Help with a relay box rewire

[ShaunCorbs]

As your on ufh you want the lowest possible kw

4 pipe with the viessmann 200 system allows your cylinder to heat to 65 and one circuit to be what ever you want temp wise

The Worcester you need a system boiler with the optional diverter kit

A heat loss is the only way but I would be surprised if you needed over 20kw

 

[HRP123]

As your on ufh you want the lowest possible kw

4 pipe with the viessmann 200 system allows your cylinder to heat to 65 and one circuit to be what ever you want temp wise

The Worcester you need a system boiler with the optional diverter kit

A heat loss is the only way but I would be surprised if you needed over 20kw

Do you have a strong view yourself on whether the Viessman is worth the extra £500-1,000 installed over the WB?

 

[ShaunCorbs]

For the modulation I would go with the better one eg lower kw but Heatloss the property first

 

[HRP123]

For the modulation I would go with the better one eg lower kw but Heatloss the property first

I have actually done the Heatloss - it showed 20kw.

 

[ShaunCorbs]

Do you have cavity wall insulation?

 

[HRP123]

Do you have cavity wall insulation?

Yes the house is insulated - new build in 2008

 

[John.g]

Thanks for your thoughts. I'm trying exactly how the savings will come from spending on a potential boiler upgrade -

Presumably the gains from a new boiler are
1. Slightly higher efficiency ratio
2. Lower minimum kw burn rate (between 2-3kw vs current 9kw)
3. Weather compensation (but is this possible with modern heat only boilers? - see below)

Are these modern heat only boilers able to have different flow temperatures for hot water vs heating circuits? If these new boilers still need mixing valves for the heating circuits?

I've seen that the Viesmann 200w is highly recommended however this comes with a more expensive capital outlay and it appears fewer engineers who work with them. The WB Life would be easier to fit and cheaper but has a higher min kw (around 3kw I think).

I'm already in the process of installing all Nest thermostats so I can control and manually adjust things as easily as possible. Have been running the boiler successfully range rated down to around 24kw instead of 40kw. I've just installed an Eddi to make use of solar excess from the recently installed solar panels.

The main issue I find is that the minute the underfloor heating (only) calls for heat, this seems to burn a much higher amount of gas (based on 30 min meter reads) than what the theoretical value should be. So lets say the u/f heating area open is 100m2 x 100w = this should be 10kw right? The boiler almost always will burn close to the max (e.g. 20-24kw) when trying to satisfy just this need.

Just came across this thread, the UFH may be using 20 to 24kw if you are happy with the 30 minute readings, don't know how these are taken but I would certainly verify them by taking say exactly a 60 sec reading between photos of the REAL Gas Meter in M3, that will prove the readings one way or the other.

I think I asked in your other post how many loops etc is emitting this 20 to 24kw as a loop should, with a flowrate of 2LPM and a 7C to 8C dT, emit ~ 1kw, you should be able to read off the flowmeters flow rate in LPM and knowing the manifold flow/return temps calculate reasonably accurately the heat demand.

 

[HRP123]

Just came across this thread, the UFH may be using 20 to 24kw if you are happy with the 30 minute readings, don't know how these are taken but I would certainly verify them by taking say exactly a 60 sec reading between photos of the REAL Gas Meter in M3, that will prove the readings one way or the other.

I think I asked in your other post how many loops etc is emitting this 20 to 24kw as a loop should, with a flowrate of 2LPM and a 7C to 8C dT, emit ~ 1kw, you should be able to read off the flowmeters flow rate in LPM and knowing the manifold flow/return temps calculate reasonably accurately the heat demand.

Thanks for this follow up post, appreciated. So I had a look at the manifolds - they each have 8 loops. One of the manifolds does not have flow meters. Going to try and observe the flow rate on the other manifold one of these days.

I have checked the home hub readings against the gas meter and it is correct. I have a Ring camera position with snapshot history so in real time I can see which heating circuits/pumps are open, and the past half hour gas consumption readings.

For example last night I left only the underfloor heating on overnight to do a test. It showed that each hour it was on, the gas consumption was around 22kwh per hour (around the range rated max output). UF loops wise I cannot tell exactly was on but I think it may have been around 100m2 which is you assume is 120 watts psm = 13kwh theoretical usage? Let's say even 15kwh with inefficiencies. So wondering why this is coming out to close to the max output the boiler is range rated too instead of 15kwh.

Really appreciate the time you are taking to provide help.

 

[HRP123]

Just came across this thread, the UFH may be using 20 to 24kw if you are happy with the 30 minute readings, don't know how these are taken but I would certainly verify them by taking say exactly a 60 sec reading between photos of the REAL Gas Meter in M3, that will prove the readings one way or the other.

I think I asked in your other post how many loops etc is emitting this 20 to 24kw as a loop should, with a flowrate of 2LPM and a 7C to 8C dT, emit ~ 1kw, you should be able to read off the flowmeters flow rate in LPM and knowing the manifold flow/return temps calculate reasonably accurately the heat demand.

Sorry just read again you were mentioning based on loops - let's say half the 16 total loops or 8 loops were on - this should work to 8kwh.