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.
[automerge]1580290217[/automerge]

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.
[automerge]1580290723[/automerge]

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.