Help with understanding my CH system

[Bluesheep]

Hi folks,

I've just moved into a new house and I'm fighting a losing battle with my boiler system. I'm hoping for some insight/help from the experts here!

Firstly, I'm not sure I understand my system properly. I've got quite an old house, and I suspect some of the previous residents have done some 'inventive' plumbing. I have:

- Vokera 20e boiler
- Hot Water tank downstairs
- Small tank in loft (is this an F&E tank? How would I know?)
- Immersion heater connected to boiler
- Hot Water tank thermostat (strapped to tank, wired in, but I'm not sure where to)
- 5-2, 2 channel heating control (Hot Water/Heating)
- 1 room thermostat (wired into something, but not sure where)
- Danfoss water pump (needed to provide pressure for shower, despite shower being next to the tank!?!)

So, I understand this to be a gravity DHW and pumped CH system, am I right? If so, what I've read is that you need HW on to have the CH work, but thats not my case.

I've got two problems:

1. The boiler keeps entering 'reset' mode, presumably because its overheating. I had the bolier serviced thinking this was the problem, and they replaced the thermistor, but the problem still occurs.

2. When we switch the system to DHW only, the upstairs radiators heat up. From my reading this is 'back syphoning', and I need a flow check valve, which I definitely can't see near the boiler.

Thank you in advance for any help!

 

[45yearsagasman]

This could take a long time, so count me out. Too many pre conceived ideas and wrong terminology.

 

[Bluesheep]

How about if I stripped it back to:

"My boiler keeps getting a red light on the front and needs to be reset" and "When I put the hot water on, but not the heating, my upstairs radiators get hot"

I'll freely admit to my ignorance, and promise to have a professional do any work that may be required. I'm just keen to have a better understanding of things that have the potential to cost me lots of money.

 

[bengasman]

Overheating is usually a flow problem.
Flow problem is either knackered pump or or blockage.
I doubt that you have a Danfoss pump.

Take some time off, sit yourself down with a cuppa, and read through FAQ.
It will give you the basic knowledge or your heating system.

 

[DP]

1. The boiler keeps entering 'reset' mode, presumably because its overheating. I had the bolier serviced thinking this was the problem, and they replaced the thermistor, but the problem still occurs.

Which Vokera is it? Looked on website, don't see ant 20e

2. When we switch the system to DHW only, the upstairs radiators heat up. From my reading this is 'back syphoning', and I need a flow check valve, which I definitely can't see near the boiler.

I see that is bad plumbing. Fitting check valves is OK but another component likely to fail and make things worst. Better to locate and fix problem

So, I understand this to be a gravity DHW and pumped CH system, am I right? If so, what I've read is that you need HW on to have the CH work, but thats not my case.

Doubt it. Not many boiler suitable for gravity HW system. Can you select CH without HW coming on?

Only header tank in loft would suggest you have have unvented cylinder (very good hot water pressure) or combination hot water cylinder

 

[Whitespirit66]

Or possibly primatic.

 

[DP]

Or possibly primatic.

Unlikely as all Vokera (for the domestic market anyway) until recently were seal system boilers

 

[holty]

Which Vokera is it? Looked on website, don't see ant 20e

mynute 20e.

OP. turn hot water on. check the pipes leading to a rad that gets warm. and find out with side it is that gets warm first. then turn on the central heating. if the pipe gets cold and the other pipe to the rad gets hot. then you have an issue with your heating circuit.

 

[D_Hailsham]

Vokera 20e boiler

Do you mean the Mynute 20E? If not, can you give the GC (Gas Council) number of the boiler? It will be on the data plate.

If you can post pics of the boiler and all the components, it would help. General views are better than close ups as we need to see how they are connected together.

 

[Jake1886]

Yep a few photos would help us highlight what you have and help identify to you what is what.

 

[Bluesheep]

I appreciate the help guys, let me follow up with the questions:

- Pump is 'Grundfos' Not Danfos
- Boiler is a Mynute 20e

Firstly, I've solved the resetting problem. I had turned the boiler thermostat down from about 70 degrees to 60 degrees. After the first post about the pump/flow I thought it through and checked the thermostat on the hot water tank. This was set to 70 degrees, so I think when HW was on, it was getting constant demand for heat. I've turned the boiler back up and the water tank down, and everything seems fine.

Radiators then - I understand the test for the heating circuit, and I'll try that. I've been looking a bit more into the system and I've got a Drayton Lifestyle heating control system with two 2 port valves. Could the control valve for the HW be in the wrong place on the network?

 

[Deleted member 63160]

Could the control valve for the HW be in the wrong place on the network?

Maybe. Does your anti virus interfere?? This often causes network issues.

 

[D_Hailsham]

Firstly, I've solved the resetting problem. I had turned the boiler thermostat down from about 70 degrees to 60 degrees. After the first post about the pump/flow I thought it through and checked the thermostat on the hot water tank. This was set to 70 degrees, so I think when HW was on, it was getting constant demand for heat. I've turned the boiler back up and the water tank down, and everything seems fine.

The hot water cylinder thermostat should be set to 60 degrees. The boiler temperature needs to be higher, say 70C, or the water in the tank will not get heated to the required temperature.

I've got a Drayton Lifestyle heating control system with two 2 port valves. Could the control valve for the HW be in the wrong place on the network?

The normal place for motorized valves is on the flow. The pipe should divide in two with a Tee joint and there should be a motorized valve in each side branch. This is normally near the hot water cylinder.

The Mynute 20e is a sealed system boiler, so I'm not sure why there is a small tank in the loft. Are there two tanks there or just the one? What size are they (measurement them!)?