Hot water is fine but space heating doesn't work

stevenmo

I am using VITODENS 100-W as heating system for both domestic hot water and space heating ( through floor) . Now the hot water is fine but the space heating doesn't work. I have this problem for about 2 months. There is not any fault showing in the indicator. I tried reset the machine but it still doesn't work. I know it may be circulation pipe problem since the pipe is quite old, but I don't know how to further diagnose this issue. For example, how to tell if the thermostat is working fine? if it's a pipe problem, how to tell how bad it is？

EBEBRATT-Ed

No. I don't understand How a Vitodens 100-W could have anything to do with ac unless you have a chiller

mattmia2

Unless by "air conditioning", you mean domestic space heating of the room.

JUGHNE

Are you down under?

That would clear some things up.

stevenmo

Sorry, my fault. It's not AC, it is a kind of system that warm the room through heating on floor.

ratio

While it doesn't agree with colloquial usage, 'air conditioning' is technically correct & I understood what you meant then I read 'room is cold'. I think we'll want some pictures of the boiler piping. An overview of the whole setup & some details of the pumps etc.

stevenmo

The problem is, I don't have any idea or any info about the pumps and the heating system. I don't have the document of the piping from previous owner of the house. Here it's the photos:

Ironman

You could have a bad thermostat, a bad circulator, the loop could be air bound, etc, etc. There are several possibilities.

Can you post a pic of the gauge that shows the system PRESSURE?

Where are you located?

kcopp

Looks like the boiler has 1 loop to a plate heat exchanger. The piping is pretty odd for a primary/ secondary set up. Then out to the floor on the other side of the plate HX. lots of chances for air to get bound up.

stevenmo

Here it's gauge. I am in Vancouver. So I have a question: How to tell if it is a bad thermostat or a bad circulator? Is there any indicator to show that the thermostat is working?

GroundUp

Do you need space heating in Vancouver while the rest of North America is having 90+ degree highs this week? Does the home have air conditioning and is it running? Maybe I'm looking at this wrong, but I feel like the room is probably cold because the AC is running and is not properly balanced- nothing to do with the boiler

Ironman

How about the boiler being in Warm Weather Shut Down? In other words, it won't allow space heating when it's above 68*F outside.

stevenmo

We don't need heating now, the heating is broken for a few months. We don't have other air conditioning.

Jamie Hall

You ask how to tell if the thermostat or circulator -- or some other component -- is bad. You say that the domestic hot water is heated by the Vitodens, as is the space -- but that while the hot water is OK, the space heating isn't.

OK. That lets the Vitodens off the hook; if it runs for domestic hot water, it would run for space heat -- if something either told it to or allowed it to.

First thing to do is the simplest: turn the thermostat up all the way, as high as it will go. This should turn the pump which circulates water through the heating system on. If it does, well and good -- the thermostat and its wiring are probably basically OK, although possibly off calibration. If not, it still might not be the thermostat itself -- but here things get a bit complicated to trouble shoot, unless one is rather good at tracing electrical circuits and using a multimeter, because you are going to need to find out what device(s) control what components (pumps, burners, valves) and track down which one -- or ones -- isn't functioning properly.

Are you?

stevenmo

I have turned the thermostat up to the highest for about 2 hours, still doesn't work yet.

kcopp

I agree the outdoor temp is too high for the boiler to work. The sensor must be locking out the heat function.

ratio

He said the heat's been down for a few months. While the WWSD is undoubtedly holding off the heat at the moment, there's still an issue to be solved. Unfortunately, the system needs to be operating for the simpler diagnostics to be performed.

@stevenmo, it might be time to call a professional.

HVACNUT

Like others said, its probably in WWSD.
Can you post a pic of the display panel while the thermostat is all the way up?
Can you hear anything running in the boiler room while the thermostat is all the way up?

You said you don't have the piping document. Boiler manual? Start reading. If it's not a programming issue, then you'll likely need a pro.

stevenmo

Sorry, what you meat by WWSD? Here it's the thermostat:
I don't hear anything special running in the boiler room. But it has sound sometimes because the boiler works for both space heating and domestic hot water, so it is hard to tell it's working for which one.
I only have boiler manual but not piping.

BillyO

does the unit have a diverting valve? could be stuck

Ironman

WWSD = Warm Weather Shut Down.

I explained it in my previous post above.

stevenmo

I don't think it's because of WWSD, a few months ago, it's quite cold ( < 15'C ) here. A diverting valve? I have no idea what it looks like, seems we haven't.

HVACNUT

Call a pro with Viessmann knowledge.

Ironman

HVACNUT said:

Call a pro with Viessmann knowledge.

Agreed. You're in way over your head. Someone needs to be on the job that has the tools, instruments and knowledge of how to diagnose and repair. We can't do that just by viewing your pics.