Hi Everyone:

I've been renovating an older property. During the course of this, I've modernised the Central Heating system. This started out as: Getting a new condensing boiler, replacing the rads, adding TRVs and installing a programmable room thermostat with an optimising facility.

I've now been told by various people that I should be putting in a weather compesation circuit. I've studied what has been said on this forum and some others, but I'm struggling to see how to integrate it. Also, finding programmable thermostats was easy compared to doing a web search for "weather compensators." What I have learned about weather compensators does make me think it might be a good idea to have one. However, I can't tell if it is overkill or not.

Can anyone offer advice on a good website to learn more about weather compensation? Also, who sells these things?

Thanks for your help.

Cheers, -------------- Mark

With an optimising programmable room thermostat you should need to worry about the weather compensator. Hope you can programme both time and temperature as this facility saves loads.

DocB: I will shortly be having a new heating system installed. It will include solar panels, ASHP, condensing oil fired boiler, heat store and a weather compensator controller. The latter will be a Resol DeltaSol E controller with Resol HKM2. Their website address is www.resol.de, if you are interested. This was recommended by my installer - I know nothing about them and can declare no connection with them.

I was interested to read tony's comment that having time and temperature control "will save loads" - I hope he is right! I will let you know in due course. The whole system will cost around £13K so I think it will probably not pay-back in my life time unless the price of oil goes through the roof relatively soon!(I am 61).

Jeff B

I have a weather compensating controller on my boiler. They work in two ways. Firstly they will adjust the start time of the boiler to take account of the temperature difference between inside and outside. Having learnt the buildings response times the boiler will be switched on later in mild weather. They same applies in the evening when the boiler will predict the cool down period and switch off as early as possible.

The other benefit is that they will adjust boiler flow temperatures to suit, ie higher outdoor temperatures means they will reduce boiler flow temperature.

In your case the controller will presumably control the flow from the thermal store rather than from the boiler.

A couple of questions about your proposed system:
1. Why the ASHP as well as the oil boiler?
2. How do you ensure that the condensing boiler works in condensing mode when heating the thermal store?

Nigel - thanks for your response. I have opted for an ASHP simply to further reduce my reliance on oil. I would not previously have included one on cost grounds bar for the fact that Trianco have recently launched a 12KW ASHP for ~ £2K which is a lot less than I have seen to date. I thought for £2K it was worth the gamble! As to your second question, I cannot answer that one. I assume that the installer has thought of that but I will certainly raise it with them.

Tony - thanks for your response. I understand that the Resol DeltaSol E controller will control both time and temperature.

Tony:

I was hoping an optimising programmable thermostat would do the trick. Perhaps I've been diverted off track by weather compensation. What I have read about it does suggest that it is more of a commercial application. On the other hand it will regulate room temperture more accurately than a thermostat to keep a steady temperature. I think a thermostat will heat up to the desired temperature, then shut down the boiler but the heating inertia in the system will allow the temperature to keep increasing in the regulated room. Eventually this will peak and the room will begin to cool until it gets below the trigger to fire up the boiler again and the whole process will repeat. Also there is this ability of a weather compensator to adjust the output temperature of the CH water produced by the boiler. I thought this was the key to keeping it in a condensing mode.

Cheers, ----------- Doc

Doc B - thanks for your response. I also looked at GSHP's as I may have just about enough ground but it is too expensive (and would wreck the garden!). It might be worth having a look at the Trianco ASHP as it appears to be very good value for money. Some folk on this forum seem to think that ASHP is crazy for the UK climate but where we are in West Wales it is very rare for the ambient temperature to fall below 4- 5C during the day time in winter and the Trianco output at 5C is claimed to be 7.2 KW (CoP approx. 2). In fact looking at the Met Office website I see that the lowest average minimum monthly temperatures (from 1971 to 2000) here were 2.9C for January and 2.6C for February (I presume these would be night time temperatures). For solar we are going for three EWF TWI Darkline T2 flat plate collectors as I believe these are only slightly less efficient that vacuum tubes and a lot more reliable. We have gone for overkill on the panels in terms of surface area but have specified a large (300 litre) heat store to compensate. I particularly wanted to maximise the contribution from solar to space heating in the spring and autumn.

I have the same dilemma as you regarding how the system will control/prioritise the various heat inputs i.e. solar first, then ASHP, then oil fired condensing boiler last. I am assured that the Resol controller will take care of this. I will let you know how we get on after the system is installed (in a few weeks time I hope)! It would be good if you could provide some feedback from Interbuild - I look forward to reading it.

Hi All
I'm really interested in your comments.
I'm a new member and have just bought an old house with poor insulation and there is not much I can do about it. We have a wood burning stove without a back boiler and an LPG fired boiler. I've investigated a wood chip boiler and heat pumps but they are either too expensive or cannot do the job. Peak heat loss is probably about 15kW. I'm also concerned that I work overseas for months at a time and need to leave the house in automatic frost protection mode. I thought about oil but when I look at prices and net CV's etc there is nothing to chose between oil, chips or gas. So I'll stick with gas (LPG). The best thing seems to be a combi boiler with TRVs though if I get a weather compensator do I need TRVs?
Any suggestions as to which boiler and controller to get?

Jeff B -

Back from show, but unfortunately not much better educated. Spent a long time on the Viessmann stand talking to their solar guy (forgot his name, sorry. Foreign chap with a strongish accent, but very knowledgeable about solar). For the kind of control I am trying to get, I really should have gotten their boiler (why do I smell something fishy here?). It has weather compensation on it and the solar control will talk to the boiler to tell it when solar is heating the water.

If you go for evacuated tubes then probably the heat pipe (or dry connection) is best. I think I'm right in saying that it handles overheat days better than the others. This is when the sun is still shining but there is no call for heating water. In a direct flow type of system, where the heat carrying fluid circulates through the tubes and down to the tank, then everything heats up quite hot. In a heat pipe only the fluid in the pipe heats up. It boils away (although it stays in the pipe because it's sealed) and that's it, but the fluid that carries this heat to the tank is separate. It doesn't get any hotter. Anyway, this is the way I understand it. I think the heat pipe system handles longish periods of no demand better than a direct flow type.

In addition, to change anything on the direct flow system you have to drain the whole system. In the heat pipe system if you have a problem you only need to remove the tube causing a problem. Because it's a dry connection you don't have to drain the whole system. Oh yeah - if a tube breaks in the direct flow system then everything pumps out onto the roof. In the heat pipe system you just loose one vacuum tube. The rest continue to operate.

Anyway, back to controls - From what I've been reading so far it seems Resol is the company I need to get the controls I want. They weren't at the show so I'm still researching them.

There were several other solar manufacturers at the show. However, you really get a wide range from people who make you feel like you should go wash your hands to those who you want to make your best friend. . . . Well I exaggerate a bit, but . . . . I didn't spend a lot of time looking at them, even less looking at GSHP or ASHP - there was just too much to do.

One more foot note on solar DHW. Panels or tubes, it sounds like they are all ultimately made in China. People will tell you they are made in Germany or Austria, but is that "made" as in starting with raw materials, or "made" as in we repacked them? I don't know. Hence is the tube behind a product with a one year warranty the same as a tube behind the product with a 10 year warranty and is the extra cost basically just paying for a longer warranty period?

Anyway - more when I get done reading up about Resol.


Jimmy -

My guess is you would still benefit from TRVs. If one room reaches it's design temperature before the rest of the house then the TRV in that room would shut down that rad. The weather compensator just (I think) adjusts the flow temp out of the boiler in order to keep the return temp within some magical zone called the condensing zone. In other words, a condensing boiler works most efficiently when it is condensing. The weather compensator try to achieve that by regulating the flow temp such that on a warmish day the flow temp is lower. The rationale here is (I think, again) that because the house is not very cold then not very much heat will be drawn off the rads. Thus a high flow temp will result in a high return temp and this will not allow the boiler to work in condensing mode. On really cold days the weather compensator allows the boiler flow to be hotter - because more heat is drawn off by the rads.

What I haven't learned yet is if you have both a weather compensator AND a programmable thermostat with optimising functions - do they work together or do they fight each other?

As to boilers - I guess I would say get the best you can afford. But I have heard others say get the cheapest you need. Can't remember the argument at the time. There are some with inbuilt weather compensation, but the only one I know of is the Viessmann boilers. This is not a plug for Viessmann, however.


Hoovie -

Thanks for your input. I think I just recently got to the point where you are. I don't know much about Resol yet so I need to do more research. Trouble is there aren't many people on the ground here where you can go for help. I think it'll have to be mainly from their website.

I think the basic elements I have are:

--- DHW
--- From Solar
--- From Boiler
--- Central heating
--- Weather Compensation and/or Optimising Programmable Thermostat.

I'll check out the Deltasol controllers and see what turns up. Thanks for your input.

Cheers for now everyone, and thanks for contributing.

------------------ Doc

A simple way to save money on your heating bills is by using a system like this one.

Heating save http://heatingsave.co.uk/

Over 98% of central heating systems use a time clock, boiler and room thermostat to control the heating. A hopelessly inefficient system based on technology that was around 100 year ago! None of this much mattered when oil was $10 a barrel - it's now between $120 and $147 and its still summer!

Replacing your central heating clock with a HeatingSave controller can save you 100's if not 1,000's off your heating bill! Usually paying for itself in less than a year!

Jonnyboy - They seem to have an interesting combination of features. Personally I don't like stats that try to learn the system response rate. It's a nice idea but not for people who like to adjust their stats constantly. They mess with the settings while it's learning and confuse the heck out of the stat. Then they wonder why the system is coming on at strange times.