Pls Help - Seriously confused over whole heating system

[NikkiD]

Hi all

Am desperate for some expertise at the moment before I yet again embark on spending more pennies on plumbers. Sorry if this seems a bit long, will try and keep as brief as possible.

We moved into our house a year ago and have been baffled by the heating system ever since!

We have a Worcester Bosch Combi boiler, a danfoss programmer, hot water cylinder with a thermostat attached stored in one of our bedrooms, attached to which is a honeywell motorised mid-position valve. Also, we have no room thermostat, just trv's on all radiators.

The problem we have is that in order for us to have any heating, we have to select hot water on the programmer. The radiators seem to heat up fine, but some then cool down completely but the boiler continues to fire on and off every 10 mins until the programmer goes off.

If I move the adjustor on the 3 port valve from auto to override and hold this in place, I am able to select only heating on the programmer and the boiler fires up. However, if I select hot water on the programmer, the boiler will not fire no matter where I hold the adjustor on the 3 port valve. If I open any of the taps downstairs, the boiler fires up and I am able to get hot water on demand. However, I cannot get hot water on demand in the bathroom upstairs unless I have the hot water, and hence the heating on at the same time. Is this normal?

Is someone able to explain to me what kind of system this is as this is driving me crazy. We have had numerous plumbers out, all of which have stated something different. Some have said that this is just the way the system has been set up, others have said to flush the system (which we did to no avail) and the last engineer thought it was a problem with the 3 port valve. I thought that having a combi boiler would serve heating and hot water separately and therefore eliminated the need for a hot water cylinder, but hey, I'm no expert either? Also, is it not beneficial for us to have a room thermostat to control the overall temperature in the house?

Your advice would be greatly appreciated.

 

[spacethegas]

what model boiler is it ?

i rarely come across a combi feeding a cylinder, but it is possible.

do you have large house with a number of bathrooms ?

which taps are fed from the combi as opposed to the hot water cylinder ?

 

[NikkiD]

Hi spacethegas

It's a 35cdi.

No, we have a 3 bedroom house, downstairs shower room and 1 upstairs bathroom.

The taps in the downstairs shower room and kitchen are fed from the combi and the upstairs bathroom taps appear to be fed from the cylinder!

 

[diverdee]

its perfectly fine to have a combi running a fully pumped system.sounds like he has plumbed it right but got the electrics all wrong.it needs rewiring as a fuuly pumped y plan with room stat controling switched live to combi.you must have a unvented hot water tank i assume

 

[NikkiD]

Hi Diverdee and thanks for your response.

Sorry for my lack of knowledge, but how would I know if the system were unvented? We have a cold water storage tank in the loft and there doesn't seem to be an expansion vessel located near the hot water tank - does this mean the system is vented?

 

[diverdee]

yes if u have hot water tanks it means it a open vented system.does the boiler have a pressure gauge and if so what does it read and how many valves do u have on the pipework

 

[NikkiD]

The pressure gauge is at 1.5 bar on the boiler. What valves on pipework (boiler)?

 

[diverdee]

sounds like combi running some taps and a fully pumped sealed system running a vented tank and heating.the plumbing sounds fine just the wiring seems very erratic no room stat just means boiler will stop firirng when boiler gets to temp then refire as the heat is pumped away.as for no heating when selected on clock would point to either wrong wiring or faulty valve head.sorry but sounds like u need a visit from a sparky and start again.any decent sparky will have it sorted for you in a hour either fixed or understand the problem