System boilers with high modulation radio and independently head/DHW coil flow tempe

[ringi]

So as to get the best condensing when running heating, the flow temperature from the boiler needs to be set as low as possible, by installing radiators that are sized for 50c => 30c (often called oversized.) However the DHW tank must be heated to above 60c, so needs a flow temperature from the boiler of 70c.

Yet most system boiler I have seen only allows one flow temperature to be set, does this not make it impossible to operate a system so it condenses most of the time while running the radiators?

Also combi are about with a modulation range of as such as 10:1 but system boilers seem to have a much lower modulation range, how come?

(I am staring to consider the heating options for a property I brought at auction last week; it will have 5 bedrooms, ideally each on its own zone, as I will be letting it “room by room”. However it has solid walls, so the peak heating demand will be high.)

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Cylinder needs it's own VT supply! Easy!

 

[IDCHAPPY]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

A zone for each room?? Christ, you may as well put heat meters in the flows to each room if you are going that far :lol:

 

[lame plumber]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

best get your hmo licence sorted first from your council before you start installing your system

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

We had issues with HMO! It's the environmental health dept usually..... What a pain in the arris for you poor landlords can't cram 35 students in a 5 bed one bath any more! What??? Some detectors, periodic inspection, locks fire doors.....

 

[lame plumber]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

full fire alarm systems, smoke free escape routes, alarms in each room................... the list grows and some uni towns arent granting hmo licences in some areas to bring the housing balance back to families and a few students.

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

The HMO licence is a bit of a pain, but it is reasonable what they ask for, it is not hard to meet the standard on fire alarms, fire doors etc. Also it does help reduce the number of competitors:yes:

I am starting with a house that is in a very poor state, therefore most of the work that trip people up, has to be done anyway, for example a fire door costs very little more then a normal decent door, and all the doors need replacing anyway.

Likewise with the heating, the current radiators are very old, most likely full of muck so a complete replacement is on order.

I wish that heat meter were more reasonability priced, if forced I can put a data logger on all the 2 way values to prove how much each room is asking for heat. But I expect my tenants will be “high end” enough that it is not an issue.

I yet to decide if I will zone each room with a timer/thermostat, or just have one timer and TRV in each room – the cost of zoning is not too unreasonable if done when a system is installed. However I can’t zone unless the boiler can cope with a VERY low heat demand.

 

[lame plumber]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

so how are you charging for HW? keep it simple and sweet, programmer on long periods and wh fm 0500 -2300 with trvs on rads and a room stat in landlord area thats tamper proof. divide bill amongs tenants

 

[IDCHAPPY]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Thank feck I never become a huge landlord, i rent out one property but the minute profit comes before the standard of housing of the people you rent out to. I'm out

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

I am not going to charge seperatly for HW or heating, however the tenancy agreements will have a fair usage limit, and if the utilities cost more than that, than the tenants get billed. Having some ideal the relative usage between tenants could be useful, just tenants knowing that I can check may get them to turn down the radiator rather than opening a window.

 

[Roger Welton]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Ideal vouges allow for different flow temps to be set for heating and HW demand, as do intergas, baxi (avanta), ATAG, viesman to name but a few.

Best bet is to find a local chap who knows his onions.

 

[chris watkins]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Cylinder needs it's own VT supply! Easy!

Should that not be CT supply ?

 

[chris watkins]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Ideal vouges allow for different flow temps to be set for heating and HW demand, as do intergas, baxi (avanta), ATAG, viesman to name but a few.

Best bet is to find a local chap who knows his onions.

Are these all using the built-in weather comp, Roger ??

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Vogue uses weather comp but shouldn't we be telling op about keston c55 as this is the best boiler for the job. Built in shunt pump to LLH and DHW / ch temps .

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Vogue uses weather comp but shouldn't we be telling op about keston c55 as this is the best boiler for the job. Built in shunt pump to LLH and DHW / ch temps .

Thanks Ermintrude,

Apart from having a smart pump and a much higher peak output then most domestic boilers what make the Keston C55 the best option. I must admit that I have never heard of Keston, but that is no reason off itself not to use them.

The Min Kw output seems much too high, as at time I could just have one radiator needing heat, unless the Keston C55 is a high water content boiler like the AVC HeatMaster TC range.

If only the HeatMaster 25/35 TC was more reasonability priced and covered by standard service contract, it would likely be my 1[SUP]st[/SUP] choose solution.

 

[Ermintrude]

System boilers with high modulation radio and independently head/DHW coil flo...

The keston is a disaster! It was posted in jest. Depending on heat load for ch I would fit an ideal logic plus or if you need more than 30kw fit two on to your ACV SLME which can be used as a LLH. Get a weather driven blending valve off of the cylinder so that it only draws the heat needed from the hot cylinder for the CH and cylinder is always full of meltingly hot wasser. Also fit water saving taps and showers.

 

[Roger Welton]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Are these all using the built-in weather comp, Roger ??

Yes just need outside sensor, and diverter valve (vouges can use s /y plan)

 

[chris watkins]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Yes just need outside sensor, and diverter valve (vouges can use s /y plan)

I am sure the others can also be made to work with an existing S plan with the use of a Horstmann programmer & some wiring mods but I agree for new install a diverter is the way to go.
It should be possible to add heating zones as OP requires maybe control each with a programmable room thermostat.

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flo...

The keston is a disaster! It was posted in jest. Depending on heat load for ch I would fit an ideal logic plus or if you need more than 30kw fit two on to your ACV SLME which can be used as a LLH. Get a weather driven blending valve off of the cylinder so that it only draws the heat needed from the hot cylinder for the CH and cylinder is always full of meltingly hot wasser. Also fit water saving taps and showers.

I don’t have a DHW tank in the property at present, so all options are open.

Having a buffer tank setup as a LLH does solve the problem of the boiler short cycling when the load is low so maybe the best option. (I rather not have this cost if it is avoidable.)

However how does an ACV SLME with the radiators running of it and an Ideal Logic Plus boiler allow the boiler to condense well while driving the radiators. Would the tank not have to be heated to 70c for the DHW?

How is the cost of the ACV SLME justified compared to a normal DHW tank and a separate buffer tank?

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

SLME is beautiful bit of kit. Depends on size. Yes it's more expensive but delivers 15% more water t 60c than a same size cylinder. Also you run it at 63c then it's always condensing, but should really be supplying it with water at 80c but if you configure a blending valves on the CH u can keep rads lower than 45 and return them into boiler so u take water away from cylinder after it's heated it and run it through rads to cool it then bump it through boiler , flowing into boiler at 40c ish and leaving at 80 so a lot of condensing going on.

Where are u btw?

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

SLME is beautiful bit of kit. Depends on size. Yes it's more expensive but delivers 15% more water t 60c than a same size cylinder. Also you run it at 63c then it's always condensing, but should really be supplying it with water at 80c but if you configure a blending valves on the CH u can keep rads lower than 45 and return them into boiler so u take water away from cylinder after it's heated it and run it through rads to cool it then bump it through boiler , flowing into boiler at 40c ish and leaving at 80 so a lot of condensing going on.

Where are u btw?

Thanks Ermintrude,

How does the installed price of a SLME along with a “normal” boiler compare to an AVC HeatMaster TC?

If I am not mistaken most boilers require the flow rate to be high enough that the temperature increase between return and flow is only 20c, so how can you go from 40c to 80c in one pass?
(I was assuming that the boiler will be connect into the outer tank, mid->top to heat for DWH, and bottom->mid to heat to the lower temperature for radiators to get the condensing.)

The property is in Stockport, it will be a few months until it is empty and work can start. At present I am trying to get an ideal of system type, so I can start to plan room layout etc, taking into account the space needed.

 

[Ermintrude]

System boilers with high modulation radio and independently head/DHW coil flo...

Best get it designed and incorporate some PT.

The boiler don't need to lift it as cylinder is a buffer. So water hits boiler 40c leaves 63c hits cyl but blends down to tmv setting. Only ramps up to top cylinder up. But that's from 65 ish and still condenses.

Is it price or performance you want? If it's price, just bang in an ariston unvented and a pair of solo boilers. Let tennants worry about bills.

SLME a bit more than a screwfix unvented. Depends on size and who buys it.

 

[Ermintrude]

System boilers with high modulation radio and independently head/DHW coil flo...

This is probably as far as the discussion should really go, if you hire a decent firm they will spesify and set up . If you start telling them what and how probably not get too far. I was just thinking how much I detest being told how to do install when clearly designed in some one else's head. And not on a drawing / calc sheet.

 

[newcastle phill]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

So as to get the best condensing when running heating, the flow temperature from the boiler needs to be set as low as possible

I think its the return and not the flow that needs to be lower than 55 as thats approximately the dew point.

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flo...

I will be paying the Gas Bill on this property! However I can offset running costs against income tax, but, “capital” costs can only be offset against capital gains tax if I every sell the property (and the system is still in use.)

 

[chris watkins]

Re: System boilers with high modulation radio and independently head/DHW coil flo...

I will be paying the Gas Bill on this property! However I can offset running costs against income tax, but, “capital” costs can only be offset against capital gains tax if I every sell the property (and the system is still in use.)

Do you want a bill for all the system design info given on here so you can offset that as well ??

 

[Worcester]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

If not fitting muliple DHW tanks for the multiple occupancy, and choosing a simple mild steel buffer (good choice ) then why not install a direct hot water system on the buffer tank (external Heat exchanger) - saves storing two lots of water, no G3 or legionella issues, and as much hot water as they want on demand, add in honeywell evo for each flat, (or go cheapskate and use Pegler Terrier i-Temp )

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Direct = lime scale ? But then again it's cheaper?

 

[ringi]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

If not fitting muliple DHW tanks for the multiple occupancy, and choosing a simple mild steel buffer (good choice ) then why not install a direct hot water system on the buffer tank (external Heat exchanger) - saves storing two lots of water, no G3 or legionella issues, and as much hot water as they want on demand, add in honeywell evo for each flat, (or go cheapskate and use Pegler Terrier i-Temp )

If I only have one tank, will I not need to keep it at least 65c, so that the PHE can produce DHW? If so, then I am heating water hotter than the radiators need and hence getting less condensing.


How does a honeywell evo allow the tenants to set the heating times, I thought that it was design on the bases of one unit that transmitted the required settings to all TRV in the building. I like the window open sensor on the Terrier i-Temp, but the UI on their TRV looks a bit complex, so will tenants turn the heating off when they go out?

 

[Ermintrude]

Re: System boilers with high modulation radio and independently head/DHW coil flow te

Fit a occupancy sensor, window contacts and a I/o controller. But the cost gonna be 200 times what u save. Your over complicating this . Put in electric heaters and get sub metering from supplier or token meters. And fit a solar thermal unit for DHW. Low capital low running cost .