By-pass valve for reducing heating loop

[mmindazz]

Good day,
I have question regarding by-pass valve for my combi compackt Hreco 36 primary loop. My primary loop is going from 3rd floor to the first floor ( floor heating) , at underfloor heating manifold I have by-pass valve. Recently I have installed Honeywell evohome system and every room is fully separated. When I need to heat only small bathroom radiator all primary loop to the first floor becoming hot, so I loosing energy via primary loop. As I noticed a lot of heat going out throughout the loop. The loop is bigger than bathroom radiator itself.
My idea is to install extra by-pass valve very close to the boiler, so the primary loop become total of 4 meters length. it keeps the remaining loop of and only hot water goes to radiators. If here is request for underfloor heating by starting underfloor pump the bypass valve should close and hot water goes to the first floor. Does this system can work practically and does it safe for boiler.? The loop becomes 10 times smaller, does it effects flow and pressure, witch can trigger boiler safety's. ?

 

[Brambles]

Assuming your heat requirement calculations are correct, you have a boiler which is far too large for the system installed. Even the smallest boiler in the HREco range ( the 24kw) would be oversized. There is no simple quick fix - you need to be able to use the minimum heat output that the boiler delivers.

Talk to Intergas for their advice and the way forward.

 

[mmindazz]

I have enough information from you guys. Incoming week I will do some tests,I will contact intergas, I monitor daily gas consumption and will look more close how the boiler cycle. I have spoken with my neighbor, he has same house and same boiler, he will track gas consumption too. Afterwards I will do parameters change and will compare cycling and gas consumption with previous data. If I can prove that the boiler is to big and cause me extra money, I could try to claim from building company a new boiler.

I looked more close to smaller boilers. Smaller boilers provide with less HW flow. Current boiler 60C - 9L/min, 40c-15L/min. At the moment I have set point 65C. If I go to smaller combi boiler, could he provide enough HW?

 

[John.g]

If you assume 5c as the lowest likely mains temp and you require 45C minimum hot water temp then (boiler) 25kw=9LPM, 30kw=10.8LPM, 35kw=12.5LPM. so IMO you require at the very least a 30kw boiler.
Did you ask your neighbour if his rads are heating OK on minimum demand?, cycling is really unimportant if you can still heat only one/two rads.

 

[mmindazz]

If you assume 5c as the lowest likely mains temp and you require 45C minimum hot water temp then (boiler) 25kw=9LPM, 30kw=10.8LPM, 35kw=12.5LPM. so IMO you require at the very least a 30kw boiler.
Did you ask your neighbour if his rads are heating OK on minimum demand?, cycling is really unimportant if you can still heat only one/two rads.

I have not asked, i know he use only floor heating and bathroom, the rest rooms are close, so he use about 4kw energy.
Last your sentence is very interesting. My rads heats very good, if demand is just on one rador two or three..., it heats perfectly.

 

[John.g]

So what is your problem exactly?, is it just the boiler efficiency in running in a cycling mode? and the query in post #1. The boiler efficiency has to be affected in some way as the boiler does a pre and post furnace purge after each stop/start but the loss in efficiency would not be recovered for years and years, if ever, by installing a new boiler.

 

[mmindazz]

So what is your problem exactly?, is it just the boiler efficiency in running in a cycling mode? and the query in post #1. The boiler efficiency has to be affected in some way as the boiler does a pre and post furnace purge after each stop/start but the loss in efficiency would not be recovered for years and years, if ever, by installing a new boiler.

The main question was regarding reducing primary loop, to safe energy and afterwards we all together find out that my boiler is oversize and that boiler is going constantly to cycling Stop/starts because of return temp. And probably as you mentioned he never goes to his minimum load 8kW, because he has not enough time to modulate from starting point ( with high load) to minimum. The main issue how much this boiler is economic with constant cycling my goal is to keep as minimum gas and electrical cost for my house. If not evohome system I would never noticed that I have a such problem.
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I planning to call to Intergas to ask how can I optimize my boiler to work most economical.
Just to be sure if I good understood regarding radiators capacity. Hereby attached picture with my radiator. It stated that capacity is 1200W, it's correct?

I wandering if my evohome system can work good at my house. As I stated before, i divided my home to zones and with evohome system I regulate each room independently. As example: nigh time, heat demand ON for UF and one room, remaining rooms are OFF. Target Living room - 21C, Room - 22C, Closing/opening/starting UF pump/stopping/ Modulating boiler all goes via evohome. The total heat demand is 3,5kW ( boiler produce minimum 8Kw), boiler continues starting and stopping( because of return temperature), Evohome adjusting water flow continues to keep set point. would be this scenario still economic compare with standard situation: UF pump runs constant, room radiator fully opens, boiler still starts on/off but not so often.
P.S remaining rooms set points is 20C so as soon temp drops evohome will open too and combine the system slightly bigger. In standard situation the remaining rooms are slightly open to keep rooms from freezing.

i can still return evohome. it cost me 350 euro.

 

[John.g]

Can,t comment on the evohome controls as I have no experience of them.
I have a oil fired boiler which doesn't (and can't) modulate so it and all other oil fired boilers spend their entire lives cycling on/off, I can't find the numbers just now but I was quite surprised at how little the cycling affected the efficiency even with very low heat demand.

 

[mmindazz]

Can,t comment on the evohome controls as I have no experience of them.
I have a oil fired boiler which doesn't (and can't) modulate so it and all other oil fired boilers spend their entire lives cycling on/off, I can't find the numbers just now but I was quite surprised at how little the cycling affected the efficiency even with very low heat demand.

I believe that combi gas boiler is not like oil fired boiler

 

[John.g]

You will generally see a minimum flow requirement set for HW flow to ensure that the combi is continuously running when in HW mode, it is probably ~ 2.5 to 3 LPM in your boiler depending on what the max HW temperature intergas allow, possibly 60C?,

 

[mmindazz]

You will generally see a minimum flow requirement set for HW flow to ensure that the combi is continuously running when in HW mode, it is probably ~ 2.5 to 3 LPM in your boiler depending on what the max HW temperature intergas allow, possibly 60C?,

I have maximum 65C on winter, summer time 55c-60C
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I was looking more and more about my system and I find out, that building company installed wrong system at all.

Hereby translated email with googletranslate. I suppose to have this system: no UF pump in living room, independents lines for first and second floor, 2 thermostats, O got nothing.

I would like to know how does the system looks like?
e are pleased to inform you that the floor heating system in your home has been upgraded. This upgrade increases the comfort and improves the energy efficiency of your home.



The renewed central heating boiler offers 2 heating lines: a low temperature heating line for the floor heating and a high temperature heating line for the radiators on the floor. Because the radiators can now also be supplied with a higher temperature, the dimensions are smaller, the room heats up faster and the system uses less energy. The two heating lines can be operated independently of each other, since the central heating boiler is now also operated by two thermostats. One thermostat for the floor heating in the living room and one for the radiators on the floor. In combination with the thermostatic radiator valves on the floor, the temperature can be regulated per room. The room thermostat on the floor is wireless and works like a remote control. The thermostat must be placed in the room with the highest temperature demand. When the thermostat measures a too low temperature, the central heating boiler will switch on. With the thermostatic valve on the radiator you determine which radiator heats up at that moment.
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I have maximum 65C on winter, summer time 55c-60C
[automerge]1578328906[/automerge]
I was looking more and more about my system and I find out, that building company installed wrong system at all.

Hereby translated email with googletranslate. I suppose to have this system: no UF pump in living room, independents lines for first and second floor, 2 thermostats, O got nothing.

I would like to know how does the system looks like?
e are pleased to inform you that the floor heating system in your home has been upgraded. This upgrade increases the comfort and improves the energy efficiency of your home.



The renewed central heating boiler offers 2 heating lines: a low temperature heating line for the floor heating and a high temperature heating line for the radiators on the floor. Because the radiators can now also be supplied with a higher temperature, the dimensions are smaller, the room heats up faster and the system uses less energy. The two heating lines can be operated independently of each other, since the central heating boiler is now also operated by two thermostats. One thermostat for the floor heating in the living room and one for the radiators on the floor. In combination with the thermostatic radiator valves on the floor, the temperature can be regulated per room. The room thermostat on the floor is wireless and works like a remote control. The thermostat must be placed in the room with the highest temperature demand. When the thermostat measures a too low temperature, the central heating boiler will switch on. With the thermostatic valve on the radiator you determine which radiator heats up at that moment.

P.S it suppose to be special boiler with 2 burners?

 

[John.g]

No two burners, you will have high temp (at boiler SP temperature) water supplying your rads and a thermostatic mixing valve to reduce this high temperature water to a lower temperature for your UFH, I would think.

 

[mmindazz]

No two burners, you will have high temp (at boiler SP temperature) water supplying your rads and a thermostatic mixing valve to reduce this high temperature water to a lower temperature for your UFH, I would think.

they mention that lines will be separated and can be control each floor, it means suppose be installed mixing valve with motorized valve?

 

[John.g]

I have never seen a UFH system or a combined Rads + UFH but I imagine it would require two circ pumps, one conventional boiler circ pump which would run in any one or combination of rads+UFH, in other words, in all modes, the second circ (& blending) pump would not be required to run if rads only in use.

 

[mmindazz]

Just come back home. Reduced some parameters, one of it boiler maximum load. From 70% went down to 20%, its around 7kw maximum load. If I good noticed I believe he can modulate even lower, after reducing parameters, the water temperature went down to 40C, believe it was minimum load. And it was modulating from 40C to 75C depending of heat demand.

Evohome- I will return back to the shop. This system is not build to every boiler and every home. With evohome my boiler consume more gas than before. One of reason is that it separate rooms in zones and each room controls by it self. It supper nice, but not in my house. Boiler is oversized - one radiator on is 1.2kw, boiler can delivery minimum7kW, tha with evohome system its cycling non stop, starts for 30-60s and goes of, after few minitus its starts. it goes all day non stop. The second thing UF heating - UF pump controlled by BDR91 relay and its starts and stop independently, It runs for 1 minute and stops for 5 min. time changing by heat demand. can be longer or shorter, but the boiler is all the time modulating. So what happens, UF pump runs for 1min, boiler runs to, pump stops, boiler still runs, after 1 min boiler goes of because of return temp. after 5 minutes the pump starts and in no time the line become cold, boiler starts again. And of the day I have boiler starting stopping somewhere around 100 times.
I bring old my system back and compare the boiler behavior with reduced parameters.