file shows you have it set to heat the water in the cylinder to 55C, it shows what I think is the actual temperature in the cylinder as 60C....

My 700 very accurately controls my cylinder temperature, when on it never overshoots. Might your sensor have been somehow misplaced? Might it not be seeing the proper increasing temperature of the cylinder as it is being heated, so it goes into a long cycle of giving priority to heating the cylinder?

It reheats my (open vented) cylinder in around 20 to 30 minutes.

Sorry, that is my fault as I originally went through all the options taking notes of the settings, but I have since changed some values, the cylinder temperature being.one of them (reduced from 65 to 55) so I guess I should really go through the menu and update everything again, so any dependent values are also changes.

My original issue stemmed from the boiler taking an hour to heat the cylinder and therefore preventing the heating from working. This was due to a) the cylinder temp being set to 65 and b) my son have late night showers, so using a lot of hot water. I'm sure there are settings that could be improved.

Having reduced the cylinder temp to 55 I've turned on the anti legionella function.