Central heating problem

[68wayne19]

Hi I’m new to this forum and I’m hoping someone can shine a light on a problem I have with my central heating.

The system I have is a gravity fed system; tank in the loft, glowworm boiler micron 50FF,hot water tank in the airing cupboard and 10mm pipes feeding the radiators.

The central heating has never been great circulation wise, however since I replaced a noisy pump with a grundfos ups3 pump it’s created a problem. Central heating has become the best it’s ever been and the hot water is just as good however when heat is required on both I loose heating to the central heating side of the system. I’ve added X800 to clean the system, however this has removed a lot of the sludge via the filter.

I’ve had 2 quotes regarding a replacement boiler with 1 suggesting that the boiler is ok although both have said the piping is wrong in the airing cupboard but not telling what is wrong.

Coincidentally my father-in-law had a new boiler fitted by British Gas for a similar problem, however after the new boiler was fitted the problem was still there until the piping was changed in the airing cupboard. Which makes me think why has the system been ok for over 30years to suddenly needing to be re-piped in the airing cupboard. The only thing I can see that’s changed with my father in law’s is the vent pipe and cold water supply from the tank in the loft have been moved to next to the pump. Hope some can help. Thanks in advance

 

[terryplumb]

When did you change the pump ,and did your problem arise immediately the new pump went in ,or did all work well for a period after pump installation ?
Is your system Y plan ,with a 3 port motorised valve ?
If unsure post pics of all piping around the hot water cylinder.
And finally did you do any work in or near the wiring centre ?

 

[68wayne19]

Yeah the system has a 3 port motorised valve. Problem pretty much started after fitting the new pump, old pump was a basic 3 speed pump. When the old was working everything was fine however not the best as 1 radiator in question never really got hot, however with the new pump fitted that radiator is the hottest it’s ever been. Wiring has not been touched for a long time and the valve seems to work fine.
Thanks for replying to my previous post

 

[HERTS P&D]

Adjust your control so that the hot water comes on 30 minutes before the heating comes on in the morning.

Andy

 

[terryplumb]

What makes you think the 3 port valve is working fine ? It's the valve that opens to both ports to allow CH and DHW simultaneously. So it's either a wiring issue /3 port valve issue . If the pump has been worked on ,and its in close proximity to the wiring ,then you may have inadvertantly caused a loose connection. The wiring centre would be my first port of call.

 

[68wayne19]

Hi Terry, when the pump was changed the wiring was disconnected and connected at the pump end, control centre not opened. When I say the 3 port valve seems fine is because; select hot water only valve moves to the correct position, select central heating only and valve moves to the correct position, select both and the valve moves to the centre to allow simultaneous flow to both. When in this position it appears that flow is decreased to the central heating part of the system.
Occasionally the vent pipe gets hot and the return pipe from the hot water cylinder element gets hot.

 

[terryplumb]

If the valve was indeed moving to the central position ,you would get both radiators and hot water cylinder heating up. So it clearly is not opening to both ports ,as you think it is.
Changing the pump will not make the operation of the motorised valve function in a different way .
If the valve is not working as it should ,it's defective or the wiring to it is.

 

[ianmcd]

you may need a flow reducing valve of some description , fitted on the return from the DHW coil at the cylinder, you say you used X800, hope you havent left that in the system ?

 

[Alec_t]

select both and the valve moves to the centre to allow simultaneous flow to both.

The flow resistance of the DHW path could well be a lot less than that of the CH path. If so, the majority of the flow would then be via the DHW path, leaving the rads cooler than when only CH is demanded. A flow reducer on the DHW path, as Ian suggests, could overcome that.

 

[68wayne19]

If you take a look at the photo attached and the rough sketch of the layout I have. The filter is only on the central heating side of the system this was down to available space. The vent for the system is on the opposite side of the hot water tank

 

[ianmcd]

again ,have you left X800 in the system ?if you have buy another pump

 

[68wayne19]

X800 drained and replaced with inhibitor

 

[Hugh Jaleak]

If the system is getting nice and hot, then there's not a lot wrong with the Boiler, get it serviced regularly and it'll go on for a while yet hopefully.

I'd say the problem lies elsewhere, given you've an old cylinder, possibly designed for gravity circulation. I'd put money on the Cylinder is taking the Lions share of the flow when HW and CH are on, and given the heat losses with that thin jacket, it will be taking longer to reach temperature, (if at all), hence the HW is rarely getting to set temp, and so the call for HW remains for longer, meanwhile starving the CH of flow.

Would be well worth upgrading the cylinder for the new type with factory fitted insulation, and fit a Gate Valve or similar on the Return as it exits the cylinder to control the flow flow.

Also I'd suggest the Cold feed from F&E Cistern needs relocating, possible risk of the system pumping over with the current setup. The Vent needs to rise continuously form the boiler, then the cold feed to couple in within 150mm, then the pump, to create a neutral point.

 

[68wayne19]

When I mentioned my father in law had very similar problems in my initial post, the engineer from British Gas who came was unable to sort the problem other than fitting them a new boiler which they probably didn’t need. However his supervisor came along said it was piped up wrong similarly to mine, he cut off and blanked the piping to the vent and cold water that went below the floor boards and re-attached them next to the pump boiler side. Why would he have done this? It would suggest to me that rather than having the floor up to sort out a blockage, he basically moved that part of the system from under the flooring to next to the pump. After this was done their heating has been brilliant.

 

[Hugh Jaleak]

With a Fully Pumped system, you have to be careful the water doesn't take the path of least resistance, which in some cases is straight up the vent pipe, and into the F&E Cistern, rather than around the system as intended....

Given the cistern will quickly fill in this situation, with only a 15mm pipe feeding back into the system, you'll soon have a cascade of (sometimes very hot) water coming from the overflow pipe, known as 'Pumping over'. Once it stops, the system will settle and refill from the F&E cistern, with fresh water as required, which you certainly dont want as it dilutes the inhibitor. Pumping over also pulls a load of air into the CH system which you also really dont want...

By connecting the Vent then cold feed in close proximity, shortly before the pump, this has the effect of creating a 'neutral point' in the system and prevents Pumping over. Some use a air separator, such as the Myson Aerjec for this purpose, but they are often a common point for blockages, and then get cut out to be replaced by the 'H' setup of pipework.