CH not switching on until HW switch activated? Fixed...

I originally posted this on Dec. 2nd last year:

I had a new Grundfos UPS2 15 50/60 pump fitted in April this year by a local heating engineer as the other one seized and blew fuses.

Two weeks ago we switched CH on (through wall timer programmer in airing cupboard) which controls water and central heating. The Grundfos fails to switch on when calling for CH only, however if you wait for HW to come on or manually press HW to ON the Grundfos CH pump comes on too. A local service engineer had a look and replaced the actuator head only (Drayton) but it still waits for the HW to activate.

Before the new Grundfos was fitted CH had no problem coming on at separate times as did HW (twice daily). We get hot water and rads are OK - just this.

A the moment HW and CH come on at exactly the same time in the morning so everything functions as normal. HW goes off at 10am and CH at 11am. CH comes on at 2pm but does not activate Grundfos pump? If I manually activate the HW button the Grundfos switches on and I can immediately press off for HW and the pump will still keep going?

The Grundfos if showing three green lights with the middle one glowing the brightest - I thought only one should be ON to indicate speed?

So, Grundfos pump will not come on unless HW is running; it will however continue running if the HW switches off.

I am NOT an engineer and will NOT attempt fiddling with pipes and electrics, but I would like to understand what may be the fault before spending more money on something so annoying!

Thanks

Read more: http://www.diynot.com/diy/threads/c...til-hw-switch-activated.447814/#ixzz3yXpgmJJx


After further discussions with Forum Member STEM I can tell you below about the successful result...

Well Stem, I said I would get back to you, well here it is... very positive result - yippee!! Thanks for your insistence that the electrics should be checked - valuable lesson.

Like most families if there is something you want done by a family member (my son) you are usually the last person to get it. However, things were really getting bad with the heating so my son came round on Tuesday and went through the electric circuits. CH had been very intermittent and only coming on, to some degree, when water was called for as well, except that it totally failed on Tuesday!!
After one and a half hours of diagnostics he had found TWO faults - one was quite surprising; the pump. We have never heard or felt the Grundfos pump working although the little LED would come on when engaged with the hot water being switched on. Fault 1 -The pump was in fact FAULTY; it has only been in use for about 7 weeks since we switched it on in late November. All that could be heard was a little dull tick every 2 seconds and we think it was only rotating, if at all, very slowly.
Fault 2 - The other main fault was the programmer on the wall, a relay had failed on the CH side although the LED came on as normal. My son realised this and simulated it by making two conections on the separate box assembly that joins all the wires together into one box (the one with all the long row of connector points); it had something to do with the white cable, however, to cut a long story short he got a new programmer box and a new pump in case. He fitted the programmer and immediately ALL functions were re-instated. We changed the pump and immediately realised that the old (but new last year) one was obviously faulty. You can quietly hear the latest one happily turning at speed and gently feel the vibration of its movement.. result happiness!
Not very happy with the original fitter that fitted the duff one as he couldn't have checked it very well, he could have cost me a fortune trying different things. Just shows how important electricians are and how some problems can be found purely through electric diagnostics... lessons learned.
We have subsequently found out that there was a bad batch of Grunfos pumps of this type last year - looks like we were unlucky.
EVERYTHING works now as normal. Thanks again.



Read more: http://www.diynot.com/diy/threads/c...til-hw-switch-activated.447814/#ixzz3yXdzZi9I

 

Edit... deleted.
just read original post from December. It seems there is much more to this story and I was giving your son more credit than he actually deserved.

 

So by the first mention of the pump blowing fuses, the fitter changed it and fuses stopped blowing, in April? You say programmer controls heating and hot water? It's now February. Actuator was changed?

Nothing wrong with the pump you've changed. Your fitter changed this due to it blowing a fuse. The programmer has become duff and not switching, hardly a sparky miracle.

 

What's your point Gas2Air?
When the siezed pump was replaced last April the 3-way valve head was replaced also. The engineer didn't do a proper test as the CH trial did not activate at the first couple of attempts and he replied that the new three-way valve head would sort out any switching problems, but it only came on when he activated the HW boost. With this in mind he desperately wanted to drain the system and replace the 3-way valve. I refused to let him do this as I didn't think the valve was sticking, but something electrical - in fact I tested it after he left and you could easily move the valve with a spanner (which he must have known about when he changed the 3-way head. Tell me why a qualified Corgi service engineer didn't realise that the valve was OK and that it was something else?
The replacement pump for the seized one in April was obviously malfunctioning as sometimes it worked and other times it didn't until it finally gave up a week ago, so we got nothing out of it except a click every two seconds. No motion noise has every been heard or felt from this replacement pump ever, so if it was working it was very slow. After fitting the new control box we gave the incumbent pump a chance! - nothing other than clicks and no motion vibration, it was dead! In fact compared with the one we fitted this week its ability to deliver heated water had been very slow indeed taking up to half an hour just to get the rads warm. Today they are all hot within 20 minutes.
What is meant by ''its now February''?
''Nothing wrong with the pump you've changed'' - really?
Why was this problem not resolved quickly by the Corgi approved engineer - electrics can tell you everything that's happening on a circuit like this one way or the other; no its not a miracle, but it does save people a lot of unnecessary time wasting, head scratching and cash.