New system boiler problem

[D_Hailsham]

OK, so you need to keep SWMBO happy!

If you install a Honeywell CM900 series programmable thermostat for the central heating, you only need a single channel timer for the hot water side. This can go where the existing programmer is. I would suggest a Drayton Tempus 1 or Tempus 7. The Drayton LP111 or LP711 would also be suitable. The difference between the Tempus and LP versions is that the Tempus has a "Boost" button, which allows you to put the water on for an hour.

I know your main aim, at the moment is to get the system working but, when you decide to change the programmer, it would be worth rewiring the terminal block as per the "standard" scheme. This will make it much easier for any engineer to follow.

Come back to this topic when you decide to make the change, we will then have all the "history" and wiring data.

 

[oldBiker]

Mr H,
Thanks for that advice.
I will be back on the forum sometime on Friday when I have wired the existing system, and then we can take the next step forward as and when.
Thanks again,
oldBiker

 

[oldBiker]

Hi its me back again.
I wired all the pieces of kit as advised on previous posts, and I still have a problem. I have checked and double checked every single core of cable at each piece of kit.
1) Heating is OK. When advised by the programmer, if stat says go it happens.
2) Hot water, the pump starts but the boiler does not fire up, even though the cylinder is needing HW.
3) If CH is ON and I then manually switch to HW at the programmer, this in turn puts the flames out at the boiler and the pump still runs, even though there is still a requirement for heat.
4) In each case scenario, the three port valve is always in its correct position.
Your comments would be appreciated. (I am sure we are not far off cracking this problem)
oldBiker

 

[oldBiker]

Hi its me again........
Firstly the hot water cylinder is cold, and needs heating.
Checked all the voltages at the boiler, and they are as last week ie giving 50volts when HW is ON, and with HW and CH together.
Remember CH is working OK and the valve is positioning itself correctly.
Traced the cabling at the connector block, and knowing that 3 at the programmer should be the feed to the connector block which is terminal 3 at the connector block.
Across TB3 and TB6 there is 240v, so it is fine up to the connector block from the programmer.
This then feeds through the cylinder stat via terminals 1 or 2 at the connector block. I have done a voltage check at these points:
Across TB2 and TB6 (neutral) there is 50volts
Across TB1 and TB6 (neutral) there is no volts.
It appears to me that the cylinder stat is the problem and reducing the voltage to 50 volts, which is then in turn being sent to the boiler.
Just done a similar exercise on the CH, and there is 240v at TB5 across to TB6 (neutral), and 240v is at the terminal block. 240v is also going through the roomstat and coming out with 240v for the boiler switched feed, so all OK.
Not sure how the 50volts takes over as the overriding voltage, when HW and CH are on together.
Your advice would be appreciated on whether my theory that the cylinder stat is the problem.
If you need me to take voltages etc at any point except the programmer, let me know.
Hope this latest information is helpful.
Over to you experts..........
old Biker

 

[D_Hailsham]

When HW is ON or HW and CH are ON, the boiler is controlled by the HW thermostat. The HW thermostat could have been wrongly wired in the first place.

Do you have a multimeter?

If so, disconnect the wires to the HW thermostat (make a note which goes where )

Turn the stat to max and check continuity between all three terminals. Note which two are closed, e.g A and B.

Turn stat to min and note which two are closed, e.g A and C.

One terminal will be common to both, in the example above terminal "A". Terminal "A" should be connected to TB3 , together with wire from P3

Terminal "B" should connect to TB1, together with wires to Boiler SL and valve Orange

Terminal "C" should connect to TB2 together with wires from valve grey and P1.

You may find that it wires up exactly as before and you still have the problem. In which case we have to identify the faulty component.

Come back for more help if you need it.

 

[oldBiker]

Hi,
Just to clarify...
Yes I have been using my multimeter for continuity and voltages etc........
The cylinder stat has three wires connected to TB1,TB2 and TB3. Red goes to TB3, Gr/y goes to TB2 and black goes to TB1.
I disconnected the three wires to the cylinder stat, then checked continuity between TB1, TB2 and TB3 on the terminal block, with stat turned to max and then min at boiler, TB1 and TB3 were common.
Regarding the cylinder stat, with the wires disconnected to the terminal block, I have just checked continuity with the wires to the stat, and none are common.
I had previously connected the gr/y to TB3 and alternated the other two cables between TB1 and TB2...still nothing.
Hopefully this info will help........

 

[D_Hailsham]

The cylinder stat has three wires connected to TB1,TB2 and TB3. Red goes to TB3, Gr/y goes to TB2 and black goes to TB1.

I disconnected the three wires to the cylinder stat, then checked continuity between TB1, TB2 and TB3 on the terminal block, with stat turned to max and then min at boiler, TB1 and TB3 were common.

Regarding the cylinder stat, with the wires disconnected to the terminal block, I have just checked continuity with the wires to the stat, and none are common.

I think you have misunderstood what I asked you to do.

The tests I gave should be done on the cylinder thermostat terminals.

Turn the cylinder stat to max and check continuity between all three terminals of the cylinder stat. Note which two are closed, e.g A and B.

Turn cylinder stat to min and check continuity between all three terminals of the cylinder stat. Note which two are closed, e.g A and C.

One cylinder stat terminal will be common to both tests, in the example above terminal "A". Cylinder stat terminal "A" should be connected to the loose wire from TB3.

Cylinder stat terminal "B" should connect to the loose wire from TB1.

Cylinder stat terminal "C" should connect to the loose wire from TB2.

 

[oldBiker]

Mr H,
Sorry about that.........
I have only just noticed on the cylinder stat.......
The cyl stat identifies A as red and common.
B as black and normally closed (NC)
C as yellow and Normally open (NO)
I put the cyl stat up to max ie 80 degC and A and B were common
I put the cyl stat to lowest ie 50 degC and A and B were (still) common.
oldBiker

 

[D_Hailsham]

I put the cyl stat up to max ie 80 degC and A and B were common
I put the cyl stat to lowest ie 50 degC and A and B were (still) common.
oldBiker

The cylinder stat is faulty - replace it. Get a Drayton HTS3 or Honeywell L641A. The wiring is the same for both:

Connect C to TB3
Connect 1 to TB1
Connect 2 to TB2

 

[oldBiker]

Mr H,
Thanks for that.
It appears we got there in the end.
Thanks very much for your help.
You were the only one that had the perseverance with me and my ramblings over all the connections etc. I think the other plumbers that view this site and particular posting will be wondering what we were talking about.
I have looked at some of the other postings, and there are some right idiots who respond with their critical, abusive, impolite and sometimes downright rude responses, but you have been an absolute gentleman with the patience of a saint!
I would like to get in touch with you to thank you personally, and give you some form of gift (like a bottle of malt whiskey), Not sure how we could do this, maybe you could advise.........
The plumbers merchant I use is now closed until Monday, and of course come Monday morning at 0530 hrs I will be on the road again, and working away until Friday, but in the meantime my wife can collect a Honeywell cylinder stat through the week, and I will fit this on Friday next.
Again, thank you very much, your time and patience is very much appreciated, particularly because this item was working OK prior to me changing the boiler.
I have been a construction manager most of my life handling projects up to £30million, managing programmes, safety, planning and controlling up to 200 men of many disciplines. My hobby has always been building, doing all building trades from concreting, bricklaying, roofing joinery etc etc. I am basically a mechanical engineer, having served an apprenticeship over forty years ago.
This boiler replacement is part of a six room extension I have just built on my house without any assistance from anyone (apart from you).
Anyway, thanks again, I will put a further post on next Friday, hopefully to say that all is well. Remember the next step will be to replace the programmer and the roomstat...........my work never ends !!!!!!
old Biker.

 

[oldBiker]

Forgot to add............
For those of you who may think I did the gas connection myself..sorry you are wrong, I have a pal who is registered and he did this on my behalf, but he is a plumber and not an electrical (control) engineer.
Unfortunately now I have to get my wiring undertaken/approved by authorised electricians...............
old Biker

 

[D_Hailsham]

Don't bother about your local plumbers merchant. Get down to B&Q or Wickes or your local DIY shed. They will have cylinder thermostats in stock.

As for the bottle of whiskey, it's a very kind and much appreciated gesture, but I couldn't possibly accept it.

In any case you are jumping the gun a bit as the problem is not solved until your system is working correctly.

 

[oldBiker]

Will do.
Thanks.

 

[oldBiker]

Hi Mr H,
I went to 240v B and Q and purchased a Drayton HTS3. (The previous stat was a HTS2)
Connected up and still not working, however.........
voltages....
Under 50degC calling for heat:
TB6 (N) to TB3 is giving 240v
TB6 (N) to TB2 is giving 240v
TB6 (N) to TB1 is giving 240v
but boiler will still not fire.
cylinder stat set high:
TB6(N) to TB3 is giving 240v
TB6(N) to TB2 is giving 100v
TB6(N) to TB1 is giving 50v
Your advice please...............
old Biker

 

[oldBiker]

Mr H,
Not sure what happened before, but in the last couple of hours I have been fitting insulation to my modified CH pipework and tidied my workshop, and after I finished that, I thought, I will just give it a try again, and Hey Presto like magic all is working !!!!!!!!!
Gone through all the scenarios, ie HW on CH on and both on, boiler is working, valve is in correct position............so what can I say....
Thanks for your help. I will leave it a short while (a week or two) and then I will look to change the programmer and thermostat.
So watch out on this website, as Arnie said 'I WILL BE BACK'
very happy oldBiker (and wife)