Search results

Thanks for the pic. Did you have weather compensation as an extra when the Viessmann was installed? It doesn't matter if you didn't, but the instructions for adjusting the pump speed (which I'm not suggesting) do mention weather comp. Follow the instructions on page 29 for "changing the maximum...

You say you have a 35kW Viessmann 100-w system boiler; the current model is only 32kW. Can you provide the GC (Gas Council) number of your boiler - it's on the front of the installation manual. I see that the installer has balanced for a 10C CH temperature differential (65C-55C). Your boiler is...

Make and model of original boiler? Make and model of new boiler? Were the radiators balanced when the new boiler was installed? Can you post a pic/scan of the Benchmark Commissioning page in the installation manual of the new boiler?

The deltaT (difference between flow and return temperatures) of a radiator is nothing to do with how old the radiators are. It is determined by the boiler. Older boilers, with cast iron and similar heat exchangers, were designed for a 10C/11C differential. Modern condensing boiler, with very...

A 30kW boiler seems on the large size for a three bed detached house. I live in a similar house, built mid 80's, and the heating side of my 37kW combi boiler is turned down to 12kW. The required boiler output does depend on the total heating capacity of your radiators. There's no point trying...

Make sure you only change one thing at a time, e.g climate outside temperature or climate flowtemp, not both at the same time. Then monitor its effect Climate outside may be a good place to start as it is currently -10C, which may be suitable for Europe but is rather low for the UK, which only...

You are correct in thinking that, if the room does not reach the required temperature, the heat curve needs adjusting. I would try the "good insulation" settings first as your house may not be as well insulated as you think. If that has the opposite effect, i.e house gets hotter than you want...

It's good to know you have sorted your problem. It also saves me having to upload a copy of the iSense manual. Have you checked the room and outside temperatures using a different thermometer? If there is a discrepancy, this can be corrected using Calibration (4.3.6).

You need to set the correct heating curve, which will depend on the system and the environment. The iSense manual gives instructions.

The diagram of a one-pipe system shows a pipe bypassing each radiator. I presume, from what you wrote, that you have a bypass on each radiator. Is there a valve on each bypass? There should be as it determines how much of the flow passes through the radiator. Do you have any means of measuring...

You say you have seven radiators which are all in one zone, but are they all in the same loop? Or does the pipe from the boiler have a tee with one side for the upstairs loop, and the other side for the downstairs?

Maybe not; but the owner could be fined up to £5,000 for not complying with building regulations. Installers can also get into trouble - read the attached pdf.

That sounds like a 1-pipe system. One Pipe and Two Pipe Systems by D_Hailsham posted 14 Dec 2009 at 5:06 PM The water temperature entering the radiator decreases the farther you get from the boiler, so radiators have to be increased in size to compensate. Balancing is also completely different...

Can anyone identify the Aqualisa shower in these two pics? How old is it? What is a suitable replacement?

They may say they are OT boilers but they can't be. Can you give some examples?

All OT compliant products have to respond to Data IDs 0 (master/stat & slave/boiler status), 1 (CH water temp setpoint) and 3 (slave configuration). All other Data IDs, e.g actual water temperature, modulation level, water presssure etc. are optional. Some stats may ask for this information, and...

Just wire it as per the yellow lines in your pic; no other connections are required. The OT connections can be either way round; and the links on L2 need to stay in place (or be replaced if already removed).

If link L1 is present, the cylinder stat C terminal is fed from room stat terminal 1, which gets its supply from programmer CH On. There is then no way you can have separate CH and HW times; it's all controlled by CH timings. An S plan (two motorized valves) does not require a connection to...

There is no white wire on the cable to the "Mid position or HW valve" terminal block, so it cannot be a mid position valve. It must be an S Plan with separate CH and HW valves. The cylinder stat will not work without a connection to C terminal.

Have a look at the Myson Heatloss Manager