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C/H pump not working unless HW is switched off

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masonmjs

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My system comprises a Kingspan 180L unvented hot water tank, Danfoss FP715si controller and a Bosch Worcester Greenstar Ri boiler, which works perfectly as far as I can see (and is serviced by BG every year).

The problem is that the CH pump will only start if I switch the HW to manual, if they both come on together (as programmed) the CH pump will not run with the HW on. The system uses a Center EHE0200157/U 22mm three-port, mid-position valve.

This problem started shortly after a new tank (as above) was fitted and actually did operate OK for a week or two but then it started to go wrong. Initially both CH and HW would come on OK but the CH would stop circulating after around 2 hours running and would only work if I switched HW to manual as above, now it won't even allow the CH pump to start.

HW is only heated via the boiler, I have not connected the immersion heater so it is not part of the problem and can be ruled out.

Can anyone suggest what could be wrong and how to check it please (I am a control systems engineer by discipline so hopefully I can follow guidance and test as appropriate).

Thanks in advance.
 
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Murdoch said:
Why aren’t you getting the installer back?
Click to expand...
I'm not truly convinced it was anything he did, it was working to start with after all, and only started to have this fault around 2 weeks afterwards. The other reason is that I can't get him to communicate with me now, he left without giving me an installation certificate (it's an unvented tank), he promised to post it and has not done so. I'm not even convinced he was certified to install the tank as I have checked around a few of the biggest training companies and he is not registered with any of them. It is certainly the last time I will be using MyJobQuote to find a tradesman as they don't even ask for proof of certification as far as I can see. (I was also stupid on that front and didn't ask to see it).
 
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Can anyone help with this problem, just a few pointers would help, it has worked since the tank was installed but it only works sometimes now with the CH and HW programmed to come on together. The HW seems to take control and stop the CH circulating.

I am working around it just now by switching the heating and the HW on at different times but that is not likely to be good for the wallet I surmise.

Please help if you can ...

Thanks and Merry Christmas
 
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I thought 3 ports on unvented weren’t allowed, it’s got to be 2 2ports and an auto bypass.
it’s to do with the dhw port being open when off that can overheat the tank.
you need to get your installer back to change it
That’s basics, god knows what else he’s done
 
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Stu-B said:
I thought 3 ports on unvented weren’t allowed, it’s got to be 2 2ports and an auto bypass.
it’s to do with the dhw port being open when off that can overheat the tank.
you need to get your installer back to change it
That’s basics, god knows what else he’s done
Click to expand...

Three ports are allowed on unvented but need an additional 2 port downstream.
 
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Here you go buddy
 

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All replies here are helpful thanks guys, the plumber who installed the system left the house without signing an installation certificate and is refusing to answer messages or calls, so I doubt he will be coming back.

The original system used a 3-way valve and he told me that it could be used for the unvented tank, which actually came with all the correct safety valves and expansion tank etc (it is a Kingspan Ultrasteel tank) and included a 2-way/port valve.

Sadly they also took with them the installation booklet for the tank which did show various systems in which the tank could be installed so I have nothing to go on now. I did recently call in a local guy to have a look at it with a view to paying him to sign off the tank, he said it looked OK but that it was missing a vent valve for bleeding/venting the system.

Can anybody tell me if it is possible/allowable to run this system with a single 3-way (mid-position) valve, or does it absolutely need to have two valves in the system. If I understand it correctly, if I need the two valves I can add the two-way valve that came with the tank as suggested above ?

Thanks again
 
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masonmjs said:
My system comprises a Kingspan 180L unvented hot water tank, Danfoss FP715si controller and a Bosch Worcester Greenstar Ri boiler, which works perfectly as far as I can see (and is serviced by BG every year).

The problem is that the CH pump will only start if I switch the HW to manual, if they both come on together (as programmed) the CH pump will not run with the HW on. The system uses a Center EHE0200157/U 22mm three-port, mid-position valve.

This problem started shortly after a new tank (as above) was fitted and actually did operate OK for a week or two but then it started to go wrong. Initially both CH and HW would come on OK but the CH would stop circulating after around 2 hours running and would only work if I switched HW to manual as above, now it won't even allow the CH pump to start.

HW is only heated via the boiler, I have not connected the immersion heater so it is not part of the problem and can be ruled out.

Can anyone suggest what could be wrong and how to check it please (I am a control systems engineer by discipline so hopefully I can follow guidance and test as appropriate).

Thanks in advance.
Click to expand...
At the moment, until rectified, you have a mid position valve, so any fault finding will/should apply with this type of installation. You should be able to follow this link fairly logically to identify your present problem.
When you say the CH pump doesn't run then if referring to the circulation pump, the boiler isn't firing either?

Y Plan central heating system (flameport.com)
 
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If it's just a 3 port alone, as others have said it will need changing to two 2 port zone valves.

If it's a 3 port along with a 2 port then you should probably have it changed to two 2 port valves. I've never come across a situation where it ever correctly operates and tbh just causes hassle. Why installers think it's a good idea to do this i'll never know as it's easy to swap a 3 port out for a couple of 2 port valves.
 
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Many thanks for your help guys, I contacted Kingspan to get their input and they have confirmed that I need to get the supplied 2-port valve fitted and wired as suggested in the tank installation document (removed by the installer !) so I have approached a local plumber to get that done, and hopefully to get the tank installation signed off finally.

Oops, I just noticed that there were more replies after I had posted the above, on the subject of the 3-port valve, the Kingspan installation booklet does actually include a 3-port + 2-port installation (I guess it covers my situation exactly where a vented tank is replaced by an unvented one and the 3-port was existing) and I am keen to avoid having to buy any additional hardware (I have the 2-port valve that was supplied with the tank). Am I correct in thinking that with the extra 2-port valve installed the 3-port actually then becomes a 2-port ? or something other than mid-position valve ??
 
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If still retaining the diverter valve and just installing a 2 port valve in the cylinder circuit then you may still have a problem but if installing 2 x 2 port valves then no problem, hopefully.
 
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John.g said:
At the moment, until rectified, you have a mid position valve, so any fault finding will/should apply with this type of installation. You should be able to follow this link fairly logically to identify your present problem.
When you say the CH pump doesn't run then if referring to the circulation pump, the boiler isn't firing either?

Y Plan central heating system (flameport.com)
Click to expand...
Yes that is exactly what is happening, boiler switches off, pump stops, then all is good if I switch off the HW.
 
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Yes, understood, but is there only one (or two) 2 port valves being installed, if only one, then the diverter valve must still operate IMO as normal but with the extra security of a normally closed two port valve.
 
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John.g said:
Yes, understood, but is there only one (or two) 2 port valves being installed, if only one, then the diverter valve must still operate IMO as normal but with the extra security of a normally closed two port valve.
Click to expand...
the original 3-port valve is still fitted, I intend to fit an additional 2-port valve and wire up in accordance with the Kingspan installation guide.
 
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