Banging, clanking and pounding!

[Daf]

I have just moved house and the new one has a nice an shiny central heating system that has both pumped hot water and central heating. Seems that I have a valve that is an 'either' type which means that I either heat up the hot water or the radiators. Not both at the same time.

The tank has a lovely Danfoss thermostat fitted to it.

There is a header tank in the attic underneath the main cold water tank.

The time controller is a Danfoss SET5 and has been set up as a 7 day device. Underneath that there's a connector box that has more cables and connections than a BT exchange. It takes in a mains cable and provides a power feed to the SET5 controller. This in turn sends back wires to the connector box to turn on the heating and hot water. Out of the box I can see three more cables. One goes to the valve, another to the tank thermostat and the last one goes to the pump (yes you guessed it Danfoss!!!!).

The boiler is down in the utility room and just says BAXI on it (cos Danfoss probably don't do boilers!)

All in all, much improved over what I used to have.

The very first night we moved, I turned the system on and all went perfectly. It ran beautifully for two hours until both my wife and I decided that it had become too hot (the radiators please) and it needed turning down. First thing I noticed was that EVERY radiator had a TRV fitted (thought that you had to have at least one that was straight through?). Anyway, I adjusted the TRVs on all radiators down to an acceptable level for each room. I left the radiators in two bathrooms fully open just in case. All went well for half an hour until the system stared pounding as if pipes were being hit by a blacksmith with a lump hammer. Turns out that some of the TRV on the radiators were causing the noise problem. Sorted all but one of them out using a hammer and a pair of pliers on the pin.

Thanks for getting this far, here are my questions:

What else can I try on the TRV which is sticking?

My wife would like a room thermostat set up in the hall so that she can feel that she is in control of the heating (she's in total control of everything else . My local plummers merchants has sold me a Honeywell T6360B which I'd like to fit in the hallway. What cable should I 'break' to install this? Should it be the live/on out of the time controller for the Central Heating before it hits the connector box or should I only interupt the central heating live/on cable that goes to the valve?

How does the boiler know when to fire up? I can't see a cable anywhere? Does it have a flow switch?




I have bled the system but not balanced the radiators.

 

[ChrisR]

You need the Instr for your boiler, or look at the connection strip, and the wiring diagram for W plan, if that really is waht has been used. Y plan much more common. Find them here, Solutions for Homes, etc
http://content.honeywell.com/uk/

 

[meldrew's_mate]

My wife would like a room thermostat set up in the hall so that she can feel that she is in control of the heating (she's in total control of everything else

Mrs M is also in control, control of the dummy 2nd roomstat on the lounge wall, the real one is hidden in the hall. Every time I come home it's on MAX, does this sound familiar.

So to your "diverter". Could it really be a mid position valve, but if you don't have a balancing valve on the hot water cylinder load it may just feel like a diverter until the DHW is hot?

ChrisR has already covered how to connect the new (NOT DANFOSS!!) roomstat, though you may find that your pump is actually a GRUNDfos just to add insult.

Is the misbehaving TRV on the rad in the wrong flow direction?

 

[Daf]

Mrs M is also in control, control of the dummy 2nd roomstat on the lounge wall, the real one is hidden in the hall. Every time I come home it's on MAX, does this sound familiar.

I do not have the b@lls to try this!

So to your "diverter". Could it really be a mid position valve, but if you don't have a balancing valve on the hot water cylinder load it may just feel like a diverter until the DHW is hot?

I couldn't really tell you what it is. Just that when I started up the system one evening after emptying the hot water tank during the day I noticed that it took around twenty five minutes before the central heating started up and the boiler had been flat out all that time.

Looking at the pump, I can see the valve sitting above it. From the valve, one pipe heads towards the tank and the other towards the floorboards.

ChrisR has already covered how to connect the new (NOT DANFOSS!!) roomstat, though you may find that your pump is actually a GRUNDfos just to add insult.

You are quite right. It is a Grundfos so the original plummer must have been working using a rhyming plan I've been on the site and I can't see where I can get the info as to where I should place the break in the cable for the thermostat? HW cable to valve only or turn everything off (HW power to valve & pump) ? Is the advice dependent on whether it's a W or Y Plan?

Is the misbehaving TRV on the rad in the wrong flow direction?

Gave this another go last night. It now works fine for settings off, 1,2,3 and 5. However, set it to 4 and that drummer from the Muppet Show turns up and starts playing tunes on the radiator. I'm OK about this as a 3 is acceptable for me for the moment. The real issue is how to wire the thermostat.