DIYnot
Local | Network
   DIYnot > Forums
Local | Network
DIYnot Network Local DIYnot Network Local  
  Forum IndexForum Index     RulesRules    HelpHelp     Join FREERegister Free     About CookiesCookies     SearchSearch     LoginLogin 

Vaillant ecotec 637 and Megaflo controls

Goto page 1, 2, 3  Next
 
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating
Search this topic :: View previous topic :: View next topic  
Author Message
bonesetter

from United Kingdom

Joined: 23 Feb 2012
Posts: 27
Location: Hertfordshire,
United Kingdom

PostPosted: Thu Feb 23, 2012 8:30 pm Reply with quote

Hi all this is my first post.

Have been lurking through the threads on Vaillant ecotec and Megaflo controls to find out how I can improve my systems efficiency as Gas bills around 1250pa.

House is a detached five bedroom with two bathrooms both with showers and one also with a bath.

Two years ago the existing three bedroom house which is brick built with cavity walls and timber suspended floors was extended on two floors with pitched roof to modern building regs. The existing has recently had cavity wall rockwool insulation blown in.

A new unvented Vaillant ecotec plus 637 and Megaflo CL170HE was installed in loft space and wired up with a room stat, honeywell ST9400C programmer, two 2port valves all marshalled into a plastic junction box, also new water main installed.

The boiler was set to 75deg C output temp Megaflo to 60degC and all works fine apart from the gas bill.

I am looking for better efficiency from the system and try to get the boiler return temp down as low as practical so it can actually be a condensing boiler.

What I've done recently to tune system:
1. Discovered from the IDHEE "Whole house heating method" the losses are about 17kW including nominal 2kW for DHW.
2. Reset max boiler output to 25kW.
3. Set boiler flow temp to 60degC.

Just checked boiler temps and with outside 12degC and room stat hovering on 20degC the boiler flow is 57degC and return is 49degC with boiler firing.

The DHW was originally on constant but now timed to come on for three half hr sessions per day, which is a bit marginal with boiler set at 60degC for reheat.

Having read about the Vaillant VRC470 weather compensating programmer and VR65 I am trying to discover whether fitting these will enable the system to run more efficiently than present.

I spoke to Vaillant about this but its all a bit uphill with them and they have no technical manuals available.

One advantage apparently with vaillant controls the DHW reheat will improve as not be limited by the present 60degC flow temp.

Should I get the Vaillant controls or not bother?

Any comments gratefully received.
Back to top
 Alert Moderators

If you do not want to see this advert, click here to login or if you are new click here to join free.
Agile

from United Kingdom

Joined: 26 Jun 2004
Posts: 53497
Location: London,
United Kingdom
Thanked: 3405 times

PostPosted: Thu Feb 23, 2012 9:15 pm Reply with quote

bonesetter wrote:
Hi all this is my first post.

Have been lurking through the threads on Vaillant ecotec and Megaflo controls to find out how I can improve my systems efficiency as Gas bills around 1250pa.

The boiler was set to 75deg C output temp Megaflo to 60degC and all works fine apart from the gas bill.

What I've done recently to tune system:
1. Discovered from the IDHEE "Whole house heating method" the losses are about 17kW including nominal 2kW for DHW.
2. Reset max boiler output to 25kW.

3. Set boiler flow temp to 60degC.

Any comments gratefully received.


If the heat loss is 17 kW then why did you set the max power to 25 kW?

If you dont set the boiler max flow temp to 70 C then you will not properly heat the water and cause the boiler to cycle.

You could set the water to 55 C and the boiler to 65 C.

In fact for your house thats a very reasonable gas bill.

Weather comp saves about 2%-12% depending on how you use it. Hardly worth it if you adjust the boiler according to the season manually.

Thick pullovers significantly reduce heating costs. As do wearing duffle coats indoors.

Tony
Back to top
 Alert Moderators
ALEC1

from United Kingdom

Joined: 21 Nov 2009
Posts: 9501
Location: London,
United Kingdom
Thanked: 714 times

PostPosted: Thu Feb 23, 2012 9:23 pm Reply with quote

where i have replaced on off controls with vaillants weather compensation My clients have saved uoto 20% of there gas bill...
Back to top
 Alert Moderators
bonesetter

from United Kingdom

Joined: 23 Feb 2012
Posts: 27
Location: Hertfordshire,
United Kingdom

PostPosted: Thu Feb 23, 2012 10:44 pm Reply with quote

Don't know the accuracy of 17kW calc as it's a whole house calc and 25kW is a starting point for me, it's got to be better than 37kW.

If I can find the info I can do a room by room calc. for more accuracy.

I set the o/p temp to 60deg to see how the heating would perform.

Will the boiler modulate better with the vaillant controls on CH and DWH than the existing on/off controls?

When operating correctly with CH demand should boiler modulate down then run continuously at it's lowest temperature for max efficiency

Is it feasible to achieve a 20deg drop between flow and ret at boiler and will this only be when rooms are cold and rads losing heat faster, do you guys achieve this when installing new systems?

Does the boiler also modulate circ pump speed along with burner modulation?
Back to top
 Alert Moderators
ALEC1

from United Kingdom

Joined: 21 Nov 2009
Posts: 9501
Location: London,
United Kingdom
Thanked: 714 times

PostPosted: Thu Feb 23, 2012 10:48 pm Reply with quote

yes with weather comp the boiler modulates much better in heating

and with the cylinder sensor the boioer aims to satisfy the demand as quickly as possible. You should match the cylinder coil to the hot water output on the boiler...


with compensation controls the flow temp drops to below 55c so the delta t becomes irrelevant...

the pump has two speed and below a certain threshold drops to low speed...
Back to top
The following user says thank you to ALEC1 for this useful post:
bonesetter (25 Feb 2012)
 Alert Moderators
bonesetter

from United Kingdom

Joined: 23 Feb 2012
Posts: 27
Location: Hertfordshire,
United Kingdom

PostPosted: Thu Feb 23, 2012 11:24 pm Reply with quote

Many thanks ALEC1 this is the kind of info I need to know.

The local plumbers merchants sell the VR65 an VRC470 for 196.00 inc VAT for both, is that a good price? I'm sure the cost would soon be recovered with better efficiency.

One regret, in my ignorance, is the Megaflo as while it is apparently a good bit of kit and fitted by many with the Vaillant, the Unistore with it's NTC thermistor for analogue temp control appeals more to me. If it could be fitted to the Megaflo I'd give it a try.
Back to top
 Alert Moderators
bonesetter

from United Kingdom

Joined: 23 Feb 2012
Posts: 27
Location: Hertfordshire,
United Kingdom

PostPosted: Sat Feb 25, 2012 4:16 pm Reply with quote

How successful is it fitting the Vaillant VR10 thermistor in the Megaflo?

Can this be done with original thermostat in place or does this just pull out of dry pocket and VR10 fit straight in or is adaptor needed any probs with dissimilar metals?

Or does the method of creating a small pocket in the insulation so VR10 in contact with cylinder wall work better?

Or you could buy my Megaflo and I'll get Unistore icon_biggrin.gif

Would fitting VR10 be good for DHW control or should I forget about it.
Back to top
 Alert Moderators
mickyg

from United Kingdom

Joined: 24 Aug 2005
Posts: 15949
Location: Hertfordshire,
United Kingdom
Thanked: 3200 times

PostPosted: Sat Feb 25, 2012 4:30 pm Reply with quote

the vaillant controls will be an improvement and you should be able to fit the cylinder sensor to the megaflo, but one of your issues is your massively oversized boiler, who on earth chose that?? the lower end modulation on that boiler i think is about 12kw which will give you cycling issues, which is not good for efficiency
Back to top
The following user says thank you to mickyg for this useful post:
bonesetter (25 Feb 2012)
 Alert Moderators
ALEC1

from United Kingdom

Joined: 21 Nov 2009
Posts: 9501
Location: London,
United Kingdom
Thanked: 714 times

PostPosted: Sat Feb 25, 2012 4:59 pm Reply with quote

it can be fitted to a megaflo, but the manufacturers won't approve..so don't bother ringing them...


just replace the current immersion stat with the supplied sensor...
Back to top
The following user says thank you to ALEC1 for this useful post:
bonesetter (25 Feb 2012)
 Alert Moderators
muggles

from United Kingdom

Joined: 28 Oct 2005
Posts: 4697
Location: Devon,
United Kingdom
Thanked: 621 times

PostPosted: Sat Feb 25, 2012 8:29 pm Reply with quote

Your boiler is massively oversized, so unfortunately it's never going to be as efficient as it could be, sounds like you'd have been better off two models lower with a 624, or even three models lower with a 618. The boiler you have simply can't modulate down to a low enough output. The Vaillant controls should help, but having an engineer swap the 637 for a 624 or 618 and flogging the old one on eBay might be well worth considering.
Back to top
The following user says thank you to muggles for this useful post:
bonesetter (25 Feb 2012)
 Alert Moderators
bonesetter

from United Kingdom

Joined: 23 Feb 2012
Posts: 27
Location: Hertfordshire,
United Kingdom

PostPosted: Sat Feb 25, 2012 8:55 pm Reply with quote

Haven't bought any new controls yet.

My builder's trade is a plumber, his electrician wired up the control system and all neatly done. The builder bought all the hardware req and I wasn't involved with checking the kW.

The condensing boiler and megaflo is all new technology to me and only discovered by accident as a local builder was revamping his house. I happened to walk past as his plumber was working in the garage on the final stages of installing a Vaillant and megaflo and he described the installation to me which was handy.

My builder had also installed similar equipment in other projects and I had seen examples of his work so had no reason to question things unduly. I can see now I should have been more involved as coming from an engineering background myself.

One thing I want to achieve is doing calcs for the kW required when the house is warmed up to say 20C so I can compare this figure with the lowest the boiler can modulate down to. I see from the spec with 60C flow and 40C return the boiler is 12.7-38.2kW. At a flow setting of 60C I get about 57C flow and 49/50 ret with boiler firing so I guess it is modulating.

I have surveyed all the rads and will estimate the total o/p although Stelrad tell me their figures are based on 80C flow and there are some tables somewhere in their rad bible which give o/p at lower temps.

I see 37kW equals about 127k BThu/hr so a big increase. The side extension to the house increased vol by about 50% so 80k +50% = 120k so I guess that was the builders thinking.

We did notice a big jump in our gas bills hence after a couple of yrs I've started to look into the heating system to see what can be done to improve things.

The first thing was get a new gas meter installed, which was free, so should be calibrated ok. I used to run the HW constantiy but now time it 3x per dy. We were on a direct debit gas account with quarterly readings but when it got to 650 in credit I cried "enough", got refunded and changed to a system where I read meters monthly. The BG online account is quite handy as you can look at the history and compare usage with last years.

One more thing. Our present timer/programmer has 1hr override for HW which is really useful, nothing worse than a cold shower it doesn't improve my temper, but I suspect I can only get that facility with the VR10 installed as opposed to the cyl stat, can anyone verify that?
Back to top
 Alert Moderators
muggles

from United Kingdom

Joined: 28 Oct 2005
Posts: 4697
Location: Devon,
United Kingdom
Thanked: 621 times

PostPosted: Sat Feb 25, 2012 9:49 pm Reply with quote

Outputs of rads running at 60/40 F&R temps are roughly half the quoted output in the standard spec sheet. You should have a 20'C difference between flow and return temperatures at the boiler, a smaller difference means it's not condensing and therefore not running efficiently. Your smaller difference is another symptom of an oversized boiler, and possibly poor system design. It is, however, not an indication that the boiler is modulating, it will do that anyway, it's just an indication that your radiators are emitting heat into the rooms.
Back to top
 Alert Moderators
ALEC1

from United Kingdom

Joined: 21 Nov 2009
Posts: 9501
Location: London,
United Kingdom
Thanked: 714 times

PostPosted: Sat Feb 25, 2012 10:36 pm Reply with quote

muggles, compensation controls force the flow temperature down as low as possible, thus ensuring both the flow and return temps are as low as possible without compromising comfort...

almost all the time the flow is below 55, an the reurn lower, thus the boiler is always condensing.

OP, vaillant controls cope well with an oversized boiler....don't fret about it!
Back to top
 Alert Moderators
muggles

from United Kingdom

Joined: 28 Oct 2005
Posts: 4697
Location: Devon,
United Kingdom
Thanked: 621 times

PostPosted: Sun Feb 26, 2012 8:25 pm Reply with quote

Indeed they do, but they still aren't going to be as effective on an oversized boiler as they are on a correctly sized one. They'll cope, but the results could be better...
Back to top
 Alert Moderators
ALEC1

from United Kingdom

Joined: 21 Nov 2009
Posts: 9501
Location: London,
United Kingdom
Thanked: 714 times

PostPosted: Sun Feb 26, 2012 8:30 pm Reply with quote

on that i agree totally...
Back to top
 Alert Moderators
Search this topic :: View previous topic :: View next topic  
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating All times are GMT
Goto page 1, 2, 3  Next
Page 1 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Similar Topics   Replies   Views   Posted 
Controls for new heating system (WB 30cdi + Megaflo) 2 20 Fri Mar 09, 2012 12:01 am
Vaillant ecotec controls 3 360 Sat Dec 29, 2007 10:14 am
Controls on Vaillant Ecotec Pro 28 4 120 Mon Nov 17, 2014 10:36 am
Heating controls for vaillant ecotec boiler and UFH 12 2340 Tue Apr 21, 2009 3:56 am
Vaillant Ecotec Plus 637 with Honeywell controls 2 40 Mon Jul 02, 2012 7:19 pm


 
DIYnot
Find an Expert | Find a Supplier | Search DIYnot.com
Network | Advertising | Newsletter
DIY | DIY How To | @home | DIY Wiki | DIY Forum
By using this site you agree to our Terms of Service / Disclaimer.
Please read our Privacy Policy. Copyright © 2000-2014 DIYnot Limited.