pump stays on when programmer off

[jimbarr]

Hi, I have just joined this forum but have already learned much from just reading, the problem I have has baffled several heating engineers/electricians/plumbers.

The full history would take ages but I believe this is the basics of the problem.

The system is fully pumped with reliable potterton profile boiler, honeywell mid pos valve, ACL lifestyle programmer, honeywell room stat, rads stats on all radiators, etc. I think it is a single feed system for rads.

The system has been modified and added to during the last twenty years and most rads are working fine and hot water is available when needed.

One radiator has always been tricky, a bit cool, but after a lot of mucking around a new status quo has emerged.

The problem radiator gets hot, but then after an hour our two it goes off even though other rads are Very hot. I have removed the valve stat and it still stays cold.

The other problem is that even when all the system is in OFF mode, the pump sometimes runs e.g. all night.

 

[JohnD]

edited, sorry, I misread the problem



When the pump runs all night, is it in cold weather?

 

[jimbarr]

Yes pump runs during cold weather but the rest of the system is OFF, no red leds on programmer, no boiler fired up.

Do you know the pin-outs for a Honeywell T63608 room stat? I am trying to draw a COMPLETE circuit for the controls and the drawing in the programmer documents does NOT show this stat.

Cheers
Jim

 

[JohnD]

No idea about anything else, but the "cold weather" thing might be due to a (1) frost stat, or (2) a cold-weather override, whose purpose is to ensure (1) the system doesn't freeze (2) when it's really cold, your house gets extra heat.

 

[jimbarr]

I can see why pumping the system would reduce freezing liklyhood, however, this is happening when the temperature is well above freezing.

Somehow, the pump circuit is complete when everything else is off, I cannot be sure but at least one of the folk who have looked at the problem have left me saying "that should fix it" and also the feeling they may have changed something they did NOT understand!

One person mentiond "common live" in connection with pump and midpos valve and that I should change the valve, but it is less than 18 months old and his logic lacked conviction!

I have higher quals in electronics and electrical engineering and if I can only build up the complete control circuit I might get a handle on where the fault might be.

Thanks for you help so far JohnD

Best wishes, Jim

 

[kevplumb]

check the pump overrun stat

 

[jobloggs]

If you have a 3 port diverter (y plan) valve then there is a live feed from the programmer back to the wiring system and onwards to the 3 way valve. Ive sussed this out from the wiring diagram for my pegler system.

However not being an expert on these valves I get lost then but I suspect of the valve is misfunctioning it may be then calling for the pump. (is your boiler also firing or cycling on/off when this happens.)

You should be able to get a wiring diagram for your system on the web. I know there is a good training program on the pegler website which might point you in the right direction.

 

[jobloggs]

look at sections 3.9 to 3.12 on

http://www.pegler.com/training/cpd/Index.htm

For this setup with programmer off for both CH & HW there is live feed to the grey wire of the 3 port valve.

There must be some fault in your 3 way valve sending a live feed to pump.

 

[jimbarr]

This is really helpful, why did it take two years to find this forum!

OK, I presume the pump overun stat is on the boiler, it is a potterton profile, where is it? please. if it is jammed on surely the pump would NEVER switch off at all?

jobloggs, that Pegler tutorial is magic reminds me of courses I did in Aus and USA on Xerox and Oracle! very well done.

Strange that they do not include common faults as well as normal running, or have I just not looked far enough?

There seems to be a permanent live to PL on the boiler according to the tutorial, and this gives power to the pump via the orange wire but this is always there, what stops the pump being always on?

 

[jobloggs]

Sorry I don't know much about different types of boilers.

The wiring diagram that camr with my controls showed permanent live to boiler if required. I assume some modern boilers require power all the time to work the electronics etc. Mine is a simple oil fired one and only needs power switched to the fan and oil pump to fire it when required.

As I read the wiring diagram power always gets to the 3 port valve even when the programmer is off. Power must be getting to the pump from the valve if it runs when the programmer is off. Hence the valve is telling the pump to run when it shouldn't be so faulty valve or else faulty logic.

Does your boiler run as well as the pump when programmer is off.

 

[jobloggs]

Can't even get bold to work where I wanted it to. Used to wordprocessor where you just highlight text and hit bold