Boiler connection 22mm

[Roger of Weston]

I have a 40CDi combi boiler in a 1920s house. The heating does not get hot just warm. I have 22mm from the boiler to under the floor but then connects to original half inch/15mm copper lagged with hessian. I believe I am losing heat as some of the runs are quite long. A local plumber said I need 28mm flow and return at the boiler , connecting into the 22mm to increase the heat flow. What do you recommend. I can’t get under the floors because of laminate, vinyl and tiles. The plumber suggests connecting 28mm from boiler to 22mm where it goes into the floor downstairs and to the upstairs.

 

[Scott_D]

How many radiators do you have?

 

[centralheatking]

I have a 40CDi combi boiler in a 1920s house. The heating does not get hot just warm. I have 22mm from the boiler to under the floor but then connects to original half inch/15mm copper lagged with hessian. I believe I am losing heat as some of the runs are quite long. A local plumber said I need 28mm flow and return at the boiler , connecting into the 22mm to increase the heat flow. What do you recommend. I can’t get under the floors because of laminate, vinyl and tiles. The plumber suggests connecting 28mm from boiler to 22mm where it goes into the floor downstairs and to the upstairs.

Tell us a bit more please. How many rooms, how many rads, number of bathrooms, type of house and insulation and glazing. Has it been serviced, do you have a filter has it been dosed with inhibitor do the rads warm at the top bottom. These are all questions your plumber ought to be asking. Centralheatking

 

[DuncanM]

22mm usually for main flow and return 15mm tails to radiators. Need to upgrade the pipework completely if 15mm runs are being used for main flow and return. It's a pain, but get a hatch cut or lift the floors to get it sorted. Once it's done it's done.

 

[Last Plumber]

A 15mm pipe will only carry somewhere in the mid 20,000 BThU's on an open vented system and maybe a tad more on closed/sealed. At a push you may get near to 30,000 but I wouldn't bank on it. There are lots of factors involved and each installation is different but it sounds like you need to enlarge the pipework to suit the flow required by the emitters (rads etc). Your plumber/Heating Engineer should be able to calculate the output from the system and going off distances and routes, tell you what size pipe is required.

 

[Roger of Weston]

Thanks for the reply. I don’t think glazing or insulation are an issue here as I not saying the house is not getting warm, It’s the radiators that are not getting warm. The heating system has been checked, flushed and inhibitor added so this is all good. The 22mm from the boiler is a short run to the under floor and to the upstairs. Once under the floor and upstairs then it is 15mm. I have a 40 kw boiler and have been advised this is more than adequate to heat the radiators. My plumber believes I am not delivering enough heat through the 15mm pipe work due to the long runs and poor insulation. He has suggested increasing the short run of 22mm to 28mm straight off of the boiler to increase heat flow. Is this an option.

 

[centralheatking]

A 15mm pipe will only carry somewhere in the mid 20,000 BThU's on an open vented system and maybe a tad more on closed/sealed. At a push you may get near to 30,000 but I wouldn't bank on it. There are lots of factors involved and each installation is different but it sounds like you need to enlarge the pipework to suit the flow required by the emitters (rads etc). Your plumber/Heating Engineer should be able to calculate the output from the system and going off distances and routes, tell you what size pipe is required.

I tried two new back to back 3 kw panel rads in my last house on a 15mm drop. It was not possible to get both up to roasting heat. Centralheatking

 

[Roger of Weston]

Do you think/believe connecting 28mm to the 22mm outlets on the boiler will make a difference ???

 

[centralheatking]

Tell us a bit more please. How many rooms, how many rads, number of bathrooms, type of house and insulation and glazing. Has it been serviced, do you have a filter has it been dosed with inhibitor do the rads warm at the top bottom. These are all questions your plumber ought to be asking. Centralheatking

Before anybody suggests new pipes etc. it is common sense to see if the existing system is operating properly as per my post above ...Chking

 

[Stu-B]

Do you think/believe connecting 28mm to the 22mm outlets on the boiler will make a difference ???

A few feet of 28 won’t make a noticeable difference if that’s what you’re asking. A general rule for an average sized central heating system would be 22 on the main flow and return with short stalks of 15 to the rads, then you’ll get good flow and nice hot rads.

but as chKING says, we need more info really.

 

[ShaunCorbs]

What’s the boiler temp doing when the heating is called

also new boiler / install / has it ever worked ?

 

[king of pipes]

How old is the boiler please

 

[Last Plumber]

I tried two new back to back 3 kw panel rads in my last house on a 15mm drop. It was not possible to get both up to roasting heat. Centralheatking

Maybe not. There are other factors involved as you no doubt know.
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Do you think/believe connecting 28mm to the 22mm outlets on the boiler will make a difference ???

As @centralheatking said, we need more info. Do you know the output of the central heating system upstairs and down?

 

[centralheatking]

Maybe not. There are other factors involved as you no doubt know.

I thought I had an even chance of them both working ..conventional system 3 story gaff 30kw wall hung with 28mm flow and return pump 2.5m directly above tried all 3 speeds Centralheatking
I even tried one flow in to the rads as they were back to back and one return so water had to pass through both
ie no t’s with just one lockshield in and one out.
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Do you think/believe connecting 28mm to the 22mm outlets on the boiler will make a difference ???

As above most likely not. If you go through the checklist we will be able to help you. Plus when you switch it on from cold the feed will be hot how long is it before the return warms up and the boiler modulates ie switches in and out automatically Chking

 

[Last Plumber]

I thought I had an even chance of them both working ..conventional system 3 story gaff 30kw wall hung with 28mm flow and return pump 2.5m directly above tried all 3 speeds Centralheatking

I would expect that to work to be honest.
The pair are only 20500 BThU, so 15mm should supply enough in theory. Could something have been restricting flow in that drop?
Could the rest of the system have a lot less restriction than the 15mm drops? (unlikely but not impossible).
Guessing!! not seen it.

 

[centralheatking]

I would expect that to work to be honest.
The pair are only 20500 BThU, so 15mm should supply enough in theory. Could something have been restricting flow in that drop?
Could the rest of the system have a lot less restriction than the 15mm drops? (unlikely but not impossible).
Guessing!! not seen it.

No one can see it now it’s all in a skip. I sold that property to a developer for its land value and it was demolished last Autumn 2019.

 

[Last Plumber]

Excellent!

A lovely sized plot it was too. A stroll from the sea, sunsets and plenty of fresh air.

Perfect setting to mull over Central Heating problems.

 

[Roger of Weston]

This is my 3rd winter in the house and the heating has never been good. If I set the thermostat to 23 degrees the boiler never turns off. I have had the heating on 24 hrs a day since November to keep moderate heat in the house. Viewed the house in August and moved in in December. My plumber has calculated that the 16 yer old boiler has more than enough btu to adequately supply the rads. My theory is the 15mm pipe work long runs are not efficient. I may have to consider a 22mm re-plumb of the heating.

 

[ShaunCorbs]

Do the rads get hot all over ?

 

[Roger of Weston]

Yes the rads get hot top to bottom.

 

[centralheatking]

This is my 3rd winter in the house and the heating has never been good. If I set the thermostat to 23 degrees the boiler never turns off. I have had the heating on 24 hrs a day since November to keep moderate heat in the house. Viewed the house in August and moved in in December. My plumber has calculated that the 16 yer old boiler has more than enough btu to adequately supply the rads. My theory is the 15mm pipe work long runs are not efficient. I may have to consider a 22mm re-plumb of the heating.

So at 23 deg the boiler unit never modulates what we mean is that the pump might run but the burner set will ignite and close down, your unit just carry’s on. I asked you to tell us from cold when starting your bolier how long it takes for the return pipe to get hot and your boiler to modulate
I am going to leave this open to the others as you seem incapable of providing answers to simple questions all we want to do is help .....centralheatking

 

[Roger of Weston]

Centralheatking
wow you’re rude.
It might surprise you to know that not everyone has central heating knowledge or an understanding of the terminology. I know you are here to help for which I am most appreciative. I most likely haven’t answered the simple questions because I don’t know the answers. If you would be so kind as to put your questions in a list form I will do my best to answer, as long as they are simple questions.

 

[ShaunCorbs]

Yes the rads get hot top to bottom.

sounds like it’s not a boiler issue or pipe work more likely the rads arnt sized correctly for the rooms

 

[Roger of Weston]

I don’t think it is a rad size issue as the rads don’t get hot, only warm. The house is quite warm as we keep the heating on 24 hrs.

 

[Stu-B]

I don’t think it is a rad size issue as the rads don’t get hot, only warm. The house is quite warm as we keep the heating on 24 hrs.

You’re best sticking to one story here to get the best advice
In one post you say rads get hot all over, and in another you say they don’t get hot only warm.
No wonder chKING got a little annoyed

time to start again methinks.
How did your plumber calculate the heat output of the 16yo boiler? Did he look at the data badge or run the boiler and gas rate it? Maybe you have a pump running a little weak if it’s the same age as the boiler.
Tbh issues can be hard to diagnose without being stood in front of the boiler, a good gas engineer can tell you a lot by running the boiler, listening to what noises are being made whilst feeling the pipework.
good luck pal

 

[Chuck]

I don’t think it is a rad size issue as the rads don’t get hot, only warm. The house is quite warm as we keep the heating on 24 hrs.

A numbered list of questions for you, as requested:

Qn 1. How much gas the boiler is using when it is on with the thermostat up to 23 degrees? (Take two gas meter readings an hour apart and report the values here.)

Qn2. What is the Central Heating Water target temperature set by the controls on the boiler?

Q3. What is the Central Heating Water flow temperature being reported on the boiler display?

Q4. Is the 'heating demand' light (it's blue on a Worcester Bosch boiler, which is what I think you must have) on continuously?

Q5. Can you hear the boiler shutting down after running for a few minutes, then waiting a while and then firing up again in a cycle while the blue demand light remains lit?

 

[king of pipes]

A 16 year old combi boiler is old its quite possible the pump is getting weak and its performance is dropping off you have a heating engineer get him to gas rate the boiler on high rate see how much heat its delivering a few pictures of the boiler may also help. Kop

 

[Last Plumber]

An experienced Heating Engineer should easily be able to come to a conclusion with this based on his/her knowledge.

If the rads are not getting warm enough, the cause could be a multitude of things.

I don't think you'll get the answers to your problem on a forum because the people you are talking to have not seen or tested your installation and there are too many possibilities with this kind of fault.

It could be a boiler issue - one of many - or indeed an installation problem. whether that be undersized pipework, partial blockages or other restrictions, short circuiting etc. it really needs an accurate diagnosis.

I think the best thing is to find a highly recommended Engineer and trust their conclusions or suggestions based on the results of their investigations.

Flow and return temperatures are always a good place to start with these things in my opinion, as they will give a good indication of where to start looking.

I hope this helps.