plumbing problems

pkd09

Looking for some advice. I build my house in 2008 its around 3100 sq feet. The contractor put in a baxi he 25 combi boiler to run the underfloor heating through out the house. It has never really worked properly and really struggles when its cold. I have had two plumbers look at the system, one is advising that I need a bigger boiler 30kw and the other wants to increase the pipe size from the boiler to the manifold from 3/4 inch to 1 inch and put a header in, so the boiler feeds it not the manifold. Any comments grateful

Slippin Jimmy

You will probably get a better reply in the heating and plumbing forum.

slimjimmc

Moved to Plumbing & Heating.

galwaytt

pkd09 wrote: »

Looking for some advice. I build my house in 2008 its around 3100 sq feet. The contractor put in a baxi he 25 combi boiler to run the underfloor heating through out the house. It has never really worked properly and really struggles when its cold. I have had two plumbers look at the system, one is advising that I need a bigger boiler 30kw and the other wants to increase the pipe size from the boiler to the manifold from 3/4 inch to 1 inch and put a header in, so the boiler feeds it not the manifold. Any comments grateful

[sigh]..sounds like my house !

Seriously, only for my boiler is currently AWOL, my UFH has worked off a 30kW boiler - but the boiler is not feeding the manifolds directly.

I have a buffer tank that the UFH draws to it's manifolds from, and the boiler is on a very short leg to the buffer. I think this is better, from a boiler-cycling perspective.

My point being I think a boiler connected directly to an UFH manifold is not the best solution imho - and this is something I had in my previous house.

pkd09

galwaytt wrote: »

[sigh]..sounds like my house !

Seriously, only for my boiler is currently AWOL, my UFH has worked off a 30kW boiler - but the boiler is not feeding the manifolds directly.

I have a buffer tank that the UFH draws to it's manifolds from, and the boiler is on a very short leg to the buffer. I think this is better, from a boiler-cycling perspective

My point being I think a boiler connected directly to an UFH manifold is not the best solution imho - and this is something I had in my previous house.

thanks for that,boiler awol makes two of us.mine is airlocked in the top of the house.dont know much about boilers but i keep being told mine is for a 3 bed house

froshtyv

pkd09 wrote: »

Looking for some advice. I build my house in 2008 its around 3100 sq feet. The contractor put in a baxi he 25 combi boiler to run the underfloor heating through out the house. It has never really worked properly and really struggles when its cold. I have had two plumbers look at the system, one is advising that I need a bigger boiler 30kw and the other wants to increase the pipe size from the boiler to the manifold from 3/4 inch to 1 inch and put a header in, so the boiler feeds it not the manifold. Any comments grateful

You can probably be sure that the mechanical side of the system is not correct.
What i mean by this is that when connecting the underfloor heating to the boiler, there is no by-pass valve or header arrangement used. When the mixing valve on the ufh starts to close, the boiler pump has no where to circulate to and will try to force the mixing valve open.
A simple solution is to install a by-pass valve or header between the boiler and underfloor heating pump and mixing valve.
A bigger boiler will not solve your current issue.
What type of pipes were used to feed your ufh manifolds? Copper or multilayer?

pkd09

Thanks for the advise. Since posting i have contacted manufacturer and they gave same advice. So will be getting plumber to put in a header and a weather compensating valve. Fingers crossed. In relation to the pipes,the plumber used copper.

jack_t

Hi pkd09,

could you advise which weather compensating valve and controller you're installing? I am planning to install it for my system before next winter.

antoinolachtnai

I don't know much about it really, but would turning the boiler down low solve this problem? You would obviously need to leave to leave the boiler running longer to get the same amount of heat output, but that's no big deal.

froshtyv

antoinolachtnai wrote: »

I don't know much about it really, but would turning the boiler down low solve this problem? You would obviously need to leave to leave the boiler running longer to get the same amount of heat output, but that's no big deal.

Your boiler is designed to work at high temperatures to achieve its best efficiency so by turning its flow temperature down you will end up using more oil in the long run.
A mechanical mixing valve would be the easiest solution, but i assume there is one fitted on your UFH already?

froshtyv

pkd09 wrote: »

Thanks for the advise. Since posting i have contacted manufacturer and they gave same advice. So will be getting plumber to put in a header and a weather compensating valve. Fingers crossed. In relation to the pipes,the plumber used copper.

Depending on the length of run, you generally get enough flow using 3/4" copper.

antoinolachtnai

froshtyv wrote: »

Your boiler is designed to work at high temperatures to achieve its best efficiency so by turning its flow temperature down you will end up using more oil in the long run.
A mechanical mixing valve would be the easiest solution, but i assume there is one fitted on your UFH already?

It's a condensing gas boiler, no? These are by and large designed to run at their greatest efficiency at lower temperatures. Obviously the differential is very important too.

http://www.cleaver-brooks.com/About-Us/News/Articles/2013/Operating-A-Hydronic-Boiler.aspx

froshtyv

antoinolachtnai wrote: »

It's a condensing gas boiler, no? These are by and large designed to run at their greatest efficiency at lower temperatures. Obviously the differential is very important too.

http://www.cleaver-brooks.com/About-Us/News/Articles/2013/Operating-A-Hydronic-Boiler.aspx

My mistake, i was referring to an oil boiler.
A gas boiler is a different story when it comes to modulating.
This needs to be setup correctly though, along with the mechanical setup of the system.
Depending on the pump in the gas boiler there could be case where you wouldnt need an additional pump for the UFH or a mixing valve if the flow temperature can be controlled correctly.

antoinolachtnai

I just mention it because turning down the temp and running the heating for a longer period might solve the OP's immediate problem for the short term. It probably isn't a fantastic solution, but it might help.